Incident angle-dependent effective surface impedance (Z/sub S/) of Electromagnetic Crystal (EMXT)

Electromagnetic crystal (EMXT) surfaces are modeled with effective surface impedance method. Effects of oblique incidence are studied using a technique similar to the waveguide simulator method for analyzing infinite phased array. Numerical results are compared with an analytical model. EMXT samples are characterized by open-ended waveguide reflection measurements using different aperture sizes (WR28 and WR22). The measurements confirm the angular dependence of the EMXT surface impedance. A rectangular waveguide with EMXT sidewalls is modeled by using the angle-dependent effective surface impedance as the sidewall boundary condition. Excellent agreement between this model and full-wave finite-element simulation of the entire waveguide structure is obtained.