Ultra Low Noise Microwave Dielectric Oscillators at 3.8GHz and 10GHz and High Q Tunable Bragg Resonators

The thesis is divided into three parts. The first part of the thesis describes the
design and development of two prototypes of an ultra-low phase noise 3.8GHz
dielectric resonator oscillator. The first prototype included vibration measurements
with a reasonable phase noise measurements developed for Selex-ES. The phase noise
for the first 3.8GHz oscillator is -117 dBc/Hz at 1kHz offset and -150 dBc/Hz at
10kHz offset. The second prototype was the improved modular yet compact oscillator
was then developed which demonstrated a significantly improved phase noise
performance of -125.6 dBc/Hz at 1kHz offset and -153 dBc/Hz at 10kHz offset which
is the lowest noise reported in the literature in this frequency band using a ceramic
dielectric resonator.
In the second part of the thesis, a design and measurement of a high Q broad
tuning aperiodic Bragg resonator operating at 10GHz is described. The resonator
utilises an aperiodic arrangement of non (λg/4) low loss alumina plates (ℰr=9.75, loss
tangent of ~1 to 2 ×10-5) mounted in a cylindrical metal waveguide. The insertion
loss, S21, varied from -3.9 dB to -6.4 dB while the unloaded Q varies from 81,650 to
61,020 over the tuning range of 100MHz (1%).
In the third part of the thesis, simulation, design and measurement of a low
noise Bragg resonator oscillator operating at 10GHz is presented. The oscillators
demonstrated a phase noise of -153 dBc/Hz at 10kHz offset and -123 dBc/Hz at
1kHz offset for an unloaded Q of 190,000. To achieve these results extensive
optimization of different transistors with different power level and noise figure has
taken place.