| 题名 | 声时精度的影响因素分析及信号处理方法研究 |
| 作者 | 周艳 |
| 学位类别 | 博士 |
| 答辩日期 | 2008-05-27 |
| 授予单位 | 中国科学院声学研究所 |
| 授予地点 | 声学研究所 |
| 关键词 | 声时测量 信噪比 阈值 经验模态分解 相空间 |
| 其他题名 | Factors Analysis and Signal Processing in Accurate Transit Time Measurement |
| 学位专业 | 信号与信息处理 |
| 中文摘要 | 信号传播时间的测量是目前信号检测中的重要课题，其应用领域十分广泛，如超声检测、流量计、激光测距等。目前的时间间隔测量技术精度可以达到皮秒量级，但接收信号到达时间检测的不精确限制了该技术的应用，本文就以声时测量的典型应用之一——超声波流量计为例，分析了系统中影响声时测量的主要因素，并就信号处理的方法做了初步的研究。 文中首先对影响绝对声时的流场、换能器特性、温度这三个主要因素做了简要分析。其次，从时间间隔测量角度出发，对影响声时测量精度的因素作了分析。信噪比是影响接收信号判定的首要因素，研究不同的信噪比下，系统能达到的测量精度具有现实的意义；信号的时域波形不是时间的线性函数，加上噪声的影响，因此过零检测的阈值的选择会影响信号检测精度；带宽越宽，信号的上升时间越快，越有利于时间间隔测量，但同时系统的信噪比也会降低。文中对部分结果进行了实验验证。 针对影响因素采取的相应措施对系统测量精度的提高比较有限，目前随着高速器件的开发，采集接收信号并进行前置处理以提高测量精度，成为提高声时测量精度的发展方向之一。文中对经验模态分解和相空间重构的方法重建信号做了初步的分析，对实验中的接收信号进行了处理，有一定的效果，但还有待进一步改进。 最后，总结了本文的分析结果，并提出了以后的研究方向。 |
| 英文摘要 | Transit-time measurement is an important issue in signal detection. It is widely used in applications such as Ultrasonic detection, Flowmeter, laser range finder and so on. Even the time interval measurement achieved ps level, the accuracy of received signal limited its application of it. Several factors affecting accuracy of transit time in ultrasonic liquid flow measurement are analyzed, and the signal processing method is investigated. The analysis is based on transit time ultrasonic flow measurement. First, factors affecting accuracy of absolute transit time such as flow filed，sensor performance and temperature are briefly analyzed. Then, factors affecting accuracy of transit time measurement are analyzed. SNR is the first factor in signal detection, discussing the accuracy of measurement in different SNR is significant. Since signal wave is not the linear function of time, and is affected by noise, threshold of zero-crossing is very important for accuracy of measurement. When band width become wide, the rising time will be fast, it is useful for transit time measurement, but the SNR will degrade simultaneously. The choice of band width is a compromising result. The three factors above affect each other in system. The analysis and data verification is made in detailed. Improvement of accuracy according to above analysis is limited. The digital signal processing became an important issue along with the development of high speed DSP. Processed sampled signal in proper digital way will improve the accuracy of transit time. Empirical Mode Decomposition and phrase space reconstruction are used in received signal processing, and the effect is obviously, but the result can be improved further. At last, the conclusion of the thesis is given, and the further jobs in the future are put forward. |
| 语种 | 中文 |
| 公开日期 | 2011-05-07 |
| 页码 | 70 |
| 内容类型 | 学位论文 |
| 源URL | [http://159.226.59.140/handle/311008/434]  |
| 专题 | 声学研究所_声学所博硕士学位论文_1981-2009博硕士学位论文 |
| 推荐引用方式 GB/T 7714 | 周艳. 声时精度的影响因素分析及信号处理方法研究[D]. 声学研究所. 中国科学院声学研究所. 2008. |
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