Three-dimensional band-stop frequency selective structures

Frequency selective surfaces (FSSs) have been extensively investigated in the past few decades. A traditional two-dimensional (2-D) FSS, consisting of a periodical array of conducting patches or slots/apertures, cannot realize a desired number of transmission zeros/poles leading to a quasi-elliptic or elliptic filtering response. In this paper, based on a review of research work related to traditional 2-D FSS, a new class of three-dimensional band-stop FSS consisting of a 2-D periodic array of vertical microstrip lines are described, whose propagation modes and coupling with air can be controlled to obtain a desired frequency response. A generalized equivalent circuit based on multi-mode resonator theory is also introduced to explain the operating principle of these high-performance band-stop FSSs.