A sixth‐order SIW bandpass filter based on combining single‐ and dual‐mode cavities with high selectivity at Ka‐band

Abstract

In this paper, a novel substrate integrated waveguide quasi-elliptic bandpass filter is proposed by combining single- and dual-mode cavities. Two single-mode cavities with TE101 mode are directly coupled to the dual-mode resonance cavity which employs a pair of disturbing metallic via-holes to make the resonant points of TE101 and TE102 mode in one passband. Based on the conventional box-like topology, two additional single cavities are used to achieve wider bandwidth and simplify the design difficulty. In addition to two transmission zeros (TZs) realized by the cross-coupling technology, nonreasoning node will generate an additional TZ at a higher frequency to improve the upper stopband performance. Finally, a sixth-order filter, having the passband frequency of 24.25–27.5 GHz for 5G application, with three TZs, is simulated, fabricated and measured to demonstrate and verify the proposed structure. The test results show the insertion loss is 1.7 and 3 dB bandwidth is 3.37 GHz. The three TZs improve out of band rejection of the filter.