Electromagnetic Backscattering Mechanisms of Frequency Selective Surfaces for Effective Analysis of Radar Cross Section by the First-Order Approximation of Floquet Modes

Abstract

Full-wave analysis of finite but electrically large frequency selective surfaces (FSSs) substrates for the radar cross section (RCS) estimation is too time-consuming and unbearable for practical applications. Such FSS substrates can be either absorbing or reflective types and are widely used as radomes of antennas for stealth applications, where the electromagnetic (EM) backscattering is of much concern. This large EM problem is simplified by applying Floquet mode decomposition on the scattering fields, where the Kirchhoff approximation is employed to find the backscattering fields for RCS estimation. The resulted formula allows one to explore the scattering mechanism for RCS enhancement or reduction. Besides, the approximation is used to resemble the FSS radome by equivalent substrates. Thus, the transmission and reflection coefficients of the equivalent dielectric substrates are similar to those from FSS elements under an infinite array assumption. Afterward, the resulting EM problems of antenna radiations and scattering can be easily analyzed using the equivalent substrates of EM materials. Numerical examples of planar FSSs to form radomes demonstrate the feasibility of numerical simulations’ proposed work. The presented work can also be directly applied for fast analysis of EM shielding effectiveness by FSS substrates.