A Dual-Polarized Bandpass Frequency Selective Surface With Stable Response

In this letter, a dual-polarized 3-D frequency selective surface (3-D FSS) based on 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 good angular stability and easy implementation. By an equivalent circuit model, its operating principle 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.