Wave Height Field Measurement Using a Compact Dual-frequency HF Radar

Compact high frequency (HF) radar using small antenna has been widely accepted in ocean surface current mapping, but is challenging in measurement of wave height, particularly wave height field, due to its broad beam. First-order Bragg scattering theory has been explored to estimate sea state, including wind speed and wave height, from the first-order ocean echo, which provides a capability of distinguishing waves information over different directions. However, this method is troubled by the calibration of direction dependent spreading factor. A new approach is proposed by adopting a dual-frequency compact radar, and the ratio of power of Bragg resonant waves associated with two frequencies, rather than that of a single frequency, is utilized to simultaneously eliminate the effect of spreading factor and estimate wave height. In addition, direction finding algorithm such as multiple signal classification (MUSIC) is employed to obtain wave field information. Preliminary results are presented to verify the effectiveness of the proposed algorithm.