DUAL-MODE DUAL-BAND BANDPASS FILTER DESIGN USING OPEN-LOOP RESONATORS

摘要

This letter presents a novel dual-band bandpass filter using dual-mode open-loop resonator. Non-degenerate modes of the dual-mode resonator are excited by loading a center-loaded T-shaped stub and its nature is investigated through the even-odd mode analysis. Based on the aforementioned dual-mode resonators, a compact dual-band filter is designed. Results verify that the fabricated filter with the central frequencies of 1.8 and 2.4 GHz and the fractional bandwidth of 8.3 and 12.9% are obtained. Also, there are several transmission zeros located at both sides of each passband. It provides the filter with improved selectivity and stopband suppression.