A compact dualband bandpass-to-bandstop tunable filter for wireless applications

A compact dualband bandpass-to-bandstop tunable filter based on short stub loaded stepped impedance resonators is designed. It uses pin diode for bandpass-to-bandstop filter transformation and varactor diodes for tuning of the center frequency. The filter is designed on Taconic RF-35 substrate to obtain two close dualbands with tuning of center frequencies in the range 1.66-1.88GHz and 1.98-2.29GHz in bandpass mode and dualstops in the range 1.57-1.65GHz and 1.75-1.90GHz in bandstop mode.