Numerical comparison of techniques for estimating Doppler velocity time series from coherent sea surface scattering measurements

A number of techniques for estimating: the Doppler velocity time series fro m coherent sea surface scattering measurements are compared by observing th eir behaviour with computer simulated signals. These techniques include the finite difference instantaneous frequency estimator, the covariance moment estimation technique, tracking the peak of the short-time Fourier transfor m and tracking the peak of the cross Wigner-Ville time-frequency distributi on. This comparison is achieved by examining the ability of each technique to track the instantaneous frequency of a unity amplitude. sinusoidal frequ ency law, complex exponential signal embedded in white Gaussian noise. The response of the estimators to various signal conditions. including low sign al-to-noise ratios, high Doppler frequency excursions and high modulation f requencies, is investigated. Using the results. consideration is given to t he suitability of each technique for estimating the magnitude, phase and po wer spectrum of the Doppler velocity time series. These are fundamental qua ntities required for studying sea surface scattering mechanisms and remotel y sensing oceanographic properties.