An Active Frequency Technique for Precise Measurements on Dynamic Microwave Cavity Perturbations

A new method for the dynamic measurement of the passive parameters of a microwave cavity is described. Both the resonant frequency (f0s) and the loaded Q factor (QLs,) are measured simultaneously from active frequency signals generated by a closedloop circuit containing the test cavity. Resonant frequency deviations of up to 20 MHz are measured with an accuracy of better than ±0.25 percent, and loaded Q-factor variations (from 500 to 7000) are measured with an accuracy of better than ±1.2 percent. The unperturbed cavity resonance was at 2452.0249 MHz, and the time of measurement of each cavity parameter was < 1 s.