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

这项研究的目的是研制一种用于探测积雪中物体的极化FM-CW雷达。在1990-1991年期间，我们建立了一个工作在1-2 GHz微波频率的具有极化测量能力的FM-CW雷达系统。首先，将极化和合成孔径技术结合到雷达系统中，使其能够从目标获取详细的信息。开发了包括天线和微波电路在内的各种技术，并结合了控制系统的软件实现以及雷达回波的计算机可视化。其次，在新泻大学的电波暗室中，以金属板为目标，验证了该雷达系统的性能，论证了方位向高分辨率成像和极化信息的重要性。第三，在新泻县山口村进行了几次实地测量，以探测被埋在天然积雪中的物体。该雷达可以清晰地探测到埋在至少100厘米深的自然积雪中的金属目标和人体，产生高分辨率的目标图像。特别是，合成孔径图像可以在杂波严重的环境中提供清晰的目标边界。除了主要的研究目标外，我们还可以实现安装在面包车上的实时操作雷达系统，以探测埋在路肩积雪中的防护线和护栏。利用专门设计的数字信号处理电路对该系统进行了进一步的开发，为雪域铲雪作业提供了可能。

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.