Refocusing through the unknown building wall with a filtered backprojection algorithm

A filtered backprojection (FBP) algorithm incorporating the layered medium Green's function to take into account the wall effect is proposed for through-the-wall imaging (TWI). A refocusing time factor is introduced to obtain a dynamic image at different focusing time. The image at the time instant when the defined image entropy reaches the minimum is stored as the output of the imaging result. Numerical results show that the proposed method is efficient to provide high quality focused image under unknown wall characteristics.