UWB radar target sensing and imaging for granular materials research applications

In this paper, we investigate a first-generation prototype of a radar system that will provide a minimally invasive fully automated measurement of individual and bulk particle movement in a 3D volume. The radar system comprises inexpensive tracer particles as targets, a test signal generation and measurement unit, and a post-processing unit for imaging. The proposed target is a square retroreflector, which is made up of three orthogonal square metal plates. An array of wideband antennas surrounding the testbed is operated in monostatic mode using swept-frequency VNA measurements that are processed to mimic an ultrawideband (UWB) bandpass pulse. In our first-generation prototype, we synthesize a linear array by moving the testbed relative to a single antenna. The testbed contains one or more targets deployed in a free-space (rather than granular material) volume. We perform delay-and-sum beamforming to reconstruct an image of the testbed. Images are generated for the retroreflector at two distinct orientations (normal and oblique) relative to the array.