Design procedures are presented for varactor tuned microwave bandpass and bandstop filters constructed in Microwave Integrated Circuit form. The tunable bandpass filters were based on a combline filter incorporating novel input and output coupling networks which compensate for the frequency dependence of the coupling between the resonators. Using this filter, tuning over an octave band with an acceptable response and approximately constant passband bandwidth is possible. The tunable bandstop filters consisted of a uniform impedance main line with capacitively decoupled resonators located at intervals along it. A novel design technique is presented for evaluating the correct phase shifts between the resonators of this filter in order to obtain the optimum symmetrical frequency response. Detailed computer analysis of the filters, including both varactor and integrated circuit loss, and the effects of tuning is presented. The measured performances of several practical devices, constructed in Suspended Substrate Stripline, and operating in the frequency range 2-10 GHz are presented, these agree closely with computed performances.

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A microwave enhanced advanced oxidation process using hydrogen peroxide (MW/H₂O₂-AOP) was used for the release of nutrients and the destruction of solids from secondary municipal sewage sludge. The significant factors affecting the MW/H₂O₂-AOP that would yield maximum soluble substrates were studied. Using a computer statistical software package for experimental design and data analysis, four factors including microwave heating temperature, heating time, hydrogen peroxide dosage, and sludge solids content, were selected and examined. The initial sludge TS content and hydrogen peroxide dosage were the most significant factors for the solubilization of COD and nutrients release under the experimental conditions selected in this study. Overall, the maximum solubilization of nutrients was obtained at 2.5 % of total solids content, 2% of hydrogen peroxide by weight, 5 min. of microwave heating and 120 ºC. The effects of combination of microwave treatment and oxidative reagents on solids destruction and nutrients release were also investigated. Microwave enhanced advanced oxidation processes (MW-AOP), such as MW/O₃, MW/H₂O₂ and MW/H₂O₂/O₃, were conducted at 100 °C. In terms of nutrients release and solids reduction, the MW/H₂O₂/O₃-AOP yielded the best result. Subsequently, three factors including microwave heating temperature, hydrogen peroxide dosage, and ozone dosage, were investigated. The best result, in terms of the release of phosphate and ammonia, and solids reduction, was obtained with additions of 2 % hydrogen peroxide by weight and ozone dosage of 5.09 mg/ml, and operating at 120ºC. About 95%, 32% and 78% of TP, TKN and COD were released into the solution, respectively. The microwave enhanced advanced oxidation processes, with and without an addition of ferrous sulfate (MW/H₂O₂-AOP and MW/H₂O₂/Fe+²-AOP), were also studied for reducing solids, and solubilizing nutrients from the secondary sewage sludge. For the MW/H₂O₂/Fe+²-AOP, the best results of solubilization, in terms of orthophosphate, ammonia and soluble chemical oxygen demand, were obtained at treatment temperatures of 40 ºC, the yields decreased as the temperature was increased. The highest yields of solubilization were obtained at 60 ºC for orthophosphate, and at 80 ºC for both ammonia and soluble chemical oxygen demand. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

The object of this research was the construction of a microwave spectroscope at 1.25 cm. wavelength. The double modulation method, which was used here, is discussed. The system was tested with ammonia, and the inversion spectrum identified. The effect of using various harmonies of detection is shown. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

A new technique has been devised to obtain time-resolved measurements of small spectral line shifts. Two linear neutral density wedges with opposite transmission gradients were placed over the top and bottom of a monochromator exit slit in such a way that a wavelength shift of a spectral line resulted in a change in light intensity transmitted through the wedges, which was monitored by two photomultipliers. To test this technique, an N II line, for which Griem has calculated the Stark shift as a function of electron density, was observed in the emission spectrum of a small theta-pinch using a monochromator of 10 Å/mm inverse dispersion. Space and time resolved line shift measurements were made and were associated with the axial velocity and the electron density fluctuations of the plasma. An uncertainty of 0.015 Å was estimated, which, for the 1.5 Å line used, corresponds to a shift to width ratio of 10⁻², believed to be lower than any previous shift measuring technique. Time of flight velocity measurements and conservation of mass considerations have confirmed the results as both reasonable and self-consistent. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

The microwave resonator method for studying small amplitude surface waves in liquids has been improved by making the time measurement more accurate and much more convenient. It was used to measure the oscillation frequency of the surface as a function of liquid depth. Discrepancies between the experimentally obtained results and theoretical predictions due to the rigidity of the mercury meniscus where contact is made with the walls of a cylindrical resonator were found. From these an accurate value for the effective reduction in radius of the resonator because of the meniscus effect was obtained. A method was developed for applying strong electrostatic fields (about 20 kV/cm) onto the fluid surface without interfering with the measuring technique. An interesting result of this was the observation that the field cleans the surface from contamination. This phenomenon manifests itself in a marked reduction in the damping of surface waves just after a large field is applied. A resonator of square cross-section was used to demonstrate the Fourier analyzing property of rectangular resonators. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

An investigation into various methods of calculation of the high frequency performance parameter f[formula omitted] for microwave heterojunction bipolar transistors is presented. Two high frequency representations of the device are developed: equivalent circuits consisting entirely of lumped circuit elements, and a two-port network based on drift-diffusion equations. Proper account is taken in these representations of the phase delay associated with carrier transit time through the base and base-collector space charge region. Also included are the charging time effects due to the various parasitic circuit elements associated with actual devices. A single-sided isolated structure is used in simulations and it is found that both representations yield remarkably similar characteristics for the behavior of unilateral gain U with frequency. For devices in which the dominant factors limiting high frequency performance are the parasitic resistances and capacitances, it is found that U rolls off at 6 dB/octave through the region where U = 1 and the values predicted for f[formula omitted] via these two methods, as well as via the widely-used analytical expression involving f[formula omitted] and (R[formula omitted]C[formula omitted])[formula omitted], are in agreement. However, when the periods of the oscillations are on the order of the carrier transit times, and the device parasitics are sufficiently low so as to not limit performance, resonance effects occur in U in the region where U = 1 and the prediction of f[formula omitted] obtained via the two equivalent circuit approaches deviates markedly from the predictions of the analytical expression. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

Comparative studies were carried out on the curing kinetics, physical and mechanical properties of conventionally and microwave cured epoxy resins. Epoxy resins Araldite LY 5052 and DLS 772 were used for this study. 4 4' Diaminodiphenyl sulfone was used as a hardener in the preparation of both systems. Nuclear magnetic resonance and gel permeation chromatography were used to identify the chemical structure of the resins. Differential scanning calorimetry was used to monitor the curing kinetics of conventionally cured epoxy samples while a microwave heating calorimeter was used to monitor the curing kinetics of microwave cured epoxy samples 'in situ'. These studies were carried out under non-isothermal and isothermal conditions. For both conditions, there was a significant increase in the fractional conversion of the microwave cured samples compared to the conventionally cured samples. The curing reactions for samples cured using microwave heating took place over a smaller temperature range. Higher reaction rates were observed in the samples cured using microwave heating.There were some differences in the kinetic parameters of the non-isothermal curing reactions of samples cured using microwave and conventional heating. For the Araldite LY 5052 / 4 4' DDS epoxy system, the microwave cured samples had higher activation energy than conventionally cured samples, while for the Araldite DLS 772 / 4 4' DDS epoxy system, the microwave cured samples had lower activation energy. The activation energies of the microwave isothermal curing of both Araldite LY 5052 / 4 4' DDS and Araldite DLS 772 / 4 4'DDS epoxy systems were lower than the activation energies of the conventionally cured samples.Infrared spectroscopy showed that the curing reaction followed the same path during conventional and microwave heating. It also revealed that the reaction rate of the microwave cured samples was higher than the conventionally cured samples.For both epoxy systems, the microwave cured samples had a higher glass transition temperature (Tg) , higher cross-link density (v) and lower molecular weight between cross-links. These showed that the microwave cured samples had a more compact network structure than the conventionally cured samples, which is an indication of better mechanical properties.A microwave reaction system was used to successfully dissolve conventional and microwave cured samples of Araldite DLS 772 / 4 4' DDS epoxy system. The chemical structure of the decomposed product was determined.

The microwave spectra of three unstable molecules, bromine isocyanate (BrNCO), iodine isocyanate (INCO), and bromine thiocyanate (BrSCN), have been observed and analyzed in the frequency range 16-54 GHz. The infra-red spectrum of aminodifluoroborane (BF₂NH₂) has been investigated in the region 3700-400 cm⁻¹, and one band, the 2¹₀ vibrational band has been recorded at a resolution of 0.004 cm⁻¹, and the rotational structure analyzed. BrNCO: BrNCO was generated from the flow reaction of Br₂ with silver cyanate. The spectra of two isotopic species were observed: ⁷⁹BrNCO and ⁸¹BrNC0. They contain strong a-type transitions as well as some weaker b-type transitions which could not initially be assigned. In addition, the transitions show both Br and N quadrupole hyperfine structure. A novel method has been developed which uses perturbations in the Br structure to evaluate all the rotational constants, as well as the Br quadrupole tensor, entirely from a-type R branch transitions using a global least-squares fitting programme. This has allowed some b-type transitions to be assigned. The molecule has been shown to be planar and a partial r₀ structure was determined. The principal values of the Br quadrupole tensor have been evaluated and have provided some information about the type of bonding involved in the Br-N bond. INCO: INCO was observed in the flow reaction of I₂ with silver cyanate. Many strong a-type transitions were observed as well as some very weak b-type transitions. These transitions showed I and N quadrupole hyperfine structure; many perturbations in the I structure were observed. The method developed in the analysis of the spectrum of BrNCO using such perturbations to obtain otherwise unobtainable rotational constants was extended to include centrifugal distortion constants. The planarity of INCO has been confirmed and a partial r₀ structure was determined. The principal values of the I quadrupole tensor have been evaluated and have provided some information about the type of bonding involved in the I-N bond. BrSCN: BrSCN was generated in the flow reaction of Br₂ with silver thiocyanate. The spectra contained both a- and b-type transitions, all of which showed Br quadrupole hyperfine structure. The rotational constants and all five quartic centrifugal distortion constants were obtained for two isotopic species: ⁷⁹BrSCN and ⁸¹BrSCN. The rotational constants confirm the thiocyanate configuration, and a partial r₀ structure has been obtained. Also, the principal values of the Br quadrupole tensor were evaluated which show that the Br-S bond is essentially covalent, with small amounts of π and ionic character. BF₂NH₂ : BF₂NH₂ was generated by heating solid BF₃ NH₃. The wavenumbers of 7 of the vibrational fundamentals have been obtained, and from the analysis of the 2¹₀ band, an accurate set of rotational and quartic centrifugal distortion constants of the ground vibrational state have been obtained and the rotational and quartic centrifugal distortion constants of the 2¹ level have been evaluated. Also a Coriolis type perturbation was observed, probably due to the combination level v₇ + v₁₁ , which has provided an estimate of the wavenumber of the v₁₁ fundamental which has not yet been observed. / Science, Faculty of / Chemistry, Department of / Graduate

A refractory self-aligned gate fabrication process for gallium arsenide MESFETs has been developed and applied to a sample and hold circuit. The process has been shown to reduce the parasitic end resistance of MESFETs which can be a limiting factor in their microwave performance. A mask set was designed to be compatible with Cascade Inc. probes which allowed on chip microwave measurements to be made. Usable gain was measured up to 18GHz on FETs and 5GHz on buffer amplifiers with the microwave probes at the Communications Research Centre in Ottawa Ontario. The microwave probes were also used to test sample and hold operation. The maximum tested sampling rate was limited by the test equipment to 250 MHz. The fabrication process included a plasma etch for producing an undercut 'T' gate structure for self-aligned ion implantation. A method of sputtering a thermally stable alloy of TiW refractory metal was developed to provide suitable Schottky contacts to GaAs. It was found that a rapid thermal anneal following the self-aligned implant maintained suitable TiW/GaAs Schottky characteristics and yielded MESFETs with reduced end resistance when compared to those fabricated by the more conventional selective implant process. A technique was developed to reduce the gate resistance of self-aligned MESFETs using an evaporated metal overlayer. Also, procedures for fabricating airbridges using a single evaporation and Metal-Insulator-Metal (MIM) capacitors using silicon nitride as the dielectric were developed. The effect of gate resistance on the microwave performance of the self-aligned MESFETs was investigated by modeling with the EEsof Inc. microwave software package, Touchstone. The modeling showed that self-aligned MESFETs are capable of giving greater high frequency gain than are selective implant devices with the same design geometry. The operation of the sample and hold circuit was simulated using a version of SPICE that included the Sussman Fort GaAs MESFET model. The simulations showed that the sample and hold could be used for gigahertz sampling. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate