The work reported In this thesis is concerned with the fabrication and characterisation of microwave lumped element overlay capacitors for used at 10 GHz. The research has included the investigation and selection of suitable materials for use in the component manufacture, and,the development and optimisation of the necessary fabrication processes, which at the outset of' the project, were not available to the author. For this reason, and for the benefit of other research workers involved in the construction of microwave thin film components, the presentation of the processing data in this thesis is biased towards step-by-step accounts of' each of the major processes. The processing data is then readily available in a practical, and useful, form. Of' particular interest in the processing field, is the novel technique developed for the deposition of' the capacitor dielectric material without etching. This work was carried out in collaboration with a fellow research student, and is covered by a U.K. Patent. The microwave measurement of the capacitor properties have been performed using microstrip resonators. To enable these measurementsresonators to be accurately designed, measurements have been performed on, and results documented for, the transmission characteristics of microstrip lines on quartz substrates, and for the properties of micros trip gap discontinuities, and microstrip gap-and-step discontinuities, at X band. The technique for the measurement of the overlay capacitor properties is novel in that the capacitor is measured "in situ", and bond wires, which are a characteristic of' other measurement techniques, are not required. This permits a higher measurement accuracy, due to the reduction in connector parasitics. In addition, the equivalent circuit approach to the calculation of the capacitor properties is used, and not the perturbation approach, which permits large changes in frequency and Q factor during the course of the measurements, and this allows very measurements to be obtained. Results are presented for measurements performed on overlay capacitors, using silicon dioxide and alumina dielectric materials, and these indicate that capacitors with useful values of capacitance and Q factor can be produced at X band. Theories are presented for the capacitor electrode inductance and resistance, and these enable the dielectric constant and Q :factor of the capacitor dielectric materials, to be evaluated from the measured ccapacitor properties. Values of' the dielectric properties thus obtained are shown to be in good agreement with the characteristics of the dielectric materials in isolation, measured by a :fellow research student, using cavity techniques.

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The work reported in this thesis is concerned with evaluating the properties of materials used for lumped element microwave circuits. The investigation included surface roughness measurements of commercially available alumina and glass substrates, measurement of the surface resistance of evaporated, electroplated and bulk conductors, and measurement of the dielectric properties of alumina and silicon dioxide films. Factorially designed experiments were used to study the effects of the processing parameters for electroplating and RF sputtering on the quality of the metal and dielectric films obtained. The surface resistance measurements were performed using a cylindrical H011 cavity. The design of the cavity allowed a calibration curve to be drawn such that measurement of the return loss at resonance alone allowed the sample surface resistance to be read directly from a graph with an accuracy of ±0.0013Ω. The simplicity of the method is a significant advance on former methods. The effects of various surface finishing processes on the surface resistance of bulk conductors of copper and brass have been studied together with an investigation of the effects of the electroplating parameters on the surface resistance of copper films deposited from two acid solutions. The surface resistance of the metal films formed from those solutions was found to be dependent upon the current density, stirring rate, temperature and chemical composition of the solution. Results are also given for gold, silver and copper films deposited from commercially available plating solutions. The effect of film thickness on the surface resistance of evaporated copper films was also studied, the results being in good agreement with the theoretical values. The investigation of dielectric film properties required the construction of an RF sputtering unit. This is described in detail. The dielectric film properties were measured using a co-axial cavity. The effects of three sputtering parameters on the quality of the films obtained were studied. The application of a longitudinal magnetic field during sputtering was found to be particularly beneficial. A new technique has also been developed for the deposition of films onto selected areas of a substrate without the need for etching. This work was performed with a fellow research student and is covered by a UK Patent application. This method was required for the fabrication of microwave planar capacitors where the substrate and the capacitor dielectric were made of the same material.

A widely used analytical, image charge, model of the SNMM was analysed for the first time in terms of its ability to predict the response of the SNMM to both bulk and thin film dielectrics. For the first time it was shown that the uncertainty in fitting to the model reduces from 10% to 5% when the length of the tip protruding from within the cavity is reduced from 2mm to 1mm. A 5% uncertainty in fitting to the image charge model for the measurement of the relative permittivity of bulk samples is demonstrated.

Brillouin scattering has been used for many years in optical fibre temperature and strain sensing applications, due to the dependence of both the power and the frequency shift of the scattered radiation on these two quantities. Simultaneous temperature and strain sensing is possible if both the power and frequency shift are measured. Much work has been published which presents either power or frequency shift measurements alone. Simultaneous measurement, however, has been less well documented, with all recent cases using direct detection of the backscattered power. As the input pulse power is increased, nonlinear processes ensue, compromising the accuracy of the sensor. These processes were investigated both experimentally and theoretically for a range of input pulse durations, focussing on their effect on Brillouin Power and frequency shift measurement.