Frequency-Tunable Low-Q Lumped-Element Resonator Bandstop Filter With High Attenuation

Abstract

This paper presents a new lumped-element absorptive bandstop filter topology. It exhibits infinite attenuation at the center frequency and no reflection regardless of the quality factor (Q-factor) of the resonators. The new topology exhibits the absorptive characteristic with extremely low-Q resonators, whereas an absorptive bandstop filter topology in the literature cannot be used for such resonators. This superiority of the new filter topology is verified by comparing it with the topology in the literature. The filter designed using the new topology can change its center frequency by tuning only the capacitor values of the resonators. A 1.6:1 frequency tuning range maintaining the absorptive characteristic has been obtained by measurement.