Differentially Detected Channelized Resonator Filter

Abstract

Two resonators are connected together so they share the same input transducer but the output transducer for the second channel is 180° different in phase from the first. The result is zero output voltage for the direct transmission from input to output transducer. This helps achieve high out-of-band rejection. If the resonant frequencies of the two channels are now designed to be slightly different, the two channels will no longer cancel: and if the difference in frequency makes the crossover at the 3 dB pt, the two outputs will add to make a continuous, steeply sided, pass band filter. Such a narrow-band filter has been made and various problems and their solutions are presented.