Fast Algorithm For Scattering Of Targets Over Layered Half Space

There are many interests in the scattering and radiation problem of targets over a half space or layered half space. Its application can be found in many domains such as OTHR(Over-the-Horizon-Radar), radar stealth technology, target recognition, remote sensing and so on. The scattering of half space and targets is quite different from the scattering of a single target due to the interaction of half space and targets. A fast algorithm for calculating the electromagnetic scattering of targets over layered half space is proposed in this paper. The innovational works of this paper are the introduction of incident wave in the case of layered half space, the analysis of polarization characteristics of reflected wave, the fast calculation of far radiation field of an arbitrary oriented dipole over layered half space and so on.The main contributions of the dissertation are as following:1. The fast calculation of far radiation field of an arbitrary oriented electronic and magnetic dipole over layered half space.The half space Green function is expressed in the form of Sommerfeld Integral whose expression is very complex and numerical integration is extremely time-consuming. To solve this problem, the far field formulation of an arbitrarily oriented dipole over a layered half space including anisotropic medium is given in this paper based on the reciprocity theorem. This formulation is also can be used in anisotropic medium.2. The analysis of polarization characteristics of reflected wave(the line polarized incident wave case).In the past algorithms of half space problem, the polarization characteristics of layered half space reflected wave is often ignored. In this paper, the polarization state of reflected wave is systematically analyzed, which includes the isotropic and anisotropic case. Effects of incident wave polarizing angle and the half space dielectric parameters on polarization state of reflected wave are investigated.3. The research of electromagnetic scattering of targets over layered half space using a semi-analytic method.A semi-analytic method is proposed to solve the scattering problem of targets over layered half space in this paper. A new division method of Finite Difference Time Domain(FDTD) computational region which contains the targets itself is proposed. The reflected wave is introduced by equivalence principle with the consideration of the differences in polarization state, the field amplitude, and the phase. In time domain, the incident and reflected time domain waveform are introduced to the FDTD computational region by the same method in conjunction with Fourier transform.4. The analysis of near-field coupling characteristics of targets over half space under HPM.The electromagnetic field and energy flux density coupling into targets over lossy half space are investigated based on a semi-analytic method. In this paper, the interaction of the EM wave and the targets is computed by FDTD method. The bidirectional incident wave of the FDTD computational region is introduced by the Fresnel formula, Fourier Transform and the equivalence principle. Different incident conditions such as incident planes and polarization modes are discussed.