RF-MEMS-Based Bandpass-to-Bandstop Switchable Single- and Dual-Band Filters With Variable FBW and Reconfigurable Selectivity

Bandpass (BP)-to-bandstop (BS) switchable filters using radio frequency microelectromechanical system switch are presented here. The filters are implemented in both single- and dual-band versions with variable fractional bandwidth (FBW). Tuning of transmission zeros (TZs) and transmission poles (TPs) for BP filter (BPF) and BS filter (BSF), respectively, is achieved in both single- and dual-band cases leading to reconfigurable selectivity. The first odd-mode frequency of the filter is suppressed using a fixed capacitor and the second odd mode is brought closer to the first even-mode with another variable capacitor to form the passband(s). The second capacitor tunes both the second odd mode and TZs (for BPF) or TPs (for BSF) minimizing the requirement of any extra tuning element. In a single-band fabricated BPF, tuning second odd mode gives the FBW variation of 9.3%-72.7% with TZ on the lower side and 5.6%-55.6% with TZ on the higher side of the passband. The 15-dB FBW of a single-band BSF having TP on both sides of the stopband varies over 5.2%-20.7%. The two passbands of a dual-band BPF independently vary over 4.5%-24% and 4.5%-13%. Also, the 15-dB FBW of the first and second stopbands of BSF independently varies over 6.5%-13.2% and 1.5%-3.6%, respectively.