A Hybrid SI-FDTD Method to Analyze Scattering Fields From Underwater Complex Targets

Gradually increasing interest in the exploration of marine resources and the rapid proliferation of underwater vehicles requires the issue of electromagnetic (EM) detection of underwater complex targets (UCTs) to be solved urgently. In this communication, a hybrid method combining the finite-difference time-domain (FDTD) method and the Sommerfeld integral (SI) method is proposed to simulate the low-frequency (LF) scattering field from UCTs. In the proposed method, integral expressions and approximate expressions of the SI are used to calculate the fields in the near and far ranges, respectively. Meanwhile, the inaccuracies caused by the LF breakdown are mitigated based on the results obtained in the stable region and the trends exhibited by correct results. Subsequently, the scattering fields from the UCTs at different locations generated by an underwater two-element antenna array are simulated and analyzed. The results show that the scattering magnetic field (SMF) distributions of the targets at different locations are similar, while the field values differ significantly. The existence of targets can be ascertained from the SMF components, and the directions of UCTs with respect to the antenna can be obtained roughly by comparing their SMF components Hy.