COMPACT DUAL-BAND BANDPASS FILTER USING SPIRAL RESONATORS AND SHORT-CIRCUITED STUB-LOADED RESONATOR

摘要

A compact dual-band bandpass filter (BPF) using spiral resonators and short-circuited stub-loaded dual-mode resonator is presented. Two different transmission paths and source-load cross coupling are used to realize independently controllable bandwidths for each passband and good frequency selectivity. The coupling scheme and current distributions are applied to demonstrate the flexible design approach. A dual-band BPF is designed, simulated, and fabricated to demonstrate the performance of the proposed dual-band filter. The measured results show that the fabricated dual-band BPF has two passbands centered at 2.45 and 3.55 GHz with the fractional bandwidths of 5 and 7%. The insertion loss is 1.2 and 1.3 dB at the lower and upper passbands, respectively, and the return loss within the two passbands is greater than 17 dB. The measured results show good agreement with the simulated ones.