A novel high-selective bandpass frequency selective surface with multiple transmission zeros

The design, analysis, and measurement of a novel frequency selective surface (FSS) are proposed, which works with high selectivity in X-band and wide out of band rejection in C-band and Ku-band. The proposed FSS is achieved by cascading two-layer periodic arrays of unit cells based on square loop structure. Multiple transmission zeros are obtained for broadening the stopband on the both sides of the passband. The presented double-layer FSS is insensitive to the variation of incident angle and polarization of a striking plane electromagnetic wave. By studying the electric fields and currents excited in the proposed structure, it explains the passband characteristics and the multiple transmission zeros in the two stopbands. Experimental verifications are carried out, which are consistent with the simulated results.