Performance Evaluation of a Passive Millimeter-Wave Imager

A cross-correlating 186-GHz passive millimeter-wave imager has been built. The key components in the signal processing hardware are two 186-GHz receivers and a broadband complex correlator. To evaluate the performance of this imager, its point-spread function, beam pattern, baseline vector, and their variations with the scanning direction have been experimentally measured and derived. Some of these results are needed for optimizing the imager´s parameter settings. Others are required for implementing the modulated-beam and modulated-scene algorithms proposed in a previous paper dealing with the imager´s fringe in its point-spread function. These results will also reveal any problems in the construction process of the imager. The theoretical bases for these measurements are analyzed. Novel algorithms for deriving each antenna´s point-spread function and beam pattern, as well as the imager´s baseline vector from the measurement results of the imager´s point-spread function and beam pattern are proposed and successfully applied in the measurements. Experimental results are presented and discussed.