Active Monitoring and Control of Tunable Cavity Resonators

Evanescent mode cavity resonators are desirable for use in tunable filters due to their tuning sensitivity and high quality factors. This paper proposes a system for monitoring and controlling their resonant frequency and examines the effect of the system on resonator performance. The proposed system controls the resonator over a range from 600 to 700 MHz with unloaded quality factors as high as 670. A temperature change from 31 to 40 oC caused the resonant frequency of an uncontrolled resonator to drift 28.5 MHz, this drift was reduced to less then 1.2 MHz with the control system engaged.