A Third-Order Bandpass Three-Dimensional Frequency Selective Surface with Multiple Transmission Zeros

Abstract

We present a third-order bandpass three-dimensional frequency selective surface (3D FSS) with multiple transmission zeros in this paper. The unit cell of the proposed 3D FSS consists of an air-filled square waveguide and a cuboid dielectric block with three concentric metallic square loops. Due to its inner electromagnetic coupling in the unit cell, this FSS provides a flat passband with three transmission poles, a wide out-of-band rejection with three transmission zeros, and high frequency selectivity. In order to explain the working principle, an equivalent circuit model is established and investigated. Finally, an FSS prototype is fabricated and measured, and the results exhibit good stability for both TE and TM polarizations under incident angles from 0° to 50°. Besides, this FSS has a relatively compact unit cell.