“…In general, TR invariance can be exploited for detection and localization of obscured targets in noisy and rich-scattering environments, with high resolution. Timereversal (TR) techniques were first developed for acoustics (Fink et al, 1989) (Fink, 1992), being later successfully used in several applications including non-destructive testing and evaluation (Liu et al, 2014), sound quality enhancement (Lin & Too, 2014), atmospherics studies (Mora et al, 2012), subsurface geophysics (Fink, 2006;Leuschen & Plumb, 2001;Saillard et al, 2004;Cresp et al, 2008;Artman et al, 2010;Foroozan & Asif, 2010;Yavuz et al, 2014;Chen et al, 2016), microwave remote sensing (Reyes-Rodríguez et al, 2014), wireless communications (Fouda et al, 2012) and medicine 1 Backpropagation can be effected either physically by transmitting the time-reversed signals into the original medium, or synthetically by means of a forward simulation engine, such as the finite-difference time-domain (FDTD) method. Synthetic backpropagation is done for imaging purposes, as considered here.…”