Goal Of Near-field Electromagnetic Scattering Characteristics Computing Applications

Based on the background of fuze-warhead coordination, this thesis studies target surface modeling, computation of targets'near-field EM scattering characteristics, Doppler echo signal analysis etc. during missile-target encounter. Object information gotten by fuze should be systematically studied and effectively used in order to improve the precision of burst point control. The targets'near-field Radar Cross Section (RCS) and Doppler information extracted from echo signals are considered to be key elements of fuze's target detection and anti-interference. Compared with traditional radar target, calculation of radar fuze target's near-field EM scattering characteristics has its particularity, and So far, there is no rigorous analytical calculation method. The missile-target encounter process and fuze target's surface modeling are analyzed and faceting approach is used to analyze the target's EM scattering characteristics in this thesis, and the results are more accurate. The main research contents of the thesis are as follows:(1)The surface modeling and geometric description of targets are achieved. Several targets such as cube, standard ball, cruise missile, aircraft etc. are modeled based on AutoCAD 3D modeling software in this thesis. Faceting approach is finally chosen to describe the target geometry after comparing several different methods, such as decompounding approach, faceting approach, parameters modeling approach etc., and the target is represented as a combination of facets and edges. The target's data is extracted and sorted through programming to establish some tables such as vertex list, surface element list, edge list and so on, so as to provide original data for fuze target's near-field RCS calculating.(2)Considering the effects of body target and local irradiation caused by near-field conditions, this thesis chooses appropriate scattering centers and shelter region. Physical Optics (PO) is adopted to calculate the facet's scattered field and Method of equivalent currents (MEC) is used to calculate the edge diffraction. So as to get the correct value of the extreme point, the improved equivalent electromagnetic current expressions are used in this thesis. These expressions not only remove the extreme point in edge diffraction calculation, but also make the results more realistic. Taking facet contribution and edge diffraction into consideration, this thesis gets the total scattering field by vector superposition.(3)The basic principles of pulse Doppler fuze and the rules of Doppler frequency shift in missile-target encounter process are studied, besides, a typical model of pulse Doppler fuze is established and the fuze parameters are all analyzed and selected. The received echo signals are analyzed through time-frequency transform, wave filtering, base frequency extraction, Doppler information extraction to get targets'range and velocity information. Finally the fuze start point is given on this basis.(4) Based on faceting model and C++ Builder 5.0 software environment, a software is developed to calculate and analyze EM scattering characteristics of near-field target. The simulation results show that the RCS calculation results computed in the thesis are basically consistent with the exact analytical solutions or the actual measurement results. It proves that the approach used in the thesis is effective.