Datum correction based on wave equation inversion in time for UWB through-the-wall radar

Through-the-wall radar imaging (TWRI) based on the ultra-wide band (UWB) technology plays an important role in military and civil applications due to its powerful penetration and high down-range resolution. As a result, it has acquired great interest in the research of synthetic aperture radar (SAR) or multiple-input and multiple-output radar. Most of the existing algorithms for TWRI assume that the antenna array is parallel to the front wall. Therefore, they cannot guarantee an idea effect in real applications. The unknown tilt angle between the antenna array and the wall may induce an inevitable imaging distortion and even may lead to a false detection. To solve this problem, the authors propose a new datum correction algorithm based on backward propagation of electromagnetic wave in reverse time. Firstly, according to the time delay of echo signals, the tilt angle and stand-off distance are estimated to determine the coordinates of antenna elements. A datum plane consequently is determined as well. Secondly, a wave equation inversion problem is solved for giving a set of echo signals collected by the virtual parallel array along with the datum plane. Simulation shows that their proposed algorithm is effective and has robust stability against the noise.