| The electromagnetic scattering and radiation characteristic of objects in a pla-narly multilayered media, is of great researching values in geophysics exploring, target characteristics, target identification, remote sensing, microstrip antennas, mi-crowave monolithic integrated circuits and etc. Some electromagnetic problems in the planarly mutilayered media are analyzed using the improved Discrete complex image method combined with the stabilized biconjugate gradient with fast Fourier transform method (BCGS-FFT) in this paper. And this dissertation studies the algorithm for the efficient evaluation dyadic Green’s functions and the fast solving of the integral equa-tion for three-dimensional scattering problems in planarly multilayered media. Fur-thermore, the range profile of the buried object in the earth is studied by the radar model with the transmitting/antenna in far field, the transmitting antenna in far field and the receiving antenna in near field, the transmitting/receiving antenna in near field. The complex electromagnetic mutual interactions between the target and the earth surface are analyzed detaily and the the numerical method proposed in this papar is verified through the numerical examples. Besides, the size of the buried ob-ject is successfully reconstructed from the numerical results of the range profiles, which may facilitate target identification.Specifically, the contents are in the three aspects below.1. First, due to the impotance of Green’s functions for multilayered media prob-lems, we thoroughly study the discrete complex image method (DCIM) for computing spatial Green’s functions. The characteristic of spectral Green’s functions in kp plane is studied, and the true reason for the two paths of kz plane should be in the layer with the minimumεr (usually the free space layer) of the direct discrete complex image method is explained. We propose an improved discrete complex image method. The spatial domain Green function obtained by the proposed method is accurate both in the near- and far-field regions. The paths of the proposed method in kz plane can be in the layer where the source point and field point are. The CPU time used to per-form the improved DCIM is less than 1s for computing the fields with a hori-zontal source-field separation from 1.6×10-4λ0 to 16λ0. It avoids the short-coming both of the traditional DCIM and the direct DCIM. The derivation lays a good foundation for the efficient evaluation of the electrically large objects buried in multilayered media.2. Combining with the improved DCIM, BCGS-FFT is extended to analyze the scattering characteristic of arbitrary shaped buried objects (including electri-cally large objects) in both lossless and minim-loss multilayered media. For volume integration, the spectral Green’s functions are split to further reduce the approximation time. The dissertation has independently derived out the formulas of the extended Green’s functions of primary partand the reflected part, which satisfy the cyclic convolution and cyclic correlation.3. Tightly based on own research, this dissertation discusses the method of buried target identification mainly about range profile. The basic concept and obtained way of range profile are introduced. Using the radar model by the transmitting/receiving antenna in far field, the transmitting antenna in far field and the receiving antenna in near field, the transmitting/receiving antenna in near field, we analyze range profile of the objects buried in the earth. Range locations of the range profiles are in good agreement with the results ex-pected from the ray theory. Furthermore, the size of the buried object is suc-cessfully reconstructed from the numerical results of the range profiles. |
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