Interference-Mitigated Doppler Frequency Estimation for Broadband Incoherent ADCPs in Ocean Current Profiling

Abstract

Acoustic Doppler current profilers (ADCPs) are important acoustic remote sensing instruments for measuring ocean current velocity profiles in marine observation systems. This paper addresses the degradation of real-time velocity measurement performance in broadband incoherent ADCPs used for ocean current profiling under strong interference. The pulse-pair method is analytically interpreted as a first-order spectral moment estimator of the observed Doppler spectrum. A point-scattering-based volume echo model is established, and the impact of strong interference on Doppler spectral structure is analysed, revealing the generation of a bimodal spectrum. To mitigate this issue, a method based on spectral integration is proposed to identify interference components and extract valid spectral regions for Doppler frequency estimation. Based on the filtered spectrum, an interference-mitigation Doppler frequency estimation algorithm is developed. Simulation results show that, compared with the conventional pulse-pair method, which suffers from severe bias and up to 200% variance degradation under strong interference, the proposed method effectively mitigates interference effects, maintains near-unbiased mean performance and limits variance degradation to approximately 30%. These improvements enhance the robustness and reliability of Doppler-based ocean current measurements and demonstrate the potential of the proposed method for acoustic remote sensing applications in challenging marine environments.