Research on Polarimetric Radar for the Detection of Objects Buried in Wet Snowpack

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This research is aimed at developing a polarimetric FM-CW radar for the detection of objects buried in snowpack. During the period of 1990-1991, we have established an FM-CW radar system operating in the microwave frequency of 1-2 GHz with polarimetric measurement capability. First, the polarimetric and synthetic aperture technique are incorporated in the radar system which enables to retrieve information from targets in detail. Various techniques including antennas and microwave circuits are developed, coupled with the software implementation that control the system as well as computer visualization of the radar echo. Second, the performance of the radar system is verified in an anechoic chamber of Niigata University using a metallic plate as a target, demonstrating the high resolution imaging in the azimuth direction and the importance of polarimetric information. Third, several field measurements were carried out to detect objects buried in natural snowpack at Yamakoshi village, Niigata Prefecture. The radar could detect metallic targets as well as human body embedded in natural snowpack at least 100 cm deep clearly, producing high resolution images of the targets. Especially, the synthetic aperture image provided the clear boundary of the targets in severely cluttered environment. In addition to the principal research objectives, we could have realize a real-time operating radar system, mounted on a van, to detect guard wires and guard rails buried in snowpack on road shoulders. This further developed system utilizing a specially designed digital signal processing circuit may contribute snow shoveling action in snowy region.