Circular estimation of the flow velocity using coherent Doppler sonar

The problem of coherent Doppler frequency estimation is addressed here applied to the domain of active hydroacoustics in a context of high Signal to Noise ratios. Pulse-to-pulse coherent Doppler sonars allow non-intrusive high-resolution velocity measurements that are often delicate to analyse, due to the nature of the return signal. We present here a novel pulse-to-pulse coherent Doppler estimator using signal processing techniques defined in the circular domain aiming to better reconstruct the noisy phase of the Doppler signal at high temporal resolutions. This Linear Circular estimator was tested on hydroacoustics synthetic measurements and its robustness to noise was demonstrated compared to the standard pulse-pair algorithm. The study suggests its high potential for time-resolved quasi-instantaneous velocity estimation, and turbulence statistics evaluation. The Linear Circular estimator's robustness to noise also suggests potential interests in applying such methods for incoherent scattering evaluation.