A Time-Domain Measurement System for UWB Microwave Imaging

A fully automatic time-domain measurement system for ultra-wideband (UWB) microwave imaging is presented. The system uses a pair of movable antennas to transmit and receive custom UWB pulse designs with each antenna able to be independently controlled to rotate about a region of interest. A full measurement, consisting of both incident and total field collections, is completed within 20 min using custom software. The collected data is processed to reconstruct images of three test objects. Imaging results demonstrate the system can localize and recognize different shaped objects, and differentiate multiple objects. The precision of antenna positioning and the impact of random noise on the microwave signal are investigated. The maximal positioning error for the antennas allows for accurate use of the system up to 7 GHz. A comparison between the time-domain system and a frequency-sweep method shows both methods allow for accurate imaging results. The signal-to-noise ratio and image quality may be improved with time-domain results when properly selecting a time window for the received signal.