Q-Band Millimeter Wave Imaging in the Far-Field Enabled by Optical Upconversion Methodology

Abstract

Millimeter-wave (mmW) imaging has evolved to the point where it offers distinctive remote sensing capabilities in many application scenarios, such as port and harbor security, search and rescue, and navigational aids, due to its unique ability to penetrate atmospheric obscurants. Some of the applications being considered require passive imaging, imposing challenging sensitivity requirements to detect the low power levels in this spectral region. One metric used in this regard is the noise equivalent power (NEP), which quantifies the sensitivity of a detector. By utilizing a unique detector technology based on optical upconversion a low NEP value is achieved as compared to other RF methods, without the use of cryogenic cooling or low noise amplification. In addition, the overall size and weight may be reduced as compared to other imaging methodologies. As such, the construction and development of a passive mmW imaging system utilizing optical upconversion was undertaken, operating in the Q-Band to collect radiation between 33 and 50 GHz. Herein, we describe the passive mmW imager architecture and operation. Also presented are imaging results obtained using this approach as well as key imager metrics that have been experimentally validated.