| Ground penetrating radar is used to work in the way of electromagnetic wave and its echo characteristics reflected from the object,by analyzing the characteristics of the echo, and then judging the distribution state and the structure of the material in the shallow stratum, a geophysical exploration method is also analyzed. It has the advantages of high resolution and high efficiency. It has been widely used in engineering, environment, resources and other shallow geophysical exploration fields. However, the ground penetrating radar has some limitations as well as other geophysical exploration methods,mainly refers to the detection depth, multiple wave and other clutter interference is serious, the traditional exploration radar polarization single transceiver mode get a limited amount of information, and the antenna is coupled with the surface complex, temporarily unable to solve the defects.The traditional ground penetrating radar because of its single polarization transceiver, lost a lot of information of the other polarized reflector. In this paper, a full polarimetric ground penetrating radar system is used to increase the polarization mode of the transmit antenna, and the receiving antenna and its central vertical cross polarization transceiver mode are added. As a result, the situation is in parallel with the direction of the measured line H polarization, and the direction of the vertical line of V polarization. When transmitting antenna and receiving antenna parallel in the direction of the measuring line HH model, when the both vertical and direction of the measuring line VV mode, when the transmitting antenna and receiving antenna parallel in the direction of the line, and also a vertical in the direction of the measuring line for HV or VH model, in which HH, VV for CO polar pattern, HV, VH for cross polarization mode. Based on the above antenna polarization mode and full polarimetric GPR system, through the analysis of the reflector reflection signal vector components and properties, geological structure and geometric shape information is obtained more accurately.The whole polarization ground penetrating radar system should be calibrated after the measurement. The purpose is to adjust the interference caused by the hardware system and the data acquisition environment. If not fully polarimetric detection of radar measurement data of amplitude and phase calibration, then the real situation of the measurement results obtained with the reflector will produce large errors. Polarization radar system calibration of the is to determine the polarization scattering matrix of four measurement channels gain, gain including amplitude and phase. At the same time, we also need to estimate accepted by transmit antenna and antenna cross polarization aberration of gain. After the calibration parameters are determined, the system response can be removed in the obtained data to obtain relatively accurate results.In this paper, using the three-dimensional finite difference time domain method to establish the forward simulation program, forward simulation of typical reflector, the reflecting objects are buried in sand obtained typical objects with different rotation angle of polarization characteristic response, and polarimetric calibration of dihedral reflector in sand layer data, in order to improve the full polarimetric GPR system in sand layer of target recognition ability. |
PDF Full Text Request