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

Bale, Simon (2012) Ultra High Q Resonators and Very Low Phase Noise Measurement Systems for Low Noise Oscillators. PhD thesis, University of York.

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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.