Spectral domain analysis of conducting patches of arbitrary geometry in multilayer media using the CG-FFT method

A conjugate gradient-fast Fourier transform (CG-FFT) scheme for analyzing finite, flat, metallic patches in multilayer structures is presented. Rooftop and razor-blade functions are considered as basis and testing functions, respectively. An equivalent periodic problem in both domains (real and spectral) is obtained and solved. Aliasing problems are avoided by performing a window on the Green´s function. The spectral domain periodicity makes it feasible to take into account almost all the harmonics and to reduce the ripple in the computed current distributions. Nearly all the operations are performed in the spectral domain, including Green´s function computations. Several results of convergence rates, current distributions and radar cross-section (RCS) values are given and compare favorably with measurements or results obtained by other methods