Two‐dimensional synthetic aperture imaging of targets behind reinforced concrete walls

Abstract

Abstract Synthetic aperture imaging of targets closely behind a reinforced concrete wall, modelled by a periodic structure by using the proper Green's function (GF) of the structure, is studied. To compute the GF accurately, using the rigorous coupled‐wave analysis (RCWA) is proposed. The radiation of a line source in the spectral domain as a summation of plane waves is represented. Illuminating the periodic structure by each plane wave, Bragg modes by RCWA are computed. Then, the GF is estimated as the superposition of all the Bragg modes' contributions. The numerical Finite Element Method results of COMSOL validate the results of our semi‐analytical approach. Having COMSOL numerically calculated backscattered fields of a target behind the wall and the simple free‐space GF, the synthetic aperture image of a target is not focussed. Employing the phase of the proper GF instead of the simple free‐space GF, the target image is successfully refocussed. The effect of the number of Bragg modes on the estimation of the GF and also uncertainties in the distances between reinforced metallic bars on the target image is investigated.