Compact Integrated Substrate Gap Waveguide Bandpass Filter with Two Transmission Zeros

In this paper, a K-band compact fourth-order broadband bandpass filter (BPF) based on an integrated substrate gap waveguide (ISGW) is proposed. Significant size reduction is achieved through the introduction of two reversely placed split ring resonators (SRR) and two half-mode cavity resonators. At the same time, a transmission zero (TZ) is introduced on each side of the passband through cross-coupling to improve the selectivity of the filter. The periodic electromagnetic band gap (EBG) layer at the top of the structure prevents the radiation leakage caused by the engraving of SRRs. The center frequency of the filter is 22.5GHz, the 3dB fractional bandwidth is 21%, the passband insertion loss is 0.6dB, and the size is 0.67λ<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</inf> * 0.67λ<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</inf>.