Simulation of anisotropic artificial impedance surface with rectangular and diamond lattices

Infinite lattices of patches covering grounded dielectric slabs were simulated using Ansoft HFSS. Both rectangular and diamond unit cells were studied. For waves propagating along rectangular unit cells, the transverse cell dimension has no effect on the surface impedance or dispersion characteristics. For diamond unit cells, the surface impedance and dispersion characteristics vary significantly for different transverse cell lengths when the wave propagates along the shorter unit cell dimension. For waves propagating over the longer dimension, surface impedance and dispersion remain similar. Results show that at a given frequency, the impedance can be varied by changing the length of the cell in the propagating direction. For rectangular cells, impedance in orthogonal directions is independent of each other, and an anisotropic impedance tensor can be created based on the size and orientation of the cell.