Fast Computation of Resonant Metasurfaces in FDTD Scheme Using Dispersive Surface Susceptibility Model

A new framework of scattering analysis of metasurfaces composed of an assemble of resonant scatterers, with a multistage analysis procedure, is presented. The metasurface analysis using this framework utilizes a dispersive surface susceptibility model (SSM) and a finite-difference time-domain (FDTD) method, replacing the traditional brute force simulation with the physics-based SSM. The SSM extraction for characterizing scatterers is provided, which then is used to replace detailed practical scatterers in numerical simulation. The SSM with the frequency-dependent features' behavior is described by multiple-Lorentz pole pairs, and the coefficients of the Lorentz model are obtained by using a rational fitting method. An easy-to-implement FDTD algorithm combined with the Lorentz-described SSM is proposed and presented. The efficiency of the proposed framework is proven by comparing it with conventional FDTD. The validity of the proposed framework is verified using commercial EM simulation software. The use of this analysis procedure is demonstrated by two example scatterers. Through the examples, we discuss the requirement of the meshing lattice size, sensitivity of the algorithm to the incident angle, and influence of the edge effects on the bistatic radar cross section (RCS) computation.