A Microstrip Switchable Filter With Four Operating Modes

This letter presents a novel microstrip switchable filter with four operating modes, i.e. single-band bandstop filter (SB-BSF), all-stop filter (ASF), single-band bandpass filter (SB-BPF) and dual-band bandstop filter (DB-BSF). The proposed switchable filter consists of a switchable bandstop/all-stop filter (SW-BSF/ASF) and a switchable dual-mode resonator (SW-DMR). The measured results show that the SB-BSF mode is centered at 2 GHz with 10 dB attenuation fractional bandwidth
$(\text{FBW}_{10\ \mathrm{dB}})$
of 50.2%, the ASF mode has a better than 12 dB attenuation from dc to 4.3 GHz, the SB-BPF mode is centered at 1.92 GHz with 3 dB FBW of 9.7% and minimal insertion loss (IL) of 1.95 dB, and the DB-BSF mode is centered at 1.61/2.36 GHz with
$\text{FBW}_{10\ \mathrm{dB}}$
of 21.1%/20%. Simulated results agree well with measured results.