Numerical Simulation of the Doppler spectrum of a flying target above dynamic oceanic surface by using the FEM-DDM method

To study the Doppler (DP) spectrum of a flying target above dynamic oceanic surface, a two-level quasi-stationary algorithm (TLQSA) of the finite element method (FEM) with domain decomposition (DDM) is developed. The DP spectrum of a fast-moving target requires small time-sampling rate. At most time steps, scattering from the flying target is solved by the FEM solution in only one subdomain. Meanwhile, the interactions between the target and rough sea surface in other subdomains are obtained by solving the global DDM coupling matrices. The slowly moving sea surface is evolved at a larger time step and the DP of oceanic clutter is obtained through all-subdomain FEM calculation. Numerical simulations of the DP spectrum from a target flying above dynamic oceanic surface with and without the presence of a ship-like object are obtained. The functional dependence of the DP spectrum in both the time and frequency domains upon sea surface wind speed, target altitude, observation angle, etc., are demonstrated and discussed.