3-D Closely Spaced Dual-Band Frequency Selective Surface Based on Square Waveguide

In this paper, a three-dimensional (3-D) frequency-selective surface (FSS) is proposed to realize two close passbands with high selectivity. In each unit cell, one modified parallel-plate waveguide (MPPW) propagation path and one I-shaped slots (ISS) propagation path are constructed to generate three transmission poles and two transmission zeros. The E-field analysis of transmission poles and zeros is provided to understand the operating principle of the proposed FSS. According to the simulation results, the proposed 3-D FSS can achieve two closely spaced passbands with the center frequency ratio of passbands 1.1. Furthermore, the proposed FSS exhibits stable frequency responses under a large variation of incident angles for dual polarizations.