Improving the frequency stability of microwave oscillators by utilizing the dual-mode sapphire-loaded cavity resonator

摘要

The design and experimental testing of a novel control circuit to stabilize the temperature of a sapphire-loaded cavity whispering gallery resonator-oscillator and improve its medium-term frequency stability is presented. Finite-element software was used to predict frequencies and quality factors of WGE_(7,0,0) and the WGH_(9,0,0) modes near 9 GHz, and separated in frequency by approximately 80 MHz. Calculations show that the novel temperature control circuits from the difference frequency can result in a frequency stability of better than one part in 10~(13) at 270 K. Also, we present details on the best way to couple orthogonally to two modes of similar frequency but different polarization.