Wave Imaging Sensors Research Articles

New Technology and Applications on Passive Millimeter-Wave Sensors

Some new technology and applications on passive millimeter wave (pmmW) sensors are reviewed. The development of passive millimeter wave imaging sensors, operating at W band, that are currently being manufactured for commercial markets using standard automated assembly processes. is described. The focus was to adapt the night vision passive thermal infrared imager performance models and apply them to pmmW imaging systems for prediction of field performance for the task of small watercraft and boat identification. A novel method of human presence detection using pmmW sensors is presented. The method focuses on detecting a standing human from a moving platform in a cluttered outdoor environment using pmmW radiometry. Finally the research and development in passive millimeter wave imaging and performance improvements is discussed. The future passive millimeter wave sensors are expected.

Target identification and navigation performance modeling of a passive millimeter wave imager

Human task performance using a passive interferometric millimeter wave imaging sensor is modeled using a task performance modeling approach developed by the U.S. Army Night Vision and Electronic Sensors Directorate. The techniques used are illustrated for an imaging system composed of an interferometric antenna array, optical upconversion, and image formation using a shortwave infrared focal plane array. Two tasks, target identification and pilotage, are modeled. The effects of sparse antenna arrays on task performance are considered. Applications of this model include system trade studies for concealed weapon identification, navigation in fog, and brownout conditions.

Modeling passive millimeter wave imaging sensor performance for discriminating small watercraft

Passive millimeter wave (pmmW) imagers are quickly becoming practical sensor candidates for military and nonmilitary tasks. Our focus was to adapt the Night Vision [U.S. Army Research Development and Engineering Command, Communications and Electronics Research Development and Engineering Center, Night Vision and Electronics Sensors Directorate (NVESD)] passive thermal infrared imager performance models and apply them to pmmW imaging systems for prediction of field performance for the task of small watercraft and boat identification. The Night Vision Lab's infrared sensor model has been evolving since the 1950s, with the most current model being NVThermIP [Night Vision Thermal and Image Processing (NVThermIP) Model Users Manual, Rev. 9 (U.S. Army RDECON, CERDEC, NVESD, 2006)]. It has wide recognition as an engineering tool for sensor evaluation. This effort included collecting pmmW signatures for a representative set of targets, conducting an observer perception experiment, and deriving the task difficulty criteria that can be used in NVThermIP for identification of boats. The task difficulty criteria are used by designers and managers to create systems capable of meeting specific performance criteria in the field.

Passive millimeter wave imaging sensors for commercial markets

We describe the development of passive millimeter wave imaging sensors, operating at W band, that are currently being manufactured for commercial markets using standard automated assembly processes. A description of HRL Laboratories' millimeter wave imaging chipset is presented, focusing on parameters that limit sensor performance, such as detector 1/f noise, low noise amplifier noise figure, and gain drift. We conclude with a discussion of ongoing research and development in passive millimeter wave imaging and performance improvements that can be expected for future imaging sensors.

Liquid water fade margin requirements for infrared and millimeter wave runway imaging sensors in fog

Liquid water content and particle size distribution at each ten meters in the vertical for a deep advection fog and a shallow radiation fog are analyzed to determine the liquid water loss at millimeter and infrared wavelengths. The liquid water fade margin is calculated along a three degree glideslope in each fog from the current height above the runway to the touchdown point. Millimeter wave fade margin requirements are calculated from the vertical distribution of bulk liquid water content and infrared fade margin requirements are predicted from the vertical distribution of dropsize. Fog dropsize distributions for both fog layers are well fitted to a gamma distribution with a median drop diameter of approximately 9 microns. Millimeter wave imaging sensors operating in a shallow radiation fog are shown to require less than 1 dB of one-way liquid water fade margin. In the deep advection fog, one-way liquid water fade margin requirements at 8.6 mm, 6.8 mm, and 3.2 mm are predicted to be 1, 2, and 6.7 dB respectively. In comparison, the one-way liquid water fade margin requirements at near, middle, and far infrared wavelengths are two orders of magnitude greater than at millimeter wavelengths and indicate the fog layers are opaque to infrared imaging sensors even near the touchdown point. The specific attenuations predicted in the two fogs are consistent with previously reported values.