MORIYAMA et al: CLASSIFICATION OF TARGET BURIED IN THE UNDERGROUND BY RADAR POLARIMETRY

Manuscript received November 5, 1998. Manuscript revised January 8, 1999. † The authors are with Niigata University, Niigata-shi, 9502181 Japan. †† The author is with University of Illinois at Chicago, IL, 60607-7018, USA. * Presently, with Fujitsu System Integration Laboratories Ltd. ** Presently, with NEC Saitama Corp. SUMMARY This paper discusses the classification of targets buried in the underground by radar polarimetry. The subsurface radar is used for the detection of objects buried beneath the ground surface, such as gas pipes, cables and cavities, or in archeological exploration operation. In addition to target echo, the subsurface radar receives various other echoes, because the underground is inhomogeneous medium. Therefore, the subsurface radar needs to distinguish these echoes. In order to enhance the discrimination capability, we first applied the polarization anisotropy coefficient to distinguish echoes from isotropic targets (plate, sphere) versus anisotropic targets (wire, pipe). It is straightforward to find the man-made target buried in the underground using the polarization anisotropy coefficient. Second, we tried to classify targets using the polarimetric signature approach, in which the characteristic polarization state provides the orientation angle of an anisotropic target. All of these values contribute to the classification of a target. Field experiments using an ultra-wideband (250 MHz to 1 GHz) FM-CW polarimetric radar system were carried out to show the usefulness of radar polarimetry. In this paper, several detection and classification results are demonstrated. It is shown that these techniques improve the detection capability of buried target considerably. key words: radio applications, subsurface radar, FM-CW radar, scattering matrix, polarization anisotropy coefficient, power polarization signature