Signal Processing Method Based On OFDM System Ground Penetrating Radar

As a non-destructive detection technology,Ground Penetrating Radar(GPR)has been widely used in geological exploration,archaeology,water conservancy and other research fields.Stepped frequency continuous wave ground penetrating radar(SFCW-GPR)has received widespread attention in the GPR research field due to its advantages of higher dynamic range and stronger immunity to radio interference.With the further motivation of various application requirements,GPR system is constantly developing towards the direction of multi-channel,multi-band,high-resolution and high operation efficiency.However,each frequency carrier of SFCW GPR system must be generated,sent and received sequentially,and it takes a long time to finish the full spectrum scan,which affects the high efficiency of GPR.In addition,the transmitting and receiving antenna is close to the ground in practical engineering applications,and the reflected wave from the ground is much stronger than the target echo.The performance of GPR reconstruction algorithm will decrease sharply in the case of strong ground clutter.This thesis carried out the following research work in view of the above problems.By analyzing the principles of Orthogonal Frequency Division Multiplexing(OFDM)technology and combining the characteristics of SFCW GPR system,the model of OFDM GPR system is presented.Then the main parameters and signal processing methods of GPR are analyzed in detail.Compared with the SFCW system,the ground penetrating radar with the OFDM has improved the operation efficiency effectively,which can simultaneously send and receive multiple carrier signals.By analyzing the characteristics of sending and receiving signals of OFDM system,channel estimation is adopted to obtain the target distance information,and the feasibility of this method is proved in the simulation experiment.In order to further improve the imaging speed of OFDM-GPR,Compressed sensing(Compressed sensing,CS)technology is combined into it,which reduces the number of subcarriers required for signal transmission,thus improving the acquisition speed of OFDM-GPR.The feasibility of OFDM-CS ground penetrating radar is verified by CS imaging experiments.Based on the analysis of classical clutter suppression techniques,and considering the strong anti-interference ability of OFDM system,a frequency domain clutter suppression algorithm based on least square estimation is proposed.Finally,the simulation results show that the algorithm can effectively suppress the strong ground clutter and recover the target information.