正弦水面平面波/高斯波束散射回波谱峰特征分析

Spectral Peak Characteristics of Plane/Gaussian Beam Scattering from Sinusoidal Water Waves

展示平面波/高斯波束照射时正弦水面电磁散射回波的多普勒谱峰分布特征.基于Bragg共振散射理论可知,水面电磁散射回波多普勒谱峰所对应的频率由水波相速度决定,然而,最近相关水槽实验发现:正弦水面散射回波的多普勒谱不仅包含与水波相速度相对应的Bragg共振峰,而且还存在等频率间距的谐波峰.为了能更好地解释这一现象的物理或数学本质,文中基于粗糙面电磁散射一阶小斜率近似理论(SSA-I)分别推导给出了平面波/高斯波束照射时正弦水面后向电磁散射回波的频谱模型.理论模型结果显示,谐波峰是由于频谱分析过程中频率泄漏效应导致的,而不是水面回波真实的物理现象.

The spectral peaks of electromagnetic (EM) scattering echoes are presented when the sinusoidal water surface is illuminated by a plane EM wave and a Gaussian beam.It is generally recognized that the Doppler frequency corresponding to the spectral peak is determined by phase velocity of the water wave.However,the results of the recent wave tank experiment demonstrate that not only the spectral peak corresponding to the phase velocity of water wave but also other equally spaced harmonic peaks can also be found when an EM wave is illuminated on a sinusoidal water surface.To better explain these phenomena,a theoretical model for the spectra from the simple water wave are derived by the first-order small slope approximation theory (SSA-I).The theoretical model results show that the harmonic peaks are caused by the frequency leakage effect,rather than the real physical phenomenon of the water surface echoes.