  An accelerated analysis method for non-uniform metasurfaces in FDTD is
presented for the first time. The non-uniform metasurfaces are modeled by a
distribution of susceptibilities, homogenized parameters. Those
susceptibilities are calculated from scattering coefficients of each elements
based on Generalized Sheet Transition Conditions (GSTCs). Next, susceptibility
modeled metasurface is simulated in 3D FDTD in a form of surface polarization
currents. For simplicity, this paper only consider frequencies well below
resonance, where the susceptibility is an approximate constant.
