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Recently there has been a significant amount of interest in the area of wideband and ultra-wideband (UWB) signaling for use in indoor wireless systems. This interest is in part motivated by the notion that the use of large bandwidth signals makes systems less sensitive to the degrading effects of multipath propagation. By reducing the sensitivity to multipath, more robust and higher capacity systems can be realized. However, as signal bandwidth is increased, the complexity of a Rake receiver (or other receiver structure) required to capture the available power also increases. In addition, accurate channel estimation is required to realize this performance, which becomes increasingly difficult as energy is dispersed among more multipath components. In this thesis we quantify the channel response for six signal bandwidths ranging from continuous wave (CW) to 1 GHz transmission bandwidths. We present large scale and small scale fading statistics for both LOS and NLOS indoor channels based on an indoor measurement campaign conducted in Durham Hall at Virginia Tech. Using newly developed antenna positioning equipment we also quantify the spatial correlation of these signals. It is shown that the incremental performance gains due to reduced fading of large bandwidths level off as signals approach UWB bandwidths. Furthermore, we analyze the performance of Rake receivers for the different signal bandwidths and compare their performance for binary phase modulation (BPSK). It is shown that the receiver structure and performance is critical in realizing the reduced fading benefit of large signal bandwidths. We show practical channel estimation degrades performance more for larger bandwidths. We also demonstrate for a fixed finger Rake receiver there is an optimal signal bandwidth beyond which increased signal bandwidth produces degrading results. / Master of Science

Nowadays high speed and high data rate communication are highly demanded. Consequently, wideband and high frequency transmitter and receivers should be designed. New transmitters and receivers should also have low power consumption, simple design and low manufacturing price in order to fulfill manufacturers’ requests for mass production. Having all above specifications, six-port correlator is a proper choice to be used as modulator and demodulator in transmitters and receivers. In this thesis the six-port correlator is introduced, modeled and simulated using Advanced Design System (ADS) software. A simple six-port transmitter/receiver system with a line of sight link is modeled and analyzed in BER, path length and noise terms. The modulation in this system is QAM, frequency is 7.5 GHz and symbol rate is 500 Msymbol/s. Furthermore two methods are proposed for high frequency and high symbol rate M-PSK and M-QAM modulation using six-port correlator. The 7.5 GHz modulators are modeled and simulated in ADS. Data streams generated by pseudo random bit generator with 1 GHz bandwidth are applied to modulators. Common source field effect transistors (FETs) with zero bias are used as controllable impedance termination to apply baseband data to modulator. Both modulators show good performance in M-PSK and M-QAM modulation.

The computational requirements of scientific research are constantly growing. In the field of radio astronomy, observations have evolved from using single telescopes, to interferometer arrays of many telescopes, and there are currently arrays of massive scale under development. These interferometers use signal and image processing to produce data that is useful to radio astronomy, and the amount of processing required scales quadratically with the scale of the array. Traditional computational approaches are unable to meet this demand in the near future. This thesis explores the use of heterogeneous parallel processing to meet the computational demands of radio astronomy. In heterogeneous computing, multiple hardware architectures are used for processing. In this work, the Graphics Processing Unit (GPU) is used as a co-processor along with the Central Processing Unit (CPU) for the computation of signal processing algorithms. Specifically, the suitability of the GPU to accelerate the correlator algorithms used in radio astronomy is investigated. This work first implemented a FX correlator on the GPU, with a performance increase of one to two orders of magnitude over a serial CPU approach. The FX correlator algorithm combines pairs of telescope signals in the Fourier domain. Given N telescope signals from the interferometer array, N2 conjugate multiplications must be calculated in the algorithm. For extremely large arrays (N >> 30), this is a huge computational requirement. Testing will show that the GPU correlator produces results equivalent to that of a software correlator implemented on the CPU. However, the algorithm itself is adapted in order to take advantage of the processing power of the GPU. Research examined how correlator parameters, in particular the number of telescope signals and the Fast Fourier Transform (FFT) length, affected the results.

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Ultra-wideband (UWB) communication new technology with ability to share the FCC allocated frequency spectrum, large channel capacity and data rate, simple transceiver architecture and high performance in noisy environments. Such communication advantages have paved the way for emerging wireless technologies such as wireless high definition video streaming, wireless sensor networks and more. This thesis examines orthogonal frequency coded surface acoustic wave (SAW) correlators for use in advanced UWB communication systems. Orthogonal frequency coding (OFC) and pseudo-noise (PN) coding provides a means for UWB spreading of data. The use of OFC spectrally spreads a PN sequence beyond that of CDMA because of the increased bandwidth; allowing for improved correlation gain. The transceiver approach is still very similar to that of the CDMA approach but provides greater code diversity. Use of SAW correlators eliminates many of the costly components that are needed in the IF block in the transmitter and receiver, and reduces much of the signal processing requirements. The OFC SAW correlator device consists of a dispersive OFC transducer and a wideband output transducer. The dispersive filter was designed using seven contiguous chip frequencies within the transducer. Each chip is weighted in the transducer to account for the varying conductance of the chips and to compensate for the output transducer apodization. Experimental correlator results of an OFC SAW correlation filter are presented. The dispersive filter is designed using seven contiguous chip frequencies within the transducer. SAW correlators with fractional bandwidth of approximately 29% were fabricated on lithium niobate (LiNbO3) having a center frequency of 250 MHz and the filter has a processing gain of 49. A coupling of modes (COM) model is used to predict the experimental SAW filter response. Discussion of the filter design, analysis and measurements are presented. Results are shown for operation in a matched filter correlator for use in an UWB communication system and compared to predictions.

Radio wave propagation measurements provide a way to accurately and reliably characterize environments to assist in the development and optimization of wireless communication systems. As digital radio systems occupy wider bandwidths and use multipath signal combining to enhance quality of service, knowledge of time dispersion and the multipath structure of radio channels become increasingly important. The wideband measurement system presented herein provides a practical means to precisely measure the delays and strengths of individual multipath components which arrive at a radio receiver. Presented in this Thesis are fundamental theory, practical implementation, and simulation models for a sliding correlator measurement system. The sliding correlator technique is explained in detail and large-scale measurement survey is presented. Techniques for statistically quantifying the characteristics of propagation using the sliding correlator measurements are presented and compared. The development of simulations of the sliding correlator system is described, and simulation results are used to test conventional and newly developed post-processing algorithms. This Thesis presents a practical view of the sliding correlator measurement system, but its foundations are rooted in the theoretical results which are explained and derived herein. Propagation researchers and students in the wireless communication field may find this work and the cited references useful for continued study of wideband propagation measurements or for application of the sliding correlator system as a wideband measurement solution. / Master of Science

International Telemetering Conference Proceedings / October 23-26, 2000 / Town & Country Hotel and Conference Center, San Diego, California / The Tracking and Data Relay Satellite System (TDRSS) Multiple Access (MA) Return Service provides a communication path that originates at a customer platform (either a spacecraft or other type of emitter) and is routed through a geosynchronous Tracking and Data Relay Satellite (TDRS) back to a customer control center or data acquisition location. Conventional operations provide Space Network (SN) customers with MA Service based on a schedule generated from user requests. The MA Service currently provides return link telemetry services to customer platforms with real-time, playback, and science data rates up to 100 kbps. This paper describes an integrated approach, using state-of-the-art technology and fault-tolerant architecture, to develop the next generation of TDRSS MA beamforming equipment. New designs will result in significant reduction in beamformer size and cost by at least an order of magnitude relative to the current MA equipment. This new equipment will provide the potential for increased usage of TDRSS MA services. The paper describes the in-development Demand Access (DA) Return Service that provides a new class of service using next generation technology.

Orientador: Michael John Brennan / Resumo: O principal problema em companhias de água são os vazamentos em tubulações subterrâneas, devido a sua limitada fonte de recursos hídricos. Correlacionadores de ruídos de vazamentos são usados frequentemente para localizar vazamentos. A detecção de sinais de ruídos de vazamentos ocorre por meio da coleta de dados por sensores, aos quais estão inseridos em lugares extremos ao da localização de um suposto vazamento. Estes dados são correlacionados, obtendo o atraso do tempo entre estes sinais de vazamento. Para converter o atraso do tempo em distância, a velocidade de onda do ruído de vazamento necessita ser conhecida, frequentemente, este tempo é estimado por meio de dados históricos de velocidade ou por tabelas. Usualmente a velocidade não é medida diretamente pelo tempo, sendo uma potencial fonte de erro. Esta tese estuda os fatores que afetam a velocidade de propagação do ruído de vazamento em tubulações de água subterrâneas. Eles envolvem as caraterísticas do filtrado do sistema sensor-tubulação e a potencial faixa de frequência onde o ruído de vazamento possa estar presente, e o efeito da banda de frequência na estimação do atraso do tempo. Os efeitos de distorção na precisão da estimativa do atraso do tempo, são também estudados com foco na quantização e corte dos sinais de vazamento. O efeito de quantização é devido a um convertedor analógico digital. O corte dos sinais de vazamento acontece quando a amplitude do sinal excede os limites do intervalo dinâmico da instrumen... (Resumo completo, clicar acesso eletrônico abaixo) / Doutor

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