No description available.

The aims of this research work were to investigate the microwave properties of photoconductive semiconductor switches (PCSS), and how the properties might be used to optically control microwave and millimetre wave devices. Tunable devices (such as antennas, filters and metamaterials) have the ability to increase flexibility performance in multiband systems for example. In this thesis the performance of microwave switches from microstrip discontinuities, with high resistivity silicon dice placed cross the gaps were investigated. Under optical illumination, the electrons in silicon can be excited from the valence band to the conduction band. This photoconductivity in silicon has been employed to design a small microwave switch that can be operated using optical signal. The optically activated switch offers a wide range of applications. Potential applications have been demonstrated in integrating the microswitch in microstrip patch antenna, microstrip couple line filter, and Electromagnetic Band Gap (EBG) structures.

No description available.

A new simplified theory for analyzing printed strip monopole antennas, both with and without the parasitic elements is proposed. Also, the particular situation of a strip monopole fed by a coplanar waveguide (CPW) and surrounded by a rectangular ring has been considered. These antennas are proposed for wireless home link applications, which operated at the frequency of 5 GHz band. A new, simple space-domain integral equation for determining the current distribution on the printed strip monopole antenna on an infinite ground plane has been derived. By applying this integral equation, a simplified theory for analyzing the behavior of printed monopole antennas has been established. To demonstrate the validity of the theory, prototype antennas have been fabricated and tested. Discussions of the theoretical and measured results are presented.

No description available.

No description available.

Electromagnetic waves at microwave frequencies are strongly scattered by rain. Rain fade is the mechanism that limits the performance of terrestrial microwave telecommunication systems. To predict the Quality of Service (QoS) at a node in heterogeneous networks of line-of-sight, terrestrial, microwave links; requires knowledge of the spatial and temporal statistics of rain over scales of a few meters to tens or hundreds of kilometres, and over temporal periods as short as one-second. Current internationally recognised models are not able to predict QoS, even for an individual link. This project aims to produce a radio network simulator that will predict the correct first and second order joint, rain fade statistics on heterogeneousnetworks of arbitrary geometry.Meteorological radar databases provide rain rate maps over areas with a spatial resolution as fine as a few hundred meters and a sampling period of 2 to 15 minutes. Such two-dimensional, rain rate map time-series could be used to predict the QoS provided by arbitrary millimetre-wave radio networks, if the sampling period were considerably shorter i.e. of the order of 10 s or less. This work analyses the spatial and temporal rain rate variation by using data gathered as part of the Chilbolton Radar Interference Experiment (CRIE). Numerical algorithms have been developed to interpolate one, two and three dimensional (1D, 2D and 3D) rain rate fields to a finer sampling interval. A series of radar derived rain maps, with a 10 minute sample period, are interpolated to 10 seconds. Stochastic algorithms have been developed to preserve important statistics present in the CRIE data while introducing rain rates at new data points which preserve a priori statistics determined from other datasets. The resulting fine-scale spatial-temporal rain rate fields form the basis of a link simulation tool. The performance of several links is simulated and the simulation statistics are compared with international models and measured data.

The primary goal of this research work is to investigate the use of slot loading in reduced size planar fed microstrip patch antennas and develop new antenna structures based on this technique. At present, little theoretical investigation or design methodology exists to support the design of compact structures and research in this field is largely empirical. Moreover, little work exists on the use of planar fed designs. This necessitates a primary requirement to firstly address this knowledge gap. To facilitate this, a mathematical modelling technique that can be applied to such structures is developed. This is based upon the segmentation and Green's function approach. Using this model, the performance of slot loaded structures in terms of circuit characteristics including resonant frequency, input impedance, and Q factor is determined. Using this knowledge, a design procedure is established and subsequently used to provide a framework for the design of novel slot loaded antennas for specific applications. Several new slot loaded patch antenna configurations are designed that produce size reduction whilst allowing the use of a planar feed. The validity of the designs are confirmed through the use of commercial full-wave modelling software package Ensemble. Three linear polarised antennas are presented which are shown to achieve size reduction of 12, 40 and 55% respectively. Several compact circular polarised antenna structures are successfully implemented producing size reduction of up to 43%. A novel design for a reduced size antenna with a dual frequency response is also presented with a tuneable frequency ratio of between 1.03 — 2.0. Prototypes of the aforementioned antennas are fabricated and tested, and practical results are shown.

Bibliography : leaves 219-227 / xix, 227 leaves : ill ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Electrical and Electronic Engineering, 1993?

A model is developed which is capable of predicting the pressure field of a rectangular source, as measured by a finite-sized receiver. This novel method treats the problem in a new way, which allows an integration to be performed over the area of the receiver. Previously it has only been possible to model two circular transducers coaxially aligned. The model is used to identify a receiver, which can be used to measure the highly focussed pressure field from a phased array, with only a negligible effect due to the receiver size. Productions from the model are compared to experimental data, and show a good correlation. A parabolic mirror used to focus the field from a circular device in air has been studied, and a model developed to predict the pressure field produced by this device. This is done by an approximation of the mirror surface to a grid of finely spaced points. The model correlates well with measured results. In addition, an image of a defect in a solid sample was produced. Arrays are then used to image solid samples in air. This is done using three techniques. The first is a combined phased source and receiver, which is shown to locate a wire accurately and to measure a step in the surface of a sample. A 2-D array is shown to image a defect in a composite plate, and the potential for a fast through-transmission air-coupled system is indicated. In addition, two post-processing techniques are used on data recorded using an array receiver, to locate an object in air. Of these two techniques, ellipse crossing is shown to have better results for large signal to noise ratios, and SAFT for lower ratios. The combination of theoretical modelling and experimental observations has indicated that the transducers and arrays constructed for use in air are well-understood, and that their characteristics can be predicted.