FSS with a waveguide filter unit cell

When a Frequency Selective Surface (FSS) is irradiated by electromagnetic waves with different incident angle, drift of resonant frequency usually occurs as the incident angle changes. To solve this problem, a 3-D FSS design is presented, using metal post loaded waveguide filter as a unit cell. In this article, the poor angle stability of resonant frequency of a waveguide FSS is analyzed, and the mechanism of secondary radiation from metal post is used to improve the pass-band frequency stability of a waveguide filter as FSS irradiated by Transverse-Electric(TE) waves. This designing method is verified by numerical simulations. Moreover, the Wood's anomaly destructive to the frequency stability design of FSS is also discussed.