A Dual-Polarized Bandpass Frequency Selective Surface with Stable Response

In this letter, a dual-polarized three-dimensional frequency selective surface (3-D FSS) based on the square metallic waveguides (SMWs) is proposed, which produces a flat passband with two transmission zeros in a relatively wide rejection. Because all resonances occur along propagation direction without complex resonators, a small unit cell size and simple geometry is achieved, resulting in a good angular stability and easy implementation. By an equivalent circuit model, the physical operating principle of the proposed 3-D FSS is explained. At last, the measured results of an implemented FSS show that a stable response under the incident angles up to 60 for dual polarizations is realized.