Experimental Study on Dielectric Constant and Boundary Estimation Method for Double-Layered Dielectric Object for UWB Radars

A microwave ultra-wideband (UWB) radar system has an advantage for high range resolution and penetrating ability in dielectric object, and is promising for the applications, such as non-destructive testing for aging road or bridge and noninvasive human body inspection. We have already developed an accurate internal imaging approach based on the range points migration (RPM) method, combined with the efficient dielectric constant estimation method. However, the former method is applicable to only the situation that high conductive target is buried into a homogeneous dielectric medium, and is not suitable for the case of multi-layered dielectric structure, such as human body or layered concrete object. As a simple expansion aiming at multi-layered dielectric object, this paper proposes a novel dielectric constant and boundary extraction method for a double-layered case, where the exiting Envelope method is appropriately extended to boundary extraction of the inner layer. The results from finite-difference time-domain (FDTD) based numerical simulation and experiment, demonstrate the effectiveness of our proposed method.