Ultra High Q Resonators and Very Low Phase Noise Measurement Systems for Low Noise Oscillators

This thesis describes research into ultra high Q Bragg resonators, low phase
noise measurement systems and low noise oscillators.

The thesis is divided into three parts. The first is concerned with the
modelling, design and implementation of an extremely high quality factor Bragg
resonator. This resonator utilises an aperiodic arrangement of non $\lambda/4$
low loss alumina plates mounted in a cylindrical waveguide. An ABCD parameter
waveguide model is developed to simulate and optimise the cavity. The
dielectric plates and air waveguide dimensions are optimised using a genetic
algorithm to achieve maximum quality factor by redistributing the energy loss
within the cavity. An unloaded quality factor ($Q_{0}$) of 196,000 was
demonstrated at 9.93 GHz.

In the second part the design, implementation and measurement results for an
ultra-low noise floor cross correlation residual phase noise measurement
system are shown. A measurement noise floor of -200 dBc/Hz is achieved for
100,000 correlations. Residual phase noise measurements are also performed on
low noise L-Band microwave amplifiers. The key features of the cross
correlation technique and the different window functions required during
measurement are discussed.

In the third part the residual phase noise performance of several microwave
components is evaluated in order to establish their potential utility in a low
phase noise oscillator. In the first part of the chapter the designs for a
Gallium Nitride (GaN) power amplifier are presented along with the
measurements of its noise figure and residual phase noise performance. In the
second part of the chapter the designs and performance of an emitter coupled
logic (ECL) static digital frequency divider are presented.