Scattering by a finite periodic array of strips

An investigation was conducted of the scattering of electromagnetic waves incident on a large but finite number of equally spaced parallel thin conducting strips with arbitrary shape. The boundary element method is used to discretize the integral equation for the induced current into a large matrix equation. To obtain the solution of the matrix equation, the conjugate gradient method (CGM) is used. In each step of iteration, the product of a large matrix and a vector must be calculated, which is computationally expensive. However, for a finite periodic structure, the coefficient matrix is block Toplitz, so the fast Fourier transform algorithm can be used. No aliasing problems occur because the circular convolution can be computed exactly by the discrete Fourier transform.<>