Through-the-wall target localization using dual-frequency CW radars

A simple through-the-wall radar system for moving target localization is proposed. This scheme is based on trilateration and range estimation from three independent dual-frequency CW radar units. The dual-frequency technique uses phase comparison of the transmitted and received CW signals to provide an estimate of the range-to-motion. The difference in frequency of the two CW carriers determines the maximum unambiguous range of the target. The range estimates from the three independent CW radar units are then combined using trilateration for target localization. The composition and thickness of the wall, its dielectric constant, and the angle of incidence all affect the characteristics of the signal propagating through the wall. The propagating signal slows down, encounters refraction, and is attenuated as it passes through the wall. If unaccounted for, the non-line-of-sight propagation due to refraction and the slowing down of the waves will introduce a bias in the estimated target location. Our scheme takes into account the presence of the wall and corrects for its refraction and speed of propagation effects. Proof of concept is provided using simulated data. The results show that the proposed dual-frequency CW radar system is able to correctly locate and track moving targets behind walls.