Dual-mode bandpass filter with independently tunable center frequency and bandwidth

This paper presents a compact dual-mode tunable bandpass filter (BPF) with independently tunable center frequencies and bandwidths based on varactor loaded transmission line dual-mode resonator. The center frequency can be controlled by tuning the even-mode and odd-mode resonant frequencies of the dual-mode resonator. The bandwidth of passband can be tuned by fixing the odd-mode and changing the even-mode resonant frequency. To validate the proposed structure, two-pole microstrip tunable BPF is presented and experimentally verified.