published_or_final_version / Electrical and Electronic Engineering / Master / Master of Philosophy

Thesis (M. Phil.)--University of Hong Kong, 1997. / Includes bibliographical references (leaf 98-101).

M.Ing. / Pulse Compression is a technique that may be employed for the generation of extremely high amplitude current and voltage pulses. These pulses can be as short as 50 to 100 ns, and may have amplitudes in the kiloampere and kilovolt ranges. Pulse Compression entails the compression of relatively "flat" pulses in the time domain, to pulses of very high amplitudes and extremely short duration. The pulse amplitudes and durations necessary to be achieved in this research, lie in the range where the switching speeds and other parameters of semiconductors are inadequate and where even the working life of conventional gas discharge apparatus are drastically reduced by the extreme switching demands. The burden of excessively high current densities and unmanageable current rise-rates can be transferred from the semiconductor switches to electromagnetic switches, by making use of pulse compression. Pulse compression can be carried out simultaneously or separately for the compression of the current or voltage content of pulses derived from slowly switched sources, to obtain pulses of extremely short duration and very high amplitudes. The main theme of this dissertation is Current compression. Current compression is accomplished through series-resonance in capacitors and saturable inductors connected in a transmission-line configuration. Energy is transferred in this process from one stage to the next, with reduction in pulse-time in each successive stage and a commensurate increase in amplitude. The generated pulses can attain gigawatt amplitudes and nanosecond durations, whilst loading on the semiconducting switches remains low. In addition to design of the pulse-compressor proper, the work also includes design and development of a voltage-controlled pulse power supply, suitable for generating the initial pulses which are to be compressed. Multistage pulse compression is based on the non-linear characteristics of saturable inductors. Dynamic analogue-time simulation is indispensable in a study thereof, as new theory has to be validated and because non-linear analysis is complex and capable only of being executed by employing approximation methods. Because of the difficulties involved, a considerable amount of attention has been devoted to the development of suitable analogue-dynamic simulation programs for execution on a digital computer. A numerical technique has been developed to express non-linear parameters in differential form. This technique makes it possible to model and simulate virtually any non-linear, physically realizable lumped parameter system with ease. The program is based on State Space techniques and has been developed for its versatility, to accomplish the simulation of a wide variety of circuit configurations.

Thesis (Ph. D.)--Florida State University, 2003. / Advisor: Dr. Frank Gross, Florida State University, FAMU-FSU College of Engineering, Dept. of Electrical and Computer Engineering. Title and description from dissertation home page (viewed Oct. 3, 2003). Includes bibliographical references.

by Wai Ho Mow. / Thesis (Ph.D.)--Chinese University of Hong Kong, 1993. / Includes bibliographical references (leaves 116-124). / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Spread Spectrum Technique --- p.2 / Chapter 1.1.1 --- Pulse Compression Radars --- p.3 / Chapter 1.1.2 --- Spread Spectrum Multiple Access Systems --- p.6 / Chapter 1.2 --- Definitions and Notations --- p.8 / Chapter 1.3 --- Organization of this Thesis --- p.12 / Chapter 2 --- Lower Bounds on Correlation of Sequences --- p.15 / Chapter 2.1 --- Welch's Lower Bounds and Sarwate's Generalization --- p.16 / Chapter 2.2 --- A New Construction and Bounds on Odd Correlation --- p.23 / Chapter 2.3 --- Known Sequence Sets Touching the Correlation Bounds --- p.26 / Chapter 2.4 --- Remarks on Other Bounds --- p.27 / Chapter 3 --- Perfect Polyphase Sequences: A Unified Approach --- p.29 / Chapter 3.1 --- Generalized Bent Functions and Perfect Polyphase Sequences --- p.30 / Chapter 3.2 --- The General Construction of Chung and Kumar --- p.32 / Chapter 3.3 --- Classification of Known Constructions ...........； --- p.34 / Chapter 3.4 --- A Unified Construction --- p.39 / Chapter 3.5 --- Desired Properties of Sequences --- p.41 / Chapter 3.6 --- Proof of the Main Theorem --- p.45 / Chapter 3.7 --- Counting the Number of Perfect Polyphase Sequences --- p.49 / Chapter 3.8 --- Results of Exhaustive Searches --- p.53 / Chapter 3.9 --- A New Conjecture and Its Implications --- p.55 / Chapter 3.10 --- Sets of Perfect Polyphase Sequences --- p.58 / Chapter 4 --- Aperiodic Autocorrelation of Generalized P3/P4 Codes --- p.61 / Chapter 4.1 --- Some Famous Polyphase Pulse Compression Codes --- p.62 / Chapter 4.2 --- Generalized P3/P4 Codes --- p.65 / Chapter 4.3 --- Asymptotic Peak-to-Side-Peak Ratio --- p.66 / Chapter 4.4 --- Lower Bounds on Peak-to-Side-Peak Ratio --- p.67 / Chapter 4.5 --- Even-Odd Transformation and Phase Alphabet --- p.70 / Chapter 5 --- Upper Bounds on Partial Exponential Sums --- p.77 / Chapter 5.1 --- Gauss-like Exponential Sums --- p.77 / Chapter 5.1.1 --- Background --- p.79 / Chapter 5.1.2 --- Symmetry of gL(m) and hL(m) --- p.80 / Chapter 5.1.3 --- Characterization on the First Quarter of gL(m) --- p.83 / Chapter 5.1.4 --- Characterization on the First Quarter of hL(m) --- p.90 / Chapter 5.1.5 --- Bounds on the Diameters of GL(m) and HL(m) --- p.94 / Chapter 5.2 --- More General Exponential Sums --- p.98 / Chapter 5.2.1 --- A Result of van der Corput --- p.99 / Chapter 6 --- McEliece's Open Problem on Minimax Aperiodic Correlation --- p.102 / Chapter 6.1 --- Statement of the Problem --- p.102 / Chapter 6.2 --- A Set of Two Sequences --- p.105 / Chapter 6.3 --- A Set of K Sequences --- p.110 / Chapter 7 --- Conclusion --- p.113 / Bibliography --- p.124

In this thesis, the pulse diversity technique in radar systems in high clutter environments is investigated. In this technique, different pulse compression methods are used in each pulse in the transmitted burst to increase the unambiguous range. In pulse diversity, the design of filters used in the receiver is as important as designing the transmitted waveform. At the output of pulse-burst filter that processes pulse-by-pulse, as many channels as the pulses in the burst occur. Each of these channels is matched to a certain range interval. In order to improve the detector performance, the phase codes used in the transmitted pulse-burst waveform and their corresponding filters must have good auto-correlation and cross-correlation properties, either individually or as their sum. In the literature some phase codes, having mentioned properties, are present. However, the performance of these codes in radar applications is not fully evaluated. The studies in the thesis show that the codes in the literature cannot be used directly in radar applications. In the scope of thesis, optimization criteria suitable for radar applications are defined and applied according to the mentioned requirements. Then, the obtained phase codes are tested in the radar simulator and the obtained results of the simulations are evaluated.