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Reseach On The Key Technologies Of LFM Underwater Acoustic Communication Based On Parametric Array

Posted on:2018-11-05Degree:MasterType:Thesis
Country:ChinaCandidate:L F HeFull Text:PDF
GTID:2348330512983226Subject:Engineering
Abstract/Summary:PDF Full Text Request
In recent years,with the further development of marine resources and coastal defense,we not only greatly increase the demand for underwater acoustic equipment,but also improve the technical requirements for underwater acoustic communication.However,on the one hand,due to the complex noise of the shallow sea acoustic channel,space-time-changes of remote underwater acoustic communication brings serious multipath interference and fading;On the other hand,the area of the channel is seriously polluted by the traditional acoustic waves with omnidirectional and low frequency,which is result in low utilization of underwater acoustic channels and no security in military use.To deal with these problems,this thesis proposes LFM underwater acoustic communication technology based on parametric array.The self-demodulation effect of the acoustic wave in the medium can produce low-frequency sound waves with high directivity and small side lobes.The acoustic wave with high directivity can suppress the multipath effect and reduce the pollution to the surrounding sound field,and realize the directional confidential communication.At the same time,the M-linear chirp communication technology has strong anti-Anti-Doppler effect and anti-channel attenuation capability.And the M-linear chirp has a good pulse compression detection performance in the low signal to noise ratio.Firstly,the second chapter analyzed the characteristics of acoustic channel in the shadow water,and described the nonlinear acoustic principles of parametric array.Besides,the chapter Simulated and analyzed the signals' directivity and acoustic field of the demodulated signals based on parametric array,and established a underwater acoustic channel multipath model base on acoustic ray theory.Secondly,based on the "Berktay" theoretical model,the third chapter derived the theoretical formulas of the LFM self-demodulation signal with the DSB_AM and SSB_AM modulation algorithms of the acoustic parametric array.Furthermore,this chapter optimized the DSB_AM and SSB_AM algorithms which was to reduce the unnecessary power dissipation problem.Then,in order to better analyze the theoretical model and communication performance of LFM underwater acoustic communication.The chapter 4 designed the parameter array communication system,and briefly described the various modules and signal processing technologies and methods.Then,this chapter also analyses the Coding and decoding principle of the signal and the simulation of the algorithm in detail.Further,we designed communication system simulation model based on MATLAB / Simulink tool.Finally,the chapter5 designed and built the whole hardware system test platform,including system launch signal test,SSB_AM modulation algorithm test and communication data transmission test.The experimental results show that,on the one hand,the directional transmission characteristics of the acoustic array are better than the traditional omnidirectional low frequency sonar communication.On the other hand,the improved SSB_AM modulation algorithm improves the energy conversion efficiency of the system.Therefore,the LFM acoustic communication method based on parametric array has certain engineering value and application prospect.
Keywords/Search Tags:Parametric acoustic array, Nonlinear interaction, Underwater acoustic communication, Linear frequency modulation(LFM)
PDF Full Text Request
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