The Propagation Of GPR Pulse In The Lossy, Dispersive, And Inhomogeneous Earth Medium

By the use of broad-band electromagnetic wave in impulse forms, Ground Penetrating Radar (GPR) is used to detect the internal structure of the earth. Transmitting in the earth, GPR electromagnetic wave decreases rapidly with dispersive phenomena. The dispersion may lead to the aberration of electromagnetic wave, affection of the explanation of electromagnetic exploration data, even results in the default of electromagnetic exploration.. Improvement of the explanation of Ground Penetrating Radar's exploration data is based on the research of the propagation of GPR electromagnetic wave in the dispersive medium. With the help of improved FDTD method, this paper is devoted to analyze the propagation of GPR electromagnetic wave in the dispersive earth medium. The main work and achievements of the paper are as follows:1. With the help of the peculiarity of GPR pulse, total field formulation is improved and the improved absorbed boundary condition of PML is discussed. All these efforts predigest the computing and advance the efficiency.2. To deduce the difference format of Maxwell's equation in the dispersive lossy medium, the electromagnetic field E and density D and flux H are normalized, the dispersive dielectric relation is reflected in the electromagnetic field E. The currency electromagnetic simulation programme of FDTD method which adapts to dispersive or no dispersive medium is authorized.3. Adopting the amending FDTD method, this paper simulates the propagation of GPR electromagnetic wave in the second-order Debye dispersive earth medium, and relatively analyzes with no-dispersive parameter of geological medium. By the numerical simulation to dispersive medium, this paper discusses the factors of affecting the aberration of GPR electromagnetic wave, and offered reality basis for the research of reversion of electromagnetic exploration data.4. With the use of theoretical analysis and numerical simulation, the author researches the affection of medium's parameters to the propagation of electromagnetic wave of different frequency in the lossy dispersive medium. The medium's the conductivity and dielectric constant is the direct factor which changes the speed and attenuation of GPR wave. When antenna's frequency is added, the speed of electromagnetic wave runs fast, and attenuation of electromagnetic wave is enhanced. A conclusion can be drew is that the dispersion can't be ignored if broad-band electromagnetic wave was used to detect the object.