Research on Doppler Spectrum of Electromagnetic Echoes Scattered from Wind-Driven Wave and Swell

The mixed wind waves and swell often co-exist in the actual marine environment, however, most of current studies of the electromagnetic scattering from ocean surface only focus on the wind waves. This paper mainly investigates the Doppler spectral features of electromagnetic scattered echoes from mixed swell and wind waves. Based on the nonlinear sea waves model, the various types of mixture of swell and wind wave with different weights are simulated. Then the electromagnetic scattering modeling from time-varing rough nonlinear mixed waves is performed by the analytical second-order small-slope approximation method. Finally the numerical simulations are developed and analyzed, it is found that wind-dominated mixed waves show more significant Doppler shift than the counterpart of swell-dominated mixed waves in medium to large incident angle region.