Doppler Estimation Based on Dual-HFM Signal and Speed Spectrum Scanning

High-accuracy real-time Doppler estimation is one of the key problems in underwater acoustic communication systems. Using the dual-hyperbolic-frequency-modulation (dual-HFM) synchronous signal is an effective solution; however, the Doppler estimation accuracy is limited by the sampling frequency in the traditional methods. In this letter, we propose a high-accuracy speed spectrum scanning method based on the Doppler invariant and the frequency spectrum properties of the HFM signal. This signal processing system uses dual-HFM waveform as a synchronous signal, constructs the speed spectrum function at the receiver, and then obtains the Doppler estimate through one-dimensional scanning. This method breaks through the speed resolution limit induced by the sampling frequency in the traditional method and obtains a high-accuracy estimate. The influences of signal transmission and processing parameters on the Doppler estimation is analyzed, and the parameter selection criteria is presented to improve the reliability of the estimation. The results of both numerical simulation and underwater communication experiments prove the effectiveness of the proposed method.