Analysis And Calibration Of Transmission Polarization Rotation For Ground Penetrating Radar Based On Ideal Interface And Gaussian Rough Surface

Ground penetrating radar(GPR)is a geophysical method that uses antennas to transmit and receive high-frequency electromagnetic waves to detect the characteristics and distribution of substances in a medium.It has characteristics of high-precision,non-destructive,fast data acquisition and strong anti-interference ability.Therefore,ground penetrating radar is widely used in engineering,archaeology,agriculture,hydrology,military and other fields.The traditional ground penetrating radar uses only one type of antenna for data acquisition,and only obtains single polarization data of the target.It can not fully describe the various properties of the target.Full polarimetric ground penetrating radar is a new ground penetrating radar technology that uses four different polarization antennas to measure the target and can receive electromagnetic waves of different polarization directions to describe the polarization effect of the target.The polarimetric characteristics of the target can be described by the scattering matrix.The scattering matrix contains four components measured by four different polarized antennas.By analyzing the correlation of these components,more comprehensive polarimetric information of target can be obtained.The polarimetric data contains many information of the targets,but there are many factors that can cause distortion of the polarization information.When the plane electromagnetic wave propagation through the ground surface and the soil,the propagation properties are different from the vacuum propagation properties.So the received signal contains not only the information from subsurface targets,but also the information from the ground surface and the soil.In order to obtain more accurateinformation about the scattering of the subsurface targets,we have to educe or eliminate the effects of the subsurface.In this paper,we discuss the reason why the direction of polarization of the electromagnetic wave is rotated when it propagation through the media interface,and the polarization rotation characteristics of plane electromagnetic wave from rough surface was presented.This paper is mainly introduced from the following aspects:1.The transmission coefficient formulas of vertically polarized waves and parallel polarized waves passing through the ideal interface are introduced.On the basis of this,the causes of the polarization rotation of electromagnetic plane wave from ideal interface and the influences of the rotation on scattering matrix of target are analyzed.2.The transmission coefficient formulas of vertically polarized waves and parallel polarized waves passing through the Gaussian rough surface are introduced.Then,the relationships between transmission and scattering coefficients,scattering angle,scattering azimuth and polarization mode are analyzed.On the basis of this,the influences of the rotation from rough surface on scattering matrix of target are analyzed.3.Based on the influences of polarization rotation from ideal interface and rough interface on the target scattering matrix,the calibration formulas of polarization rotation from ideal interface and Gaussian rough interface are derived.4.The full polarimetric data of the plate and the dihedral with the angle of 45° in the direction were measured in the laboratory.The scattering matrixs after calibration of these two targets were calculated with the calibration formulas of ideal interface and Gaussian rough interface respectively.5.The polarization scattering correlation coefficients of the scattering matrix corrected by the ideal interface and Gaussian rough interface polarization rotation correction method and the standard scattering matrix of the corresponding target are calculated respectively,and the calibration results of the two calibration methods are compared and analyzed.