Compact Circle Ring Resonator Bandpass Filter

A new dual-mode bandpass filter (BPF) which is mainly formed by a ring resonator with an open stub perturbation is introduced in this article. The ring resonator inward extend in order to meet the need of the compact size. Meanwhile the orthogonal input and output feed-lines were introduced to generate coupled orthogonal modes. Two transmission zeros are generated which further improve the frequency selectivity and the isolation of the BPF. The simulated and measured results show that the proposed filter has good frequency response characteristics.