Analysis of frequency selective surfaces using two-parameter generalized rational Krylov model-order reduction

Generalized rational Krylov model-order reduction techniques are applied to the spectral Galerkin system describing frequency selective surfaces, resu lting in surface reflection coefficient models that depend on both the freq uency and the incident angle of the exciting wave. The procedure is compose d of three steps: construction of the spectral Galerkin system, linearizati on of that system, and reduction of the linearized system. The linearizatio n of the spectral Galerkin matrix is carried out using two-dimensional (2-D ) polynomial interpolation and the generation of a "two-parameter" companio n form of the polynomial system. The subsequent model-order reduction is ba sed on the concept of generalized Krylov subspaces, which are defined in th e text. It results in a small system with a frequency and incident angle de pendent output that matches the two-parameter polynomial interpolant system transfer function and its derivatives at many points in the frequency/inci dent angle plane. The technique is applied to the characterization of sever al frequency selective surfaces, and numerical results that demonstrate the accuracy of the techniques over a broad band of frequencies and range of i ncident angles are presented.