Article ID: 16.20190178
A new three-dimensional (3-D) frequency selective surface (FSS) based on rectangular waveguide cavities is presented, which realizes a quasi-elliptic bandpass response by multiple transmission zeros/poles. Each unit cell of the proposed FSS is composed of an empty rectangular waveguide cavity and a cuboid circuit board with two back-to-back square loops. With the help of the rectangular waveguide cavities, the electrical and magnetic coupling paths are constructed, resulting in two transmission poles. The constructed out-of-phase signal paths cause two transmission zeros in the upper stopband. To explain the operating principle of the proposed FSS, an equivalent circuit model is given and analyzed using the odd- and even-mode method. A prototype of the proposed FSS is fabricated and measured. The measured results agree well with the simulated results, and show that the FSS can achieve a stable response to variations of incident angle from 0° to 60° for both TE and TM polarizations with wide out-of-band rejection. In addition, the proposed design also realizes a relative small unit cell.
