Perfectly-matched bandstop filters using lossy resonators

Normal realizations of bandstop resonators with finite unloaded Q suffer from degradation of performance due dissipation loss. In this paper, it is shown theoretically that there exists a class of second-order networks which simultaneously exhibit an ideal bandstop resonance, with infinite stopband attenuation, and a perfect match at all frequencies. Theoretical analysis is backed up with experimental results for three different physical realizations.