Enhancing Accuracy in Doppler Frequency Shift Estimation and Velocity Measurement for Doppler Velocity Log Applications: A Comparative Study

This research examines the prominent role of sonar technology, especially the Doppler Velocity Log (DVL), in the determination of ship velocity. The DVL employs a four-beam Janus configuration to measure a ship's velocity relative to the waterbed by transmitting acoustic pulses along different azimuth-oriented beams. The study focuses on a scenario where a ship moving through a waterbed produces a Doppler frequency shift, a critical parameter for determining the ship velocity. This paper presents a thorough comparison between the correlation-based broad-band pulse-pair method and the narrow-band least squares method for the determination of Doppler frequency shift. The selection of these methods dynamically adapts to varying water depths. The algorithms are developed and simulated in MATLAB, followed by implementation in Digital Signal Processor (DSP), and further validated through trials in diverse water bodies. Results indicate the broad-band pulse-pair method excelling in low-depth scenarios, while the narrow-band least squares algorithm performs optimally in higher depths. Dynamic algorithm switching based on the water depth exhibits an adaptive approach, enhancing the accuracy of Doppler shift estimations. This study contributes valuable insights for optimizing DVL frequency estimation, providing a practical solution for underwater navigation across varying depth conditions.