Examensarbete vid Fasta Tillståndet Elektronik

Abstract

A relativistic magnetron (RM) is a high-power microwave (HPM) source. The main objective of the RM is to generate directed electromagnetic pulses with high power, which can be used in e.g. HPM weapons and for electromagnetic compatibility testing. These pulses can disturb or damage electronic equipment. One of the main challenges when designing an RM is to generate the advantageous TE11 wave mode to the circular waveguide and antenna with high efficiency and peak power. This thesis investigates a new design of the RM, developed at the Swedish Defence Research Agency (FOI), referred to as the FOI magnetron. This design is based on the A6-magnetron and employs four large and two small cavities in the diffraction output of the RM, compared to the conventional design that has six identical cavities. The FOI magnetron has previously shown results that indicate the possibility of generating the TE11 wave mode.

In this thesis, a literature study was performed to better understand the governing physical laws of the RM. This was followed by parametric studies using the ​​particle-in-cell code MAGIC3D for simulating the RM. To validate the simulation models, a model of a conventional RM was constructed and the results were compared against the published simulation results by Daimon and Jiang (2008).  Lastly, different geometrical properties, applied magnetic field, and applied voltage of the FOI magnetron were studied to see how they impacted the RM performance. Apart from the diffraction output, the geometry of the interaction region was studied to investigate the effect on frequency and power. The goal was to generate a clean TE11 mode in the waveguide of the RM with high efficiency.

The validation yielded results that were in good agreement with the ones obtained by Daimon and Jiang (beam-to-microwave efficiencies of 37% and 36% respectively). The parameter studies of the FOI magnetron gave results that indicate a clean TE11 mode with a beam-to-microwave efficiency of ∼35% and peak powers up to 1 GW at frequencies of approximately 2.5 GHz. The studies on the interaction region showed that a shift of approximately 0.12 GHz was possible when making the rear part of the interaction region 4.5 cm longer. It was found that the length of the front of the interaction region can to some extent affect the output power. Lastly, it was found that a fraction of the output power (∼10−17%) that leaves the interaction region propagates back toward the input region and the voltage source. 

Abstract

Intra-Body Communication (IBC) is a prospective technology where human tissue may be used as a signal medium in order to transmit useful data within the human body. Proposed applica- tions of this technology are prosthetics control or implanted device communication, potentially by establishing an Intra-Body Area Network (IBAN), which could further be enhanced by other IoT applications and 5G radio systems. Previous research at Uppsala University has shown the fat tissue to be a promising medium due to its low permittivity and loss tangent. This form of implementation is named Fat-IBC.

This thesis aimed to produce a Fat-IBC enabled device, as a proof of concept. This project successfully produced and characterized phantom tissue, produced a basic demonstrator device in the form of a 3D-printed arm prosthetic, and integrated a wireless communication system into the arm prosthetic. The communication system was implemented using Arduino microcontrollers and XBee RF modules, based on the 802.15.4-based ZigBee protocol at 2.45 GHz.

Muscle, fat, and skin phantom tissues were produced, with the muscle tissue being similar to other comparable tissue samples, while the fat and skin tissues deviated from such samples. A signal loss transmission test measured a -67 dB loss over 20 cm of fat tissue. Several potential issues with production and measurement were discussed. The arm demonstrator device was also tested by transmitting the control signal across phantom fat tissue, being fully functional through 10cm of tissue, and of limited function across 20cm of tissue.

Abstract

Syftet med detta projekt är att undersöka en cylindrisk kavitet samt att använda mikrovågor för att värma upp ett material i kaviteten. Detta gjordes genom att mäta kavitetens Q-faktor och resonansfrekvens med och utan material. Sedan valdes grafit ut som det materialet som skulle testas och mer noggranna mätningar gjordes på just det materialet, och programmet QZero användes för att få ut mer noggrann data samt gav en felmarginal på Q-faktorn. Efter det gjordes simuleringar i programmet Comsol av kaviteten med och utan grafit och jämfördes med de faktiska värdena. För att mäta temperatur av materialet i kaviteten designades en hållare som en pyrometer skulle fästas vid och riktas mot materialet i kaviteten. Även en strömförsörjning till pyrometern installerades. För att skicka in mikrovågor i kaviteten användes en signalgenerator som var kopplad till en förstärkare. Förstärkningen mättes och förstärkarens effekt noterades. I slutändan nåddes inte de temperaturer som krävdes för pyrometern, så en elektrisk termometer användes för att mäta temperaturen på grafiten och detta jämfördes sedan mot den energin som absorberades av grafiten, då energin tillförd till grafiten och grafitens specifika värmekapacitet var känt. Prestandan av experimentuppställningen undersöktes också. For den tomma kaviteten mättes en Q-faktor på 3200 och resonansfrekvensen var 2.4 GHz. Detta stämde bra överens med simuleringarna i Comsol. När grafit fördes in i kaviteten sänktes Q-faktorn till 300. En avvikelse upptäcktes mellan de faktiska mätningarna och simuleringarna. I simuleringen sänktes Q-faktorn bara till 2570, en andledning till detta tros vara antingen vara hur materialet valdes, då det fanns olika typer av grafit med olika inställningar att välja mellan i Comsol. En annan felkälla kan vara något fel med uppställningen på grund af hur avancerat Comsol var. I värmeexperimentet hade förstärkaren en låg verkningsgrad vilket ledde till överhettning om för stor effekt användes. Experimentet begränsades därför till att använda upp till två watt. Vid exponerig under 30 sekunder värmdes grafiten upp till 100-150$\degree$C, vilket var avsevärt lägre än den teoretiska uppvärmingen till 1700$\degree$ beräknad från energin tillförd till grafiten. Antagandet är att temperaturen hamnade i ett jämnviktsläge kring 100-200$\degree$C eller att resonansfrekvensen ändrades vilket ledde till en minskning av energi tillförd till grafiten.

Abstract

The purpose of this paper is to achieve wireless power transfer inside a resonating cavity, and thereby apply this to charge batteries. The idea is to convert radio frequency waves into direct current, which can charge the batteries. This was done by creating an LC-antenna, which in turn was connected to a rectifier. A data logger was also built, this to be able to read and log the power within the cavity to examine its power distribution. Because of COVID-19 restrictions, access to laboratory and equipment was limited. Due to this, smaller experiments where performed to make sure that all parts worked as intended before trying to perform tests inside the cavity resonator. The results were varied, some favorable, some not. However, all experiments gave insight and further understanding on the issue.

The cavity operations had varied results. The data logger was able to pick up, at most, 7.6 % of the power output by the function generator. However, some problems arose with the rectifier which resulted in it not working for higher frequencies. Though, it was capable of rectifying RF signals at lower frequencies from a function generator, which was used to charge a battery. Consequently, there was no charging of batteries inside the cavity. However, three dimensional wireless power transfer was achieved. With some improvements to the current designs, the main goal could be accomplished

Abstract

High power impulse magnetron sputtering has shown a lot of promise as a way of depositing photocatalytic thin films of titanium dioxide at low temperatures, however, the films deposited are often amorphous and display uncertain photocatalytic abilities. This thesis explores the deposition and characterization of photocatalytic thin films deposited with high power impulse magnetron sputtering. 

Multiple films were deposited with reactive sputtering in both the oxide and metal mode of operations at different temperatures, duty cycles and substrate biases. The crystal structure, microstructure and photocatalytic activity of the samples were then characterized in order to correlate to each other as well as the growth conditions. Crystallinities were determined via a combined use of gracing incidence x-ray diffraction and Raman spectroscopy, microstructures were explored in cross-sectional images taken using scanning electron microscopy and the photocatalytic ability was measured by quantifying the rate constant during degradation of stearic acid while under UV-illumination. 

It was found that the crystal structure of the sputtered films was influenced by the deposition mode used: oxide mode depositions yielded an anatase structure while metal mode depositions resulted in rutile or mixed structures. The only crystalline films were formed with substrate heating, the application of bias was found to correlate with the formation of more rutile and the most crystalline films were deposited with a higher duty cycle. 

Photocatalytic films were successfully deposited at room temperature, even though they were amorphous. Interestingly, the anatase samples were not found to be the most reactive, instead it was found that the crystal structure only displayed a weak correlation to the reactivity of the films. The findings in this work suggest that the reactivity was also heavily influenced by the surface roughness of the samples as well as their microstructures.

Abstract

Mikrovågsuppvärmning är en viktig process som används i många industriella tillämpningar. Användningen av mikrovågsuppvärmning inom industri är dock inte lika utbredd som den har potential till att vara på grund av orsaker som säkerhet, strålning och brist på kunskap. Arbetets mål är att få ökad förståelse för hur materialegenskaper som permittivitet, termisk ledningsförmåga och elektrisk ledningsförmåga påverkar upphettning i mikrovågsugn. För att åstadkomma detta utförs simuleringar samt experiment på grafit som undersöks under mikrovågsuppvärmning i kiln anpassad för mikrovågsugn. Resultaten jämförs med liknande simulationer av det dielektriska materialet regolit. Händelsen simuleras först i COMSOL Multiphysics varefter korresponderande laboration utförs i verkligheten. För att åstadkomma fungerande simulation i COMSOL kalibreras den med hjälp av en tidigare utförd simulation av kiln i mikrovågsugn samt med COMSOLs egna Microwave Heating-tutorial. Under arbetets gång läggs mycket energi på att optimera simuleringen utefter diverse problem, exempelvis att simulationen är väldigt krävande. Slutligen uppnås fungerande simuleringar som relaterade väl till det riktiga experimentet.

Abstract

Radar är fundamentalt i modern krigsföring. Med en radar kan man avfyra vapen från säkra avstånd och med precision mäta in mål. En radarstörare har som mål att förhindra en radar från att mäta in sitt mål. Då radarn fungerar genom att sända ut specifikt modulerade radiovågspulser och lyssna efter ekot från omgivningen kan störaren förhindra detta genom att antingen sända mycket starkt brus, eller genom att sända radiovågspulser med samma specifika modulation. Den senare metoden kallas för DRFM-störning, där förkortningen står för Digitalt RadioFrekvens-Minne, vilket antyder att störaren kan minnas radarns modulation och själv använda den. Om radarn använder en ny modulation (eng: waveform) för varje puls kan störaren inte använda modulationen den minns från förra pulsen utan måste vänta på att nästa puls träffar den innan den kan repetera pulsen, vilket begränsar dess störförmåga.

Denna rapport tänker sig att radarn har en begränsad uppsättning av modulationer att byta mellan, och undersöker olika sådana uppsättningar och bedömer och jämför dem på olika mått av radarprestanda och störtålighet. Radioprestandamåtten inkluderar hur mycket förstärkning och hur fin upplösning man får av modulationen, hur väl modulationen kan hantera mycket snabba mål, och hur stora "sidolober" som uppstår runt starka mål. Sidolobsfenomenet är jämförbart med det optiska fenomenet där små men ljusstarka saker på natten kan se ut att ha en ljus halo eller ljusa utstrålningar runt sig. Störtålighetsmåtten kvantifierar hur distinkta de olika modulationerna i radarns uppsättning är, och på så vis hur väl radarn kan urskilja en modulation från de andra, tillsammans med hur liten sannolikheten är att störaren lyckas välja just den modulation vi kommer använda till nästa puls.

Resultaten visar att metoden av modulationsbyten kan ge nästan lika stor störtålighet som en välkänd metod, PRI-jitter, ger själv och något högre i kombination med den metoden. Bättre störtålighet visas gå hand i hand med sämre mått på radarprestanda, men mindre strukturerade spektrogram vilket antyder att de kan vara svårare att upptäckas av radarspanare. Försämringen i måtten på radarprestanda innebär inte nödvändigtvis en lika stor försämring i faktisk radarprestanda, då sidoloberna tar an en brusartad karaktär vilket leder till praktiska fördelar gentemot de vanliga fixa sidoloberna.

Abstract

Institutionen för fasta tillståndets elektronik vid Uppsala universitet tillverkar och testar solceller och för att säkerställa deras funktion. I dagsläget används en halogenlampa vid testningarna som har gått ur produktion. För att hitta en lämplig ersättare är syftet med detta projekt att söka efter och undersöka ljuskällor som uppfyller givna specifikationer från uppdragsgivaren. Ljuskällans ljusspektrum bör sträcka sig mellan våglängderna 350-1200 nm, ha ett homogent ljusflöde, samt ha en irradians på 1000 W/m2. På grund av en rådande pandemi kan funna ljuskällor inte testas och det utgås därför enbart från leverantörernas ljusspektrum.

De flesta lamporna som hittats är av typen LED, vilka har ett smalt spektrum och är därför inte tillräckliga för att uppfylla kravet på specifikationen gällande våglängderna. En växtlampa har även hittats och som enligt leverantören har ett fullt spektrum. För att säkerställa detta behövs vidare mätningar, vilka inte kunde utföras under projektets gång. En annan lampa som också verkar vara en lämplig ersättare är solsimulatorn från G2V, som har ett kontinuerligt spektrum på intervallet 400-1100 nm. Lampan har en livslängd på cirka 50,000 h och en irradians på 1120 W/m2. Beroende på lampans specifikationer kan den kosta mellan 8,000-21,000 USD, vilket är dyrare än önskat. Denna lampa uppfyller därför samtliga krav, bortsett från priset som anses vara högt.

Abstract

The purpose of low probability of intercept (LPI) radar is, on top of the standard requirements on a radar, to remain undetected by hostile electronic warfare (EW) systems. This can be achieved primarily by reducing the amount of radiated power in any given direction at all times and is done by transmitting longer modulated pulses that can then be compressed digitally in order to retain range resolution. There are multiple different methods of performing pulse compression modifying either the phase or frequency of the transmitted waveform. Another method for attaining LPI properties of a radar is to avoid having a large main lobe in the transmit pattern and instead having lower gain patterns. This then results in a need for post-processing of these patterns by summation of weighted combination of these low gain patterns in order to reform the high gain patterns and thus retain angular resolution. In this work a number of pulse compression waveforms are analysed and compared using their ambiguity properties in order to ascertain which ones can be used in a radar system. They are then used in simulation with GO-CFAR detectors using a variety of analysis tools, specifically the short term Fourier transform (STFT), Wigner-Ville distribution (WVD), quadrature mirror filter bank (QMFB) and spectral correlation density (SCD). Their performance against the detector is based on the rate that the waveforms trigger an alarm and the lower the alarm rate the better the performance. The base reference in terms of performance for these evaluations was set as a triangular FMCW waveform. The results show that the polyphase coded waveforms have good radar and LPI properties in comparison to the FMCW. The frequency hopping codes showed good LPI properties with a large number of frequencies in the sequence but suffer from large ACF side lobes and poor Doppler tolerance. The best LPI results were achieved by a phase coded signal with a random order to its phase terms whilst still maintaining a perfect periodic autocorrelation function (PACF). Potential issues remain with high frequency out of band emission that could lead to a mismatch due to receiver bandpass filtering. The low gain patterns investigated were expanded to include two way patterns for a 2D array and array element tapering. The method works and can be further optimised in order to minimise emissions but adds a significant increase to integration times when the array size grows large.

Abstract

There is an increasing interest in using new composite materials in microwave devices, to reduce size and weight while maintaining similar performances. A new promising material group is named magneto-dielectric materials, which have the permittivity and permeability values both larger than one. Compared to the commercially used dielectric materials, magneto-dielectric materials can achieve a larger miniaturization factor with the equivalent properties as dielectric materials. There is a very limited availability of commercial magneto-dielectric materials. A recent addition was from Rogers Corporation with MAGTREX 555, [1], that is available as a printed circuit board laminate. The material is limited to 500 MHz operational frequency due to its increased magnetic and dielectric losses.

In this thesis the purpose is to understand the loss mechanisms, characterize and understand the state-of-the-art magneto-dielectric materials at microwaves, and to produce a magneto-dielectric material in the lab to understand the material better. A new material was developed with magneto-dielectric properties. The material was based on a polymer base of polystyrene that serves as a dielectric material and doped with nickel nanoparticles that produce the magnetic properties. The contents of the nanoparticles in the mix is a design variable. Nickel-polystyrene samples with different nickel contents of 0%, 2.3% and 4.5%, were produced in the lab and measured in-house to understand the loss mechanism and RF performance.

Abstract

We have deposited bulk, monolayer and few-layers as well as large-scale 2D layered MoS₂ thin films by pulsed DC magnetron sputtering from an MoS₂ target. MoS₂ has gained great attention lately, together with other layered Transition Metal Dichalcogenides (TMDCs), for its unique optical and electrical properties with thickness-dependent bandgap. MoS₂ also transitions from an indirect to a direct bandgap when thinned down to monolayer. This is intriguing in the fabrication of novel solar cells and photodetectors. Sputter-deposition has the advantage of producing large-scale, high-quality films, which is paramount for layered MoS₂ to be applicable on an industrial level. The quality in terms of crystallinity and c_⊥-texture of sputtered bulk MoS₂ was evaluated as a function of several deposition process parameters: process pressure, substrate temperature and H₂S-to-Ar ratio. X-ray Diffraction (XRD) results revealed that the high substrate temperature of 700 °C together with reactive H₂S process gas improved the quality regardless of pressure. However, the quality was slightly improved further with increasing pressure up to 50 mTorr. We also found that the quality improved with increasing temperature up to 700 °C using pure Ar as the process gas. Rutherford Backscattering Spectrometry (RBS) analysis showed that with the addition of H₂S the stoichiometry of MoS_x improved from MoS_1.78 using pure Ar to fully stoichiometric MoS_2.01 at 40% H₂S in the H₂S/Ar mixture. Cross-sectional Transmission Electron Microscopy (TEM) imaging revealed the high-quality 2D layered structure of the MoS₂ films and a maximum thickness of 5 nm of c_⊥-growth MoS₂ before the onset of the undesirable c_∥-growth. These results provide a solution with respect to the ongoing challenge of obtaining high quality and good stoichiometry of sputtered TMDC films at elevated temperatures.

Formation of monolayer and few-layers MoS₂ was confirmed by Raman and Photoluminescence (PL) spectroscopy. The peak separation of the E¹_2g and A_1g Raman-active modes for MoS₂ monolayer was measured to 19.3 cm^-1 on SiO₂/Si, increases substantially in the transition to bilayer MoS₂ and exhibits bulk values from four layers MoS₂ and above. This result serves as a good indicator of monolayer as well as few-layers MoS₂ formation. The monolayer film exhibits a strong photoluminescence peak at 1.88 eV owing to its direct optical bandgap, as compared to the indirect one of bilayer and thicker films. X-ray Photoelectron Spectroscopy (XPS) spectra of the monolayer MoS_x film indicate successful sulfurization of the molybdenum atoms and absence of residual sulfur. XPS also showed ideal stoichiometric MoS_2.03 ± 0.03 of the monolayer film. Furthermore, a uniform MoS₂ monolayer was successfully grown on a 4" SiO₂/Si wafer, demonstrating the large-scale uniformity that can be achieved by sputter-deposition, making it highly applicable on an industrial level.

Abstract

The aim of this thesis is to optimize the design of the Fat-IBC-based communication of a novel neuroprosthetic system in which a brain-machine interface is used to control a prosthetic arm. Fat-based intra-body communication (Fat-IBC) uses the fat tissue inside the body of the bearer as a transmission medium for low-power microwaves. Future projects will use the communication system and investigate ways to control the prosthetic arm directly from the brain. The finished system was able to individually control all movable joints of multiple prosthesis prototypes using information that was received wirelessly through Fat-IBC. Simultaneous transmission in the other direction was possible, with the control data then being replaced by sensor readings from the prosthesis. All data packets were encoded with the COBS/R algorithm and the wireless communication was handled by Digi Xbee 3 radio modules using the IEEE 802.15.4 protocol at a frequency of 2.45 GHz. The Fat-IBC communication was evaluated with the help of so-called "phantoms" which emulated the conditions of the human body fat channel. During said testing, packet loss measurements were performed for various combinations of packet sizes and time intervals between packets. The packet loss measurements showed that the typical amount of transmitted data could be handled well by the fat channel test setup. Although the transmission system was found to be well-functioning in its current state, increasing the packet size to achieve a higher granularity of the movement was perceived to be viable considering the findings from the packet loss measurements.

Abstract

The thesis aims to develop a prototype for a Smart Case for Remote Radio Kits at the department of Demo & Event at Ericsson in Kista.The smart case consists of a mechanical structure (the case itself with ) and an electronic system that includes a temperature sensor, a LCD display showing the temperature, a GPS (global positioning system) module for positioning the case, a GSM (Global System for Mobile Communications) module and a microcontroller Arduino UNO. The Case is modelled in 3D with the help of CAD software and then printed with a 3D printer. A down-scaled prototype is built with the help of the 3D printer and the 2D drawing will be used when the full scaled model is produced. The Arduino UNO handles temperature sensor and GPS measurements, LCD display, and the transmission of measurement data using GSM module via text message (SMS) to a cell phone or to a server over the Internet. The projected ended up with all the drawings and models finished for the Case as well as the implementation of down-scaled prototypes. The electrical system was tested and finished individually. But the complete system cannot be assembled inside the Case due to the time limitation. This means that the project can be further extended, where a full scale model can be developed and the electrical control system can be assembled together and mounted inside the Case.

Abstract

The ability to easily customize and produce specialized MW-components for research and industry is a real challenge and the need is identified, as standardized parts have limited use and can limit design freedom. This study aims at exploring if there are simple ways to manufacture rectangular X-band waveguides with operating frequency of 8-12GHz with novel polymer additive manufacturing and chemical metal deposition that can match Computer Numerical Control (CNC) manufactured rectangular metal waveguides in performance. X-band was chosen mostly because of it having a good size to start printing trials and x-band components being in heavy use where a lightweight would be beneficial. Also, to evaluate the manufacturing results by measuring and comparing s-parameters and weight between measuring standard and manufactured waveguides. Furthermore, to use the preexisting models for approximating the attenuation due to surface roughness. Different designs were tested with different polymers and electrodeposition techniques and approaches. Two of the benchmarked techniques gave better results; first, using a modular design with a combination of different polymers and an industrial copper plating technique; second, a single polymer one-piece design using an acrylic carbon paint and a small scale in-house electroless copper deposition. The performance of conventionally manufactured rectangular metal waveguides was not matched but the two investigated techniques show on results that the techniques could possibly be modified in the future to match the performance of conventionally manufactured waveguides.

Abstract

In this report the feasibility of using a dual-tag setup in an indoor positioning system was investigated. The reason for the dual-tag setup was to be able to estimate both position and orientation. The system was designed using UWB-technology, with an time of flight trilateration algorithm to calculate the position. The orientation was then estimated from the relative position between the two tags. The system was tested both with stationary tags, but also with the tags moving along two paths. These tests were conducted for different separation distance between the tags, namely 20 cm, 30 cm and 40 cm. The result was that the mean position error for stationary tags was less than 8 cm for all separations and the mean orientation error was less than 3$^\circ$ for all separations. For the moving tag tests a decrease of the error in orientation of about 30 \% could be observed for a separation of 30 and 40 cm compared to 20 cm. However this difference is small in absolute values so more tests are needed to draw any conclusion about whether 30 and 40 cm tag separation performs better than 20 cm tag separation. The performance of the system could also be increased further by optimizing the anchor placement as well as the calibration of the antenna delays of the UWB-modules. 

Abstract

En 8-bitarsdator är i dagens samhälle gammal teknik. De kan knappast konkurrera med dagens moderna datorer som arbetar snabbare och med större tal. Genom att del för del ändå konstruera en 8-bitarsdator ges dock än idag stor insikt i hur datorer i allmänhet är konstruerade. Med bakgrundskunskap inom grundläggande digital elektronik kan enskilda moduler förstås, vilket sedan leder till en förståelse för datorn i stort. Detta projekt kretsade alltså kring att konstruera en 8-bitarsdator. Denna dator ska efter projektets slut kunna finnas kvar i syftet att användas i undervisning av digital elektronik. 8-bitarsdatorn innefattar flera moduler som var för sig kan både simuleras i mjukvara och konstrueras för sig. Därefter kunde alla moduler sättas samman. Datorn kan enkelt programmeras för att köra olika program, och kan med hjälp av så kallade flaggor hoppa i programkoden för att upprepa kod. Den resulterade datorn har vissa förbättringspotentialer, men fungerar väl enligt förväntningarna. Med strategiska val av färger på kablage och ett stort antal lysdioder blev datorn lättare att förstå och undersöka.

Abstract

En god elektromagnetisk kompatibilitet (EMC) är en viktig faktor vid konstruktion av kretskort. EMC syftar på ett systems kompatibilitet med sin omgivning och en god EMC innefattar att ett elektriskt system inte interfererar med sig själv eller närliggande system. Kartläggning av EMC kan göras med en EMC-skanner vilken mäter det elektromagnetiska närfältet kring ett mätobjekt. Målet med det här projektet är att konstruera en EMC-skanner vars rörelsemekanism är baserad på CoreXY-teknik. Långsiktigt är målet att skannern ska kunna användas för att skapa 3D-kartor av EMC:n hos kretskort.

EMC-skannerns mekaniska konstruktion utgick från en design från den digitala plattformen Thingiverse och bestod av aluminiumprofil och delar utskrivna med 3D-skrivare. För mätningar av det elektriska respektive magnetiska närfältet användes en närfältsprob. Rörelsen hos EMC-skannern styrdes av ett styrkort bestående av en Arduino och en RAMPS 1.4 med tre stegmotordrivare. Projektets arbetsgång bestod i att finna en lämplig design av skannern, skriva ut delar med 3D-skrivare, montera skannern, koppla och programmera komponenter för EMC-skannerns styrning samt att utföra en enklare provmätning. Slutprodukten blev en EMC-skanner med fungerande rörelser i x-, y- och z-led och vars rörelsemekanism i xy-planet baserats på CoreXY-teknik. Provmätningar visade att skannern kan användas för att mäta elektriska och magnetiska närfält från ett plant mätobjekt förutsatt att närfältsproben placeras tillräckligt nära detta. För att effektivt kunna använda EMC-skannern för att utföra mätningar på kretskort krävs vidareutveckling främst av skannerns styrning.   

Abstract

Two methods using lumped element (lumped parameter) methods to model flexible bodies have been presented. The methods are based on the concept of using a Guyan reduced stiffness matrix to describe the elasticity of a body. The component to be modeled has been divided into two parts using FE software and the mass and inertia tensor for the respective part of the component have been retrieved. The first method has been based on including the elements from the stiffness matrix in compliant constraints. The compliant constraints have been derived and a prototype has been implemented in MATLAB. It has been shown that using compliant constraints and stiffness parameters from a Guyan reduced stiffness matrix it is possible, with highly accurate results, to describe the deformation of a flexible body in multibody simulations.

The second method is based on springs and dampers and has been implemented in the simulation environment Dymola. The springs and dampers have been constructed to include coupling elements from a Guyan reduced stiffness matrix. It has been shown that using the proposed method it is possible, with highly accurate results, to describe the static deformation of a flexible body. Further, using dynamic simulations of a full robot manipulator model, it has been shown that it is possible to use the spring-damper model to capture the deformation of the links of a manipulator in dynamic simulations with large translations and rotations.

Abstract

Autofokus i en kamera fungerar genom att elektroniskt ändra avståndetmellan lins och sensor, och låta en dator avgöra när motivet är ifokus. I detta projekt testades en metod där fokus fås med hjälp aven flyttbar sensor inuti kamerahuset. Kamerahuset byggdes med hjälpav 3D-printning, och elektroniken styrdes med en Raspberry Pi. Vidareanvändes en metod där linsen projicerar på en yta som sedanfotograferas av, istället för direkt på en fotosensor. Resultat varen fungerande kamera, men med bristfällig bildkvalitét. Utifrånresultatet kan slutsatsen dras att metoden även skulle fungera ikommersiellt syfte.

Abstract

This project has been done as a part of a bachelors degree in engineering at Uppsala university. The project was supervised by Jörgen Olsson at the division of solid state electronics.

The goal of this project was to develop a distortion effect that can be used with an guitar and a amplifier. The effect was to have controllable distorsion, volume and tone control including bass and treble. The circuit is also supposed to be run using a 9V battery as power supply, which means that the in circuit currents shold be low. When the circuit was finished it was also analyzed through different measurements and simulations.

The distortion of the circuit was achieved using diodes to get a nonlinear amplification. The goals of the circuit controls was achieved, and although a low circuit current was achieved, it only satisfied the goal of 1 mA when high distorsion was set for the circuit.

When measuring and simulating the system, some major differences was found. The simulated frequency response characteristics was found to be very different from the measured. This is likely due to the simulation program not being

Abstract

The thesis has dealt with transparent conducting oxide (TCO) materials, with a focus on Al:ZnO and with studies on Sn:In₂O₃ and ZnO. TCOs are a material group that is used for its properties of being conductive and at the same time transparent. In solar cells, a top layer of TCO is often used to allow light to transmit into the cell and then conduct the resulting current.

A set of growth parameters was chosen and optimized through a literature study and experiments. The depositied thin films were characterized by optical and electrical characterization methods. Rf-magnetron-sputtering was used as the deposition method, where the influence of O₂, argon and substrate temperature were the parameters to be studied. As a part of the characterization a model for spectroscopic ellipsometry on Al:ZnO was made, enabling faster measurement of transport properties. The main parameter affecting the TCO properties was found to be oxygen flow and the optimum flow value for each material has been determined. Substrate heating did not show any significant improvement on the resistivity of Al:ZnO with a minimum value of ~5.0*10^-4 Ωcm while no heating resulted in a value of ~6.0*10^-4  Ωcm. These values are comparable to the state-of-the-art from the literature.

As a demonstration of application, the developed AZO and ZnO were applied to CIGS solar cells and these were compared to a reference. The newly developed AZO and ZnO was comparable to the reference but a lower mean fill factor indicates that improvements can be made.

Abstract

In biomedical applications realistic phantoms are becoming more useful for validation and testing of precursor systems. These artificial phantoms require stable and flexible tissue-mimicking materials with realistic dielectric properties in order to properly model human tissues. We have fabricated a low-water-content, low cost, mechanically and electrically stable, good shelf life and multi-layered heterogeneous phantom consisting of skin, fat and muscle tissues. We have chosen semi-solid type phantom for each tissue layer. The size and thickness of the each layer is chosen based on the average thickness of human tissue. Altering the ingredient composition wisely we can alter its dielectric properties also. By reason of no osmosis occurrence, the tissues can be employed to construct heterogeneous phantoms or even anthropomorphic phantoms without causing any changes in geometry or electrical properties. The performance of the fabricated phantom is carried out using an open-ended coaxial slim probe system by Agilent Technologies. Nearly all previous studies were based on very high frequency( VHF), so we present ultra-wide band (UWB), 500MHz-20GHz multilayered phantoms. We have measured our phantom after 2 month time period and we got quite good results for the dielectric properties without having significant variations. Thus, our fabricated sets of ATE phantom have good long lasting properties with good physical and dielectric stability.

Abstract

Two identified setbacks for CIGS based devices in order to obtain higher efficiency

are parasitic absorption in the window layer structure and losses in open-circuit

voltage due to bad interfaces. This study investigated how the performance of the

solar cell is affected by depositing intrinsic ZnO (i-ZnO) and ZnMgO with atomic

layer deposition (ALD) instead of the conventional sputtering.

No significant improvement in fill factor was obtained by the use of ALD compared

to sputtering, leading to the conclusion that pinholes in the sputtered film are not a

detrimental factor for the cell. As the thickness of the i-layer increased, an

increase in FF was observed for the ALD-deposited i-layer, whereas a decrease

was observed for the sputtered i-layer. The open-circuit voltage was considered

constant between the two series with only small fluctuations, indicating that the

defect chemistry of the i-ZnO/CdS interface was not improved with the use of ALD.

In this study it is shown that a gain in short-circuit current can be obtained for

CIGS solar cells in the high energy region of the spectrum by reducing the

thickness of the i-ZnO, as well as alloying the ZnO with Mg. When compared with a

baseline layer sample with a sputtered i-layer thickness of around 90 nm, the

estimated gain in short-circuit current density without a loss in fill factor was 0.14

and 0.20 mA/cm2 for ALD and sputtering, respectively. For the series with a

ZnMgO i-layer, the highest estimated gain was 0.17 mA/cm2. This was observed

for the sample with a 4:1 (Zn:Mg) pulse ratio, whereas higher Mg contents yielded

a too high band gap that resulted in an electron blocking barrier.

Abstract

The aim of this master thesis was to create automated system tests on airborne radar systems. Automated tests can reduce time spent on repetitive and monotone work and instead create time for exploratory testing and customer criteria testing. Nightly builds and well designed tests can improve robustness and create a more stable system for the user.

The project started with a pre-study, which consisted of researching the system in question, researching the possibilities of automated tests on said system and different tools that could be used in the project. Furthermore the pre-study contained interviews, visits and workshops within SAAB, with topics including automated tests, automation software and the SAAB GlobalEye system.

The solution included two separated tests, one regression test and one startup test. The regression test verifies that selected standard functions works with the new soft/hardware updates and the Startup test verifies that the starting sequences for selected subsystems are

executed correctly. Both of these tests were installed in the test laboratory. The tests were separated in to two parts; one control part and one analysis part. By recording the data being sent on the different interfaces while performing the tests, it's made possible to analyze the recorded data. This method enables many tests to be performed on the same set of data. The control part was solved with a third party software, called Squish, from a German company named Froglogic. The analysis part was written in MATLAB, where the test results were presented as well.

The chain of events was set up and executed by Jenkins (an open source automation software), which also served as a scheduler, to enable nightly builds.

Abstract

In the BDAS project one of the goals is to create a new solution for monitoring bone healing to complement current techniques. Data have been collected in clinical trials from infants treated for Craniosynostosis by a craniotomic surgery. The data are collected with a biomedical sensor based in microwave technology. This sensor could be able to sense changes in the composition of the different tissues in the upper hemisphere of the head, by noticing a difference in the propagation of the microwaves, as the bone injury from the craniectomy heals over time. In this thesis I analyze the validity of a proposed analytical model for the biosensor and extend the clinical data analysis in BDAS project. The validity of the model is analyzed by comparing its outcomes to available measurements from phantoms mimicking living tissues and to numerical simulations. In the data analysis two hypotheses are formulated and tested regarding the location of the measurement points with respect to a positioning grid and the healing over time too. By deriving a set of parameters for each collected dataset in the clinical trials, a distinct pattern was found which shows visible changes over the course of the healing process with this technique.

Abstract

This thesis investigated the possibility of integrating a small photovoltaic module in a wireless sensor network node prototype made for use in crop production, mainly in greenhouses. The main question was if the simple photovoltaic module could provide enough power to the prototype's recharge system in order to continuously recharge the battery and thereby reducing the time maintaining the device due to its power consumption. Through measurements, both of the energy supplied by the potential photo voltaic modules and the prototype's power demand, the conclusion was that the power would not be sufficient due to the concealing environment in which the device would be placed. However, suggestions for further work was given in how the proposed idea could be developed.

Abstract

Målet med projektet var att med ultraljudsteknik tillverka en produktsom kan bestämma positionen i ett område på 10x10 m. För att uppnådetta tillverkades tre enheter kapabla att sända och mottagaultraljudssignaler. Enheterna består av en ultraljudstransceiver, ettkretskort som kan skicka utsignal och förstärka insignal samt ettwifi-kompatibelt microkontrollerkort. Två av dessa enheter användessom referenspunkter med kända koordinater. Koordinaterna för dentredje beräknades genom att med ultraljud mäta avstånden tillreferenspunkterna. Den slutgiltiga produkten var kapabel att mätapositionen i ett område på 2x2 m. Iakttagelser påvisar däremot att ettstörre område bör vara möjligt med samma uppställning.

Abstract

Backscatter communication enables wireless communication at a power consumption orders of magnitude lower than conventional wireless communication. Instead of generating new RF-signals backscatter communication leverages ambient signals, such as WiFi-, Bluetooth- or TV-signals, and reflects them by changing the impedance of the antenna. Backscatter communication is known as a short-range communication technique achieving ranges in the order of meters. To improve the communication range, we explore the use of a tunnel diode as an amplifier of the backscattered RF-signal. We developed the amplifier on a PCB-board together with a matching network tuned to give maximum gain at 868 MHz. Our work demonstrates that the 1N3712 tunnel diode can achieve gains up to 35 dB compared to a tag without amplification while having a peak power consumption of 48 μW. With this amplifier the communication distance can be increased by up to two orders of magnitude.

Abstract

The main purpose of this thesis is to test a communications solution for the second to largest refugee settlement in the world, Bidi Bidi. A solution where it is possible to inform the refugees with necessary information, for example that the water at a specific location is currently contaminated or that food is provided at another location. The idea is to use nRF24L01+ modules which operate in the 2.4 GHz frequency band and send information through various ways. This includes turning LEDs' on and off, sending text Strings and streaming audio. The results showed that the modules are too unreliable for a refugee settlement. They also showed that it is not possible to send other types' of data while streaming audio, but there could be workarounds. It is clear that more knowledge and further investigations are needed.

Abstract

The goal of this master thesis was to automate the compensation of NC-programs. Automatic compensations can reduce errors and make the production more efficient. This is vital for increased precision and meeting the quality demands from the market.The project started with a study of how the feedback-loop between production and measurements was done at the time and also researching how the data could be sent between the different machines. This was done by researching solutions of similar problems and interviewing the machine operators. Simulations of how automation could be done with more in-depth measurements of the production machine were also made.The limitations was also evaluated. Research was done on errors and practical flaws which could be problematic for automation.The automation was implemented using Java to send the data between the measuring machine to the production machine. Furthermore a UI was created for the machine operators so that the information flow was under supervision at all times. The UI would suggest a compensation from a pre-programmed algorithm together with the measuring data, and the operator could then decide whether or not to diverge from the suggested compensation.

Abstract

Cu(In,Ga)Se2 (CIGS) is a semiconductor material and the basis of the promising thin-film photovoltaic technology with the same name. The CIGS film has a typical thickness of 1-2 mm, and solar cells based on CIGS technology has recently reached efficiencies of 23.3%. Ultra-thin CIGS solar cells use sub-micrometer thick films that require significantly less material and can be manufactured in a shorter amount oftime than films with typical thicknesses. With decreasing thickness, both electrical and optical losses get more significant and lower the overall performance. Electrical losses can be decreased by increasing the overall film quality and by utilising a graded bandgap throughout the CIGS layer. The band gap can be changed by varying the[Ga]/([Ga]+[In]) (GGI) ratio. Higher overall film quality and a higher band-gap towards the back of the absorber are expected to increase the performance.

In this work, sputtered CIGS solar cells were made with different CIGS layer thicknesses, that ranged between 550-950 nm. Increased heat during deposition was examined and shown to increase the film quality and performance for all thicknesses. Two different ways of doping CIGS with Na was examined and it was found that higher Na content lead to an increasing predominance of the (112) plane. The bandgap was graded by varying the GGI composition throughout the CIGS layer and depth profiles were made with Glow-Discharge Optical Emission Spectroscopy (GDOES). It was found that a sputtered CuGaSe2 (CGS)layer below the CIGS-layer lead to a steep increase of the GGI near the back contact. When CGS made up 10% of the total CIGS layer thickness, a significant increase in performance was observed for all thicknesses. CIGS-absorbers with a less graded region with low GGI, making up 30% or 60% of the total CIGS layer thickness were made. A decrease in GGI in that region, was shown to increase the current but lower the voltage. No substantial increase in total performance compared to a fully graded CIGS layer was seen regardless of layer thickness. For further work the optical losses needs to be addressed and work on increasing the optical path in the CIGS layer needs to be done.

Abstract

Syftet med projektet är att konstruera en inverterad pendel som sedan med hjälp av reglertekniska metoder ska stabiliseras. De linjära regulatorer som prövats är Proportionell, Integrerande och Deriverande (PID) -regulatorn och Linnear Quadratic Gaussian (LQG) -regulatorn som båda är populära och beprövade i industrin. PID-regulatorn är den absolut mest använda regulatorn medan LQG-regulatorn är mer raffinerad och i vissa avseenden en optimal regulator. Regulatorerna programmerades in i mikrokontrollern Arduino Nano som skickar signaler till en motordrivare som styr den stegmotor som ska balansera pendeln. Mycket av arbetet har handlat om att skapa en uppställning som tillåter goda förutsättningar för att pröva regulatorerna. I uppställningen finns delar som utformats i Computor-Aided design (CAD) -verktyget OpenSCAD och skrivits ut på en 3D-skrivare. Den givare vi använt för att mäta pendelns vinkel är en potentiometer infäst i dessa 3D-utskrivna delar. Motorn kunde styras till sin maximala kapacitet och en uppställning har skapats. Dock skulle en starkare motor och en mer robust uppställning möjliggöra en avsevärt bättre reglering. Regulatorerna klarade inte av att stabilisera systemet mer än ett fåtal sekunder, detta bland annat pågrund av tidsbrist till att justera regleringsvariablerna.

Abstract

Both military and civil aircrafts depend on a built-in identification system called SSR on a daily basis. IFF is the military adaption of the system for use by fighter jets in order to separate friendly aircrafts from foes but also to coexist with commercial aircrafts. The system is built around two devices, an interrogator on the own aircraft and a transponder on the target. The aim is to be able to perform an interrogation with as high probability of correct identification as possible. There are several factors that can compromise or prohibit a friendly aircraft from answering to an interrogation and it should therefore not be classified as a foe.

In this master thesis work, the ability of identification for Saab AB’s new fighter jet Gripen E has been investigated. A system model has been created using Simulink and Matlab, mirroring a full link connection between the IFF E-scan system on Gripen E and a target aircraft. The model includes six subsystems, covering the fighter jet’s antenna array system in both transmitter and receiver mode, the transponder equipment, link budgets and signal propagation. Different data sets with main and control beam antenna patterns for the Gripen E IFF system are loaded into the model via user selected beam steering..

It has been found that the model simulates the environmental effects on the transmitted patetrns at different distances well. It can be used to investigate how the antenna coverage changes when applying beam steering to the E-scan system and at which distances identification is possible for a chosen steering angle. 

Abstract

Målet är att syntetisera ett material, genom sintringsprocess, som kan användas som ett dielektriskt substrat för utveckling av sensorer. Det dielektriska materialet har keramisk materialstruktur och innehar högt dielektricitetskonstant med låga dielektriska materialförluster. Denna uppgift kräver att dielektriska materialet ska vara stabilt och inneha isotropiska egenskaper efter att genomgått sintringsprocess. Proverna förberedes med TiO₂ och även i kombination med TiO₂ tillsammans med CuO och Al₂O₃. Proverna mäts i frekvensområdet 500 MHz till 20 GHz. Mätningarna utförs med Vector Network Analyzer, FieldFox N9918A från Keysight. Resultat som visas och jämförs i arbetet är tagna vid 2.45 GHz eftersom det används och är standardiserat för medicinskt frekvensband. Högsta uppmätta dielektricitetskonstant har värdet av 16,6. Resultaten visar även låga förluster i dielektrikumet.

Abstract

A demonstration robot for conferences and fairs has been built from scratch. The demonstration robot is meant to create lasting impressions at the company booth at conferences or fairs. Thus, the robot needs traits that attract people to the booth and makes sure they remember that company. In this project, traits such as being able to move, do facial expressions and play audio have been developed. The robot has also been designed to draw as much attention as possible to the booth. This was achieved by building a robot that consists of a rolling sphere with a head that always remains on top. All movements are carried out from inside the sphere by four different motors. One motor moves the robot back and forth, two motors spin a flywheel to turn the robot and the last motor rotates the head. These motors are mounted at different places on an internal structure. The internal structure is connected to the sphere at two points, one on each side of the robot. At the top of the internal structure, magnets are placed. Thus, it can attach the head at the outside of the sphere by mounting magnets in the head. All movements of the robots are controlled by a hand controller, which has been made in this project. The head has a built-in display simulating two eyes. The display is driven by a Raspberry Pi. An internal speaker is built-in inside the head, connected to the Raspberry Pi. Each simulated eye consists of 64 squares that can be programmed to be in different colours, thus making it possible to express a wide range of facial expressions.Two PCBs were designed and manufactured to control the robot. One was placed inside the robot, and the other inside the hand controller. The PCBs can communicate over Bluetooth, which makes it possible to control the robot from the outside.All parts of the robot have been designed in a CAD program and subsequently 3D printed. 3D design in CAD was learned from a novice level, since there was no previous knowledge of this in the project group.In addition, a registration form has been developed that allows visitors to register at the booth. Making it easier for the company to connect with visitors after the conference or fair. The registration form is connected with the Raspberry Pi in the head of the robot via Wi-Fi. Thus, when new registrations occur, the robot can print the names of them while audio is played.

Abstract

I denna rapport undersökts effect förbrukning och uppmätt antal Lumen för en rad olika LED-lampor, reslutatet jämförs sedan med specifikationerna för respektive lampa. Slutsatsen är att även fast det är problematiskt att mäta antalet Lumen från en lampa, så går det att uppvisa liknande resultat som förpackningen påvisar. Effektförbruknings mätningar har mindre felkällor vilket ger ett noggrannare resultat.

Abstract

In this study, the financial and economic viable of perovskite-SHJ tandem solar cells were determined using a detailed bottom-up cost model and energy-yield calculations. Attention to specific advancements in perovskite solar cell layer technology and large-scale deposition have been taken into account to create a realistic, viable commercial scale option for tandem production. A reference tandem technology is used to determine the overall manufacturing cost and minimum sustainable price. Models used show that the tandem technology has the potential to be cost competitive with existing silicon technology given the uncertainty and sensitivity of the values used in this study. It was examined further how non-STC energy yield and service life contributes to the overall economic viability of the tandem module within residential, commercial and utility scale of application. Given the reference tandem module, it is expected to be competitive at the residential level with existing silicon technology if perovskite layers' service life is greater than 20 years. In commercial and utility application, the tandem model is not economically viable due to the reductions seen in the area- and project-related installation costs for existing technology. This thesis concludes by presenting the current limitations in perovskite technology that would inhibit adaptation of this into commercial-scale production and presents alternative applications in which tandem modules would be more favourable.

Abstract

The kesterite Cu₂ZnSnS₄ (CZTS) is considered as a possible absorber layer in future photovoltaic (PV) applications. The abundance of its constituent elements along with the material being non-toxic and having a direct band gap of around 1.5 eV make it an attractive material for solar cell applications. So far, cells with an efficiency of 12.6 % have been achieved. The limiting factor is the finished cells' open circuit voltage (V_OC) deficit which has been attributed to structural defects in the material. Problems with sustaining a sulfur-enriched atmosphere during the annealing step of material production have been observed, and are thought to be partially responsible for the high density of structural defects. Elemental sulfur is commonly used for inducing a sulfur-enriched atmosphere in the anneal. In this study, four combinatorial and polycrystalline CZTS thin films were prepared and annealed in different conditions with regards to time, sulfur source and amount. The samples were characterized using energy dispersive-, Raman- and photoluminescence spectroscopy. The effect of the anneal on the different composition regions were analyzed and secondary phases were identified. Introducing CuS as the sulfur source during the anneal reduced the decomposition of the CZTS phase, and lowered the density of the defect complex [Zn_Cu + Cu_Zn], while enlarging the single phase region. Strictly and highly Sn-rich compositions of CZTS was observed to yield both high cation order and photoluminescence intensity, and a link between the two parameters was observed.

Abstract

Thin-film solar cell research is central to the electricity production of the near future. Photovoltaic technologies based on silicon have a significant portion of the global market and installed capacity. Thin-film solar cells are port of the emerging photovoltaic technologies that are challenging silicon for a part of the electricity production based on solar power. These thin-film technologies, such as copper indium gallium selenide (CIGS) and cadmium telluride (CdTe), are lower cost and require less energy to produce, but also require rare materials. An alternative to these technologies are thin-film solar cells based on more abundant materials. To develop these new materials at Uppsala University, combinatorial synthesis is used. This method produces a significant amount of data across different measurement methods. The data needs to be analysed and combined to gather information about the characteristics of the materials being developed. To facilitate the analysis and combination of data, a database tool was created in MATLAB. The result is a program that allows its User to combine energy-dispersive X-ray spectroscopy (EDS), Raman spectroscopy and Photoluminescence spectroscopy measurements done on solar cell absorber layers. Absorber layers are the section of solar cells where sun lighet is absorbed, and electron-hole pairs are created. The program provides multiple figures and graphs combining the different data collected, enabling the User to draw conclusions about the characteristics of the sample and its suitability as an absorber layer. The combinatorial synthesis database tool created could be user for combinatorial synthesis analysis of other material samples that are not necessarily absorber layers for thin-film solar cells. This report describes both the development of the tool and the code itself.

Abstract

Usage of class D audio amplifiers has become increasingly widespread in recent years, mainly due to their high efficiency, which can reach almost 100 %. Class D amplifiers can also be compact, making them suitable for mobile applications. In contrast, the most efficient conventional amplifiers such as class B can reach a maximum efficiency of 78.5 %. The high efficiency of class D amplifiers can be attributed to the switching stage, which in the case of a half-bridge design consists of two amplifying MOSFETs. These MOSFETs are never on at the same time, which minimizes the quiescent current and thereby the power losses. The goal of this project was to design, simulate and construct a half-bridge class D audio amplifier. A working amplifier with 80 % efficiency was built, with power losses occuring mainly in the voltage regulators. Simulations of the amplifier corresponded well with the constructed amplifier apart from issues originating from the aforementioned voltage regulation as well as the triangle wave generator. The goal of the project was achieved and the finished amplifier possessed good sound quality and little unwanted noise. To further improve on the design, better voltage regulation, a full-bridge configuration and a feedback loop could be utilized.

Abstract

In this Master Thesis different approaches to mobile localization within construction environments are investigated. At first an overview of different sensors commonly used within localization is presented together with different map representations and a system consisting of a laser scanner and wheel encoders is chosen.

The hardware is prepared for the open source ROS environment and three different algorithms for localization are tested. Two algorithms, Gmapping and HectorSLAM, used for Simultaneous Localization and Mapping, are compared. The best map is then used by a Monte Carlo localization algorithm, AMCL, for autonomous navigation.

It is found that HectorSLAM produces the most accurate map, given that the grid refinement level is fine enough for the environment. It is also found that the maximum Kullback Leiber distance, used in AMCL, needs to be calibrated in order to perform a sufficient navigation. 

Abstract

Thermoelectric materials are important in today’s society with a variety of applications. The material properties that determinate the efficiency of a thermoelectric device are mostly constants. In order to develop more efficient thermoelectric devices new materials and solutions need to be made. Minimizing the thermal conductivity in thermoelectric materials is of great interest to make them more effective.

One effective way of lowering the thermal conductivity is to introduce holes in the lattice and create a phononic crystal. The main focus of this master thesis has been on how to place these holes and to optimize the geometry to minimize thermal conductivity. The method used in this report is based solely on simulations, which were done using Comsol Multiphysics 5.2a. The results are compared to already published results. Different geometries are tested to see how it affects the thermal conductivity and to optimize the phononic crystal. The Maxwell-Eucken model is also used to see how porosity affects the thermal conductivity and to analyze what the lowering in thermal conductivity depends on.

The result showed a substantial reduction in thermal conductivity when creating a phononic crystal compared to bulk silicon. The simulated reduction compared to bulk silicon is up to 98.5% when introducing holes in the lattice, while Maxwell-Eucken only predicted a 74% reduction due to porosity.

The conclusion is that by creating holes in a periodical pattern, phonon dispersion will occur, which lower the thermal conduction significantly.

Abstract

Today, Scania CV AB is facing challenging demands on functionality and performance within their vehicles. The electronics are increasing rapidly and to stay competitive on the market, concerns regarding reliability of electronic systems needs to be evaluated. Prognostics and health management (PHM) is a concept where reliability of, for example, electronic control units (ECUs) are assessed. It requires customized systems for each specific environment, due to different strains and stresses. One approach is to have canaries (components with reduced soldering mass) implemented into ECUs as an indication that something is about to happen. Another essential aspect is the continuous real-time data acquisition from sensors, that can be used for different algorithms and models, which could provide forecasts on remaining useful life (RUL) of the ECUs. An appliance is the big data acquisition, where a database will collect data from vehicles, which means that ECU data need be communicated differently than today.

This is why this master thesis project investigated canaries on printed circuit boards (PCBs) when they were subjected to vibrations as well as thermal cycling (TC), which are common parameters within vehicles. The PCBs consisted of both lead (Sn-Pb) and lead-free (SAC305) soldering for material comparison, since a transition to lead-free electronics is happening. Several fatigue tests were performed to collect as much information as possible. For further advances towards a PHM implementation, thermal shock (TS) tests on ECUs were performed as well. The ECUs were shocked in a temperature cabinet while being in active state. The internal temperature sensor was communicated with via controller area network (CAN). Scania’s CAN program was used and the data was logged in a computer, which in turn was compared to the data from the surrounding thermocouples, placed in specific spots.

The results that were achieved clearly showed that lead-free PCBs are much more sensitive to stresses (both vibrations and TC). It was also shown that canaries failed in a much higher extent than regular resistors. The real-time data acquisition from the ECU could successfully be managed, where continuous data was logged. Also, the TS tests showed how the correlation between sensors indifferent positions was. Finally, the results from these tasks were discussed for future work.

One have to keep in mind that this is just the beginning of a many-years project within Scania. The results and progress within this master thesis project will hopefully be a step in the rightdirection.

Abstract

Målsättningen med projektet var att utforma ett smart system förjordfuktsmätning innehållandes sensorer, datalagring samt visuellpresentation av mätdata i en applikation. Lagringen sker på enwebbserver i en databas och presentationen i form av en applikationför Android samt en webbsida. Resultatet blev en lyckad slutprodukt iform av en kapacitiv sensor tillverkad av laminerat kopparfolie sommed en mikrodator av typ ESP8266 skickar data via WiFi tillwebbservern. Databasen som lagrar datan är skapad i MySQL ochdatabaskommunikationen har skrivits i PHP. Förutom att visualiseramätdata kan applikationen och webbsidan kommunicera med ESPn samtskicka notiser till användaren i form av push-notifikationer då växten behöver vattnas.

En slutsats från projektet är att sensorer för jordfuktsmätningrelativt enkelt kan skapas från lättillgängligt material och att ettsmart system kan utvecklas med få och billiga komponenter. En annanslutsats är att vid utveckling av en produkt som består av fleraprocesser som ska samverka tillsammans finns stor risk att oväntadefel uppstår. Ska en produkt vara kommersiellt gångbar krävs en långtid av betatestning för att vara säker på att produkten inteinnehåller brister.

Abstract

Ljud behöver inte nödvändigtvis studeras via en mikrofon, det går också att utnyttja dess unika rörelsemönster. Ljud vibrerar med en specifik frekvens beroende på vilken ton det har. Syftet med följande rapport är att undersöka hur en vibrationssensor för en gitarrstämmare fungerar och hur gitarrstämmaren med vibrationssensor skulle kunna konstrueras. Det finns många olika applikationer till en vibrationssensor.

I den här rapporten ges en detaljerad beskrivning till hur en analog gitarrstämmare fungerar, och hur man med en helt analog krets kan konstruera en gitarrstämmare som stäms med hjälp av en vibrationssensor. Arbetet undersöker också olika typer av vibrationssensorer, hur man själv kan konstruera en gitarrstämmare samt hur en lämplig kretslösning kan se ut.

Först undersöks olika typer av sensorer som sedan kopplas till en lämplig krets. En stor del av arbetet utfördes i laborationssal med funktionsgenerator och oscilloskop. Signalen som sensorn detekterar går via en krets med filter, förstärkare, komparator och frekvens- till spänningsomvandlare. Slutligen informeras användaren om den aktuella gitarrsträngens frekvens är nära den eftersökta frekvensen via en koppling med dioder.

Det visade sig att den bästa sensortypen är en piezoelektrisksensor. Kretslösningen kan däremot bli relativt komplicerad och mindre noggrann om en analog lösning önskas då den kräver många komponenter. 

Abstract

The buffer layer is a crucial component in thin film solar cells. Defects at the interface between absorber and buffer layer lead to high recombination rate and the band structure at the interface highly affects the performance of the solar cell. In this thesis a method to synthesize thin films containing cadmium, zinc and sulfur, CdZnS, by chemical bath deposition has been developed and evaluated. A higher current from the device is expected when replacing the common buffer layer cadmium sulfide, CdS, with the more transparent CdZnS. It is also possible that the alternative buffer provides a more favorable energy band alignment at the interface with the absorber Copper-Zinc-Tin-Sulfide (CZTS). The deposition process was developed by studying depositions on glass. Increasing [Zn²⁺]/[Cd²⁺] initially led to films with higher band gap (E_g). By varying deposition time the time before colloidal growth became dominant was observed. Addition of triethanolamine showed that triethanolamine binds stronger to zinc ions than to cadmium ions. Two recipes that led to E_g=2.63 eV were evaluated as buffer layer in Copper-Indium-Gallium-Selenide (CIGSe) and CZTS solar cells. The short circuit current of the devices increased in general with the CdZnS buffers compared to CdS. The best CZTS cell with a CdZnS buffer layer had 7.7 % efficiency compared to the 7.5 % reference. For future research it is recommended that the effect of thickness variation and deposition temperature is evaluated and that additional material characterization is performed in order to further understand and develop the deposition method.

Abstract

The information from numerous sensors placed in modern vehicles is crucial for maximum performance. In the future, when commercial vehicles become fully autonomous, this information needs to be accurate in order to guarantee optimal performance as well as safety. Accuracy is specifically important in components that are essential for the vehicle operation, such as the gearbox. Sensor solutions in modern gearboxes require an improvement, especially when it comes to low speed detection. This is important in automatic transmission, which is the preferred choice in commercial vehicles, so that the gearbox control unit can shift gears in optimal way.

This thesis project investigates the possibility of high accuracy speed and angular position detection in gearbox by multiple sensing. This was done with the use of distributed sensors covering the region of a single period on a gear structure. Hall sensors with analogue output were implemented for this purpose. Also, GMR sensors were introduced in this application, only in single unit measurement configuration.

The results show that the accuracy of low speed detection is higher with multiple sensors. Particularly in the case of braking down to zero speed, the accuracy is significantly increased in comparison to digital speed detection. However, at higher speed the accuracy is nearly the same. Therefore, one possible solution could comprise the use of multiple sensing at low speed and digital detection at high speed. 

Abstract

An increase in conversion efficiency of CIGS thin film solar cells has been reached at Ångström Solar Center (ÅSC) due to an introduction of a post-deposition-treatment (PDT) with potassium fluoride (KF) on the CIGS absorber layer. The PDT will however affect the growth of the cadmium sulfide (CdS) buffer layer normally deposited on the CIGS layer. The purpose of this study has therefore been to increase the conversion efficiency of the CIGS solar cells by optimizing the process parameters when growing CdS with a chemical bath deposition process (CBD) on CIGS with KF-PDT. The purpose has also been to understand how CdS grows on CIGS with KF-PDT. CdS has been deposited with CBD on both CIGS with KF-PDT and on soda lime glass samples by varying process parameters such as time, bath temperature and concentrations. The solar cells were characterized using current-voltage measurements as well as external quantum efficiency measurements. Further methods of analysis were profilometry, x-ray fluorescence spectroscopy and scanning electron microscopy. It was found that the solar cells with the best performance were obtained at a bath temperature of 70 °C, process time of 3 min after preheating the cadmium acetate and ammonia solutions for 6 min and using the concentrations of the baseline process for CBD of CdS at ÅSC. The best cell of this sample resulted in a conversion efficiency of 19.1 % without antireflective coating.

Abstract

I detta projekt byggdes en fjärrstyrd robot som styrs över Wi-Fi, ochstreamar video till användaren av vad den ser. Som komplement körsäven en temperatursensor för att utöka robotens möjlighet att kännaav sin omgivning. Huvudkomponenten är en Raspberry PI 3 modell B, därall kod för styrning och hemsidekontrollerna körs. Resultatet är enrobot som kan styras utanför synhåll och kan sända tillbaka en stabilkameraström så länge den är kopplad till ett stabilt nätverk.Dessvärre sjunker resultatet i takt med nätverkskvalitén. Vid ettsvagare nätverk blir det långa laddningstider för kameraströmmenvilket leder till att roboten blir mindre responsiv. Det tillsammansmed den förlorade kameraströmmen resulterar i att roboten ärobrukbar. Vid tillräckligt svaga nätverk, eller vid nätverksproblemkommer roboten repetera sin sista order tills dess att kontakt äråterupprättad.

Abstract

This master thesis was completed at Limes Audio in Umeå. Limes Audio are specialized in speech enhancement software which is mostly used in conference phones. Their software is used to reduce noise, echo cancellation as well as reduction of distortion. When a conference phone is malfunctioning it can be troublesome to find the cause of the problem. Common issues that lead to perceived poor audio quality are rattling plastics, loose parts and an environment with demanding acoustics. There is a need for automatic tests to run on conference phone which can diagnose audio quality and the acoustics of the environment where the conference phone is located in. A previous master thesis by Wilhelmsson called "Estimating Loudspeaker Distortion and Room Reverberation Time Using a Speakerphone" focused on evaluating several tests run in MATLAB for analyzing acoustic characteristics of a room. The goal of this thesis was to continue the work of the master thesis by Wilhelmsson. Previous tests served as a basis for this thesis. The tests where modified and rewritten in C and run on a Linux computer connected to a specific conference phone model.

In the extended test made in this thesis using sine sweep signals, the reverberation time as well as the distortion for the conference phone setup was determined. The calculated reverberation time was compared to the results using Room EQ Wizard and gave almost identical results.

Total harmonic distortion was not easy to relate to the perceived audio quality. There is a need to further develop methods to take into account other types of distortion than the total harmonic distortion. Rub & buzz is one kind of distortion that could be of interest. To investigate pass or fail thresholds for reverberation time as well as distortion is central for further development of this test software.

Abstract

Diamond-like carbon (DLC) is a versatile material which exhibits excellentmechanical, electrical and optical properties making it suitable for applications rangingfrom biomedical implants to engine components. The properties of DLC thin films aredetermined by the bonding configuration (sp3/sp2 fraction) of its carbon atoms. Inorder to prepare DLC thin films for desired applications, it is essential to control andestimate the sp3/sp2 fraction precisely.

Raman spectroscopy is widely employed for the estimation of sp3/sp2 fraction due toits non-destructive nature, high probing depth and possibility of quick acquisition. Thequality of information obtained from Raman analysis depends largely on the structureof DLC thin films, which varies from one deposition method to another. Using theexisting approaches for the estimation of sp3/sp2 fraction for a particular type of DLCthin films could entail large errors and thereby result in misleading conclusions. For anaccurate analysis of the film structure, it is therefore important that a carefullydesigned strategy is employed. In this work, Raman spectroscopy is employed forstructural investigation of DLC thin films deposited by High Power ImpulseMagnetron Sputtering (HiPIMS). Owing to the unique DLC film properties obtainedfrom HiPIMS, Raman spectroscopic investigations were made by developing ananalysis routine relevant for HiPIMS-deposited films. The developed approach isvalidated by complementary analysis of film density. The method is further employedfor investigating the compressive stress and thermal stability of the resulting films. Theanalyzed films were deposited using different buffer gas (Ar and Ne) and ion energy toproduce a range of sp2/sp3 ratios. Raman measurements were performed using visible(532 nm) and UV (325 nm) lasers. Film density was determined using X-RayReflectivity (XRR) and chemical composition using Elastic Recoil Detection Analysis(ERDA). The compressive stresses of the films were determined usingwafer-curvature method and thermal stability of the films was investigated byperforming Raman measurements on films annealed from 100 degrees C to 600degrees C.

By developing an analysis routine and employing appropriate fitting method, it wasshown that the Full Width at Half Maximum (FWHM) of the G peak in the Ramanspectrum is the most relevant parameter for estimating the sp3/sp2 fraction. Theaccuracy of the analysis routine was verified by studying the evolution of sp3/sp2fraction and film density with respect to ion energy. The correlation between sp3/sp2fraction and film density was good. The differences in mass density and compressivestresses between Ar- and Ne-HiPIMS deposited films were also found to beconsistent with the estimated sp3/sp2 fractions. The structural evolution of theannealed films, investigated by Raman spectroscopy, showed that the Ne-HiPIMS filmsexhibit a transition from sp3 rich structure to sp2 rich structure at ~450 degrees Cwhereas the transition for the Ar-HiPIMS films occurs at ~300 degrees C. This impliesthat the Ne-HiPIMS films are thermally more stable than the Ar-HiPIMS films.

Abstract

High-power microwave, HPM, systems can be used as non-lethal weapons with the ability to destroy or disturb electronics, by damaging internal circuits and inducing high currents. Today microwave sources are being developed with peak powers exceeding 1 GW, one of these devices is the vircator, a narrowband source which is unique to the HPM community. In order to understand and develop microwave sources like the vircator it is necessary to have computer models, as simulations gives an invaluable understanding of the mechanisms involved during operation, saving time and development costs.                                                                  This thesis presents the results from a theoretical analysis and a simulation study using a well known electromagnetic particle-in-cell code, Computer Simulation Technology Particle Studio. The results are then compared to measured data from a HPM system, the Bofors HPM Blackout. The results show that CST PS can be used to design and study the coaxial vircator with good results. 

Abstract

A systematic study was conducted on MIS capacitors, breakdown structures andTLM structures to study the quality of dierent layers and processes involvedin the manufacturing of vertical-enhancement-mode MISFETs. Furthermore, theinuence of of a nal post-metalization annealing-step is analyzed drawing theconclusion that it is advantageous to submit nal MISFET devices to an annealingprocess lasting at least 30 minutes and to a minimum of 300C to improve themodulation capabilities of the MISFET's gate module, although degradation ispresent on both metal contacts and the blocking capabilities of the p GaN layer.

Abstract

The photovoltaic industry attracts a lot of interest from researchers worldwide due to active integration of the solar cells. The main idea here is to convert solar energy into electricity. One type of solar cell that shows potential in replacing today’s crystalline silicon cells is the thin film solar cell (TFSC). Yet, the sun absorbing semiconductors used in the commercial TFSCs contain scarce elements such as indium, cadmium and tellurium, which may cause problems if the technique is going to grow to a big scale energy producer. Earth abundant sun absorbing materials are therefore of great interest, and several possible replacements are under investigation. 

In this project two olivine structured ternary metal chalcogenides were investigated: manganese silicon sulfide (Mn₂SiS₄) and iron silicon sulfide (Fe₂SiS₄). The goal was to deposit thin films by reactive magnetron sputtering from manganese/iron and silicon targets with mixture of Ar and H₂S gas. Afterwards the films were crystallized by a sulfurization process at high temperature. The samples were created with a composition gradient and investigated by SEM, EDS and XRD. Results showed that a single phase of Mn₂SiS₄ was successfully created in thin film form for the first time.

Multiple attempts on manufacturing Fe₂SiS₄ were performed, but didn't show sufficient progress yet. The analysis showed formation of pyrite (FeS₂), pyrrhotite (Fe_1-xS, x<0.2) and SiS₂ phases instead of the targeted material. In both cases it is important to provide additional studies to determine if the selected compounds could be used as an absorber layer in TFSC structures.

Abstract

In this thesis Cu(In,Ga)Se2 (CIGS) solar cells with different sodiumdoping of the CIGS absorber and varying Al2O3 rear surface passivationlayer thickness have been manufactured and electrically characterised.

Baseline samples and samples without passivation were used asreferences for the passivated samples. For the passivated samplesbetween 1 and 7 nm of Al2O3 were deposited by ALD. The electricalcharacterisation included current-voltage (IV, JV), quantum efficiency (QE, EQE), capacitance-voltage (CV) and temperature dependent currentvoltage (IVT, JVT) measurements.

The results show that it is indeed possible to use a tunnel current toconstruct an electrical contact, but that the electrical contact isvery sensitive to sodium doping. The samples with post-depositiontreatment and without Na start to block the tunnel current when thepassivation layer reaches a thickness of about 2 nm, while no blocking of the tunnel current could be observed for the samples with Na pre-deposition. The samples with pre-deposition treatment showed acontinued increase in efficiency all the way to a passivation layerthickness of about 7 nm. When trying to construct samples with eventhicker passivation layer the CIGS started to peel off. For thisreason the optimal thickness for the pre-deposition treated samplescould not be found. The samples with the highest efficiency was thesamples with pre-deposition treatment and thick passivation layer. Those samples showed an increase of 3 percent (absolute) compared tothe unpassivated sample with the same deposition treatment and 1.6 percent higher efficiency compared to the baseline sample. Concluding that tunnelling passivation layer is comparable to the passivationlayer with point contact methods.

Abstract

This report is the result of a conducted Minor Field Study (MFS), to the greatestextent funded by the Swedish International Development Cooperation Agency(SIDA), in an attempt to design a system for evaluating smaller solar power systems indeveloping countries. The study was to the greater part conducted in Nairobi, Kenyain close collaboration with the University of Nairobi. The aim was to develop asystem that would use easily available components and keep the costs to a minimum,yet deliver adequate performance. The system would measure certain parameters of asolar power system and also relevant environmental data in order to evaluate theperformance of the system. Due to the specific competence of the collaboratinggroup at the University of Nairobi, a Kinetis Freescale K64-microcontroller with anARM-Cortex processor was selected as the core of the design. Components wereselected, schematics were drawn, a circuit board was designed and manufactured andsoftware was written. After 12 weeks a somewhat satisfying proof-of-concept wasreached at the end of the field study in Kenya. The project however proved howdifficult it is to go from first idea to a functional proof-of-concept during a limitedtimeframe, and also in an East-African country. The final proof-of-concept was testedat Mpala Research Centre in Kenya and despite containing some flaws proved that itwould indeed be possible to design a working system on the principles discussed inthis report. The system is open-source, so anyone may use and modify it.

Abstract

This study addresses quality control for Light Emitting Diodes (LED) according to fouraspects, the power factor of LED lamps, their harmonics and total harmonic distortion (THD), the luminosity for total power to radiated power ratio. It focuses on four brands and six different LED lamps, and concludes that IKEA's LED lamps pertain as the quality lamp, with a power factor over 0.9, THD less than 4% and a power to radiated light of over 4%. 

Abstract

A robot capable of balancing itself on two wheels has been built and programmed. While balancing, the robot keeps within a limited area. The robot has a face with two eyes and a mouth, consisting of LED-matrices, which switch between six different facial expressions. The robot is programmed using Arduino boards, one of which implements PID regulators to control the motors.

Abstract

In a future situation with a large implementation of photo voltaic (PV) in the local distribution grid one expects voltage and current related problems to occur due to the large portion of excess electricity from the PV fed into the grid. In this study it was concluded, based on experiences from Germany and Italy, that energy storages are assumed to be beneficial in order to address these problems. The location of storages needs to be distributed among the low voltage grid (400 V) to be able to reduce excess produced electricity from PV as well as deliver peak reducing power (“peak shaving”). This suggests that large scale techniques are not suitable for this purpose since they will be dependent on transmission bottle necks. The energy storages would be most efficient if set up as a combination of a local storage, at the end consumer, and an aggregated storage distributed within the low voltage grid. Techniques suggested are advanced gel-based lead silicon batteries for rapid power response and fuel cell systems with separate electrolysis unit for bulk storage. Thus the systems can divide the needed amount of energy to store in a more efficient way. This suggests that a business model could be a leasing or rental based system where the end consumer subscribes for the technique and services. The major benefits from the energy storage was found to be reduced power flows in the grid (both load- and production wise) as well as reduced volatility in the system. Furthermore, the energy storage would be able to serve as back-up or black start source (also referred to as “cold start” in case of power outages), as well as offering filtering services for reduction of noise and harmonics. Since the major benefits are of systemic nature the most likely actor to gain from energy storages would be distribution system operators (DSO). Therefore the Swedish regulations needs to be adjusted so DSO’s are allowed to, firstly, include the costs for energy storages and, secondly, deliver energy from energy storages without being considered as producers.

Abstract

Over the past decade, there has been a drastic development of the single-board computer market. These computers are now in a position where they can compete with classic embedded hardware. Such fast improvement has led ASSA ABLOY, a well-known lock and security company, to see value in replacing some of their existing access control hardware with an off-the-shelf single-board computer. Therefore, a comparative study of single-board computers was performed for this company. Some of the compared properties were price, performance (i.e. CPU, memory, USB, network, operating temperature and power consumption) and other relevant information such as operating systems, open/closed source hardware and future availability. Information and testing data from nine different computers was compiled and analyzed. This data was then used to determine the best-suited candidates that could possibly replace the current access control hardware. They were chosen in accordance to three different categories: performance, power consumption and open source hardware. The ODROID C1+, the Raspberry Pi A+ and the A20 OLinuXino Lime2 proved to be the best candidates for these three categories respectively. Furthermore, it was also concluded that the company behind a computer is just as important as the computer itself, where the best company in this study was determined to be Olimex.

Abstract

pH-sensorer som tillverkas med samma processer som används inom halvledarindustrin kan göras små och billiga, och dessutom enkelt integreras på ett chip med annan elektronik. I detta exjobb har tunna filmer av aluminiumoxid (Al2O3), titandioxid (TiO2) och tantaloxid (Ta2O5) utvärderats för användning som sensorlagret i pH-sensorer.

Oxiderna deponerades med ALD (Atomic Layer Deposition) och karaktäriserades med ellipsometriska mätningar. Gränssnittet mellan oxiden och elektrolyten undersöktes sedan med elektrokemiska mätningar. Först mättes spänningen över gränsnittet för olika pH-värden. På detta sätt kunde spänningens känslighet för pH-förändringar bestämmas. Det var också möjligt att uppskatta hur stor driften av spänningen var. Vidare mättes gränsnittets småsignalimpedans. Det förväntade termiska bruset kan beräknas från realdelen av impedansen. Till sist gjordes CV-mätningar (Cyclic Voltammetry) för att verifiera att oxiderna var heltäckande.

Både tunn titanoxid och tantaloxid hade känsligheter nära 55 mV/pH, medan aluminiumoxid uppvisade betydligt lägre känslighet. En tunnare oxid reducerar gränssnittets impedans, vilket leder till lägre termiskt brus. En tunnare oxid reducerade även drift i spänningen för titandioxid. Därför kan både tunn titandioxid och tunn tantaloxid anses vara bra kandidater för sensorlagret i pH-sensorer.

Abstract

Approximately 450 000 people have diabetes in Sweden today, and the number of diabetics only rises. Monitoring blood sugar several times a day is a fundamental part of managing the disease, and reducing the risks of complications. Today’s glucose monitoring devices are invasive and require small needle sticks for a measurement. Providing a painless method of monitoring the blood sugar level would relieve the lives of diabetics world-wide.

The objective of this project was to investigate the absorption spectra of aqueous glucose concentrations (100 to 5000 mg/dl) in the mid infrared region with Fourier Transform spectroscopy (FTIR), and finally implementing a hand-held monochromatic spectrometer to demonstrate a non-invasive concept. The method chosen for implementing the hand-held demo is due to the commercial availability of diodes and detectors at those wavelengths.

The results from the FTIR showed a trend among concentrations in all wavelengths, in between 1180 to 980 cm-1, specifically at 1035 cm-1, but also in the region 2920 to 2850 cm-1. The hand-held spectrometer did not register any transmittance of the glucose samples. For future implementations, 1035 cm-1 should be investigated more in-depth for a hand-held device.

Abstract

Metabolism is currently a very relevant and popular area of research in cell biology. Studying metabolism cell respiration has to be taken into account. At the moment, the most used system is both expensive and requires the cells to be moved from their standard culturing conditions to other culture dishes. The different shape and plastic of these dishes could possibly influence the cells, and hence make it difficult to compare the data from these measurements to other measurements.

In this study a system has been assembled and used to measure oxygen consumption under standard culturing conditions. The system is based on an article written by Mamchaoui et al. and uses the natural oxygen diffusion within the cell culture medium to measure the respiration. The oxygen pressure is measured at different depths within the cell culture medium, and when steady state is reached, Fick's laws are used to calculate the oxygen consumption.

In order to measure the oxygen concentration at different depths, a system was assembled consisting of an oxygen measuring system with fiber optic microsensors, a motorized vertical stage and a rigid table top pole stand. The system was evaluated by testing the reproducability of measurements, and it showed standard deviations comparable to those acquired with another system.

To conclude, it was shown that the system could be produced with less than one fifth of the cost of the Seahorse system, it can measure under normal culturing conditions and shows measuring errors close to those acquired with established measuring systems.

Abstract

The field of automation and smart devices is currently expanding. As most devices require wireless communication, the market for low budget, low power radios is growing rapidly. Many applications, such as the remote control of machines, have real time requirements with minimal latency. In this report, the market of wireless chips in the sub-GHz region has been investigated in order to give Syntronic AB an insight of the current market. Several key features such as range, data rate and output power were ranked among the available chips. To provide Syntronic with a marketing tool when reaching out to customers in the remote control field, a demonstration prototype (demo) was implemented using one of the radio chips from the list. The demo shows real time requirements with low latency between two wireless nodes. The first node takes movement data from a computer mouse and transmits it to the other node controlling an array of light emitting diodes (LEDs). This report contains the selection of radio configurations, design of a new wireless communications protocol, and implementation of the system in hardware and software. Measurements show a latency of 3.6 ms and a range of approximately 450 m which is regarded satisfactory.

Abstract

En analog krets för att driva en LED har tagits fram. Kretsen är en första prototyp till att kunna kalibrera en neutronspektrometer vid fusionsreaktorn JET. Ljuspulser i storleksordningen en nanosekund med en tillhörande elektrisk referenssignal, båda med en frekvens på 5 kHz har genererats. Tidsskillnaden mellan ljuspulsen och referenssignalen var konstant runt cirka 60 nanosekunder och var oberoende av intensitet. Vidareutveckling av prototypen är nödvändig för användning vid JET. Fjärrstyrning av frekvens och intensitet återstår att integreras i kretsen.

Abstract

An Arduino based car resembling robot equipped with heat- and ultrasonic sensors has been developed as a prototype for a rescue robot. The robot is controlled using an Android app developed in MIT App Inventor 2. In the app the sensors' information is divided in two modes; driving mode and not driving mode. The ultrasonic sensor's information is available when in driving mode, displaying the distance in centimeters straight ahead. The heat sensor's information is displayed in not driving mode, disabling motor skills, with a 8x8 pixel, blue and red color scaled picture fully updated within 2.38 seconds. An important part of the development is the Auto mode where the robot goes off on its own and signals the app user when a heat signature matching a human is detected within

35 centimeter. If the object close by is not within this temperature range, the robot turns away in another direction. Despite it's rough appearance and slow update speed, the robot fulfills the purpose of the project being able to locate a human heat signature by itself or a app user. 

Abstract

The possibility to measure voltage

over a filament at high voltage level

in klystrons and magnetrons has been

evaluated. A prototype with circuits

neccessary for measuring, power supply

and fiber optic communication has been

designed, built and tested in a

magnetron at Scandinova System AB.

These measurements lead to an

increased understanding of how

klystrons and magnetrons work and also

give the user better control over

their performance during operation.

Since measurements have been done on a

high voltage level near powerful

electric and magnetic fields, there

have been high demands on power

supply, circuit protection and

communication. Additionally, for

klystron systems, the measurement

circuit has been placed in an oil tank

with the transformers.

The complete system consists of two

major parts, a measurement circuit to

do the actual measurements on high

voltage level, as well as a control

circuit that controls the measurement

circuit and collects and displays the

data on an LCD display. Communication

between the two units is done via two

fiber optic cables.

Measurements were conducted

successfully but unfortunately power

supply became an issue and it is

recommended to pursue that subject

further in the future.

Abstract

A software for determining the temperature coefficient of solar cells and relative change in module efficiency has been developed in MATLAB. The performance parameters are subject to investigation for the client Solibro Research AB who have ordered this masters thesis report. Their interest in the results from the software is due to the importance of being able to assessing the performance of their solar cells at their test site at Ultuna, Uppsala in Sweden.

A commonly used simple model of determining the temperature coefficient is based on the assumption that the relation between the system efficiency and the cell temperature is linear. The results from the analysis made with this software tells however that this is not the case. The temperature coefficient seems to vary significantly around a mean value, and its value at lower irradiance differ from those at high irradiance. The trend for the relative change of the efficiency for varying irradiance is however somewhat consistent with the expected, when compared to what is given on the product data sheet for Solibro's SL2 modules.

Abstract

Målet med projektet var att konstruera två modeller av AM-mottagare: en kompakt och en enkel. Den kompakta modellens syfte var att bistå som prototyp till studentgruppen för att ge förståelse och tekniska referenser för AM-mottagare.Den enkla modellens syfte var att bistå som pedagogisk modell i kursen Elektronik I för att beskriva och visa elektriska komponenters funktion. En signalgenerator har använts för att sända kontrollerade AM-signaler. Kretsar för AM-mottagare har simulerats i LTSpice och konstruerats på kretskort. AM-mottagarkretsen är uppbyggd av en resonanskrets med integrerad antenn, operationsförstärkarbaserat signalförstärkarsteg, envelopp-detektor, operationsförstärkarbaserat ljudförstärkarsteg, högtalare samt en spänningskälla. Den kompakta AM-mottagaren har monterats på en skumplastskiva. Den enkla AM-mottagarens delsteg har monterats på illustrativa plexiglasmoduler. De båda AM-mottagarna är fullt fungerande.

Abstract

Noise in electronic circuits can sometimes cause problems. It is especially problematic in for example high sensitive sensors and high end audio and video equipment. In audio and video equipment the noise will make its way into the sound and picture reducing the overall quality. Sensors that are constructed to sense extremely small changes can only pick up changes larger than the noise floor of the circuit. By lowering the noise, sensors can achieve higher accuracy. 

This thesis presents an ultra low noise solution of the biasing circuitry to the bolometer used in one of FLIR Systems high end cameras. The bolometer uses different adjustable direct current voltage sources and is extremely sensitive to noise. The purpose is to improve the picture quality and the thermal measurement resolution. A prototype circuit was constructed and in the end of the thesis a final circuit with successful result will be presented. 

Abstract

En ljudförstärkarkrets som används i kursen Analog elektronik (1TE725) har felsökts och analyserats genom uppkoppling, simuleringar samt beräkningar. Studenterna har under labborationstillfället haft problem att få kretsen att fungera. Det huvudsakliga problemet har funnits vara att transistorerna i kretsens pushpullkoppling har överhettats, vilket ledde till kortslutning av dessa. Detta beror på att komponentegenskaperna hos transistorerna är temperaturberoende. I originalkretsen är därför viloströmmen i effektsteget positivt återkopplad, vilket medför att effektutvecklingen i transistorerna blir för hög och de kortsluts. Ett kretsförslag har tagits fram utifrån givna konstruktionskrav, som i stora drag är lik sin föregångare. De största skillnaderna är Sziklai-paren på utgången samt en sänkt matningsspänning till plus/minus 5V. Originalkretsen drev en Piezo-högtalare medan kretsförslaget kan driva en vanlig 8 Ohm högtalare.

Abstract

This study addresses quality control for Light Emitting Diodes (LED) according to fouraspects, the power factor of LED lamps, their harmonics and total harmonic distortion (THD), the luminosity for total power to radiated power ratio. It focuses on four brands and six different LED lamps, and concludes that IKEA's LED lamps pertain as the quality lamp, with a power factor over 0.9, THD less than 4% anda power to radiated light of over 4%.

Abstract

I detta arbete har jag undersökt en metod för att mäta glukoskoncentration och med denna metod konstruerat en mätutrustning som visar glukoskoncentrationen för ett prov på en datorskärm.

Mätningen baseras på radiovågor och permittiviteten för glukoslösningar. För att mäta permittiviteten används en mikrovågsresonanskavitet och homodyn detektering. Det gör det möjligt att mäta även mycket små prov, och detta utan att vara i direkt kontakt med provet.

Mätsystemet kan mäta koncentrationen på vattenlösningar av glukos i realtid. Jag har testat systemet på koncentrationer mellan 0 och 3000 mg/dl.

Abstract

To facilitate examination for osteogenesis and follow up after craniotomy similar head

models called phantoms are made. The head phantom should emulate the tissues

from a real head. This requires that the realistic head phantom have the same

electrical properties as relative permittivity (dielectric constant) and conductivity.

Both must be validated and matched for right frequency spectrum. Validation

measurements are performed by a coaxial slim probe connected to an Agilent

Technologies E8364B network analyzer. The range of frequency measured is from 1

to 50 GHz, but matching will only be processed for 1 to 10 GHz. The resonance

frequency for the antenna or sensor, which later will be used, is 2.4 GHz. The end

results of the head phantom consists of three different tissues or layers (skin, bone

and brain). Cavities will be created in the bone and will act as different defects or

stages of re-growing bone. Phantom cube is done for examining the influence of

implant in bone. Insertions of cube samples are made to emulate intermediates

between implant and bone.

Keywords: agar, BMP, body morphogenetic protein, bone implant, brain phantom,

craniosynostosis, craniotomy, cube phantom, phantom, re-growing bone, skin

phantom, skull phantom, tissue.

Abstract

Because of the tough competition inthe telecom business there is aconstant push for higher capacity anddata rates and the companies producingthe telecommunications equipment needmore cost effective products to stayahead of competitors. It is thereforeinteresting to evaluate thepossibilities to use unlicensedfrequency bands at higher frequenciesas a complement to the traditionallower frequency bands. This study isfocusing on the 5.8 GHz band, which ismainly used for WLAN applications. Akey component in most transmitter (TX)designs is is the quadraturemodulator, which upconverts theinformation signal to desired carrierfrequency. In this study an attempt toevaluate the commercially availablequadrature modulator ADL5375 at 5.8GHz. An AWR Visual System Simulator(VSS) model based on measurements ofkey parameters of ADL5375 isconstructed. An attempt is made to seewhether a TX design can pass thespecifications set by 3rd GenerationPartnership Project (3GPP) for theLong Term Evolution (LTE) standard. Totest this an LTE signal source wasalso constructed. No certainconclusions can be drawn withoutputting the modulator in a complete(TX) design but the results indicatethat it might be possible to use it ina (TX) design for the 5.8 GHz band.

Abstract

En ökande medeltemperatur är en av många utmaningar som världen tampas med idag. Landstinget i Uppsala län bedriver en bred verksamhet och kan med sina handlingar påverka sitt ekologiska fotavtryck. I Landstingets senaste miljöprogram är ett mål att 2 % av verksamhetens fastighetsel ska bestå av egenproducerad elenergi innan 2018. Landstinget planerar därför att inom de närmsta tre åren installera solenergianläggningar på en takyta av ca 10 000 m2.

På taket av Psykiatrins hus finns idag en koncentrerande solcells- och solfångaranläggning som förser fastigheten med både el och värme. Insikten i hur denna anläggning fungerar är bristfällig. Denna rapport har därför syftat till att, i uppdrag av Landstingsservice i Uppsala län, utreda och energikartlägga solenergianläggningen på Psykiatrins hus. Målet med detta arbete har varit att visa hur anläggningen på Psykiatrins hus fungerar, samt att ge Landstinget råd inför framtida investeringar av solenergi.

Inom ramarna för detta arbete har en mätstudie utförts under april 2015 för att se om energiproduktionen uppfyller vad som kan förväntas. Energiproduktionen har jämförts med instrålad solenergi för att bedöma anläggningens funktion och lämplighet i ett svenskt klimat.

Denna rapports slutsats är att den energi som solenergianläggningen på Psykiatrins hus producerat i april månad är rimlig, trots att Landstingsservice hade högre förväntningar innan detta arbete påbörjades. Dock bör solenergianläggningens lämplighet i ett svenskt klimat ifrågasättas. Med tanke på den prisutveckling solcellssystem haft de senaste åren och vetskapen om den direkta solstrålningens inverkan på koncentrerande solenergisystem rekommenderas Landstinget att i framtida investeringar satsa på renodlade solcells- eller solfångarsystem. 

Abstract

Sputtering is a physical vapor deposition (PVD) process used to create thin films, i.e very thin layers of material. To form compounds, such as oxides and nitrides, it may be beneficial to add a reactive gas to the process which is known as reactive sputtering. This thesis focuses on the simulation of the reactive sputtering process and, more specifically, the effect of the process pressure.

Two models have been developed. A Monte Carlo model simulates the distribution of sputtered material throughout the chamber. It is based on the binary collision model with initial conditions acquired from simulations in TRIM. The hard-sphere potential is used as interaction potential in the scattering calculations. The effect of the process pressure is studied for two different elements, sulfur and tungsten. It is found that the distribution of material is heavily influenced by the pressure. A high pressure gives a more diffusion-like distribution compared to a low pressure. As the pressure is increased the deposited material’s energy distribution is found to be shifted towards lower energies until it reaches the energy of thermalized atoms.

The second model developed is an extended Berg model that incorporates the effect of redeposition of sputtered material on the target, implantation of reactive ions in the target and preferential sputtering. Using simulations the effect of these extensions is discussed. It is found that an increased pressure may eliminate the hysteresis region which has been observed experimentally. Finally an outline is presented on how the two models can be unified into a Berg-model that takes the non-uniform distribution of sputtered material into account.

Abstract

Construction of an autonomous wind station was a project with the goal of creating a product that could collect wind data from a sensor and then transfer this data to a server wirelessly over the GSM network. The device would be powered by batteries and solar cells and function fully without requiring external power supply. This required that a small computer was constructed and programmed to store and send data at predetermined cycle times and programming of a server that received the sent data. The project also required optimization of power consumption and dimensioning of solar cells and batteries based on this.

The construction of this station demanded research both for the selection of hardware and programming software. The computer was based on a microcontroller and a GSM module that sent the data over the 2G network. An anemometer was connected to the microcontroller and measured the wind and successfully sent it to a server.

The device also succeeded in gathering enough solar power to compensate for the energy consumed by the device during 5 days of testing. However, to ensure continuous use, more long-term testing is needed.

Abstract

Parts of the auxiliary power systems at Fortum's hydro power stations are usingdirect current, which is fed from the generators at the plant and converted byrectifiers. As photovoltaic solar cells produce direct current there are severalhypothetical advantages to use solar power for the auxiliary power supply, e.g.enabling more of the power from the generator to be sold to the grid. It eliminatesthe need of an inverter, conversion losses are avoided and less load is put on therectifiers. However the exclusion of an inverter also prevents the solar cells to have adirect connection to the grid, which in turn makes them ineligible for the Swedishgovernmental solar power investment support program. The lesser load on therectifiers will not affect their lifetime according to manufacturers and thus achieves noeconomic gain. Avoiding conversion losses will increase the gain from the producedelectricity by enabling even more power to be sold to the grid. The economic gainfrom avoiding conversion losses is however too small to gain any feasibility in a smallsolar power installation at a hydro power plant, as the small size will make itexpensive in terms of investment per Wp.

Abstract

Projektets mål var att utforma och konstruera ett mätinstrument för att upptäcka variationer i ljusintensitet. Uppdraget gavs av avdelningen för fasta tillståndets elektronik på Ångströmlaboratoriet i Uppsala. Instrumentets tänkta användningsområde är att undersöka om avdelningens testuppställningar för belysning av solceller levererar en homogen ljusintensitet. Genom att placera instrumentet på olika positioner under ljuskällan ska eventuella avvikelser i intensiteten kunna avläsas. Kraven på instrumentet var batteridrift och att det skulle vara handhållet. Vidare var det önskvärt att mätvärdet representerades med en analog visare, där mätintervallet skulle gå mellan 800 och 1200 W/m².

Efter litteraturstudier och informationssökning utfördes simuleringar i programmet LTSpice parallellt med prototypframtagning i lab. Instrumentet utformades med en fotodiod, vars ström omvandlas till en proportionell spänning via en transimpedansförstärkare. Denna spänning skalas sedan upp av ett differentialförstärkarsteg för att uppnå önskat intervall och känslighet. En konstant spänning subtraheras i differentialsteget för att mätaren ska ge utslag först över 800 W/m². Spänningen läggs till sist över en analog amperemeter. I och med fotodiodens förmåga att ge ström proportionell mot ljusintensiteten erhölls linjära samband genom hela kretsen.

Projektet kunde inte slutföras inom tidsramen då varken kretskort eller hölje hann konstrueras. En fullt fungerande prototyp på kopplingsdäck blev dock klar. Vidare är alla beräkningar och komponentval gjorda och dokumenterade i rapporten. Med andra ord borde instrumentet utan problem kunna konstrueras utifrån denna rapport.

Abstract

CIGS thin film solar cells usually include a thin layer of intrinsic zinc oxide (i-ZnO) deposited on a CdS buffer layer by sputtering. However an interest has grown in using chemical vapor deposition (CVD) instead. Hence, the aim of this thesis was to study how well CVD i-ZnO performs on a CdS buffer layer in a CIGS solar cell and how the properties of the layer can be controlled when using a hot-wall CVD reactor with diethylzinc and water as precursors. The process was characterized through depositions on glass substrates and was then successfully implemented in solar cell devices. The main influences of temperature, thickness and precursor flows on resistivity, optical band gap and film structure were mapped out. The analysis methods used included X-ray diffraction (XRD), X-ray fluorescence (XRF), four point probe resistivity measurements, mechanical profilometry and absorption spectrophotometry. In addition, the solar cell devices were characterized using external quantum efficiency (EQE) and current-voltage (IV) measurements. It was found that the CVD process was sensitive to the condition of the CdS surface, which resulted in a large distribution of shunted cells when grown on aged CdS. Unexpected trends in open-circuit voltage and fill factor were found. Both these factors increased when the growth temperature was decreased, resulting in higher conversion efficiencies. Compared to i-ZnO deposited by an in-house baseline sputtering process, the CVD process resulted in cells with higher short-circuit current due to higher EQE in the short-wavelength region. It was shown that the CVD process used is capable of producing solar cell devices whose performances contest those of cells manufactured with sputtered i-ZnO.

Abstract

In this thesis CIGS absorber layers have been deposited by gas flow sputtering with an extra supply of selenium, a method that displays promise for large scale production because of its one-step sputtering route which deposits low energy particles in a high deposition rate.

In this thesis a method was developed where selenium was added to the sputtering process inside the sputter chamber in a controllable manner and in larger amount than done in previous projects. A total of five samples were manufactured with altered evaporation temperatures and an extra supply of selenium which then were finalized to solar cells using the standard baseline process of the Ångström solar center.

The characteristics of the CIGS layer and solar cells were analyzed by XRF, IV- and QE measurements. A cell with a conversion efficiency of 11.6 %, J_sc of 27.9 mA/cm², V_oc of 0.63 V and fill factor of 66.2 % was obtained on a 0.5 cm² cell area without an antireflective coating.

All samples contained cells with obtained efficiencies above 10 %, but over the whole samples the efficiencies varied considerably. The samples that were deposited with moderately large selenium evaporation provided the highest efficiencies with a relatively good homogeneity over the substrate. Results show a deficiency of copper in the CIGS films compared to the target composition. The copper content was lower than 70 % expressed in Cu/(Ga+In), which probably resulted in a low diffusion length for electrons, leading to limited cell efficiencies. 

Through the duration of the thesis issues that concerned the power supply- and the controls to the substrate heaters as well as the control of the evaporation temperature during the depositions arose that required problem solving and needs to be resolved for the future progression of this work.

The conclusions drawn from this thesis are that it is possible to vary the temperature of the selenium source and thereby control the amount of selenium that evaporates during the deposition process even though there is a lot of additional heating in the sputter chamber from both the substrate heaters and the sputter source which could affect the ability to control the amount of selenium being evaporated. That the most likely reason for the limited efficiencies is due to the low copper content in the CIGS films and that a larger amount of evaporated selenium compared to previous work did not result in higher obtained efficiencies.

Abstract

 The department of Solid State Electronics develops and manufactures solar cells. Then they need a reliable method for evaluating the performance of the solar cell. One of their rigs use a halogen lamp with a power of 300W. The lamp has gone out of production and needs a replacement. The purpose of this project is to find a suitable replacement. A suitable replacement must fulfill certain requirements; the light source has a light spectrum similar to that of the sun, a homogeneous light pattern and intensity of 1000W / m2. The lamp that the department currently uses only have a life span of 15 hours, so finding a lamp with a longer lifetime is desirable. The lamps have been tested using a spectrometer and a photodiode. With these two measurements it could be determined how similar the light source is to the sun. After testing several lamps, the results showed that many of the lamps spectrum were similar to the sun, but their intensity was too low. Therefore lenses were used to focus the light and increase the intensity. Light diffusers have been used to spread and smooth out the light. A Philips halogen lamp with a power 250W, together with lenses and a light diffuser, was found to be the best replacement and fulfilled all the predetermined requirements. A great advantage of this lamp is that it has a lifetime of 1000 hours.

Abstract

The task is to build a low-cost thermostat and design necessary elements to perform a study on water mixed glucose-impedance at different temperatures and cell growth in a temperature-controlled incubator housing a magnetic field of up to 3 mT. The incubator was designed in solidworks and made to fit petri dishes of two relevant sizes and necessary wiring. The coils designed to extend across the large of the incubator with six turns and a 4A current to yield a sixth of the required magnetic field, as field strength increases linearly with current and turns increasing either of these is advised, and a large enough homogenous field was observed to create a suitable environment for the study. A thermistor, temperature sensitive resistance, was used to get reading and a modified wheatstone bridge was used with a multiplying op-amp to stabilize and improve accuracy of readings. Using an arduino microprocessor utilizing a PID library to calculate the power needed from thermistor readings of ambient temperature and an H-bridge controller by PWM from the Arduino a thermostat capable of driving a peltier-cell was produced capable of raising, lowering and maintaining predefined temperatures. 

Abstract

The aim of my thesis is to make a theoretical model of data obtained from liquid-phase exfoliation of graphene. The production of graphene in the liquid phase exfoliation is a cost efficient method One part of this work is devotedto learn the method of production of graphene by the shear mixing technique from the graphite and to estimate some important parameters which are crucial for the process. Other part of my work is based on studying the liquid-phase exfoliation mechanism of graphene through ultrasonication technique. This method is time consuming as compared to shearmixing.

Abstract

Konceptutveckling och prototypframtagning hur man ska kunna implementera externa sensorer till ett fordon f¨or att kunna fels¨oka snabbare och enklare. Olika plattformar unders¨oktes med f¨or- och nackdelar. Efterforskning resulterade i en f¨orsta prototyp best˚aende av mikrokontroller och f¨orslag till PCB designen.

Abstract

Uppsalahem is the leading housing corporation in Uppsala with its over 160 real estate properties. Uppsalahem is owned by the municipality of Uppsala, which has a climate and energy goal that aims for 100 MW of solar energy to be installed in Uppsala by 2030. The 100 MW goal, combined with Uppsalahem’s environmental policy, is a strong incentive to investigate the possibility of installing PV modules on the many available roof areas that Uppsalahem possesses. The objective of this thesis is to create a foundation for future decisions regarding PV systems for Uppsalahem. The economic potential for PV systems on apartment buildings until 2030 was therefore calculated. The calculations were made in a computer model created in Matlab that can be used by Uppsalahem for future decision-making.

Uppsalahem owns a 2,0 MWp wind power plant that is expected to supply 35 % of the total electricity use of the corporation. The electricity produced in the plant is tax exempt, under the condition that no electricity, including PV produced electricity, is sold by Uppsalahem. As any surplus electricity cannot be sold, the profitability of all PV installations is determined largely by the electricity use of each building.

The economic PV potential was calculated for 11 scenarios starting from a base scenario that was based on the parameters deemed most likely to be true. In the base scenario, where no electricity certificates or investment support were used, the potential was 0,30 MWp 2015 and 1,59 MWp 2030. If electricity certificates or investment support is used, the potential in 2015 is 1,13 and 1,64 MWp, respectively. For 2030 the potential increases to 1,90 and 2,10 MWp. In the base scenario, PV installations can supply 1,4 % of Uppsalahem’s annual electricity use in 2015 and in 2030 1,6 % of the 100 MW goal can be met by Uppsalahem. 

Abstract

Sveriges energisystem står inför en förändring. Enligt dagens miljöpolitik ska förnybara energikällor som vindkraft, bioenergi och solenergi på sikt ersätta kärnkraft och fossila energikällor. Solel står idag för en nästan obefintlig del av den svenska elmixen vilket främst beror på att priserna på solcellssystem tidigare har varit för höga. Höga subventioner har varit nödvändiga för att en investering inte ska innebära en förlust. Idag har systempriserna sjunkit till en nivå där en ekonomisk vinst är möjlig även utan subventioner. En förutsättning för en ekonomisk vinst är att solcellerna integreras på rätt sätt i verksamheten.

För att en investering i ett solcellssystem ska vara ekonomiskt lönsam utan subventioner krävs det att producenten själv konsumerar den producerade elen. Det beror på att ersättningen för överproducerad el, så kallad överskottsel, i dagsläget inte motsvarar lönsamheten som uppstår då elen konsumeras av verksamheten själv. För att kunna få en låg andel överskottsel i produktionen krävs det att verksamheten i fråga har ett elbehov vid den tid då solcellerna producerar el, alltså då solen skiner som starkast. Examensarbetet är inriktat mot att studera verksamheter som, till skillnad från en normal villa, har ett elbehov under dagtid och under sommarhalvåret. En golfverksamhet har ett sådant elbehov och dessutom finns det stora markytor och flera byggnader i verksamheten, vilket är ett stort plus vid installation av solceller. Det fördelaktiga elbehovet medför att relativt stora solcellsanläggningar kan integreras i golfverksamheterna utan att det produceras för mycket överskottsel.

För att bestämma golfverksamheters lämplighet för solelsproduktion i Sverige har 9 golfklubbars elbehov analyserats mot solinstrålningsdata från respektive plats. De nio klubbarna är valda från olika delar av landet för att påvisa skillnader i produktion och lönsamhet beroende på lokalisation. För varje golfklubb framtogs systemstorlekar som producerar omkring 5 % respektive 10 % överskottsel per år. I rapporten presenteras huvudsakligen resultaten för systemstorlekar med 5 % överskottsel eftersom en sådan mängd anses vara försumbar. Ekonomin för de framtagna systemen analyserades och presenteras i form av nettonuvärde vid livslängdens slut, produktionspris samt återbetalningstid.

Resultaten från undersökningen visar att golfverksamheter i Sverige kan göra lönsamma investeringar i solcellssystem även utan subventioner eller bidrag. För många klubbar är nettonuvärdet större än investeringen efter 40 år, vilket innebär att investeringen har mer än dubblerat sitt värde. Produktionspriset hamnar på runt 80 öre per kWh och återbetalningstiden blir omkring 18 år. Med investeringsstöd är nettonuvärdet större än investeringen redan efter 25 år. Produktionspriset blir runt 60 öre per kWh och återbetalningstiden sjunker till omkring 10 år.

Att göra en investering i solceller innebär inte bara en ekonomisk lönsamhet för investeraren. En investering medför också positiva fördelar för miljön då solceller producerar förnybar el. Stora delar av världen arbetar idag aktivt för att få in mer förnybar el i energisystemet. Sverige har som mål att 50 % av energianvändningen i Sverige ska försörjas av förnybara energikällor år 2020. Idag är drygt 40 % av energiförsörjningen förnybar, vilket innebär att det återstår en del arbete tills målet är uppfyllt. Om golfklubbar i Sverige utnyttjar sitt fördelaktiga elbehov och investerar i solceller kan de bidra till att målet uppnås samtidigt som de gör en god ekonomisk affär. Därför rekommenderas det att Sveriges golfklubbar ser över sina möjligheter att integrera solcellsystem i sina verksamheter.

Abstract

This thesis studies the effects of Na diffusion in Cu(In,Ga)Se₂ (CIGS) solar cells,caused by electrical Potential Induced Degradation (PID) and how to prevent it. Thiswas done by subjecting CIGS solar cells a temperature of 85⁰C and an electrical biasfrom the backside of the glass substrate to the Mo back contact of the CIGS cell.When the bias was negative at the back contact the Na diffused in to the CIGS(degradation) and when it was positive the ions diffused out again (recovery). TheCIGS samples were electrically characterized with IV- and EQE-measurements duringthese conditions and compositional depth profiling was used to track the Nadistribution.This study showed that during degradation Na seemed to accumulate in the interfacesbetween the different layers in the CIGS cell. The buffer and window layers arestrongly affected by Na diffusion. Zn(O,S) buffer layer showed a clear difference inrecovery behavior compared to CdS buffer layer. The introduction of an Al2O3barrier layer between the CIGS and Mo back contact increased the degradation timefrom 50 h to 160 h. During this study it was also found that in some cases the CIGSsolar cells efficiency could be improved by degrading the cells and then recoveringthem, in the best case from 13% average energy efficiency to 15% efficiency.

Abstract

In this thesis, a novel method of reducing the rear surface recombination in copper indium gallium (di) selenide (CIGS) thin film solar cells, using atomic layer deposited (ALD) Al₂O₃, has been evaluated via qualitative opto-electrical characterization. The idea stems from the silicon (Si) industry, where rear surface passivation layers are used to boost the open-circuit voltage and, hence, the cell efficiency. To enable a qualitative assessment of the passivation effect, Al/Al₂O₃/CIGS metal-oxide-semiconductor (MOS) devices with 3-50 nm oxide thickness, some post-deposition treated (i.e. annealed), have been fabricated.

Room temperature capacitance-voltage (CV) measurements on the MOS devices indicated a negative fixed charge density (Q_f) within the Al₂O₃ layer, resulting in a reduced CIGS surface recombination due to field effect passivation. After annealing the Al₂O₃ passivation layers, the field effect passivation appeared to increase due to a more negative Q_f. After annealing have also indications of a lower density of interface traps been seen, possibly due to a stronger or activated chemical passivation.

Additionally, the feasibility of using ALD Al₂O₃ to passivate the surface of CIGS absorber layers has also been demonstrated by room temperature photoluminescence (PL) measurements, where the PL intensity was about 20 times stronger for a structure passivated with 25 nm Al₂O₃ compared to an unpassivated structure. The strong PL intensity for all passivated devices suggests that both the chemical and field effect passivation were active, also for the passivated as-deposited CIGS absorbers.

Abstract

Djupinformationen i dagens sjökort har ofta dåligt noggrannhet. Detta beror på att djupen ofta är mätta under sent 1800-tal, med dåtidens teknik. Den senaste tidens ökade användning av GPS i samband med navigation till sjöss har visat att dessa föråldrade sjökorts dåliga noggrannhet är ett stort problem.Detta projekt siktar på att ta emot och behandla data från sådan navigationsutrustning. När informationen bearbetats skickas den sedan till en server där den insamlade datan kan användas för att rita nya sjökort. Ett sådant system tillåter flertalet användare att samtidigt samla information för att förbättra sina navigationsmöjligheter.En testenhet har byggts, baserad på en liten linuxdator, en Raspberry Pi. Testenheten är även utrustad med en marin GPS-mottagare, Garmin x18-5Hz. Kommunikationen till denna sker via det seriella NMEA protokollet, vilket är standard för många liknande enheter. För att visa att systemet fungerar utrustas enheten även med en lufttrycksmätare. Lufttrycket räknas sedan om till höjd över havet. Detta resulterar i ett enkelt sätt att göra mätningar på land. En metod för att automatiskt detektera avstånd mellan GPS-mottagare och ekolod har utvecklats och testats på enheten.Testenheten är kapabel att kombinera GPS-koordinater med höjddata och sedan sända denna information till en server. Små förändringar behöver göras i enheten för att göra den kompatibel med fler GPS-mottagare och ekolod. Viss vidareutveckling behöver göras för att tillåta att flera användare samtidigt samlar in data. Det har visats att konceptet med insamling av GPS- och ekolod-data är möjlig.

Abstract

The Swedish potential of electricity production from roof mounted solar panels has been determined in three steps: accessing the existing roof top areas, simulating the amount of electricity solar panels can produce on these areas and finally analyzing how large the necessary economical change is to make the solar cells profitable.

The total existing amount of roof top areas are 319 square kilometers and the area distribution follows the distribution of people. This leads to an installed power of 47,9 GW which are expected to produce 49,0 TWh electricity per year. If the quality of the electricity is prioritized the highest the power is reduced to 3,7 GW, generating 3,8 TWh yearly, but if the hosting capacity is calculated from Sweden’s total electricity need, the capacity is 42 TWh per year.

Today, solar panels are not profitable in Sweden for houses, even though there is a subsidy of 35 % of the investment costs, discounted in 25 years. The profitability is calculated with a cost of capital of 5 %, a price on electricity of 1 SEK/kWh and an investment cost of 20 SEK/Wp. With a kept subsidy of 35 %, the price of electricity needs to rise 30 % to make the systems profitable for houses, and the corresponding increase without the subsidy is 95 %. Historically the subsidy has decreased as the costs of solar cells have decreased as well.

For apartment buildings solar panels are profitable with the governmental subsidy if the solar systems are at least 3 kWp per house hold. The corresponding price increase without the subsidy is 60 %.

Abstract

The buffer layer in Cu(In,Ga)Se2 solar cells can improve cell performance. In this work we make CdS buffer layer by chemical bath deposition (CBD) without ammonia. CBD without ammonia were sought out since ammonia is a volatile compound.

Different recipes for making CdS were tested; only one of the tested recipes actually produced something that is worth further investigating. This recipe used sodium citrate, an innocuous compound instead of ammonia. The best performance was 0.15 % off from the reference.This is almost as good as the used baseline process. However the worst almost completely killed the solar cells. Cell performance dropped by more than absolute 10 %.

This demonstrates that chemical bath deposition can have profound effects on the solar cell performance. When trying to improve the best cells only detrimental effects showed up. This might show that, a part in the recipe used, NaOH has detrimental effects on solar cells.

Ammonia free chemical bath deposition is possible, however so far it has not produced as good results as the reference. The difference is however very small, which makes it worth further investigating with moreand better solar cell material.

Abstract

För att kunna utvärdera resultaten av solcellsforskningen på Uppsala Universitet krävs anpassad mätutrustning. Idag finns en krets som kan följa maxeffektspunkten på en solpanel genom att använda en MOSFET som variabelt motstånd och styra detta via en lågpassfiltrerad PWM-signal från en enkapseldator. Enkapseldatorn mäter kontinuerligt spänning och ström via dess analog-digital-ingångar (ADC ingångar). Strömmen och spänningen skickas också analogt ned till en multimeter i testlabbet som loggar datan. Analoga signaler är mer störningskänsliga än digitala och kräver också minst två sladdar ifrån varje solpanel till testlabbet. Genom att närmare solcellen konvertera ström och spänning till digital data undviks störningar samtidigt som det blir lättare att koppla in många solpaneler med färre sladdar. Detta projekt syftade till att vidareutveckla den tidigare mätkretsen. Den skulle kunna anpassas till olika solpaneler, följa maxeffekt snabbare och stabilare än tidigare, förutom ström och spänning även digitalt skicka tomgångsspänningen (Voc) och kortslutningsströmmen (Isc), kunna mäta och skicka en ström-spännings-kurva (IVkurva) efter kommando från en cetral dator och vara utrustad med en LED för felsökningssyfte. En prototypkrets konstruerades och testades via långa kablar (60-70m) från en solcellsmodul på Ångströmslaboratoriets tak ner till testlaboratoriet som uppfyllde alla designkraven förutom ett. Det är inte möjligt att skicka ett kommando från en central dator och få tillbaka en IV-kurva. Det går att programmera om enkapseldatorn med ny programkod för att göra detta. Det är dock bara en mjukvaruändring som behöver göras för att detta designkrav ska uppfyllas. Kretsen har inte monterats och testats vid solpanelen där den ska sitta. Både mjukvaran och hårdvaran i kretsen kan utvecklas vidare.

Abstract

The photovoltaic solar cell industry is growing rapidly, but high cost per watt is still an obstacle. Thin film solar cells, especially thin film solar cells using CIGS absorbers that have the highest proven efficiency, have the potential to reduce the cost through cheap manufacturing. Academic research concerning CIGS solar cells has so far been focused on cells with absorber layers deposited by co-evaporation, which can be used to make very high efficiency cells but is a deposition process ill suited for large scale production.

In this thesis a process for depositing CIGS absorber layers by gas flow sputtering, a deposition technique enabling high rate depositions of low energy particles that is potentially easier to apply to a large scale production, has been outlined. Equipment for CIGS-deposition by gas flow sputtering has been prepared, characteristics of the process have been investigated and ultimately a series of first prototype CIGS absorber layers has been deposited as part of complete solar cells.

A lot of focus in this thesis is on the practical work and problem solving around the equipment, e.g. pulsed DC power supplies and electrical connections, heating and heating control in a reactive vacuum environment, and on the basic functionality of the gas flow sputter, how process and film properties like deposition rate, thickness uniformity etc. vary with sputter conditions like pressure, gas flow etc.

Following the process design the first prototype series produced crystalline CIGS absorbers of desired elemental composition and thickness but having rather small grain sizes, while the complete cells exhibited solar cell IV-characteristics but very poor efficiencies.

Abstract

In this repost the design of an exposure system for culture studies is presented. The apparatus can expose culture plates to a magnetic field and microwave radiation. The magnetic field is created using a pair of Helmholtz colis which can generate a field with frequencies between 0 and 100 [Hz] and with field strengths between 0 and 8 [Gauss]. Microwaves with frequencies between 1.7 and 1.9 [GHz] at power levels between 0 and 8 [W] are directed at the culture plate using a R-band rectangular waveguide. The setup includes an IR- camera used to observe the temperature distribution of the exposed medium.Trial exposures of Osteoblasts does not show any statistically viable results. 

Abstract

For several years Uppsala University together with several companies has been involved in a WISENET project aimed at improving railway transport security. By placing a sensor system near the wheels of each wagon, the temperature of the bearings can be measured and transmitted to a collector placed centrally on the wagon. This in turn transmits the collected data to RFID receivers placed intermittently along the railway.

As the signals are transmitted wirelessly, problems may occur as the antennas get dirty or coated with ice and snow. To determine the effects of these coatings, several tests were performed examining the reflection coefficient S11, the impedance Z11 and the efficiency eta of an antenna, and how they varied when various coatings were placed over the antenna. Examined coatings were ice, snow and water to determine the effects of weather, and various metal-based coatings: powdered iron both pure and partially oxidized, and iron ore granules. Finally a sample coating taken directly from a car was tested to determine how closely the other coatings resembled what appeared in normal use.

Most of the coatings gave similar results; little or no loss of efficiency and a lowering of the resonance frequency by some 75 MHz, with both iron powder samples, the ore granules and the sample coating proved nearly identical in results. Thick layers of snow gave a noticeable drop in efficiency, as did the presence of any amount of water, which also greatly affected the resonance frequency.

Abstract

To make a High Voltage Direct Current (HVDC) transmission more energy efficient, the voltage of the system has to be increased. To allow for that the components of the system must be constructed to handle the increases AC and DC stresses that this leads to. One key component in such a transmission is the HVDC converter transformer. The insulation system of the transformer usually consists of oil and oil-impregnated pressboard. Modeling of the electric DC field in the insulation system is currently done with the ion drift diffusion model, which takes into account the transport and generation of charges in the oil and the pressboard. The model is however lacking a description of how charges are being injected from the electrodes and the oil-pressboard interfaces. The task of this thesis work was to develop and implement a model for this which improves the result of the ion drift diffusion model.

A theoretical study of ion injection was first carried out and proceeding from this, a model for the ion injection was formulated. By using experimental data from 5 different test geometries, the injection model could be validated and appropriate parameter values of the model could be determined. By using COMSOL Multiphysics®, the ion drift diffusion model with the injection model could be simulated for the different test geometries.

The ion injection gave a substantial improvement of the ion drift diffusion model. The positive injection from electrodes into oil was found to be in the range 0.3-0.6 while the negative injection was 0.3 lower. Determination of the parameters for the injection from oil-pressboard interfaces proved to be difficult, but setting the parameters in the range 0.01-1 allowed for a good agreement with the experimental data. Here, a fit could be obtained for multiple assumptions about the set of active injection parameters.

Finally it is recommended that the investigation of the ion injection continues in order to further improve the model and more accurately determine the parameters of it. Suggestions on how this work could be carried out are given in the end.

Abstract

Det här projektet är ämnat att hittalämpliga kretsarkitetkturer för braeffektöverföring där energikällorna ärmycket begränsade.Två kretsar ska byggas. Den första skata emot hög växelspänning motsvarandespänningen som uppkommer i ettpiezoelement vilket utsätts för växlandetryck. I det här fallet trycket från enmänniskas fotsteg. Kretsen ska leverera3.3V likspänning.Den andra kretsen ska ta emot en lågväxelspänning, vilken motsvarar spänningfrån en trådlös överföring, och leverera3.3V.Krets 1 blev aldrig testad på grund avett fallerande högspänningsaggregat.Genom att skicka en wav-fil genom en OPförstärkareskulle en simulerad spänningfrån piezoelementet användas. Därefterskulle spänningen likriktas ochkonverteras ner till 3.3V.Krets 2 testades med en signalgeneratorsom spänningskälla. Spänningentransformerades först upp innan denlikriktades och skickades in i enspänningsreglator för att därefter ge ut3.3V. Med en liten levererad effekt frånsignalgeneratorn var det nödvändigt attbegränsa effektåtgången i lasten genompulsbreddmodulering. Effektåtgången ispänningsreglatorn begränsades ocksågenom att stänga av och på IC:n(spänningsregulatorn). När IC:n varavstängd laddades en kondensator upp somsedan tömdes i IC:n då den aktiveradesigen.

Abstract

Cu₂ZnSn(Se,S)₄ (CZT(Se,S)) has recently been shown to be a promising material to use in thin film solar cells. It has a band gap of between 1eV (CZTSe) and 1.5eV (CZTS). CZT(Se,S) solar cells have reached 10% efficiency.

The aim of this project was to find an effective way to selenise metallic Cu, Zn, Sn films in order to produce Cu₂ZnSnSe₄ (CZTSe) films, without destroying the metallic molybdenum (Mo) back contact. Another aim was to make films containing both Se and S and to study the possibility to achieve a controlled S/Se ratio in the films. Selenisation and sulfurisation reactions were carried out in quartz ampoules and samples were characterized using scanning electron microscopy, x-ray diffraction and energy dispersive microscopy.

Since Mo reacts rapidly with Se, experiments with selenisation and sulfurisation of plain Mo films were performed. The time and temperature dependence of the thickness of the reacted layer was studied, and it was found that Se reacts much faster with Mo than S does. Pre-sulfurisation of Mo appeared to hinder Se from reacting with the Mo.

The next step was to react precursor films to make CZTSe and CZT(Se,S) absorber layers. For mixed Se and S samples, the result is the same as for plain Mo samples; pre-sulfurisation, or inclusion of S in the precursor layer, can prevent selenisation of the Mo. The S/Se ratio was controlled with reaction time. 

The best efficiency of 3.2% was obtained for a CZTSe sample while the best CZT(Se,S) sample gave 2.3%.

Abstract

Today, buildings utilize 40 % of the total energy consumption. New energyrestrictions and directives have entered the construction industry. Photovoltaic is asustainable, clean and quiet solution that integrates well in the urban environment buthave not yet reached a breakthrough on the Swedish market. The conditions for solarenergy production are often set in the early planning stages where they rarely arebeing prioritized.This master of engineering project focuses on identifying problems regardingimplementation of photovoltaic in city development projects and giving suggestions topossible improvements in the planning- and construction process. It also givesrecommendations on how the conditions for energy production can be optimized inthe early zoning stage.By conducting simulations with PVsystV5.21, on three ongoing city developmentprojects in Umeå, Malmö and Stockholm and by carry out and analyzing interviewswith city planners, constructors and architects, some conclusions have been made.Several improvements, both politically, with changes in the subsidization systemand/or instatement of a new law with feed-in tariffs, and within the solar- andconstruction industry itself, with better communication between different parts of theprocess as well as better use of experience, can be made. By including photovoltaic inthe local plan it is possible to give a region large areas with orientation toward south,increasing the solar energy potential with up to 50 % which also increase themotivation for implementing photovoltaic in the project. These are essential for asignificant increase of photovoltaic in city development.

Abstract

It is widely known that the element sodium plays a vital role in providing highefficiency CIGS solar cells and that when cells are built on sodium free substrates theyneed an alternative (a substitute) sodium source. In this study a molybdenum-sodiumcompound has been deposited, investigated and evaluated as an alternative backcontact layer containing sodium. The compound had a 5 at % sodium concentrationand it was manufactured by an Austrian company called Plansee. The aim of the studywas to create an equivalent back contact in the sense of sodium delivery, conductivityand adhesion compared to a normal molybdenum back contact on a soda lime glass.

The experimental part of the study started with the construction of complete cells,which were fabricated and measured. This work took place at the ÅngströmLaboratory, Uppsala University, Sweden. The characteristics of the layer and the cellswere analyzed by current voltage measurements, quantum efficiency measurementsand secondary ion mass spectrometry analysis. Cell manufacturing involved sputtering,co evaporation and chemical deposition processes.

Results show that the molybdenum-sodium compound increases the efficiency of acell built on a sodium-free substrate. Efficiencies reached 8 % for cells without sodiumin the molybdenum and these cells produced 67 % efficiency and 80 % open circuitvoltage of the reference value. Cells with sodium in the back contact layer produced90 % of the efficiency and 95% of the open circuit voltage relative to the references.The best cell with the molybdenum-sodium compound reached an efficiency of 13.3%.

This implies that the new back contact layer acts as a sodium source but the cellshave 1-2 % lower efficiency than the reference cells built on soda lime glass. Othercharacteristics of the layer as conductivity and adhesion show no significant differenceto an ordinary molybdenum back contact.

Measurements also indicate that the sodium is probably located inside themolybdenum grains and just a small amount is found at the boundaries and in betweenthe grains. Sodium inside the molybdenum grains is difficult to extract and thereforenot enough sodium will diffuse into the CIGS layer.

The conclusions drawn from this study are that the molybdenum-sodium compoundhelps to increase the efficiency of a CIGS solar cell built on a sodium-free substrate,but it does not deliver enough sodium to constitute a substitute sodium source.

Abstract

An antenna for a wireless sensor network for trains is designed and built. The network will monitor temperature and vibrations of the wheel bearings on the train wagons. Doing this will allow for an earlier detection of damaged wheels, which will ease planning of maintenance and reduce wear on the rails considerably. The requirement of the system is that it is to be installed without any cables attached to the sensor nodes. This calls for wireless communication, and that for that antennas are needed.A train is a difficult environment to transmit electromagnetic (EM) waves in. It is full of metal and EM-waves cannot pass through a conducting material. Having much metal in its vicinity also affects the function of the antenna. This needs to be taken into consideration when making the design.The constructed antenna is a small dual-layer patch antenna. Dual layer means that it is constructed out of two sheets known as substrates of isolating material with different characteristics. The lower one of these substrates is made in such a way that integration with a circuit board is possible. Such integration would reduce the production cost considerably. The antenna is designed for direct placement on a conducting surface. This surface could be part of the train. It uses the surrounding metal as a ground plane in order to reduce its size. The result is a small patch antenna with good radiation qualities in metallic surroundings. The longest side is 18.35 mm, equaling 14.9 % of the wavelength that the antenna is designed for.

Abstract

A degree project has been carried out at Motion Control, Västerås. The degree

project “Grafisk Skärm för Inbyggda System” have developed a first prototype of an

embedded system with a display, a graphical user interface with touchscreen and

possibilities to communicate with external units.

The work initiated with surveys of critical components. A technical specification for

the desired end product was developed. With the technical specification as support,

design specifications for hardware and firmware were developed.

After the specifications were done, a circuit diagram was developed and a circuit

board was made. The components were mounted by hand.

After testing and correction of the construction the project has resulted in a first

prototype. The prototype meets a lot of the desired requirements for a completed

end product. The prototype can display the graphical user interface with good quality,

has a working touchscreen and possibilities to receive external communication. Any

processing of the external communication was not implemented. The prototype has a

good foundation for further development.

Abstract

As the importance of high frequency antennas increase in the world so does the needfor accurate measurements of the antenna performance.This project has endeavoured to create an automated scan station that can measurethe antenna performance from an EHF (extremely high frequency) antenna.These points are measured spherically around the antenna.A tested design from the Helsinki University that requires only two degrees offreedom to achieve spherical measurements was used. A network analyzer is used asthe measuring instrument along with the receiver antenna attached to the stationsarms. All components are controlled and monitored through a computer usingsoftware designed in LabVIEW.A backlash due to high tolerances on the two axle wedges was discovered duringassembly and a solution was devised using thread tape, however its effect has notbeen tested. The project was worked on during the summer holidays which resultedin delays on ordered parts, because of this the motor control from the LabVIEWprogram has not yet been implemented. This also means that the automated sequencethat performs the measurements has not been tested.With an implemented motor control and reduced backlash from the wedges the scanstation is expected to achieve high accuracy and reliability.

Abstract

Cu2ZnSnS4 (CZTS) is a semiconductor with a direct band gap of about 1,5 eV and anabsorption coefficient of 10^4 cm^-1, and is for this reason a potential thin film solarcell material. Demonstrated efficiencies of up to 6,8% as well as use of cheap andabundant elements make CZTS a promising alternative to current solar cells.The aim of this study was to fabricate and characterize CZTS films and to evaluatetheir performance in complete solar cells. For the fabrication of CZTS we applied atwo-step process consisting of co-sputtering of the metal or metal-sulphurprecursors, and subsequent sulphurization by heating at 520°C in sulphur atmosphereusing sealed quartz ampoules.The work included a systematic comparison of the influence of composition on qualityand efficiency of CZTS solar cells. For this purpose films with various metallic ratioswere produced. The results show that the composition has a major impact on theefficiency of the solar cells in these experiments. Especially zinc-rich, copper-poor andtin-rich films proved to be suitable for good cells. The worst results were received forzinc-poor films. An increase in efficiency with zinc content has been reportedpreviously and was confirmed in this study. This can be explained by segregation ofdifferent secondary phases for off-stochiometric compositions. According to thephase diagram, zinc-poor films segregate mainly copper sulfide and copper tin sulfidecompounds which are conductive and therefore detrimental for the solar cell. Zincsulfide, that is supposed to be present in the other regions of the phase diagramexamined in this study, could be comparatively harmless as this secondary phase isonly isolating and by this ’just’ reduces the active area. This is less disadvantageousthan the shunting that can be caused by copper sulfides. Contrary to the efficiencyresults, metal composition had no major impact on the morphology.A comparison of the composition before and after the sulphurization revealed thatmetal precursors showed higher tin losses than sulphur containing precursors. Apossible explanations for this was given.Another central point of this work was the examination of the influence of sulphur inthe precursor. Less need of additional sulphur in the film might lead to better materialquality. This is based on the assumption that the film is subjected to less diffusion ofthe elements and so to less dramatic changes within the film, which might result infewer voids and defects. However, our experiments could find only a weak trend thatsulphur in the precursor increases the performance of the solar cells; concerningmorphology it was observed that more compact films with smaller grains developfrom metal-sulphur-precursors.The best efficiency measured within this work was 3,2%.