【摘要】：超聲液體聲學(xué)特性測量在石油化工行業(yè)、液態(tài)食品行業(yè)以及醫(yī)學(xué)診療領(lǐng)域都有非常重要的意義。通過測量得到的聲速、聲阻抗和聲衰減等參數(shù)進(jìn)一步推導(dǎo)得到液體的密度、濃度、黏度等理化常數(shù)，在各個(gè)領(lǐng)域的應(yīng)用越來越廣泛。在這種課題背景下，針對傳統(tǒng)測量手段的不足，本文研究了基于線性調(diào)頻連續(xù)波的超聲液體聲學(xué)特性測量系統(tǒng)。 本文的主要研究內(nèi)容和成果如下： （1）基于超聲波在不同介質(zhì)界面處的傳播特性，建立了用于測量液體聲學(xué)特性的三層有界介質(zhì)透射模型。通過對超聲波在測量模型中的傳播變化情況詳細(xì)分析，設(shè)計(jì)了能夠有效測量待測液體聲速、聲阻抗和聲衰減參數(shù)的方法和具體步驟。 （2）針對三層有界介質(zhì)透射模型，結(jié)合國家移動(dòng)超聲探測工程技術(shù)研究中心的高速數(shù)據(jù)收發(fā)系統(tǒng)和DSP數(shù)字集成電路構(gòu)建起完整的超聲液體聲學(xué)特性測量系統(tǒng)。采用具有脈沖壓縮特性、抗噪和抗干擾性能優(yōu)越的大時(shí)寬帶寬積線性調(diào)頻連續(xù)波作為信號(hào)源，并根據(jù)探頭型號(hào)進(jìn)行參數(shù)設(shè)置。 （3）對傳統(tǒng)的恒包絡(luò)LFM信號(hào)做出改進(jìn)，設(shè)計(jì)基于幅度補(bǔ)償?shù)念A(yù)失真處理方案，經(jīng)過仿真和實(shí)驗(yàn)結(jié)果證明，預(yù)失真處理能夠有效解決接收信號(hào)幅度衰減和抖動(dòng)嚴(yán)重的問題。 （4）構(gòu)建實(shí)驗(yàn)驗(yàn)證系統(tǒng)，選用乙醇溶液、橄欖油和牛奶作為三種待測液體分別進(jìn)行測量，對系統(tǒng)接收到的透射信號(hào)采用基于時(shí)域互相關(guān)的時(shí)延估計(jì)算法和基于FOCUSS算法的幅度估計(jì)進(jìn)行處理，，并計(jì)算得到三種液體聲速、聲阻抗和聲衰減特性參數(shù)。通過Matlab仿真和實(shí)驗(yàn)結(jié)果對比可以看出，這兩種算法能夠較準(zhǔn)確估計(jì)出LFM信號(hào)的傳播時(shí)延和幅度衰減，結(jié)果誤差在合理范圍之內(nèi)。
[Abstract]:Ultrasonic liquid acoustic measurement is of great significance in petrochemical industry, liquid food industry and medical diagnosis and treatment. The physical and chemical constants of liquid, such as density, concentration, viscosity and so on, are further deduced from the measured parameters such as sound velocity, acoustic impedance and acoustic attenuation, which are more and more widely used in various fields. In this paper, an ultrasonic liquid acoustic characteristic measurement system based on linear frequency modulation continuous wave (LFM) is studied to overcome the shortcomings of traditional measurement methods. The main research contents and achievements of this paper are as follows: (1) based on the propagation characteristics of ultrasonic wave at different dielectric interfaces, a three-layer bounded dielectric transmission model for measuring the acoustic characteristics of liquid is established. Based on the detailed analysis of the propagation and variation of ultrasonic wave in the measurement model, a method and concrete steps are designed to effectively measure the sound velocity, acoustic impedance and acoustic attenuation parameters of the liquid to be measured. (2) according to the three-layer bounded dielectric transmission model, a complete ultrasonic liquid acoustic characteristic measurement system is constructed by combining the high-speed data receiving and receiving system of the National Mobile Ultrasonic Detection Engineering Technology Research Center and DSP digital integrated circuit. The large time broadband wide product linear frequency modulation continuous wave with pulse compression characteristics, excellent anti-noise and anti-interference performance is used as the signal source, and the parameters are set according to the probe model. (3) the traditional constant envelope LFM signal is improved, and a pre-distortion processing scheme based on amplitude compensation is designed. The simulation and experimental results show that the pre-distortion processing can effectively solve the problem of serious amplitude attenuation and jitter of the received signal. (4) the experimental verification system was constructed, and ethanol solution, olive oil and milk were selected as three kinds of liquids to be measured respectively. The transmitted signals received by the system are processed by time delay estimation algorithm based on time domain cross correlation and amplitude estimation based on FOCUSS algorithm, and three kinds of liquid sound velocity, acoustic impedance and acoustic attenuation characteristic parameters are calculated. Through the comparison of Matlab simulation and experimental results, it can be seen that the two algorithms can accurately estimate the propagation delay and amplitude attenuation of LFM signal, and the error is within a reasonable range.
【學(xué)位授予單位】：華南理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2014
【分類號(hào)】：TB52

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