Dual-Behavior Resonator-Based Fully Reconfigurable Input Reflectionless Bandpass Filters

A class of input reflectionless dual-behavior resonator (DBR)-based bandpass filters (BPFs) with reconfigurable center frequency, bandwidth, out-of-band attenuation, and intrinsic switching-off capabilities is reported. They exploit a complementary-duplexer approach, in which the resistively terminated bandstop-filter (BSF) channel dissipates the RF input signal energy that is not transmitted by the main BPF channel in its out-of-band region. Spectral reconfiguration is realized through the synchronous tuning of the counterpart resonators in the DBR-based BPF and BSF channels - i.e., without variable couplings - which results in a dynamic transmission-zero (TZ) reallocation process. The theoretical analysis of the first-order section and design examples for higher order schemes are presented. Furthermore, for experimental-validation purposes, a microstrip prototype that can be tuned within the frequency range 1.3-2 GHz is manufactured and characterized.