An Impulse Radar Nondestructive Evaluation System

A microwave impulse radar system for nondestructive evaluation (NDE) and inverse scattering imaging has recently been developed at the University of Illinois [1,2]. This automated time-domain ultra-wideband radar system consists of a Pi cosecond Pulse Lab (PSPL) 4050B step generator, a PSPL 4050RPH remote pulse head, two PSPL 5210 impulse forming networks, a Hewlett-Packard (HP) 54120B digitizing oscilloscope mainframe, an HP 54121A 20 GHz four-channel test set, a broadband Vivaldi antenna [8] array, two ultra-wideband amplifiers and two mi crowave switches. The system is automated and controlled by a computer via the IEEE-488 bus. The performance of this impulse radar NDE system will be eval uated by collecting useful measurement data from different test targets including metallic and dielectric objects. Two iterative nonlinear image reconstruction algo rithms, the distorted Born iterative method (DBIM) [3,4] and the local shape func tion (LSF) method [5,6,7], are used to process the time-domain measurement data to reconstruct the image of the target object. Our goal is to combine the impulse radar system and inverse scattering imaging algorithms to provide an NDE system with high resolution imaging capability for civil structures