DUAL RING BALUN-BPF WITH IMPROVED BALANCED PORT CHARACTERISTICS

초록

A dual ring structure for the Balun-bandpass filter (Balun-BPF) to improve balanced-port characteristics is presented. The conventional Balun-BPF has limitations in output symmetry and skirt steepness. A dual ring structure is introduced and a suitable coupling point between the two ring resonators is obtained to solve these problems. An interdigital coupled-line inverter and the cross-coupling effect between. the resonators are also discussed. The fabricated dual rang Balun-BPF, with a center frequency of 2.45 GHz and a 90 MHz bandwidth, shows excellent characteristics as a Balun-BPF without the conventional limitations.