Study on the Multidimensional Characteristics of Microwave Scattering from Nearshore Sea Waves

In the process of propagating from deep water to shallow water, the waveform and propagation speed of the sea waves change significantly due to the influence of the friction from seabed. Therefore, the nearshore sea waves are usually different from the fully developed waves in deep water. The Ku-band frequency modulated continuous wave (FMCW) coherent radar can be used not only to observe smaller scale waves with a high range resolution (0.6 m), but also to retrieve the radar radial velocity information of sea waves. Based on this Ku-band FMCW radar, an observation experiment had been carried out to obtain the multidimensional information of microwave scattering from nearshore sea waves. In the present work, we made a systematic analysis on the multidimensional characteristics of the radar echoes. Firstly, the characteristics of nearshore waves, including amplitude distribution, phase distribution, time-frequency characteristics and time correlation, are analyzed by using the measured radar data. The results of the amplitude distribution show that the theoretical Log-normal distribution can better describe the amplitude characteristics of the nearshore waves. And the results of the phase difference distribution of the nearshore waves are consistent with the theoretical model of phase difference distribution. Besides, the time-correlated characteristics of nearshore waves with target is also studied, and the decorrelation time of nearshore waves with target is longer. In addition, due to a high pulse repetition frequency (PRF) of the radar, there is a strong correlation between the pulse echo sequences at adjacent moments and the phase difference between two adjacent moments can be extracted effectively. Based on this, the radial velocity of the sea wave has been calculated from the phase difference. In summary, the results of this study can provide reference for nearshore waves analysis, modeling and prediction.