Fast Semi-Analytical Design for Single-FSS-Layer Circuit-Analog Absorbers

In this paper, analytical, empirical, and numerical techniques are integrated for analyzing and synthesizing circuit analog (CA) absorbers based on a single-layer frequency-selective surface (FSS). The proposed design approach dramatically reduces the number of full-wave simulations required for global optimization, so that the potential of fundamental FSS geometries can be exhaustively exploited. With the semi-analytical algorithm, the near optimal bandwidth-thickness can be quickly and reliably calculated for a given single-FSS-layer topology. To demonstrate the robustness of our semi-analytical approach, a square-patch and square-ring FSS absorbers at 10 dB level of absorption are revisited and optimized. The designs are constrained by available materials and standard tolerances for experimental validation. A manufactured prototype achieves a relative bandwidth of 144.15% and a normalized thickness of 0.0972λL, which is superior to existing designs with more complicated FSS patterns in the literature.