A Microstrip Switchable Filter With Four Operating Modes

Abstract

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 (FBW <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10 dB</sub> ) 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 FBW <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10 dB</sub> of 21.1%/20%. Simulated results agree well with measured results.