Analysis of wave propagation in inhomogeneous media using FDTD method and its applications

摘要

A new simulator to predict the wave propagation in inhomogeneous media is developed. The wave equation is approximated by the approximate difference equations using the finite difference time domain (FDTD) method. The effects of an aberrating layer on radar imaging are examined for various step and graded velocity profile aberrating layers. The method is illustrated for the case where the whole media is inhomogeneous. The permittivity of the medium is assumed to vary in a low-pass Gaussian manner above a constant value. This analysis of radar imaging becomes very important when the medium itself acts as many scatterers. The received echoes are calculated for various values of surface roughness and permittivity difference for both the aberrating layer and the inhomogeneous media. The effects of inhomogeneity on the point spread function (PSF) are analyzed. Later, the cross correlation between the echo signals received at different elements of the radar array are examined as a function of the distance between the elements. The effects of inhomogeneity of the medium on the cross correlation coefficients are also studied.