Bibliography: leaves 94-96. / This thesis describes the development of a low-cost microwave electronic distance measurement instrument using the Tellurometer phase-measurement principle. In a simplified form the instrument can be configured as a full-duplex 9 600 Baud datalink. The Tellurometer was invented in 1957 by the late Dr. Trevor Wadley of the National Institute of Telecommunications Research. Since then there has been a continuous development of Tellurometers that are used world-wide in the surveying profession. Sophisticated instruments are now available, but this development has been accompanied by increased costs and complexity. There is a growing need in underdeveloped countries for a simple low-cost microwave Tellurometer with good performance and maintainability. These countries survey with low budgets and cannot afford expensive equipment and do not necessarily require all the features and performance of today's instruments. To meet this need it has been the objective of this work to develop a Tellurometer with a range of 1O m to 15 km, with an accuracy in the order of 3 cm, and to keep the materials cost to within R700 per instrument. This has been reached by reducing circuit complexity, current consumption, and cost to a minimum, without compromising the required performance. Only essential features have been included, except where their inclusion has not compromised the cost. The use of a single -chip microprocessor, a simple narrow-band pattern-synthesiser, a low-cost microwave source, low-power technology and a very simple mechanical arrangement has resulted in a cheap simple instrument. Built-in test features of the software allow sophisticated maintenance with a minimum of test equipment.

Bibliography: leaves 194-198. / The following dissertation considers the single-scan two-dimensional positional accuracy of a pulsed surveillance radar. The theoretical aspects to the positional accuracy are considered and a generalized analytical approach is presented. Practical position estimators are often complex, and theoretical predictions of their performance generally yield unfriendly mathematical equations. In order to evaluate the performance of these estimators, a simulation method is described based on replicating the received video signal. The accuracy of such a simulation is determined largely by the accuracy of the models applied, and these are considered in detail. Different azimuth estimation techniques are described, and their performances are evaluated with the aid of the signal simulation. The best azimuth accuracy performance is obtained with the class of analogue processing estimators, but they are found to be more susceptible to interference than their binary processing counterparts. The class of binary processing estimators offer easily implemented techniques which are relatively insensitive to radar cross-section scintillation characteristics. A hybrid estimator, using both analogue and binary processing, is also evaluated and found to give an improved accuracy performance over the binary processing method while still maintaining the relative insensitivity to radar cross-section fluctuation.

The design of Broadband, Low-Noise and Power Microwave Amplifiers using microstrip softboard technology is investigated. The software program TOUCHSTONE (TM) by EEsof is used extensively as a basic design tool. The characterisation of the GaAs Field Effect Transistors, used for the amplifiers, is carried out. These characterisations are then used by the program in its circuit analysis. A determination of the validity of using the manufacturer's data, for the designs, is determined by comparing it to the measured data. Source-Pull and Load-Pull measurements were performed for the Power GaAs FET characterisation. The noise-parameter device characterisation is carried out in a similar way to that for Load-Pull data. Each amplifier required final tuning adjustments in order to peak the performances. The Broadband Maximum Gain Amplifier had a 10 ± 1.5dB gain over a bandwidth from 2- to 6-GHz. The Low-Noise amplifier achieved 5dB Noise-Figure and 5.4 ± 1. 4dB gain over the 2- to 6-GHz band. The Power amplifier Output Power was 390mW over the 3.7- to 4.2-GHz band. Techniques of broadband matching are investigated, with Double-Stub matching producing the widest bandwidth. A literature survey is presented on aspects of broadband microwave amplifiers, as well as a survey on Computer-aided-design at microwave frequencies and techniques of Large-Signal Transistor characterisation.

Includes bibliographical references (leaves 101-105). / This thesis describes the design and implementation of a low-cost high speed data capture card for the Hubble Sphere Hydrogen Survey (HSHS). The Hubble Space Hydrogen Survey was initiated in an effort to build a low-cost cylindrical radio telescope for an all sky redshift survey with the observational goal to produce a 3-dimensional mapping of the bulk Hubble Sphere using Hydrogen 21cm emissions. This dissertation ï¬ rst investigates the system design to see how each of the user speciï¬ cations set by the planning team could be achieved in terms of design decisions, component selection and schematic capture. The final design. AstroGIG, satisï¬ es the user speciï¬ cations by capturing data up to a full power bandwidth of 1.7GHz with an instantaneous bandwidth of ≤ 250MHz white maximizing the dynamic range. AstroGIG buffers, processes, stores and ï¬ nally transmits the data through a 4-lane PCI-Express interface to a standard PC where the majority of the processing is performed. The system implementation is then described where issues relating to the process of transforming schematics into a physical PCB, and HSHS integration are discussed. The design is veriï¬ ed through Hyperlynx simulations to give a high degree of certainty that physical implementation and production would be successful. Results from tests on the actual hardware characterizing the overall system performance are presented. Conclusions are drawn based on these results and suggestions for future work and design improvements are recommended.

Bibliography: leaves 71-73.

Bibliography: leaves 152-157. / Novel methods for prewarping filter specifications prior to realization. in Switched Capacitor (SC) form are presented. These allow the design of arbitrary response requirements, exhibiting a low amount of error that normally results from the frequency warping associated with sampled-data networks. Adjustment is applied to the pole and zero locations of a reference filter, using three distinct approaches (Center frequency "CF", Selectivity "S" and Complex Mapping "CM" pole/zero prewarping), developed for both the Lossless Discrete Integrator (LOI) and Bilinear (Bil) analog to digital transformations. The derivation of the prewarping expressions is explained with reference to these mappings, and the effect they have on the apparent pole and zero locations of an SC filter realization.

Includes bibliography. / Two new hybrid companding delta modulators for speech encoding are presented here. These modulators differ from the Hybrid Companding Delta Modulator (HCDM) proposed by Un et al in that the two new encoders employ Song Voice Adaptation as the basis of the instantaneous compandor, rather than Constant Factor adaptation. A detailed analysis of the performance, both objective and subjective, of these hybrid codecs has been carried out. Results show that overall the two codecs developed as part of this project are better than the HCDM codec. In addition the new codecs offer simpler implementation in digital hardware than the HCDM. A Computer Aided Test (CAT) system has been developed to simplify the design and test processes for speech codecs.

Includes bibliographical references. / Harmonic distortion of three phase power systems is caused by large amounts of electric power consumers using power electronic installations (e.g. drives and rectifiers). It has a number of undesirable consequences and has become an increasingly important problem with the rapid growth and ready availability of the power electronic devices and installations. A famous mathematical technique called "symmetrical components" was used to model the fundamental components of three phase systems. This method was extended to various harmonics. The aim of this thesis is to measure both the magnitude and phase angles of various harmonics which exist in three phase power systems, and to express them in symmetrical components. A digital electronics and microprocessor-based instrument was designed and constructed using the novel signal modulation technique called "+1 and -1" which was developed by the author of this thesis. This instrument was employed to achieve the above objectives.

Bibliography: leaves 175-177. / This thesis is concerned with Gallium Arsenide Metal Semiconductor Field Effect Transistor Microstrip Integrated Circuit Dielectric Resonator Oscillators (GaAs MESFET MIC DROs) - the different types, their design and their performance compared to other high Q factor (ie narrowband) microwave oscillators. The thesis has three major objectives. The first is to collate the information required to build microwave DROs. The second is to present the practical results obtained from Dielectric Resonator Bandreject and Bandpass filters (DR BRFs and DR BPFs). The last is to present and compare results from a DR stabilised microstrip oscillator and three types of series feedback DROs. Narrowband oscillators are usually evaluated in terms of their frequency stability, reliability, size, cost, efficiency and output power characteristics. In terms of these parameters DROs outperform Gunn cavity oscillators and are only bettered by crystal locked sources in terms of frequency temperature stability and long-term stability. The components of a GaAs MESFET MIC DRO possess ideal properties for the construction of a narrowband source with the exception of the long term stability of the GaAs MESFET. GaAs MESFET•DROs have the best published DRO results for efficiency, output power, power temperature stability and external Q factor. Basic oscillator theory derived by Kurokawa can be applied to both negative resistance and feedback oscillators. Impedance locus, device-line and operating point concepts provide a convenient framework for understanding hysteresis in microwave oscillators. The work by Kurokawa can also be translated into the S-parameter domain which has proved convenient for the design of microwave oscillators.

Includes bibliographical references. / The work in this thesis is primarily directed toward the design, construction and testing of an experimental multilevel partial response signalling baseband system. The system will find practical application in existing frequency division multiplexed-frequency modulated microwave links. The basic supergroup bandwidth of these links is 240 kHz. The design requires a transmission rate of 1.024 Mb/s in this bandwidth. Class-4 15 partial response signalling is the coding technique suitable to achieve this. A pilot tone scheme is used to facilitate symbol timing recovery at the demodulator. A sixth order Butterworth low pass filter approximates the ideal raised-cosine Nyquist channel. A theoretical discussion on impairments caused by deviation from this channel is given. Since the experimental system was non-ideal, it produced a degradation in the channel signal to noise ratio. This degradation, coupled with other factors, showed that further development was necessary for the system to be suitable for connection into an existing microwave link.