Frequency response from one-dimensional rough surface with the pulsed wave excitation by the FDTD method

A frequency response of one-dimensional (1-D) randomly rough surface in the far zone is investigated by the finite-difference time-domain (FDTD) algorithm. A FDTD calculation is performed with a pulse wave excitation, and the representative time-domain scattered field in the far zone is obtained directly by extrapolating the currently calculated data on the output boundary. Then the frequency response of 1-D rough surface is acquired by transforming the representative time-domain field to the frequency domain by a Fourier transform, corrected with a simple multiplicative factor. The normalized radar cross section versus frequency from 1-D rough surface with Gaussian spectrum and PM sea spectrum is compared with the result by FDTD with the sinusoidal wave illumination, which requires an individual FDTD run for every frequency. Finally, the frequency response of rough surface and the representative scattered field in the far zone versus time are analyzed in detail.