Research On Frequency Acquisition And Tracking Algorithm Of Underwater Dynamic Target Signal

With the increasing complexity of marine engineering operation requirements and the further development of underwater acoustic positioning technology,people's demand for underwater dynamic node positioning also arises at the historic moment.For underwater dynamic target positioning,the relative movement between transmitter and receiver will distort the received signal waveform,which will seriously affect the accuracy of subsequent time delay acquisition;estimation and compensation are required to eliminate the influence of dynamics on underwater target positioning.Aiming at the above problems,the thesis studies the acquisition algorithm based on the combination of coarse acquisition and fine acquisition based on FFT technology.The algorithm first performs parallel processing on the code phase,and then expands the short pulse width signal by M times to realize the dynamic signal Effective capture of frequency.Simulation and lake test data analysis show that the comprehensive acquisition algorithm based on FFT technology has higher acquisition probability and faster acquisition speed under the same conditions,and can provide reliable initial traction for the tracking process.Combining the characteristics of the traditional tracking loop,the signal tracking algorithm based on the compound loop is studied,including the second-order PLL loop combined with the second-order DLL loop and the second-order FLL loop to assist the third-order PLL loop tracking algorithm,using the complementary advantages of each loop characteristic,Realize the tracking of underwater dynamic target signal.Simulation and experimental analysis show that the second-order FLL loop assisted third-order PLL algorithm has higher accuracy and stability than the second-order PLL loop combined with the second-order DLL loop algorithm.The paper proposes a serial block iterative tracking algorithm;through the method of block superposition according to the code word,the problem of the continuous wave signal directly doing the related operation hardware realization problem is solved,and the Doppler of the weak signal under the condition of low signal-to-noise ratio is realized.Le tracking compensation uses successive iterations to solve the Doppler frequency shift problem of underwater dynamic target signals;simulation and experimental results show that this algorithm can achieve effective compensation tracking for underwater dynamic target signal frequencies,and the signal When the block cross-spectrum interval N?T>1,the higher the accuracy and stability of the Doppler frequency offset estimation of the algorithm for dynamic signals,the better the effect of tracking compensation.