Study on the Over-the-Horizon Radar-Echo-Signal Modeling of the Maritime Target in Tropospheric Atmospheric Duct

In this article, a radar-echo-signal simulation model (RESSM) of the sea targets under the condition of over-the-horizon propagation within the tropospheric atmospheric duct on the sea is proposed. In order to directly obtain the vector field at the 3DPE output section, the conversion formula from the far-field scalar pattern of the planar antenna array to the initial field of the vector 3DPE is derived at first. On this basis, the vector field of the 3DPE exit surface is taken as the incident field in the composite electromagnetic (EM) scattering calculation of sea surface with targets based on the semi-deterministic facet scattering model-shooting and bouncing ray (SDFSM-SBR) method. Then, the RESSM is developed, which is regarded as a combination of a quantity of scattering centers from the total frequency spectrum. The influences of different transmit frequencies and waveguide types on the energy distribution characteristics, propagation loss (P-Loss), and average propagation energy flow (PEF) of tropospheric atmospheric ducts are analyzed in detail. Furthermore, the radar-echo-signal (RES) of sea targets under different over-the-horizon propagation conditions is calculated. The reliability of our proposed over-the-horizon RESSM in this article is verified by its high-resolution range profile (HRRP).