Automatic Monitor for Microwave Resonators

An instrument was developed to simultaneously measure both the resonant frequency and the bandwidth (which is related to the loaded quality factor) of a resonant microwave cavity under continuous operating conditions. Voltages proportional to both parameters monitored are obtained at the output. The principle of operation, the main causes of error and the accuracy obtained for actual measurements are presented. This instrument could easily be connected to a digital data-acquisition system; it could also be adapted to study resonance phenomena at frequencies other than microwaves.