Synthesis Design of Quasi-Elliptic Tri-Band Filter-Response Amplifier Using Extracted-Pole Matching Filter Technique

This letter presents a quasi-elliptic tri-band filter-response amplifier (QE-TBFA) designed via the extracted-pole matching filter (EMPF) synthesis. The matching networks (MNs) are synthesized directly as EMPFs, enabling co-designed filtering and amplification in a single stage. A prototype centered at 2.8/3.0/3.2 GHz demonstrates three independent passbands, each with a two-pole two-transmission zero (TZ) QE response. Measurements show ~40-MHz bandwidth, over 10 dB return loss, and in-band gain approaching the maximum available gain (MAG), validating superior selectivity and compactness compared to conventional approaches.