Application of DORT and pulse inversion to detection and selective electromagnetic focusing on nonlinear elements

In this work, we present the DORT (decomposition of the time-reversal operator) technique in combination with pulse inversion (PI) applied to detection and selective focusing on nonlinear targets. When nonlinear targets of interest are present in a field of linear scatterers, the harmonic responses from the nonlinear targets can be used as a distinguishing feature when applying DORT. Furthermore, PI suppresses fundamental and odd order harmonics, retaining only the second harmonics originated from nonlinear targets of interest, thereby reducing clutter from unwanted linear scatterers and occasional natural nonlinear scatterers (rusty metals). Two-dimensional numerical simulations are presented for a basic demonstration of the proposed approach.