Near-Field Scattering Prediction Based on Refined Time-Domain High-Frequency Method

The theoretical implementation aspects of near-field wideband electromagnetic (EM) scattering prediction based on refined time-domain physical optics (TDPO) and time-domain equivalent edge currents (TDEEC) integral are proposed in this letter. First, the closed-form expressions in far-field assumption of TDPO and TDEEC integrals are derived based on a Radon transform interpretation. Then, to solve the difficulties of the traditional TDPO and TDEEC in the near-field scattering computation, a refined integral representation is formulated. Afterward, by introducing the concept of the locally expanded approximations both in phase and amplitude, a more accurate expression of the Green function in frequency domain and time domain is developed. In this way, the near-field versions of TDPO and TDEEC are proposed to predict the scattered EM field of electronically large target in the near-field zone while retaining the simplicity of the conventional forms. The validity and applicability of the proposed refined TD method in near-field calculation are demonstrated by some numerical examples in the last part.