Autofocus imaging simulation for through-wall radar by using FDTD with unknown wall characteristics

A novel through wall radar imaging (TWRI) algorithm based on phase shift migration (PSM) with autofocus ability under unknown thickness or permittivity of wall is proposed in this paper. The entropy and variance of images obtained by PSM algorithm are computed to analyze the trends of the thickness and permittivity changing. The image when the entropy is minimized and the variance is maximized is stored as the output of TWRI result. Simulation results show that the proposed method can exactly estimate the value of the wall´s thickness or permittivity and lead to high quality focused image.