A filter design method based on higher-order modes of fan-shaped half-mode substrate integrated waveguide resonator

In this paper, a novel 22.5 degrees fan-shaped half-mode substrate integrated waveguide resonator (FSHMSIWR) is presented firstly. Based on it, a filter design method by suppression or utilization of higher-order modes is proposed. When feeding on magnetic wall, the fundamental mode (TM101) is excited to generate passband response, while the higher-order modes (TM201 and TM301) can be suppressed. A pair of complementary split-ring resonators (CSRRs) are introduced to strengthen the out-band rejection. Then a single-band bandpass filter (BPF) with ultra-wide and deep stopband is realized. When feeding on electric wall, the higher-order modes can be well excited, which provides flexibility to realize multi-band BPFs only by changing the feeding position. As verification, a single-band BPF and a tri-band BPF with source-load coupling are designed and fabricated. The measured results show good agreement with the simulated ones.