Measurements of Millimeter Wave Radar from the Wave Tank at Low Incidence Angles

Millimeter Wave (MMW) radar is capable of providing high temporal-spatial measurements of the ocean surface, which has recently attracted researchers’ attention. This paper introduces the results of water surface measurements in the wave tank by using a MMW radar. Due to the measurements at small incidence angles, the scattering mechanism of the water surface is mostly considered quasi-specular, which is dominated by large-scale waves, and Kirchhoff approximation-geometric optics approximation (KA-GO) is applied for calculating the Radar Cross Section (RCS). Experimental data for tank experiments are processed and analyzed. The obtained results show the scattering mechanism is dominated by quasi-specular scattering at low incidence angles, and the proportion of the quasi-specular scattering decreases as the incidence angle increases. The transition process is usually considered to occur at incidence angles of between 10° and 25°, in which the region is influenced by the quasi-specular scattering and Bragg scattering simultaneously. In addition, a novel phenomenon is discovered, which the transition region of regular waves (about 10°–15°) is smaller than irregular waves (about 10°–25°). The obtained experiment results seem promising for a better understanding of the signal backscattering mechanism based on the MMW radar for water surface measurements at near vertical incidence. Research in this paper also provides new insights for increased resolution and accuracy in the measurements of the sea surface.