Interpolation of impedance matrices for varying quasi-periodic boundary conditions in 2D periodic Method of Moments

Periodic structures can be simulated using the periodic Method of Moments. The quasi-periodicity, i.e. periodicity within a linear phase-shift, is implemented through the use of the periodic Green's function. In this paper, we propose a technique to interpolate the impedance matrix for varying phase-shifts. To improve the accuracy, the contribution of the dominant Floquet modes and a term corresponding to a linear phase-shift are first extracted. The technique is applied to planar geometries, but can be extended to non-planar configurations.