STUDY OF ELECTROMAGNETIC SCATTERING FROM SHIP WAKES ON PEC SEA SURFACES BY THE SMALL-SLOPE APPROXIMATION THEORY

Abstract

Electromagnetic (EM) scattering properties from the ship wakes on the two-dimensional (2-D) perfect electric conductor (PEC) sea surfaces are studied by utilizing the small-slope approximation (SSA) theory. Considering the limitations of using the ideal plane EM wave incident upon a rough sea surface of the limited size, the expressions of the scattered fleld and scattering amplitude are derived by utilizing the modifled tapered incident fleld. Based on a simplifled segmented ocean spectrum model, the bistatic and monostatic normalized radar cross sections (NRCS) from the PEC sea surfaces with and without ship wakes are calculated, respectively. Meanwhile, the variation of scattering coe-cient as scattering angles is given and compared under difierent polarization states. The results show that the scattering from the PEC sea surfaces with ship wakes is evidently difierent from that without them in bistatic and monostatic scattering. This provides a basis to extract ship wake characteristics. Also it shows that the SSA is a very efiective analysis method to deal with the EM scattering from the rough sea surface. Finally, the efiect of difierent tapered factors on backscattering coe-cient is discussed, and it is concluded that an artiflcial re∞ection from the boundaries and a scattering upwarping from low-grazing incidence can be avoided just when the tapered factor is relatively smaller. This gives the theoretical basis for the analysis of EM scattering characteristics of ship wakes on the PEC sea surface.