Frequency dispersion compensation in time reversal techniques for UWB electromagnetic waves

The invariance of the wave equation under time reversal enables optimal refocusing of ultrawideband waves by time-reversal (TR) arrays. This forms the basis of recently developed TR techniques for selective (re-)focusing and inverse scattering applications. However, in electromagnetic sensing applications involving lossy or dispersive media, such as earth media, time invariance is lost and TR techniques can be significantly degraded. To alleviate this problem, a method to compensate dispersion in TR applications is proposed here. The method is based on short-time Fourier transforms and is shown to improve refocusing.