Numerical Simulation And Imaging Of Ground Penetrating Radar (GPR)

Ground Penetrating Radar (GPR) is a high-effective technique of the shallow earth physical probing. It can be applied to engineering prospect widely because of the advantages of fast development and convenience, universality, anti-jamming, strong acclimatization, high resolution ratio and so on, therefore, there is important sense in researching the basic theory and applied technique of GPR.This paper discussed three aspects of GPR, including numerical simulation, migration imaging and the GPR signal processing. Firstly, the basic principle of Finite-Difference Time-Domain (FDTD) is introduced and the 2-dimensional FDTD equation is derived from the Maxwell's equations, calculated by setting up the appropriate excitation source, cell size, the interval of space and time. Generalized perfectly matched layer (GPML) is used to absorb the outgoing wave in the simulation, considering the underground media are generally lossy media. Several representative models are simulated and get corresponding GPR sectional images. Secondly, the original GPR sections are migrated in order to make the reflection points of GPR trace records return to their real positions, because the original GPR sections commonly show the distorted underground geology body structure. Frequency-wavenumber migration is an effective and relatively economical method due to adopt FFT. GPR sectional images after migration are obtained through the frequency-wavenumber migration process, it have showed the real underground geology body structure. Lastly, the target reflected waves of GPR are usually disturbed by the strong direct waves, so that, a method based on Karhunen-Loeve (KL) transform in wavelet domain is studied. It uses the time-frequency localization characteristic of the wavelet analysis and their correlations on the direct wave and target reflected signals in multichannel GPR data. The multichannel wavelet sections are obtained via the wavelet decompose of the GPR traces and realized the direct wave removing by using KL transform. The experimental results of the experimental data and real data demonstrate that this method is effective in the direct wave removing and make the target signals obvious.