A method for single‐band and multiband filters design based on right trapezoid half‐mode substrate integrated waveguide

In this article, a novel right trapezoid half‐mode substrate integrated waveguide resonator (RTHMSIWR) is firstly proposed. Based on it, a simple filter design method is presented. By controlling the ratio of the upside length to height of RTHMSIWR, the electric field distribution becomes regular and makes the resonant mode easy to generate the passband response, correspondingly. The fundamental and higher‐order modes are available to realize single‐band or multiband responses as the ratio changes, which provides a flexible choice on band allocation. For verification, a tri‐band bandpass filter (BPF) with source‐load coupling is designed. To further achieve a better rejection between the first and second passbands, a pair of complementary split‐ring resonators (CSRRs) is introduced. Total seven transmission zeros (TZs) are produced to improve the out‐band selectivity. The measured results agree well with the simulated ones.