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Electro-Optically Guided Radar Imaging


OBJECTIVE: Develop an electro-optically guided high resolution MMW radar imaging method with enhanced information processing capability. DESCRIPTION: MMW radar imaging is commonly employed for high resolution terrain mapping and surveillance, as well as for concealed threat detection methods. However, the majority of the scanning methods currently employed utilize mechanically scanned apertures, which significantly inhibit the amount of time required for image generation. Motion-free beam steering is particularly attractive, namely because of advantages in reliability, as well as the ability to permit rapid and gross changes in scanning directionality, which ultimately enables flexible scan patterns and the ability to pan to specific points of interest. Two common methods of motion-free beam steering are phased-array antennas, and reconfigurable-plasma refraction antennas. However, as a consequence of the sheer number of components involved in phased-array beam steering approaches, these methods are typically excessively complex, as well as cost-prohibitive. Consequently, a more favorable approach would be to use a lightweight, efficient, optical front end to perform the beam steering. Recent investigative studies utilizing the transient Fresnel zone plate approach, where a spatially varying density of charge carriers is created by optical injection of plasma into a semiconducting wafer, have been demonstrated. While this methods shows promise as a potential solution to enabling high resolution, motion-free scanning, it is still inhibited by information processing limitations. In order to improve upon current image resolution thresholds, increased bandwidth is desired. However, the increase in bandwidth reciprocally increases the challenges faced in processing information. Traditional radar information processing strategies employ range bins, as a data sampling method. Such techniques are necessitated in order to increase data processing efficiency, however, the consequence of this is diminished image resolution. The proposed effort will be designed to mitigate the impact of the loss in image resolution as a consequence of data sampling in the RF spectrum, by frequency up-converting the detected RF. Assuming the signal integrity can be maintained throughout, data sampling may then be achieved through the insertion of an ultra-fast optical shutter (e.g. Pockels cell) or other means. The method must also be compatible with an optical beam steering architecture so that it may be implemented in later phases. PHASE I: The proposed effort will experimentally demonstrate proof-of-concept. Expectations for Phase I, will be to successfully frequency up-convert radar target energy in the mmW band, to an optical band, and verify that the signal characteristics may be preserved at the detection end-state, following transmission through the selected sampling method. A final report on the investigation and demonstration will be provided to the Government. PHASE II: Expectations for Phase III, will be to expand the prototype to a producible configuration and look to apply the technology to military applications such as assisting with degraded visual environment (DVE) helicopter landings. Some commercial applications consist of law enforcement, home-land defense, and hand-held devices for screening of materials (i.e. civil construction, packages, etc.). A transition to operational capability could be applicable to all military rotary-wing applications and missions. PHASE III: Expectations for Phase III, will be to expand the prototype to a producible configuration and look to apply the technology to commercial uses such as, law enforcement, home-land defense and hand-held devices for screening of materials (i.e. civil construction, packages, etc.) REFERENCES: D. G. Johnson,"Development of a High Resolution mmW Radar Employing an Antenna with Combined Frequency and Mechanical Scanning,"in Radar Conference, 2008. RADAR"08 IEEE, 2008, pp. 1-5. D. Johnson, M. Calleija, and E. Nettleton,"Development of a Dual-Mirror-Scan Elevation Monopulse Antenna System,"in Radar Conference, 2011. RADAR"11 IEEE, 2011, pp. 281-284 A. Foessel-Bunting and W. Whittaker,"MMW-Scanning Radar for Descent Guidance and Landing Safeguard,"6th International Symposium on Artificial Intelligence, Robotics and Automation in Space, June, 2001 G. W. Webb, S. C. Rose, M. S. Sanchez, and J. M. Osterwalder,"Experiments on an Optically Controlled 2-D Scanning Antenna,"1998 Antenna Applications Symposium, September 1998
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