RF Co-Designed High-Selectivity Bandpass Filter/Attenuator (BPFA) With Tunable Attenuation

This paper reports on a new type of compact RF co-designed high-selectivity microstrip bandpass filter/attenuator (BPFA) with electronically-reconfigurable attenuation levels in its passband. The reconfigurable attenuation characteristics in the BPFA are obtained by resistively loading two of its capacitively-loaded resonators with PIN diodes. The circuit’s symmetric structure enables analysis through odd and even-mode methods. For proof-of-concept demonstration purposes, an experimental prototype was EM simulated, manufactured, and measured. It demonstrated a 1.2 to 2.4 GHz passband with tunable attenuation levels ranging from 3.47 to 20.24 dB.