Incremental usage of mobile devices demand a new generation of wireless networks (5G) to provide faster data rates, more reliable coverage, monitor city infrastructure usage, and increase network capacity. The frequencies proposed for the upcoming 5G network would result in shorter broadcast distances and network dead zones, countered by incorporating transparent antennas into glass high rises. Transparent antennas possess, however a major challenge: low gain. This lower gain can be countered by means of employing antennas in an antenna array, boosting the gain and even giving the array the ability to beam form for the upcoming 5G network. The 5G dead zones can be countered with strategically placed transparent reflectors embedded into the glass surfaces of city high-rises. This dissertation shows there are significant effects due to the transparent antennas’ carrier concentration and film thickness. Changes in film conductivity and thicknesses results in shifts for filter and antenna resonances. A 4x1 GZO antenna array was constructed to operate at 5.8 GHz, and the results show approximately 10dBi of lower aperture gain between a copper version of the array and the GZO version of the array. However, the 4x1 GZO array shows an approximate 12dBi increase in gain over a single GZO antenna element. The technology developed in this dissertation has a broader impact other than for smart cities and the upcoming 5G network. Transparent antenna arrays offer sight insensitive military communication systems and eye-worn medical and commercial devices to monitor eye health and other various health signs.

This compendium contains twenty - nine refereed papers written over a period of just over forty years between 1963 and 2004. Of the total, twenty - three are full papers and six are short papers. Eighteen of them were published in international journals and eleven appeared in Australian journals. Eighteen are single author papers written by the candidate and in the remaining eleven, authorship is shared with two or more others. In instances where there are multiple authors I have indicated the portion that I claim as my own contribution. To some extent this must necessarily be subjective ; joint authors engaged in a common enterprise will usually discuss their work as it proceeds and afterwards it is not always easy to pinpoint exactly who was responsible for what amid the synergy of their interaction. The common thread that binds the papers is engineering electromagnetics and in most instances they directly address topics in either the guided and unguided wave domains, although in three instances the connection is more derivative. During my professional career I have produced a considerable number of limited circulation reports either for use within the agency in which I was employed or as the deliverables in contracts for which the agency had been contracted, as well as a number of conference papers. Of these two classes I no longer have any accurate record but a number of the papers later formed the basis of contributions to the refereed literature. Those offered for examination here are about half that number. I have subdivided the papers over nine sections bound together by some common sub - theme. A brief review is provided by way of introduction to each section and preceding each paper I have added some further comments. In these I have attempted not to simply restate information better accessed by reading the paper itself but to set it in context with other work and to indicate what its contribution to the technology of the time of its writing is seen to have been. This is of some importance in a compendium that spans so long a time. What is state of the art at one time is bedded down technology at some later date or its importance has been eclipsed by the appearance of other radically newer approaches. It is, however, the candidate ' s hope to be judged at least in part on the basis of the significance of the work at the time of its publication. Independently of the category into which I have placed any paper, a general aim that I have tried to carry with me in all my work is as close an appeal to physical principles as possible and not treat problems as solely mathematical exercises. How successful this has been is, of course, for others to judge. However it is only seldom that any real world problem can be solved without simplifying approximations and, particularly where the aim is understanding, simplicity is frequently at least as important as accuracy. Papers that appear in this compendium have been chosen to illustrate these aims. / Thesis (D.E.)--School of Electrical and Electronic Engineering, 2004.

In this thesis, two new types of electrically small feed antennas, slotted circular waveguide feeds, and microstrip dipole feeds are designed and studied for prime focus reflectors. The existing electrically small feeds used in prime focus reflectors exhibit some limitations such as asymmetrical radiation patterns, complex integration with microwave devices, requirement of struts support, and high cost. The design of these two new kinds of feeds is of particular interest since they provide symmetrical radiation pattern, and are low profile, easy to fabricate, simpler to mount on the reflector system, and low cost. Circular waveguide feeds have been a good choice for prime focus reflector systems. The main drawback of these feeds is that the E- and H-plane radiation patterns are not equal in small diameter apertures, and hence the reflector efficiency is low. In this report, an attempt is made to equalize the radiation patterns of these feeds, by slotting their wall at the open-end. Even though radiation pattern equalization is possible with these feeds, the efficiency remains still low. Therefore, chokes are introduced with the slotted waveguide feeds to improve the radiation characteristics as well as the efficiency. Slotted circular waveguides with a cavity is also studied, where slots are used as additional parameters, to equalize their radiation patterns, and hence increase the efficiency. In the second part of the thesis, microstrip dipole feeds are studied because of their light weight, low aperture blockage and ease of assembly on the reflector system. These feeds are designed for backward radiation and thus eliminate strut support. Parametric studies are conducted to improve the input impedance, miniaturize the antenna, and design for dual frequency operation. All these feeds have unequal E- and H-plane radiation patterns. Therefore, they are candidates for elliptical reflector system. To improve the pattern equalization of microstrip dipole feeds, the dipole arms are modified. Two techniques are used for this purpose, bending microstrip dipole arms, or adding corrugations. In the bent microstrip dipole case, the design is suitable for narrow band operation. In order to improve the input impedance while equalizing the radiation patterns, a corrugated microstrip dipole is designed and investigated. Satisfactory performance is obtained. All feed examples studied in this thesis are fabricated and experimentally evaluated for the input impedance match and performance on a reflector. Satisfactory results are obtained.

Graduate

In this thesis, two new types of electrically small feed antennas, slotted circular waveguide feeds, and microstrip dipole feeds are designed and studied for prime focus reflectors. The existing electrically small feeds used in prime focus reflectors exhibit some limitations such as asymmetrical radiation patterns, complex integration with microwave devices, requirement of struts support, and high cost. The design of these two new kinds of feeds is of particular interest since they provide symmetrical radiation pattern, and are low profile, easy to fabricate, simpler to mount on the reflector system, and low cost. Circular waveguide feeds have been a good choice for prime focus reflector systems. The main drawback of these feeds is that the E- and H-plane radiation patterns are not equal in small diameter apertures, and hence the reflector efficiency is low. In this report, an attempt is made to equalize the radiation patterns of these feeds, by slotting their wall at the open-end. Even though radiation pattern equalization is possible with these feeds, the efficiency remains still low. Therefore, chokes are introduced with the slotted waveguide feeds to improve the radiation characteristics as well as the efficiency. Slotted circular waveguides with a cavity is also studied, where slots are used as additional parameters, to equalize their radiation patterns, and hence increase the efficiency. In the second part of the thesis, microstrip dipole feeds are studied because of their light weight, low aperture blockage and ease of assembly on the reflector system. These feeds are designed for backward radiation and thus eliminate strut support. Parametric studies are conducted to improve the input impedance, miniaturize the antenna, and design for dual frequency operation. All these feeds have unequal E- and H-plane radiation patterns. Therefore, they are candidates for elliptical reflector system. To improve the pattern equalization of microstrip dipole feeds, the dipole arms are modified. Two techniques are used for this purpose, bending microstrip dipole arms, or adding corrugations. In the bent microstrip dipole case, the design is suitable for narrow band operation. In order to improve the input impedance while equalizing the radiation patterns, a corrugated microstrip dipole is designed and investigated. Satisfactory performance is obtained. All feed examples studied in this thesis are fabricated and experimentally evaluated for the input impedance match and performance on a reflector. Satisfactory results are obtained.

Optical methods have been used to examine the topography of the small erosion areas that are produced at the cathode and anode due to single, short duration, high current discharges. A plane parallel electrode arrangement has been used with gap separation of between one and two millimetres or less, and allowing electrical breakdown to occur under nearly uniform field conditions. The electrode erosion has been studied for discharges passed in oil dielectric, and also hydrogen, air, and argon at atmospheric pressure. High and low melting point metal electrodes have been used in the investigation. Constant current discharges have been produced by using pulse forming networks, but for slower rates of current rise in the external circuit, a single section condenser-inductance network was used. Some of the erosion areas have been suitable for examination by Fizeau reflexion interferometry, and the light profile techniques, which made possible an estimation of the volume of material lost from these areas. Observations were made using reflexion microscopy, which also served as a means for making erosion measurements. The results of the measurements of erosion loss at the anode for discharges in oil and gases, indicate that the electrode material cannot have been removed by a thermal evaporation process alone. From observations on the topography of the anode erosion areas, it would appear that the molten metal within the area is drawn into one or more peaks, and metal is lost from the area by some mechanical force action. The erosion areas at the lower melting point electrodes for discharges in oil and gas dielectric appear similar, but usually more intensive melting is produced for the discharges in oil. The molten multiple marks left on the anode and cathode, have been discussed in the light of recent research by other workers, studying the luminous areas formed at the electrodes during the discharge.

A new, differential method is described, suitable for detecting small changes in the conductivities of dilute, aqueous ionic solutions at a frequency of 3x10⁹c/s. The method essentially depends on measuring the change in 'q' of a resonant cavity containing a fine quartz tube, when the solution under investigation and water are passed through the tube in a continuously alternating stream, at a frequency of one complete change-over in eight seconds. The corresponding change in signal, picked up by a probe detector penetrating into the cavity, is viewed on a Cathode Ray Oscilloscope, after passing through suitable amplification and filtering processes. Measurements are described on a range of dilute solutions of potassium, sodium and lithium chlorides over a temperature range from 18°C to 25°C. For calibration purposes, the method has been used, in a modified form, for more concentrated solutions up to concentrations of 0.5 Normal. Assuming, from published results of other authors, that at high concentrations there is no difference between the ultra high frequency values of the ionic conductivities of these salts and the conductivities measured at low frequencies, the measured U.H.F. conductivities at low concentrations were compared with the corresponding D.C. values. They were found to exceed these by as much as 30%. This difference is in excess of the difference predicted by the theory of Falkenhagen, which has hitherto not been investigated at these frequencies. A new theory, which would explain the results obtained, is discussed in the final chapter; some justification for the new assumptions is obtained by using them to interpret the results of other workers for the variation of low-frequency dielectric constant of saline solutions with concentration.

PART I contains a description of the writer's further work on the absolute measurement of electrical resistance by the new rotating coil method of Nettleton and Balls. The preliminary investigation was published in 1934. In the fundamental equation, K, a constant, depends upon where M is the mutual inductance between rotor and stator at angle of rotation from the conjugate position where the brush is at the commutator sector's edge. K is shown to be most accurately determined at and with the field coils in the Helmholtz position. To satisfy these conditions and to render constant at the sector edges, it is necessary to construct a differential rotor consisting of two coplanar coils in series and opposition. The theory of this rotor necessitated the calculation of mutual inductances and Tables of Functions, given in Appendix II. With such a rotor, resistances of the order of one ohm are measured absolutely. above, is the angular velocity of revolution and is measured by the method described in Appendix I. Part II is a preliminary account of the writer's investigation, suggested by Dr Nettleton, on the absolute measurement of resistance by the method, proposed by Rosa in 1909, using the e.m.f. of a commutating generator. No data by any form of this method have ever been published. The basic equation of this method, has the great advantage that a frequency and the maximum mutual inductance only are required. A remarkable flat of maximum mutual inductance between rotor and stator was obtained, permitting commutation without loss of generated e.m.f. Rosa's difficulties, due to self-inductance and to break at commutation in the steady e.m.f. drawn from the resistance to be measured, are overcome by a short-circuiting device covering each commutation.

The work described covers an investigation of some of the physical problems associated with short wavelength X rays. The radiations emitted from high energy generators are discussed and it is found that the experimental results of the writer and the small number of other experimental results available do not agree with theoretical predictions for the angular distribution of the radiation. Possible explanations are given. A number of measurements of absorption coefficients of high energy radiations in various materials are reported. Values of the coefficients calculated from the theories for the various absorption processes are also given and the agreement between theory and experiment is, in general, good. a review of other measurements of absorption coefficients using various techniques and at energies up to approximately 90 MeV. show that generally speaking the theories for the various processes are substantiated. Some effects are demonstrated resulting from the change from a decrease of absorption coefficient with increasing energy to an increase with increasing energy resulting from the advent of the pair formation process. The problem of the measurement of high energy X radiation is discussed and experimental results presented which indicate that it is possible to measure the radiations in rontgens up to an energy of approximately 30 MeV. Some comparative measurements with American workers show satisfactory agreement with the dosage measuring technique of one team and demonstrate the errors introduced by the method adopted by another team. New processes which alter the effective stopping power of the materials become evident from the experimental results and values of these stopping powers are deduced. The problem of measurement of the radiation from radioactive isotopes has also been investigated and measurements made with ionisation chambers of different materials show that a satisfactory system of measurement of the dosage-rate for radiations emitted from these isotopes can be worked out from considerations of the energy absorbed. Values of stopping power calculated from these measurements show good agreement with the values given by Be the and G-ray. Measurements and calculations pertaining to the protection requirements for personnel operating high energy generators are given along with recommendations on the solution of the problem. Some photographic dosage measurements are also presented from which it is concluded that the sensitivity of photographic film measured in "blackening per rontgen" changes very slowly in this high energy region, a result to be expected theoretically. Some measurements of the distribution of radiation in and around a scattering medium and the variation of quality of the radiation inside the mass are also presented.

The aim of this work has been to evaluate fairly reliable wavefunctions for electrons in the conduction band of lithium, mainly with the aim of bringing some light to the question of whether or not there is a marked variation of the wavefunction throughout k-space. An approximately self-consistent potential was constructed, based on the Hartree-Fock-Slater equations and the atomic wavefunctions given by Holoien. The one-electron equation describing the electrons in the conduction band was solved by the method of orthogonalized plane waves, using up to 70-80 waves. The solutions were determined at the four points of highest symmetry in the Brillouin zone and at 14 other points on axes of symmetry. In effect, 126 points throughout the Brillouin zone were thus considered. The eigenvalues are in fair agreement with those obtained by previous calculations, despite the use of a somewhat different potential. It should be stressed that the potential employed was an approximation to the true self-consistent potential in the metal, and not a "pseudopotential". The main conclusions to he derived from the calculated wavefunctions are: 1: Outside the region of the atomic cores the electrons behave essentially as free; near the nuclei the wavefunct-ions behave as a combination of s and p atomic functions. 2: The form of the wavefunctions does not change much throughout the occupied part of the Brillouin zone. This is particularly true for points with the same magnitude of k. The Fermi surface is found to be distorted from a sphere, in the 110 direction. However, it does not touch the zone face, as previously predicted.