Signal Processing Algorithm Research And System Software Design Of The Doppler Velocity Log

Doppler Velocity Log(DVL) is an instrument of measuring velocity and calculating voyage byDoppler effect of underwater sonic. With the development of science technology and the payingattention to ocean development, DVL is used widely. The development of better performance andmore miniaturized’s DVL is attached important by the nations. Therefore, this paper mainly studiessignal processing algorithms and designs PC system software of DVL.Firstly, a beamforming algorithm based on phase shift beamforming is studied. Before Dopplerfrequency estimation, quadrature demodulation and beamforming of signal are carried. But thereal-time of entire Doppler velocimetry system is affected directly by the complexity ofbeamforming algorithms. To solve the problem, a fast beamforming method is proposed. Themethod makes quadrature demodulation and beamformer as a modular design by using the signalsorthogonality of quadrature demodulation and the properties of Hilbert transform. And thecomplexity of the beamformer is greatly reduced.Secondly, the frequency estimation algorithm of DVL is researched. The complex-correlationalgorithm using the fast beamforming method with different quadrature demodulation is simulatedand analyzed for Doppler frequency estimation of narrowband and broadband signals. Sensibility ofthe complex-correlation algorithm to quadrature demodulation error for broadband signal is lowerthan for narrowband signal. But the performance of the complex-correlation algorithm is alsoaffected by quadrature demodulation. Because the broadband signal uses binary phase shiftkeying(BPSK) signal, it is cyclostationary signal. So a Doppler frequency estimation method basedon cyclic statistics is proposed, using cyclic cross ambiguity function of signals to estimatefrequency. Although the complexity of this algorithm is higher, but it does not requie quadraturedemodulation, and its estimation accuracy is higher than the complex-correlation algorithm.At last, the PC system software is designed and implemented. The software is designed underthe Windows operating system, and developed by Visual C++6.0. The main features of PC systemsoftware include serial port setting, system setting, data showing, system log, help and so on. ThePC system software connects PC’s serial port with lower machine’s serial port together viaRS-232C. Then, PC system sents configuration parameters to lower machine, and receives data thatlower machine transmits to compute Doppler frequency. And then, the results and waves are shownon display area timely so as to remote real-time monitored by user.