State of the art filter bank structures achieve practically perfect reconstruction with very high computational efficiency. However, the increase in computational requirements due to the need to process increasingly wider band signals is paramount. New filter bank structures that provide extra information about a signal while achieving the same level of required efficiency, and perfect reconstruction properties, need to be developed. In this work a new filter bank structure, the interpolated FIR (IFIR) filter bank is developed. Such a structure combines the concepts of filter banks, and interpolated FIR filters. The filter design procedures for the IFIR filter bank are developed and explained. The resulting structure was compared with the non-maximally-decimated filter bank (NMDFB), achieving the same performance in terms of the number of multiplications required per sample and the overall distortion introduced by the system, when operating with Nyquist prototype filters. In addition, the IFIR filter is tested in both simulated and real communication environments. Performance, in terms of bit-error-rate, was found to not be degraded significantly when using the IFIR filter bank system for transmission and reception of QPSK symbols. / Master of Science

Software-defined radios have the agility and flexibility to tune performance parameters, allowing them to adapt to environmental changes, adapt to desired modes of operation, and provide varied functionality as needed.  Traditional software-defined radios use a combination of conditional processing and software-tuned hardware to enable these features and will critically sample the spectrum to ensure that only the required bandwidth is digitized.  While flexible, these systems are still constrained to perform only a single function at a time and digitize a single frequency sub-band at time, possibly limiting the radio's effectiveness. Radio systems commonly tune hardware manually or use software controls to digitize sub-bands as needed, critically sampling those sub-bands according to the Nyquist criterion.  Recent technology advancements have enabled efficient and cost-effective over-sampling of the spectrum, allowing all bandwidths of interest to be captured for processing simultaneously, a process known as band-sampling.  Simultaneous access to measurements from all of the frequency sub-bands enables both awareness of the spectrum and seamless operation between radio applications, which is critical to many applications.  Further, more information may be obtained for the spectral content of each sub-band from measurements of other sub-bands that could improve performance in applications such as detecting the presence of interference in weak signal measurements. This thesis presents a new method for confirming the source of detected energy in weak signal measurements by sampling them directly, then estimating their expected effects.  First, we assume that the detected signal is located within the frequency band as measured, and then we assume that the detected signal is, in fact, interference perceived as a result of signal aliasing.  By comparing the expected effects to the entire measurement and assuming the power spectral density of the digitized bandwidth is sparse, we demonstrate the capability to identify the true source of the detected energy.  We also demonstrate the ability of the method to identify interfering signals not by explicitly sampling them, but rather by measuring the signal aliases that they produce.  Finally, we demonstrate that by leveraging techniques developed in the field of Compressed Sensing, the method can recover signal aliases by analyzing less than 25 percent of the total spectrum. / Master of Science

Made available in DSpace on 2015-05-08T14:59:36Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 1565570 bytes, checksum: 641bee91a3e1ec7240272fff8310ca82 (MD5) Previous issue date: 2006-11-30 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / In this work it is discussed the improvement in the modal test for obtaining the Frequency Response Function (FRF) in low natural frequency structures by using as exciter an instrumented hammer. There are two conflicting needs in this kind of test: on the one hand, the low natural frequencies of the structure, which are usually associated with low damping, demand long acquisition time so that good resolution in the spectrum may exist. On the other hand, the sampling rate must be increased to correctly catch the short duration signal of the hammer. This leads to an elevated number of points in the signal to be acquired, and there may eventually be limitation on such number of points when using spectrum analyzers in the acquisition and obtaining of the FRFs. Thus, in this work, the selective decimation technique explored for the improvement of the test. The work includes the construction of a prototype with two degrees of freedom (S2GL) to serve as case study for the tests enabling the theoretical and experimental Frequency Response Functions (FRF) to be compared, as well as adjusting the parameters of the model. The MATLAB programming language was used for obtaining the FRFs. The efficiency of the improvement applied was verified through the frequency spectra, in which it was observed significant resemblance between the non-decimated FRF with the acquisition having a high number of points, and the decimated FRF with smaller number of points and selected so that it could preserve the correct detection of the hammer signal. / Neste trabalho discute-se o aprimoramento do teste modal para obtenção da Função Resposta em Freqüência (FRF) em estruturas de baixas freqüências naturais utilizando como excitador um martelo instrumentado. Há duas necessidades conflitantes neste tipo de teste: de um lado, as baixas freqüências naturais da estrutura, usualmente associadas com baixo amortecimento, requerem um tempo longo de aquisição para haver boa resolução no espectro. Por outro lado, a taxa de amostragem deve ser elevada para captar corretamente o sinal de curta duração do martelo. Isto leva a um número elevado de pontos no sinal a ser adquirido, havendo eventualmente limitação de tal número de pontos ao se utilizar analisadores de espectro na aquisição e obtenção das FRFs. Neste sentido, neste trabalho foi explorada a técnica de decimação seletiva para aprimoramento do teste. O trabalho inclui a construção de um protótipo com dois Graus de Liberdade (S2GL) para servir como objeto de estudo para os testes deste aprimoramento, permitindo assim, comparar as Funções Resposta em Freqüências (FRF) teóricas e experimentais, bem como ajustar os parâmetros do modelo. Utilizou-se da linguagem de programação MATLAB® para a obtenção das FRFs. A eficiência do aprimoramento empregado foi verificada através dos espectros de freqüência, onde observou-se uma significativa similaridade entre a FRF não decimada com a aquisição possuindo um número elevado de pontos e a FRF decimada com menor número de pontos e selecionada de modo a preservar a correta detecção do sinal do martelo.

This master thesis report presents the development of a geographical visualization system using taxi data. The system uses a large data base from a taxi company that have previously never used the data for visualization purposes. The taxi company requested a system that processes the data on a server on demand and visualizes it on a web client using heat map visualization as a primary visualization technique. The web client was supposed to be easy to use, provide deeper knowledge about the business of a taxi company and at the same time kept interactive with low latency for data requests. A big part of the thesis focuses on techniques for decimating an original data set to a smaller representational data set to be used for heat map visualization and sent to a web client from a server. The project continues by optimizing the system to keep latency to a minimum and finally developing a web client to explore the data. The result is a system with promising latency that is easy to use for exploring data and gaining a deeper knowledge about a taxi business.

This Master’s thesis deals with digital decimation filter design for undersampling and filtering of sigma-delta ADC signal. Filter cascade is designed in Matlab according to given requirements and is then described in VHDL language aiming for minimum area. Implemented filter functionality is compared to Matlab-generated reference filters in created verification environment. Finally the design is synthesized in specified technology and verified on gate level.

The doctoral thesis deals with development and design of novel architectures of digital filters for low-power integrated circuits. The main goal was to achieve optimum parameters of digital filters with respect to the chip area, power consumption and operating frequency. The target group of the proposed architectures are application specific integrated circuits designed for signal processing from sensors using delta-sigma modulators. Three novel architectures of digital filters optimized for low-power integrated circuits are presented in the thesis. The thesis provides analysis and comparison of parameters of the new filter architectures with the parameters of architectures generated by Matlab tool. A software tool has been designed and developed for the practical application of the proposed architectures of digital filters. The developed software tool allows generating hardware description of the filters with respect to defined parameters.

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Investigated in this thesis are the possibilities and effects of reducing CAN data collected from forklifts. The purpose of reducing the data was to create the possibility of exporting and managing data for multiple forklifts and a relatively long period of time. For doing that was an autoregressive filter implemented for filtering and decimating data. Connected to the decimation was also the aim of generating a data set that could be used for analyzing lift sequences and in particular the usage of fork adjustment functions during lift sequences. The findings in the report are that an AR (18) model works well for filtering and decimating the data. Information losses are unavoidable but kept at a relatively low level, and the size of data becomes manageable. Each row in the decimated data is labeled as belonging to a lift sequence or as not belonging to a lift sequence given a manually specified definition of the lift sequence event. From the lift sequences is information about the lift like number of usages of each fork adjustment function, load weight and fork height gathered. The analysis of the lift sequences gave that the lift/lower function on average is used 4.75 times per lift sequence and the reach function 3.23 times on average. For the side shift the mean is 0.35 per lift sequence and for the tilt the mean is 0.10. Moreover, it was also found that the struggling time on average is about 17 % of the total lift sequence time. The proportion of the lift that is struggling time was also shown to differ between drivers, with the lowest mean proportion being 7 % and the highest 30 %.

Master’s thesis belongs to the Cognitive radio network sphere. These networks utilize frequency spectrum more effectively than networks used in present radio communications. The Cognitive radio concept makes coexistence of classic and cognitive radio networks possible. Attention is aimed at spectrum sensing as the key task of the Cognitive radio. Main properties of the cyclostationary detector, as the detector, that reaches high probability of the detection at a very low signal to noise ratio with apriori knowledge of the transmitted signal's cyclic frequency, are examined in this paper. The OFDM signals, that inherit cyclostationarity from cyclic prefix, used in the real systems have been chosen for testing the properties of the detector. The influences of decimation and multipath propagation on the probability of detection are quantitatively expressed. The optimal values for the weights of the multicycle detector are determined.

The dissertation thesis deals with 3D reconstruction of the temporomandibular joint from 2D slices of tissue obtained by magnetic resonance. The current practice uses 2D MRI slices in diagnosing. 3D models have many advantages for the diagnosis, which are based on the knowledge of spatial information. Contemporary medicine uses 3D models of tissues, but with the temporomandibular joint tissues there is a problem with segmenting the articular disc. This small tissue, which has a low contrast and very similar statistical characteristics to its neighborhood, is very complicated to segment. For the segmentation of the articular disk new methods were developed based on the knowledge of the anatomy of the joint area of the disk and on the genetic-algorithm-based statistics. A set of 2D slices has different resolutions in the x-, y- and z-axes. An up-sampling algorithm, which seeks to preserve the shape properties of the tissue was developed to unify the resolutions in the axes. In the last phase of creating 3D models standard methods were used, but these methods for smoothing and decimating have different settings (number of polygons in the model, the number of iterations of the algorithm). As the aim of this thesis is to obtain the most precise model possible of the real tissue, it was necessary to establish an objective method by which it would be possible to set the algorithms so as to achieve the best compromise between the distortion and the model credibility achieve.