A Passive Millimeter Wave One Second Camera

The rapidly developing market for Passive Millimeter Wave (PMMW) imaging cameras with a frame time of one second or less includes commercial as well as military applications. Several application opportunities are listed below. An analysis is application-oriented requirements leads to the definition of camera capabilities described in terms of the field of view, minimum number of scene pixels, radiometer sensitivity, and frame time requirements. Current state-of-the-art radiometric sensitivity, at the frequency of interest, exceeds that required to sample all of the scene pixels with one receiver in less than one second. If one were able to raster scan a single receiver antenna beam over all of the scene pixels in one second, the one second camera would need only one receiver. Present-day electronic, as well as mechanical antenna beam scanning capabilities fail to meet the required scanning rate for a single channel PMMW camera system. We propose to modify a commercially-available, high-speed, mechanically scanned radar system antenna, and adapt it to the one-second camera. Additional receiving channels are needed to reduce the scanning rate requirement, not to improve sensitivity. The addition of receiver channels as a means for reducing mechanical scan rate requirements is not without problems associated with interchannel gain stability and flat field retention. The proposed effort will provide a solution to these and other problems associated with the use of more than one receiver channel when generating PMMW images.