High-Order Quasi-Elliptical Bandpass FSS Based on Substrate-Integrated Waveguide Technology for 60 GHz Applications

This paper presents a high-order quasi-elliptical bandpass frequency-selective surface (FSS) using substrate-integrated waveguide (SIW) technology for 60 GHz applications. First, a planar double-layer criss-cross slot FSS is employed to achieve second-order bandpass response and introduce a low-frequency transmission zero (TZ). Second, a long-period SIW FSS, composed of four identical criss-cross slot elements within a single period, is utilized to introduce an additional high-frequency TZ, thereby realizing a high roll-off in dual sidebands. Third, additional plane octagonal slot elements are integrated into the long-period SIW FSS to excite higher-frequency resonant modes, and a semi-open SIW cavity is utilized to improve high-frequency out-of-band rejection. Simulation results are presented to validate two proposed FSSs that exhibit outstanding performance, including the wide passband, low insertion loss, and both dual passbands with the quasi-elliptical filtering response.