Spectral Investigation of Doppler Signals From Surfaces With a Mixture of Wind Wave and Swell

The mixture of wind wave and swell is simulated based on a bimodal spectrum and nonlinear hydrodynamic theory, and the investigation of the Doppler spectra of backscattered signals from such sea surfaces in time-varying marine environment is performed by applying the second-order small-slope approximation model. The results are also compared with some popular data sets, and based on the comparison it can be found that the variation trends of Doppler shift and Doppler spectral bandwidth are different for mixed waves with various weights, which reflect qualitatively the distinct ways of influences that wind wave components and swell ones exert on Doppler signature.