Ocean Wave Measurement Using 77-GHz FMCW MIMO Radar at Low Incidence Angles

In this letter, we propose a novel methodology for retrieving wave parameters, i.e., significant wave height and mean wave period, in near-nadir looking mode using a 77-GHz frequency-modulated continuous-wave (FMCW) multiple-input-multiple-output (MIMO) radar. First, the range-Doppler spectrum is estimated from the raw radar data, and the time-Doppler spectrum in the desired direction is obtained by integrating the digital beamforming algorithm with MIMO array techniques. Next, the radial velocity series are calculated using the spectral moment method. A Fourier transform is then applied to estimate the wave height spectrum from the radial velocity series, and the significant wave height and mean wave period can be obtained by the moment estimation method. Finally, the results obtained from numerical simulations and sea surface observations demonstrate that the retrieval method can extract wave parameters with reasonable performance at small incidence angles (0°–18°).