A new conjugate gradient-fast Fourier transform (CG-FFT) scheme for analysis and design of flat metallic periodic structures

A computer code based on the CG-FFT (conjugate-gradient-fast Fourier transform) is reported for analyzing general metallic periodic screens. It is highly efficient and accurate and is being applied to the analysis and design of broadband polarizers and rotators. All Floquet's harmonics are taken into account in the spectral domain by sampling the Green's function in this domain in periodic lattice, which is the reciprocal of the lattice of the periodic structure to be analyzed. The choice of rooftop functions as basis functions and razor blade functions as testing functions leads to a very suitable scheme for iterative methods. A numerical example illustrating the results of the code is discussed.<>