Complex target reconstruction using near-field synthetic aperture radar

Abstract

This thesis describes the development of a prototype (imaging) radar system intended for discriminating between rocks of varying size under the severe environmental conditions typically present on a mine-site. Synthetic aperture radar (SAR) systems allow high-resolution measurements to be made using the motion of the sensing platform to provide at least one of the sensing degrees of freedom. They therefore provide a means of reducing the number and cost of mechanically actuated components which is particularly beneficial in a harsh environment such as a mine. A 3-D near-field imaging radar system has been developed utilising the highest available component bandwidth of 2-18GHz. This has allowed two-target range discrimination performance of better than 20mm to be obtained over a single sweptfrequency measurement within a custom-built anechoic test chamber. Bistatic antennas in an inverse-SAR configuration have been used to demonstrate the concept of a multistatic spherical-SAR system, which with a single transmitter has advantages in both cost and complexity over the equivalent multiple-transmit/receive configuration. The Fourier-domain point-target focussing templates for this bistatic configuration have then been derived using the method of stationary phase based on the earlier work of Fortuny. Further algorithms have then been developed for the calculation of templates corresponding to spheres of a particular radius, for both monostatic and bistatic configurations. Full 3-D reconstruction of complex-target topography has then been achieved through a novel sphere-summation process, with extensive simulated and experimental results obtained and analysed for both a set of spheres and a more realistic scenario consisting of a pile of rocks of varying shape and size.