Low phase noise oscillator stabilised by high quality factor AFSIW resonators

Abstract

A novel X-band low phase noise oscillator is proposed by taking advantage of the enhanced quality factor of air-filled substrate integrated waveguide (AFSIW) resonators. A pair of AFSIW resonators is embedded in a feedback loop, which forms a high-selectivity bandpass filter, to greatly reduce the phase noise of a heterojunction FET oscillator. A prototype is designed, fabricated and measured. At an output signal of 9.85 GHz, the phase noise is -146.8 dBc/Hz and the figure of merit is -210.6 dBc/Hz at 1 MHz offset frequency. An improvement of about 10 dB in phase noise performance is obtained compared with published substrate integrated waveguide resonator-based oscillators.