Dual-Band Bandpass Filter with Multiple Controllable Transmission Zeroes and Wide Stopband

摘要

A dual-band bandpass filter with multiple controllable transmission zeroes (TZ) and wide stopband performance is based on a single quadruple-mode circular ring resonator (Q-CRR). The two passbands are generated by using degenerate modes. After installing two parallel coupled feed line sections on a ring at the two ports with 90 degrees separation and two openended tri-section stepped-impedance resonators (OT-SIR) loaded on the I/O ports, eight TZs are produced in the stopband. By tuning the length and the impedance ratio of the OT-SIR and the length of the parallel-coupled feed lines, the locations of the TZs are adjusted. Measured results show good agreement with simulation.