Design Methodology and Equivalent Circuit Analysis for the Dual-Polarized Absorptive Angle-Selective Surface

This article presents a novel design methodology for the dual-polarized absorptive angle-selective surface (ASS). The ASS consists of multiple lossy frequency selective surfaces (FSSs) and a metallic ground. An equivalent circuit is first constructed to model the entire structure. Analytical derivations for the reflection and absorption conditions of the two-layer ASS are performed, with extension to ASS configurations comprising multiple layers. The analytical impedance formulas for the FSS based on strips and chip resistors are proposed and extended to the angular domain. Subsequently, a general design methodology for the absorptive ASS is proposed, which enables the realization of flexible filtering performance within the angular domain. In order to validate the proposed design methodology, two ASS examples of distinct angular responses in the angular domain are provided. The first ASS example is with a low angular band of reflection and a high angular band of absorption (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</i>–<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">A</i>). The second ASS example is with a center angular band of absorption and side angular bands of reflection (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</i>–<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">A</i>–<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</i>). The <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</i>–<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">A</i> ASS achieves reflection (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\vert S_{11}\vert \ge -1$</tex-math> </inline-formula> dB) in the angular band from 0° to 25° and absorption (absorption rate <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\ge 90$</tex-math> </inline-formula>%) in the angular band above 45° under the incidence of both TE and TM polarizations. The <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</i>–<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">A</i>–<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</i> ASS attains absorption at 20° and reflection in the angular bands from 0° to 10° and above 30°. Two prototypes of the proposed ASSs are fabricated, and the measured results agree well with the simulated ones.