Refraction Angle Approximation Algorithm for Wall Compensation in TWRI

Wall penetration of the electromagnetic wave causes target image defocused and displaced from its true position in through-wall radar imaging. To solve this problem, this letter proposes an approximate wall compensation algorithm, named the refraction angle approximation algorithm, which assumes that the actual refraction angle is approximately equal to the one whose incidence angle is the azimuth angle of the target. The assumption is reasonable since the refraction angle is less sensitive to the incidence angle and limited in a small range based on the Snell's law, and the cosine function has a small derivative at a small angle. Theoretical derivation indicates that the time delay estimation error can be ignored if the target is not so close to the wall surface around the radar. Numerical simulation verifies the efficacy of the algorithm.