<p>Theory, design and fabrication of a Surface Acoustic Wave (SAW) TV-IF filter is presented in this thesis. The filter is a linear phase bandpass filter with a passband extending from 41.25 to 47.25 MHz. Optimization techniques were used for designing the filter impulse response. Conventional photolithography was used for the device fabrication. The results obtained correspond very well to the theoretical design.</p> / Master of Arts (MA)

<p>The estimation of the direction of a plane wave incident upon a linear receiving antenna array and field-mapping techniques are considered in this thesis. The emphasis of the presentation is directed towards radar, and specific attention is given to the situation where the incident plane wave is corrupted by the effects of multipath propagation.</p> <p>First, the phenomenon of multipath and its experimental simulation are discussed. It is then pointed out how conventional linear array processing techniques fail in the presence of multipath propagation. These considerations lead us to consider other nonlinear array processing techniques.</p> <p>There are two such approaches considered. The first is the modification of statistical time series analysis to suit the array processing application. The Burg method and the least-squares (LS) algorithm developed by Ulrych and Clayton are two time-series methods which are discussed in detail. Results show that the Burg method is not applicable in this application, where it is shown that the LS algorithm behaves well at high SNR.</p> <p>The second approach considered is the maximum likelihood (ML) formulation. There are also two realizations of this approach which are discussed in depth. Both realizations are based on setting up the appropriate likelihood functions for the situation considered; then, the resulting structure is modified so that the required optimizations need only be performed in the specific parameter(s) of interest. This results in a more computationally efficient estimator.</p> <p>The first ML formulation discussed in applicable only to the specular multipath environment. In this situation, the direct and reflected signal components are symmetrically positioned in elevation about the normal of the array. This configuration results in a particularly simple estimator structure. The second ML formulation considered is the case where the individual signal components may be incident from arbitrary directions. The results indicate that both these ML methods perform better than the time-series techniques.</p> <p>The performance for each method is compared to the corresponding theoretical values. The results are checked by computer simulation and are validated by the use of an experimental multipath simulation system built during the course of this work.</p> / Doctor of Philosophy (PhD)

<p>This dissertation presents the adaptive interference cancelling procedure for use in multiple beam antenna systems. To constrain the processor from responding to a target signal, a set of orthogonal beams is used to provide the input data, and the main beam is excluded from the procedure for calculating the weights of the adaptive interference canceller. Two different adaptation algorithms are used to adjust the weights, namely, the LMS adaptation algorithm and the recursive algorithm based on Kalman filtering theory. To accelerate the convergence of the LMS algorithm, a procedure is devised to extrapolate the optimum weight vector after a short learning period.</p> <p>An adaptive interference cancelling scheme is described, and a new method (based on this scheme) is developed for elevation angle estimation in the presence of multipath, as encountered in low-angle tracking radar. The adapted weight provides information about the elevation angle through a calibration curve, which does not depend on signal and multipath parameters. Theoretical RMS error bounds on estimation on accuracy are determined for varying system and environmental conditions. These bounds are confirmed by means of computer simulation.</p> <p>Finally, the effect of misadjustment of the adaptive procedures and the effect of percentage error in the horizon reference on the estimation error are evaluated.</p> / Doctor of Philosophy (PhD)

<p>This thesis reports on the development and characteristics of an ion reflection spectrometer designed to operate in the 20 - 150 KeV range with specific application to near surface analysis of solids. The work is divided into two parts.</p> <p>Part I details the design, operation and calibration of the systems within the spectrometer. They include a high resolution electrostatic analyzer and a premium solid state detector cooled to provide an excellent resolution figure. Control of the spectrometer is via a small minicomputer programmed with machine language in a real-time operating environment. Both energy and geometrical calibration procedures as well as results are provided. Examples are given which illustrate the performance characteristics of the spectrometer. Various corrections to both ESA (eg. neutral component) and solid state detector (eg. pulse height defect) results are determined and applied where necessary.</p> <p>Part II shows the capabilities of the spectrometer as exhibited during the study of three areas of the medium energy ion-solid interactions. The first is an examination of the large angle scattering cross section behaviour for various incident ions (1 ≤ Z₁ ≤ 10) in gold layers. The results are compared to current theoretical predictions and experimental values. The second is an investigation of the neutralization of charged particles (1 ≤ Z₁ ≤ 10) as they exit from clean gold surfaces. Other experimental values, as well as various theories are discussed in relation to the observed results. The last study includes the determination of the stopping of light mass particles (H,He) in Au films. These values are obtained after the application of several corrections based on methods and results of the previous sections. The stopping powers are related to other experimental results.</p> <p>From the foregoing investigations, it is concluded that the state of medium energy ion-solid interactions is by no means as quantitative as in the higher energy regime. The energy loss processes and charge neutralization behaviour are not well understood so that there is a great need for reliable and accurate experimental measurements that can provide a solid foundation on which to base a better theoretical model of the processes involved.</p> / Doctor of Philosophy (PhD)

<p>This thesis presents a new methodology for describing adjoint network approaches to sensitivity calculations performed in various power system analysis and planning studies. Difficulties observed by previous workers regarding the exact modelling of some power network elements are overcome by proper techniques employed with special complex notation. A generalized version of the Tellegen's theorem-based approach is developed which provides the required sensitivities based on the exact a.c. load flow model for any chosen set of real and/or complex variables of practical interest. A theoretical consistency study is performed to allow proper modelling of adjoint elements for direct treatment of general complex functions. A simplified version with many desirable features is described for real function sensitivities. It employs a simple adjoint network. General sensitivity expressions common to all relevant power system studies are derived and tabulated. A new method for solving the load flow problem using Tellegen's theorem is described with several advantages claimed. A special elimination technique is used to describe the Newton-Raphson method for load flow solution in a compact complex mode. A complex version of the Lagrange multiplier approach is developed and applied to allow a general number of complex dependent variables to be defined in a particular problem. A generalized version of the class of methods of sensitivity calculations which exploit the Jacobian matrix of the load flow analysis in formulating the adjoint equations is developed. Generalized sensitivity expressions common to different modes of formulating power flow equations, e.g., cartesian and polar, are derived and tabulated for direct programming use. A unified comprehensive comparison between the Lagrange multiplier and Tellegen's theorem approaches to sensitivity calculations in electrical networks is presented.</p> / Doctor of Philosophy (PhD)

<p>This thesis addresses itself to two main veins of computer-aided design of electrical networks, namely, simulation and optimization. A critical review of the state of the art in simulation approaches to networks for analysis and sensitivity evaluation, design concepts and optimization algorithms, is presented. A new approach for the simulation and design of lumped networks in the time domain is presented. The approach is based on the transmission-line matrix method of numerical analysis. The exploitation of general simulators which can be used as a tool in the integrated design process of electrical networks is given with specific examples. A new approach for the analysis and design of cascaded networks has been developed. This approach proves to be efficient and very useful for sensitivity and tolerance analysis. The approach has also been generalized to 2p-port cascaded networks.</p> / Doctor of Philosophy (PhD)

<p>The advantages that wideband frequency modulation (FM) offers over amplitude modulation (AM) are minimum transmission power and better output signal-to-noise ratio. The discriminator in the FM receiver is important since its performance dictates the degree of capability of exploiting these advantages. Conventional FM discriminators are faced with limitations such as bandwidth of operation, linearity of conversion characteristics, dynamic range due to FM threshold, frequency of operation, reproducibility, reliability, and economics. These problems are caused by the basic restrictions found in the principle of operation, and the nature of the devices used to realize these discriminators. The subject of this thesis is to explain alternatives to overcome these problems.</p> <p>In the class of narrow band FM discriminators, we have suggested two discriminators whose operation is based on Surface Acoustic Wave (SAW) resonators, and SAW differential delay lines. For wide band FM discriminators we have developed a principle of operation based on a modified M-ary correlation receiver principle. The actual discriminator was realized with a system using a SAW chirped matched filter as the central signal processing element, and a zero-crossing detector technique is employed to minimize the errors in signal detection. The design and fabrication of a SAW chirp filter is discussed. A simple thin film technique to modify the aperture of an interdigital transducer (IDT) in order to obtain the required frequency response is explained and verified experimentally. To prove the principle of operation, a discriminator operating at 70 MHz with a bandwidth of 18 MHz has been produced. The performance evaluation of the device shows the linearity to be better than 1.8% over the bandwidth. The FM threshold occurs at -3 dB of input carrier-to-noise ratio. The parameters and measurement techniques employed to evaluate the noise performance of the chirp filter are explained, and the capability of the principle of operation for further extension of the FM threshold is explained. Finally, as applications we have proposed a multi-frequency position modulation modem. The principle of operation and implementation of this modem is discussed. In addition, applications to dual modulation schemes, such as pulse amplitude modulation - frequency modulation (PAM-FM), and applications to instrumentation systems, are also discussed briefly.</p> / Doctor of Philosophy (PhD)

<p>A review of Walsh Spectral Analysers (WSA) using direct and fast transform methods is presented. A serial processor is developed that uses long shift registers to perform a Hadamard transform. This is extended by adding additional hardware to yield coefficients in dyadic and sequency order. Incoming data is thereby stored in a permuted manner, followed by sequential retrieval and transfer to a Hadamard transform processor. This scheme is faster than an earlier processor described by Geadah and Corinthios. Also a new pipeline structure with identical stages is evolved.</p> <p>The design of a Microprocessor-based Walsh-Fourier Spectral Analyser is given in detail. It uses an off-the-shelf single board microcomputer System 80/10 in conjunction with a special purpose board. The latter includes A/D conversion circuitry, a direct memory access controller, and a frequency multiplication module (FMM). The purpose of FMM is to generate 2ᵐ sampling pulses (64 in the system built) within one cycle of the input signal; this feature is required to compute the Fourier/Walsh coefficients of a periodic signal without leakage error. The new FMM circuit is a substantial improvement over earlier designs and permits a higher frequency of operation at a low clock frequency.</p> <p>Two methods (one by Siemens and Kitai and the other by Tadokoro and Higuchi) of Walsh to Fourier conversion are reviewed. The conversion process is compared with the Cooley-Tukey FFT methods with respect to the number of multiplications, memory requirements, and effects of finite word length in computation.</p> <p>The Walsh to Fourier conversion process is implemented through software to obtain 64 sine and cosine components. The instrument is interfaced to a HP 2647A intelligent graphic terminal for the display of Walsh and Fourier coefficients.</p> / Doctor of Philosophy (PhD)

<p>The problem of on-line identification of linear multivariable discrete-time systems from input-output data is considered. A study has been made of the relative effectiveness of the four different models used in the area of identification of linear multivariable systems (transfer-function matrix, impulse response matrix, input-output difference equation and state space). The features of each model and its effect on the complexity of the identification algorithm as well as the bias of the paramter estimates while using the ordinary least-squares method have been studied. Different on-line algorithms have been proposed for the identification of the given system directly in each of the four different model representations. These algorithms estimate the parameters of the system from noisy measurements and no knowledge of the noise characteristics is required. The identification of a given multivariable system has been deccomposed into the identification of m subsystems (where m is the number of outputs) and the parameters of each subsystem are estmated independently from each other. The problem of structure determination has been considered, and algorithms have been proposed for the estimation of the structural parameters of the transfer-function matrix and the state space representations from noise-free as well as noisy measurements. Also, a two-stage bootstrap algorithm has been derived for combined parameter and state estimation of linear multivariable systems.</p> / Doctor of Philosophy (PhD)

<p>This thesis examines the transmission and reception of coherent phase shift keyed signals (CPSK) over band-limited nonlinear satellite channels in a noisy environment. First, we analyzed the performance of M-ary CPSK signals transmitted over band-limited nonlinear satellite channels in the presence of uplink additive Gaussian noise and down-link additive Gaussian noise. An expression for evaluating the exact probability of error is derived for the case of a general satellite transponder model and then this expression is applied to specific transponder models to obtain numerical results.</p> <p>Secondly, we have derived bounds on the symbol error probability for binary CPSK signals transmitted over band-limited satellite channels in the presence of uplink and downlink thermal noise. These bounds can be evaluated using previously known error probabilities for wideband channels. Numerical results are evaluated and compared with those results computed using the exact error probability expressions. The advantage of these bounds is that they can be evaluated knowing only the peak value and variance of the intersymbol interference (ISI), and the bounds appear to yield reasonably accurate approximations to the exact error probabilities when ISI is not too large. Also, a computationally efficient technique is derived to evaluate the error probabilities for binary CPSK signals transmitted over a wideband piece-wise smooth saturating channels.</p> <p>Finally, the optimal reception of binary CPSK signals over band-limited nonlinear satellite channels is investigated. A receiver structure, similar to a decision feedback receiver for linear channels, is derived to combat the ISI effect. The performance is evaluated by computer simulation techniques and it is shown that the receiver performs significantly better than the single sample sign detector. Also, it is shown that the single sample sign detector yields optimum decisions for wideband hard-limited channels.</p> / Doctor of Philosophy (PhD)