A New Reconfigurable Bandpass Filter With Adaptive Resonators for Switchable Passband and In-Band Notch

A reconfigurable bandpass filter (BPF) with adaptive resonators is proposed for a switchable in-band notch. The adaptive resonator has two identical arms in parallel. When tuning the varactors in the two arms in different manner, the adaptive resonator results to different equivalent circuits. The prototype filter discussed here is an intrinsically switchable BPF. Comparing its even-and odd-mode resonances, it shows three different states, i.e. two bandpass and all-stop states. The adaptive resonators are integrated into this prototype filter. The obtained filtering responses are that each state of the prototype filter has a switchable in-band notch. Since both adaptive resonators and the prototype filter are reconfigurable with varactors, both the passband and in-band notch are tunable and switchable. An implemented experimental circuit has soundly verified the proposed technique.