Study on Near-field Electromagnetic Scattering Characteristics of Targets Irradiated by Antenna Beam

In this paper, the near-field electromagnetic scattering problem of electrically large targets irradiated by antenna beam is solved by using the time domain physical optics (TDPO) method. Based on the surface integral equation of electromagnetic field and physical optics approximation, the near-field integral formula of TDPO can be obtained. Combined with the analysis method of the system response, the time domain radiation field of the antenna under pulse excitation is given. A fast near-field calculation formula for TDPO irradiated by an antennais proposed by using locally expanded green function approximation of the facet. This closed expression is suitable for the computation of near-field scattering after any polygon plate partition and is independent of the width of the time domain pulse.Next, with the combination of the KD-Tree acceleration algorithm of occlusion judgment, the fast and accurate computation of the near-field time-domain scattering echo and frequency-domain RCS of electrically large targets irradiated by antenna beam can be realized. The near-field RCS curves of targets irradiated by the dipole antenna in different directions or at different distances are calculated respectively. The results show that at a given distance, the near-field RCS changes dramatically with the change of incident angle, which indicates that the near-field electromagnetic scattering characteristics are closely related to the antenna pattern. At a given incident angle, the near-field RCS oscillates with distance, its value tends to the farfield RCS when the distance increases further. Compared with the simulation results by FEKO software, the error is relatively small, which further verifies the effectiveness and accuracy of the method.