Design and Performance of Low-Phase Noise Microwave Oscillators

This work verifies that the X-band microwave oscillators with the phase noise spectral density approaching -157 dBc/Hz at 1 kHz offset frequency can be reproducibly constructed. Such a performance can be achieved by frequency locking a conventional loop oscillator to the room temperature stabilised sapphire dielectric resonator using the principles of microwave circuit interferometry and operating the resonator at the elevated level of dissipated power. We discuss the noise mechanisms responsible for the flicker frequency fluctuations of the high power microwave oscillators with interferometric signal processing, as well as the technique for the high resolution noise measurements at microwave frequencies.