Over the years, phased array antennas have provided electronic scanning with high gain and low sidelobe levels for many radar and satellite applications. The need for higher bandwidth as well as greater scanning ability has led to research in the area of aperiodically spaced antenna arrays. Aperiodic arrays use variable spacing between antenna elements and generally require fewer elements than periodically spaced arrays to achieve similar far field pattern performance. This reduction in elements allows the array to be built at much lower cost than traditional phased arrays. This thesis introduces the concept of aperiodic phased arrays and their design via optimization algorithms, specifically Particle Swarm Optimization. An axial mode helix is designed as the antenna array element to obtain the required half power beamwidth and bandwidth. The final optimized aperiodic array is compared to a traditional periodic array and conclusions are made. / Master of Science

Power line communications (PLC) as applied to electrical power grid is known since long; however, PLC in microprocessors was recently introduced by VTVT Lab. Since power distribution network (PDN) inside a microprocessor is ubiquitous, therefore, any node inside a microprocessor can be accessed by attaching a simple communication circuit to it. The scheme is extremely attractive as it avoids the routing overhead of the data-path between an internal node and an I/O pin. A number of applications are possible for PLC in microprocessors such as on-line testing, monitoring/control of internal nodes, fault diagnosis etc. Feasibility of the PLC approach has been extensively studied by earlier researchers at VTVT. The feasibility studies investigated the frequency response of a microprocessor's PDN and looked for existence of passbands — frequency bands where signal attenuation through the PDN is small. Two different approaches were followed—the first approach employed analytical modeling of the high frequency characteristics of the PDN, while the second approach conducted measurements on Intel® microprocessors' PDN. Although, differences were observed in the results of the two approaches; both the approaches demonstrated existence of passbands, thus affirming the feasibility of the PLC scheme. This thesis presents a system level study conducted to estimate performance of the PLC scheme. Measurement results were used to model the PDN channel. The study provides useful insights for the design of microprocessor level PLC system. Specifically, the study estimates optimal pulse width required to maximize the system performance and the range of achievable data-rates. The study demonstrates that it is feasible to communicate data through a microprocessor's PDN without inducing large disturbances on the power line. The other work presented in this thesis is the design of low power receiver for microprocessor level PLC, also called data recovery block. The proposed design of data recovery block employs Correlation Detection (CD) receiver architecture. The design has been implemented in IBM 0.13 µm CMOS process and has been verified to operate reliably across Process, Voltage and Temperature variations. The design has a small foot-print of 300 µm x 160 µm and consumes 3.58 mW while operating from 1.2 V power supply. / Master of Science

Ultra-wideband (UWB) communication systems are highly promising because of their capabilities for high data rate information transmission with low power consumption and low interference and their immunity to multipath fading. More importantly, they have the potential to relieve the "spectrum drought" caused by the explosion of wireless systems in the past decade by operating in the same bands as existing narrowband systems. With the extremely large bandwidth of UWB signals, we need to revisit UWB channel modeling. Specifically we need to verify whether or not the traditional tap-line delay channel model is still applicable to UWB. One essential task involved in channel modeling is deconvolving the channel impulse response from the measurement data. Both frequency domain and time domain techniques were studied in this work. After a comparison, we examined a time domain technique known as the CLEAN algorithm for our channel modeling analysis. A detailed analysis of the CLEAN algorithm is given, as it is found that it is sufficient for our application. The impact of per-path pulse distortion due to various mechanisms on the tap-delay line channel model is discussed. It is shown that with cautious interpretation of the channel impulse response, the tap-line delay channel model is still applicable to UWB. / Master of Science

Yes / A microstrip line-fed wideband printed antenna is presented for radio detection of partial discharge (PD). The novel simple structure antenna has compact size of 24 × 20 × 0.16 cm3 (0.28λs × 0.23 λs × 0.002 λs) and suitable for radiometric PD wireless sensor nodes, where λs is the wavelength of the lowest frequency of the band (i.e., 0.35 GHz). The stepped and beveled radiation patch is used in combination with a slotted ground plane to achieve a wide fractional bandwidth of 119% (0.35 to 1.38 12 GHz) for a return loss better than 10 dB. Good radiation pattern characteristics are obtained across the frequency band of interest. The match between simulated and experimental results suggests that the design is sound and robust.

No / In this paper, low profile planar Metamaterial-Inspired coplanar fed waveguide antenna is presented for WLAN and Ultra-Wideband applications. The antenna is based on a simple strip loaded to a rectangular patch and zigzag E-shape metamaterial-inspired unit cell. The idea behind the proposed antenna is to enable miniaturization effect. The proposed antenna can provide dual band operation, the first one is a Wi-Fi band at 2.45 GHz having impedance bandwidth of 150MHz, the second one is an ultra wide band extended from 4.2 GHz to 6.5 GHz. Two antennas are designed and fabricated with and without metamaterial-inspired loading. The simulated and measured results regarding Return loss (S11), Gain and Radiation pattern are discussed.

No / A small dielectric resonator antenna has been designed for ultra wideband (UWB) communication system applications. The antenna element is a rectangular low permittivity ceramic block, with a dielectric constant of 9.4, and the modified T-shaped feed network includes a 50 ohm microstrip line to achieve strong coupling, and some bandwidth enhancement. The antenna performance is simulated and measured over a frequency band extending from 3100 MHz to 5500 MHz; the impedance bandwidth over this interval is 55.8% with VSWR <; 2, making the antenna suitable for UWB applications.

UWB communication is an attractive technology that has the potential to provide low-power, low-complexity, and high-speed communications in short range links. One of the main challenges of the UWB communications is the highly frequency-selective channel, which induces hundreds of overlapped copies of the transmitted pulse with different delays and amplitudes. To collect the energy of these multipath components, coherent Rake receivers are proposed, but suffer from high implementation and computational costs on channel estimation. To avoid the stringent channel estimation, several noncoherent receivers, including energy detector (ED) and transmitted reference (TR), are proposed at the cost of degraded performance. In addition, when taking into account practical issues of UWB communications, e.g., non-Gaussian impulsive noise, non-ideal antennas, and limited, significant performance degradation may be introduced by noncoherent receivers. In this dissertation, we will present low-complexity, high-performance, noncoherent receiver designs for UWB communications that i) avoid the stringent channel estimation; ii) lower the computational complexity of the existing receivers with the aid of advanced digital signal processing techniques; and iii) improve the error performance of the noncoherent receivers by accommodating practical imperfections. First, we propose three multi-symbol detectors (MSDs) for multi-symbol different detection (MSDD), which has recently caught attention in UWB communications because of its high performance without requiring explicit channel estimation. To alleviate the non-deterministic polynomial hardness (NP-hard) of MSDD, we analyze the statistical model of MSDD and propose an iterative MSD and two MSDs based on relaxation technique with near-optimal performance and low complexity. Moreover, the error performance of MSDs is further enhanced by exploiting joint soft-input soft-output MSDD and forward error correction codes. Next, we consider the non-Gaussian noise in the presence of multi-access interference, which is impulsive when the number of active users is small. To mitigate the impulsive noise effect, in this dissertation, we propose new differential UWB receivers based on the generalized Gaussian distribution and Laplace distribution and achieve better error performance. Another main issue of UWB communications is the limited radio coverage. To extend the coverage and improve the performance of UWB systems, we focus on a novel differentially encoded decode-and-forward (DF) non-cooperative relaying scheme. Putting emphasis on the general case of multi-hop relaying, we illustrate a novel algorithm for the joint power allocation and path selection (JPAPS), minimizing an approximate of the overall bit error rate (BER). A simplified scheme is also presented, which reduces the complexity to O(N²) and achieves a negligible performance loss. Finally, we concentrate on code-multiplexing (CM) systems, which have recently drawn attention mainly because they enable noncoherent detection without requiring either a delay component, as in TR, or an analog carrier, as in frequency-shifted reference. In this dissertation, we propose a generalized code-multiplexing (GCM) system based on the formulation of a constrained mixed-integer optimization problem. The GCM extends the concept of existing CM while retaining their simple receiver structure, even offering better BER performance and a higher data rate in the sense that more data symbols can be embedded in each transmitted block. Moreover, the impacts of non-ideal antennas on the GCM systems are investigated given some practical antenna measurement data and IEEE 802.15.4a channel environments.

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

To explore spectral opportunities in wideband regime for cognitive radio we need a wideband spectrum sensing receiver. Current wideband receiver architectures need wideband analog to digital converter (ADC) to sample wideband signal. As current state-of-art ADC has limitation in terms of power and sampling rate, we need to explore some alternative solutions. Compressive sampling (CS) data acquisition method is one of the solutions. Cognitive Radio signal, which is sparse in frequency domain can be sampled at Sub-Nyquist rate using low rate ADC. To relax the receiver complexity in terms of performance requirement we can use Modulated Wideband Converter (MWC) architecture, a Sub-Nyquist sampling method. In this thesis circuit design of this architecture covers signal within a frequency range of 500 MHz to 2.1 GHz, with a channel bandwidth of 1600 MHz. By using 8 parallel lines with channel trading factor of 11, effective sampling rate of 550 MHz is achieved for successful support recovery of multi-band input signal of size N=12.