Analysis of Finite Conformal Frequency Selective Surfaces via the Characteristic Basis Function Method and Spectral Rotation Approaches

An efficient characteristic basis function (CBF)-based method is proposed to analyze conformal frequency selective surfaces (FSS) that are not amenable to analysis by using conventional numerical methods typically used to model infinite, planar, and doubly periodic FSSs. The technique begins by employing the CBFs to describe the currents induced on the elements. The reaction integrals needed to derive the reduced matrix elements are computed either in the spatial domain, or spectral domain, depending on the separation distance between the blocks, so as to make the process numerically efficient. The spectral domain integrals are evaluated by making use of the spectral rotation (SR) on the spectra of the CBFs to alleviate the computational burden to be associated with full three-dimensional (3-D) Fourier transform, which is required in the conventional spectral domain approach applied to nonplanar geometries. Numerical results from the new method have good agreement with the fully spatial characteristic basis function method (CBFM) and the conventional method of moments (MoM). However, the required central processing unit (CPU) time is greatly reduced.