Study Of HF Scattering Of Targets In The Free Space And Above The Sea Surface

The scattering characteristics of objects in HF band are studied byFinite-Difference-Time-Domain (FDTD) method combing with the detecting by usingSky-Wave Over-The-Horizon Radar(SW-OTHR). First, the geometry of the complexobjects is established and the triangle patch files are given. The computable model byFDTD method is established by projection algorithm. Then, the Radar-Cross-Section(RCS) of the objects in free space and above the sea surface are computed by FDTDmethod. The characteristics of the objects are analyzed.The operating principle of the SW-OTHR and characteristics of the HF bandelectromagnetic wave are briefly introduced. The operating frequency of theSW-OTHR is usually at High Frequency(HF,3~30 MHz) band. The size of theaeroplanes and the naval vessels are similar with the operating wavelength of the SW-OTHR. In this region, the objects are in resonance scattering zone. It is convenientto choose the numerical method to calculate RCS of objects. We use the FDTD methodin this thesis.It is the precondition to establish the geometry model and electromagnetic modelof objects for studying of the scattering characteristic of the objects. The geometry ofthe complex objects are established and the triangle patch files are given. Thecomputable model by FDTD method is established by projection method. The modeling of complex objects(B-2 bombing plane, F22 fighter plane and floatingaerodrome etc.) indicated that our algorithm is satisfied with the need ofelectromagnetic modeling of complex objects.An algorithm for automatically computing the multi-direction RCS of complexobjects is given in this thesis. In addition, a method extrapolating multi-direction whenthe EM wave incident in a direct is also presented. The multi-directional (azimuthalangleφ:90°~180°, pitching angleθ:90°~180°) monostatic and bistatic RCS ofcomplex objects are computed. And the electromagnetic scattering characteristics ofobjects in several special positions are discussed and analyzed.In computing the scattering of an object in half space or layered half space, it isthe key point to introduce the plane in computed region. An algorithm introducingplane oblique incidence wave by the Total Field/Scattered Field(TF/SF) boundary inlayered half-space is presented. Then, a method dealing with the dispersive media is introduced. At last, the RCS of scattering of the floating OilTank and the naval vessels on the sea surface are computed and analyzed.