Waveguide 3-D FSSs by 3-D printing technique

In this paper, two novel bandpass three-dimensional frequency selective surfaces (3-D FSSs) based on the waveguide structure are proposed. The first 3-D FSS is composed of a square metallic waveguide with dumbbell slots which are loaded in all waveguide walls. This design can form dumbbell slot resonators and introduce a passband below the cutoff frequency of the waveguide. The second one is constituted with square coaxial waveguide unit cells, which provides coaxial and parallel plate waveguide paths. By the interaction between two propagation paths, a quasi-elliptic response takes place and improves the frequency selectivity. The results show that both of proposed 3-D FSSs exhibit dual polarized characteristics, and can provide good frequency stability for different incidence. In addition, using 3-D printing technology, these structures are easy for fabrication.