Doppler Characteristics of EM Scattering from Sinusoidal Water Waves

The spectra of electromagnetic (EM) scattering fields are presented when the sinusoidal water waves are illuminated by a plane EM wave and a Gaussian beam. In general, we always consider that the Doppler shift of EM scattering from a Bragg resonant wave is determined by the phase velocity of the water wave. However, the recent wave tank experiment [3] demonstrate that not only the spectral peak corresponding to the phase velocity of water wave but also other equally spaced harmonic peaks can be found when EM wave is illuminated on sinusoidal water waves. To better explain these phenomena, the spectral characteristics of sinusoidal surface echo in plane wave/Gaussian beam incident are simulated numerically based on MoM method. Then, a theoretical model for the spectra from the simple water waves are derived by the first-order small slope approximation theory (SSA-I). And the simulated results illustrated that all the interesting phenomena could be successfully explained by our proposed spectral model.