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1 vol. various pagings : ill. / 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 Engineering, 1972

Thesis (Ph.D.) -- University of Adelaide, Dept. of Electrical Engineering, 1972.

Thesis (M.Sc.)--University of Adelaide, 1953. / Typewr. copy.

Thesis (Ph.D.)--University of Washington.

Most multi-mode microwave cavity filters exhibit insertion-loss characteristics which deviate widely from the theoretical responses on the low frequency side of the passband. This paper describes an X-band three-mode filter which inherently overcomes the primary cause of the response discrepancy. The design includes a method of identification of the field configurations within the cavity and a method of relating the coupling produced between two degenerate modes of resonance by a probe to the relative frequency shift caused by the probe. A simple method of measuring insertion loss is shown, and both theoretical and measured insertion loss characteristics are recorded for three bandwidths, 7.4 mc/s, 10.0 mc/s, and 13.6 mc/s, all of which show no extreme discrepancy between the theoretical and measured responses. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

The path of an electromagentic wave propagated through the earth's atmosphere depends upon the homogeneity of the atmosphere. For the well mixed condition, which is the case most of the time, the wave follows a straight or a smoothly curved path. However, if the atmosphere is not homogeneous, the wave may change direction abruptly along the path. It is shown that a simple model can be used to represent the propagation path. The model is shown to consist of a beam from the transmitter to the reflection point and from the reflection point to the receiver plus a beam which travelled directly from the transmitter to the receiver. Under well mixed atmospheric conditions, the direct path is straight, while under anomalous atmospheric conditions the direct beam is allowed to follow various sized parabolic paths. The angle of arrival of ten centimeter microwaves, for a 32.5 mile marine path, was recorded for the period from August 19 to August 26, 1955. The model was found to fit the recorded data for approximately ninety per cent of the points considered. An examination of the meteorological conditions during the period indicates that high temperature and low wind velocity are conducive to abnormal propagation, but that no direct correlation can be made between angle of arrival and meteorological data. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

An approximate method is presented for determining the reflection and transmission coefficients at the boundaries of isotropic inhomogeneous regions with one-dimensional arbitrary permittivity profiles in the direction of propagation. The method is based on replacing the permittivity profile by a number of simpler inhomogeneous segments for which exact solutions are available, and using the wave transmission matrix approach to the resulting stack of inhomogeneous slabs. An application of this method, using smooth piecewise-linear profile replacements, is made to several dissipative and non-dissipative transition regions for which the wave equation has exact analytical solutions. Prom a comparison of the approximate and exact results, it appears that the accuracy obtained by using this piecewise-linear method is good provided that the width of each linear segment is maintained less than .125 λ[subscript]sλ[subscript]s being the shortest wavelength along the segment. This method is therefore particularly suited to the treatment of rapidly and moderately varying transition regions; a definite improvement over other available methods which are either more tedious to apply or do not yield accurate results. In the case of slowly varying transitions a simpler approach to the problem, based on the theory of TEM wave propagation in a non-uniformly-loaded parallel-plate transmission line, is considered. An approximate solution is obtainable when the square of the reflection coefficient magnitude is much smaller than unity. The range of validity of the approximation made is assessed by comparing exact and approximate results obtained for certain forms of non-dissipative transitions. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

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