Made available in DSpace on 2016-08-31T13:33:40Z (GMT). No. of bitstreams: 1 IsaacBTS_DISSERT.pdf: 5495741 bytes, checksum: 51971b46b62abac857269a023f55e88b (MD5) Previous issue date: 2014-12-19 / Microstrip patch antennas consist of a metallic strip over a dielectric substrate and widely used because of its small size and versatility of its dimensions and possible configurations of the patch to achieve specific characteristics of resonance frequency, bandwidth, directivity and return loss. Due this versatility of its parameters, this work presents a microstrip patch antenna proposal involving the insertion of two Complementary Split Ring Resonators (CSRR), as the variation of its dimensions, and will be developed a study of CSRR s influence in antenna s parameters, designed by Transmission Line Theory, with the objective of increasing the antenna s bandwidth and filtering certain frequencies; and manufacture a device which operates in Ultra Wideband (UWB) system. The application of dielectric multilayers will be also studied with the objective of evaluate its influence in antenna s return loss. The software ANSYS HFSS® was used as an auxiliary tool to simulate the antennas parameters and the best results, as well the evaluation about the available material, were used to build the devices and measure them to validate the results previously simulated. The simulations results matched with the expected behavior of the return loss, because the filter characteristic appeared in some frequencies and the result presented a dual-band characteristic. The experimental result for the return loss agreed with the simulated pattern, despite the dislocated frequency to higher values, but just one of the measured antennas could be used in the UWB system with fractional bandwidth of 34,12% in the resonance frequency of 4,35 GHz with return loss of -36,22 dB, allowing the operation in many wireless communication systems like the IEEE standards 802.11a, 802.11n and 802.11p / As antenas de microfita tipo patch (ou plaqueta) são antenas constituídas de um recorte metálico sobre um substrato dielétrico, e são bastante utilizadas devido ao seu tamanho reduzido e versatilidade em relação as diversas configurações e dimensões que podem ser utilizadas no patch a fim de alcançar características específicas de frequência de ressonância, largura de banda, diretividade e perda de retorno. Devido a essa versatilidade em relação aos parâmetros construtivos e eletromagnéticos, este trabalho apresenta uma proposta de antena de microfita envolvendo a inclusão de dois Anéis Ressoadores Complementares (Complementary Split Ring Resonator CSRR), bem como a variação das dimensões deste, e será realizado um estudo sobre sua influência nos parâmetros da antena de microfita, projetada através da Teoria de Linha de Transmissão, objetivando o incremento da largura de banda da antena e a filtragem de determinadas faixas de frequência a fim de fabricar um dispositivo que opere no sistema Ultra Wideband (UWB). A aplicação de múltiplas camadas dielétricas também será estudada a fim de se observar sua influência na perda de retorno da antena. Os resultados foram obtidos através de simulações utilizando o software ANSYS HFSS®, que utiliza o método dos Elementos Finitos, e os melhores resultados obtidos, juntamente com a análise do material disponível, foram utilizados para a fabricação dos dispositivos e medição dos mesmos a fim de validar as simulações realizadas. Os resultados das simulações se mostraram satisfatórios, pois a característica capacitiva do CSRR permitiu o filtro de algumas faixas de frequência, fazendo com que a perda de retorno tivesse característica dual-band. O resultado experimental da perda de retorno se mostrou concordante com o padrão simulado, apesar do deslocamento de frequência, porém apenas uma das antenas construídas se adequou para aplicação no sistema UWB, com largura de banda fracionária de 34,12% para a frequência de ressonância 4,35 GHz com perda de retorno no valor de -36,22 dB, permitindo a operação desta em diversos sistemas de comunicação wireless como padrões 802.11a, 802.11n, 802.11p entre outros sistemas

Made available in DSpace on 2014-12-17T14:55:37Z (GMT). No. of bitstreams: 1 AntonioSA.pdf: 2010232 bytes, checksum: 027e876fa92242a6ba0e73009f5debd5 (MD5) Previous issue date: 2009-08-11 / This work is the analysis of a structure of the microstrip antenna designed for application in ultra wide band systems (Ultra Wideband - UWB). This is a prospective analytical study where they tested the changes in the geometry of the antenna, observing their suitability to the proposed objectives. It is known that the UWB antenna must operate in a range of at least 500 MHz, and answer a fractional bandwidth greater than or equal to 25%. It is also desirable that the antenna meets the specifications of track determined by FCC - Federal Communication Commission, which regulates the system in 2002 designating the UWB bandwidth of 7.5 GHz, a range that varies from 3.1 GHz to 10, 6 GHz. by setting the maximum power spectral density of operation in -41.3 dB / MHz, and defining the fractional bandwidth by 20%. The study starts of a structure of geometry in the form of stylized @, which evolves through changes in its form, in simulated commercial software CST MICROWAVE STUDIO, version 5.3.1, and then tested using the ANSOFT HFSS, version 9. These variations, based on observations of publications available from literature referring to the microstrip monopole planar antennas. As a result it is proposed an antenna, called Monopole Antenna Planar Spiral Almost Rectangular for applications in UWB systems - AMQEUWB, which presents simulated and measured results satisfactory, consistent with the objectives of the study. Some proposals for future work are mentioned / Este trabalho consiste na an?lise de uma estrutura de antena de microfita projetada para aplica??o em sistemas de banda ultra larga (ultra wideband UWB). Trata-se de um estudo prospectivo e anal?tico onde s?o experimentadas as modifica??es na geometria da antena, observando-se sua adequa??o aos objetivos propostos. Sabe-se que a antena UWB deve operar numa faixa de no m?nimo 500 MHz, e atender uma banda fracion?ria maior ou igual a 25%. ? desej?vel ainda, que a antena atenda ?s especifica??es de faixa determinadas pela FCC Federal Communication Commission, que em 2002 regulamentou o sistema UWB designando a largura de banda de 7,5 GHz, numa faixa que varia de 3,1 GHz a 10,6 GHz. fixando a densidade espectral de pot?ncia m?xima de opera??o em -41,3 dBm/MHz, e definindo a banda fracion?ria em 20%. O estudo parte de uma estrutura de geometria em forma de @ estilizada, que evolui atrav?s de modifica??es na sua forma, simuladas nos softwares comerciais CST MICROWAVE STUDIO, vers?o 5.3.1, e, em seguida, testado com o uso do ANSOFT HFSS, vers?o 9. Varia??es estas, com base em observa??es de publica??es dispon?veis na literatura, referentes a antenas de microfita monopolo planar. Como resultado ? proposta uma antena, denominada Antena Monopolo Quase-Espiral Planar Retangular para aplica??es em sistemas UWB AMQEUWB, que apresenta resultados simulados e medidos satisfat?rios, coerente com os objetivos do estudo. Algumas propostas para trabalhos futuros est?o citadas

The goal for this master thesis is to develop a prototype that uses ultra-wideband (UWB) communications to wirelessly transfer electrocardiogram (ECG) data from an ECG measurement unit to an Android device (smartphone or similar) which is used to process and display the ECG signals. The prototype should consist of two hardware nodes; (1) Node one having a ECG measurement unit (an AD8232 single lead heart rate monitor), an UWB communication module (a Decawave DWM1000 module) and a microcontroller (an Arduino DUE); and (2) Node two having an Android device (an Android smartphone), an UWB communication module (a Decawave DWM1000 module) and a microcontroller (an Arduino DUE). On Node one the AD8232 monitor for ECG measurements is connected to an analog input (with an analog to digital converter (ADC)) on the Arduino and the DWM1000 module is connected to the Arduino via serial peripheral interface (SPI). On Node two the DWM1000 is connected to the Arduino via SPI to receive ECG data from Node one, and the Arduino is connected to the smartphone through a serial USB cable with an USB on-the-go adapter to send the ECG data to the smartphone, where it is filtered and displayed with an Android application. The application has the potential to add, for example, ECG analysis for diagnosing heart activities with artificial intelligence (AI) and further transmit the ECG data for remote medical care. The Arduino is programmed in Arduino IDE (integrated development environment) to handle ECG measurements and UWB communications (transmitting and receiving ECG data), which is limited to a single UWB channel because of limitations of the DWM1000 module. The Android application is created using Android studio, and it can process (with a notch filter) and display 1-12 channel ECG. The prototype has been built and tested. The results show that a single lead ECG measurement can be sent via UWB communication to a smartphone to display in real time. Multiple data channels (1-12 analog inputs on the Arduino) can be multiplexed, transmitted and displayed in real time. This thesis concludes that UWB has huge development potential, and will likely be used for various wireless devices in the future.

Timing offsets result from the use of real clocks that are non-ideal in sampling intervals. These offsets also known as timing jitter were shown to degrade the performance of the two forms of UWB systems impulse radio and orthogonal frequency division multiplexing (OFDM)-based UWB. It was shown that for impulse radio, timing jitter distorts the correlation property of the transmitted signal and the resulting performance loss is proportional to the root-mean-square (RMS) value of the timing jitter. For the OFDM-based UWB, timing jitter introduced inter-channel interference (ICI) and the performance loss was dependent on the product of the bandwidth and the RMS of the timing jitter. A number of techniques were proposed for mitigating the performance degradation in each form of UWB. Specifically, for impulse radio, the methods of pulse shaping and sample averaging were provided, whereas for OFDM-based UWB, oversampling and adaptive modulation were given. Through analysis and simulation, it was shown that substantial gain in signal power-to-noise ratio can be achieved using these jitter-reduction methods.

No description available.

Millions worldwide cannot tell when their bladder is nearing total capacity. The catheter, a tube to empty the bladder, is a vital part of life for many people. A catheter is, however, not a comfortable option, and it is the most common cause of infection in people staying in hospitals. This thesis aims to make the process more comfortable and non-invasive. The proposed idea is to use a UWB radar system with Vivaldi antennas to monitor the bladder state. Research shows that UWB radars can see a difference between a full and an empty phantom bladder. However, current research that explores the usage of UWB radar systems to monitor the bladder state does not consider regulations other than the ones set by FCC. They also only perform experiments on a phantom bladder. This thesis investigates the practical viability of using a UWB radar system designed per the restricted regulations set by Post- och Telestyrelsen. The thesis includes the design, simulations,manufacturing, and testing of the antennas as well as the radar system. The goal was to test the system in both simulations, with a phantom model and with a human body as a target, to advance the current state of research and determine its practicality forreal-life applications. The simulations showed a significant difference in reflections between full and empty bladders. The measurements from the experiments showed a slight difference in amplitude as well, although not as great as predicted due to a longer pulse. The Vivaldi antennas performed as expected according to both theory and simulations and they should work as desired in further experiments that use a UWB radar to monitor the bladder state per the PTS regulations. This thesis is solely based on an original idea and has not been influenced or derived from any external company.

Along with rapid development of sensing and communication technology, Internet of Things (IoTs) has enabled a tremendous number of applications in health care, agriculture, and industry. As the fundamental element, the wireless sensing node, such as radio tags need to be operating under micro power level for energy autonomy. The evolution of electronics towards highly energy-efficient systems requires joint efforts in developing innovative architectures and circuit techniques. In this dissertation, we explore ultra-low power circuits and systems for micropower wireless sensing in the context of IoTs, with a special focus on radio interfaces and sensor interfaces. The system architecture of UHF/UWB asymmetric radio is introduced firstly. The active UWB radio is employed for the tag-to-reader communication while the conventional UHF radio is used to power up and inventory the tag. On the tag side, an ultra-low power, high pulse swing, and power scalable UWB transmitter is studied. On the reader side, an asymmetric UHF/UWB reader is designed. Secondly, to eliminate power-hungry frequency synthesis circuitry, an energy-efficient UWB transmitter with wireless clock harvesting is presented. The transmitter is powered by an UHF signal wirelessly and respond UWB pulses by locking-gating-amplifying the sub-harmonic of the UHF signal. 21% locking range can be achieved to prevent PVT variations with -15 dBm injected power. Finally, radio-sensing interface co-design is explored. Taking the advantage of RC readout circuit and UWB pulse generator, the sensing information is directly extracted and transmitted in the time domain, exploiting high time-domain resolution UWB pulses. It eliminates the need of ADC of the sensor interface, meanwhile, reduces the number of bits to be transmitted for energy saving. The measurement results show that the proposed system exhibits 7.7 bits ENOB with an average relative error of 0.42%. / <p>QC 20160412</p>

Thesis (PhD)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: This dissertation presents modal-based techniques for the effective systematic design of quadruple-ridged flared horns (QRFHs) as reflector feeds for radio astronomy applications. A new excitation technique is proposed, consisting of a quadraxial line that terminates in the quad-ridges through the back lid of the QRFH, which allows for the integration with differential low-noise amplifiers. An equivalent circuit of this quadraxial feed is presented that allows fast synthesis of optimal feeding designs for QRFHs. In addition, the quadraxial feeding network suppresses higher-order modes significantly. The effect of eliminating these unwanted modes are investigated and the quadraxial feed is shown to outperform the coaxial feed in the known detrimental aspects of the QRFH – beamwidth narrowing for increased frequency, beamwidth variation over the upper bandwidth, high cross-polarisation levels, high co-polar sidelobes and variable phase centre – for the specific QRFH designs. Ridge-loaded modes are analysed and a large number of cut-off frequencies presented which are unavailable in literature. The pure-mode excitation of the quadraxial feed allows more effective control over the modal content in the QRFH. This is exploited in a proposed design technique where the cut-off frequencies throughout the horn are used to synthesise the ridge taper profile, in order to achieve the desired modal distribution in the aperture. The proposed feeding solution is compact and therefore is also attractive for use with cryocoolers, typically employed with front-end electronics in telescopes for radio astronomy. A prototype was successfully manufactured and the mechanical implementation of the quadraxial feed proved to be much more simple than that of the conventional feed – consisting of a coaxial line realised within the thin ridges. / AFRIKAANSE OPSOMMING: Hierdie proefskrif stel modus gebasseerde tegnieke voor vir die effektiewe sistematiese ontwerp van viervoud gerifte oopgesperde horings (VGOHs) as weerkaatser voere vir radio astronomie toepassings. ’n Nuwe voertegniek word voorgestel, wat bestaan uit ’n kwadraksiale lyn wat termineer in die vier riwwe deur die agterkant van die VGOH, wat die integrasie met differensiële laeruis versterkers toelaat. ’n Ekwivalente stroombaan van hierdie kwadraksiale voer word aangebied vir die vinnige sintese van optimale voer ontwerpe vir VGOHs. Boonop onderdruk die kwadraksiale voer netwerk ook beduidend hoër orde modusse. Die effek van die uitskakeling van hierdie ongewensde modusse word ondersoek en die kwadraksiale voer oortref die gedrag van die koaksiale voer in die bekende nadelige aspekte van die VGOH – bundelwydte vernouing met toenemende frekwensie, bundelwydte variasie oor die boonste bandwydte, hoë kruispolarisasie vlakke, hoë kopolarisasie sybande en wisselvallige fase senter – vir die spesifieke VGOH ontwerpe. Rifgelaaide modusse word geanaliseer en ‘n groot aantal afsnyfrekwensies word aangebied wat nie beskikbaar is in literatuur nie. Die suiwermodus opwekking van die kwadraksiale voer bied meer effektiewe beheer oor die modusinhoud in die VGOH. Hierdie aspek word benut in ‘n voorgestelde tegniek waar die afsnyfrekwensies deur die horing gebruik word om die rif tapsheid profiel te sintetiseer, sodat die gewensde modale distribusie in die stralingsvlak behaal word. Die voorgestelde voer oplossing is kompak en daarom ook aantreklik vir die gebruik met krioverkoelers, wat tipies gebruik word met die voorkant elektronika in teleskope vir radio astronomie. ‘n Prototipe was suksesvol vervaardig en die meganiese implimentasie van die kwadraksiale voer toon dat dit eenvoudiger is as met die gebruiklike koaksiale voer – wat bestaan uit ‘n koaksiale lyn bewerkstellig binne die dun riwwe.

published_or_final_version / abstract / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

This thesis presents a novel antenna structure that satisfies the challenging requirements of an air coupled high speed ground penetrating radar (GPR). The desired GPR system is to achieve high spatial resolution and accurate inspection results while scanning at relatively high speed for highway pavement and bridge deck inspection. This work utilizes the Ultra Wide Band (UWB) antenna design to achieve both physical and electrical requirements imposed. The design procedure starts with a short survey to discuss typical UWB antennas used for GPR applications, and various tradeoffs of each type specifically when used for Air Coupled GPR applications. Our structure anatomy is presented, followed by a theory introduction that mainly focuses on achieving good impedance matching throughout the proposed antenna structure. A proof-of-concept MATLAB model is created to evaluate the preliminary physical dimensions that can achieve minimum reflections at antenna's feed point. These dimensions are then used in SolidWorks to create a 3D model that is imported later in HFSS to obtain accurate electromagnetic characteristics. Furthermore, fine tunings are performed to the antenna structure to optimize both gain and impedance matching. The SolidWorks 3-D structural model is finally used for antenna fabrication. The measurements recorded from the field experiments using the prototypes manufactured are compared to the simulation results confirming our initial findings. Both measurements and simulation results demonstrated very small reflection loss across the 700 MHz ~ 6 GHz frequency band with a very high directed gain and radiation efficiency.