A hybrid MoM/UAPO approach for the analysis of truncated penetrable periodic structures

Periodic structures play a key role in many antenna systems. We use a non-standard hybrid technique to combine a numerical and a high frequency technique. We suppose an FSS structure so large in terms of wavelengths that a rigorous full wave technique cannot be implemented to describe its electromagnetic behavior. We extract from this structure a portion that can be analyzed with a rigorous numerical technique. For the numerical analysis we have chosen the commercial MoM code FEKO. Then we impose that the scattered field, evaluated with this commercial code, is expressed as a superposition of Floquet´s modes with unknown amplitudes and we carefully select appropriate paths to sample this field. By imposing on these paths the equality between the MoM derived scattered field and the analytical solution of the scattered field, the amplitudes of the most significant Floquet modes can be determined. Finally, by integrating the corresponding PO currents on the surface of the real FSS, a uniform asymptotic physical optics (UAPO) field description can be obtained.