HIGH PERFORMANCE TUNABLE BANDPASS FILTER WITH SEPARATELY RECONFIGURABLE PASSBAND EDGES

A high performance tunable bandpass filter (BPF) with separately reconfigurable passband edges is presented based on a novel varactor-tuned stepped-impendence stub-loaded resonator. The proposed resonator consists of three variable capacitors and a half wavelength resonator loaded with three stepped-impendence stubs symmetrically. Theoretical expressions have been derived for the resonant frequencies. Each passband edge can be reconfigured by adjusting capacitance values of the capacitors loaded on the stubs. High performances of the measured BPF are demonstrated, including low insertion loss (< 1.9 dB), good return loss (> 20 dB), a 16-49% fractional bandwidth tuning range and a wide upper stopband with better than 35 dB rejection. The proposed ideas are verified by the measured results. (C) 2015 Wiley Periodicals, Inc.