基于线性调频信号的时延估计算法研究及其在液体检测中的应用

发布时间：2018-03-23 02:22

本文选题：Chirp　切入点：线性调频信号　出处：《华南理工大学》2014年硕士论文　论文类型：学位论文

【摘要】：超声探测作为21世纪运用最为广泛的探测技术，因其无损特性，被广泛应用于工业探伤，，医学，石油探测等领域。Chirp信号(LFM，线性调频信号)是数字信号处理领域的一种非常重要的信号，被经常应用到超声探测中。时延估计是超声探测中的经典问题，该技术是超声定位，超声成像等超声应用的重要内容。因此，对Chirp信号的时延估计算法的研究具有重要的意义。 Chirp信号是一种典型的非平稳信号，因此目前很多针对平稳信号的时延估计算法直接应用到线性调频信号上并不一定适用。在这种情况下，本文首先对经典的时延估计算法，包括互相关法、高阶统计矩时延估计算法、匹配滤波时延估计算法、基于信道建模的时延估计算法和基于分数阶傅里叶变换的时延估计算法等，进行了理论学习和研究。同时，本文重点研究了基于频域加窗的时延估计法和基于时域相干的时延估计算法。这两种算法都是针对于线性调频信号的。本文分别对以上两种算法进行了数学上的理论推导，并且通过仿真，证实了其有效性。同时，分别针对以上两种算法在不同信噪比，不同多径数目等不同的仿真环境下，进行了性能的比较和分析。在本文的最后，运用基于频域加窗的时延估计算法和基于时域相干的时延估计算法，实验团队搭建了一套完整的液体检测系统，用于对不同液体介质的判断。不同的液体具有不用的传播速率和幅度衰减系数，因此，可以由此分辨不同的液体介质。传播速度和幅度衰减系数都可以通过时延估计算法得到。对介质的传播速度，幅度衰减系数等声参量的估计，是超声成像技术的重要内容。针对于我们的应用，团队搭建了自己的硬件和软件系统。在本文中，对基于线性调频信号的液体检测系统进行了详细的说明,并且进行了实际的探测实验。实验结果表明，本文讨论的两个时延估计算法具有实际的效用。
[Abstract]:Ultrasonic detection, as the most widely used detection technology in the 21st century, is widely used in industrial flaw detection and medicine because of its nondestructive properties. Chirp signal LFM is a very important signal in the field of digital signal processing, which is often used in ultrasonic detection. Time delay estimation is a classical problem in ultrasonic detection. Therefore, it is of great significance to study the time delay estimation algorithm of Chirp signal. Chirp signal is a kind of typical non-stationary signal, so many time delay estimation algorithms for stationary signal are not always applicable to LFM signal directly. In this case, the classical time delay estimation algorithm is firstly studied in this paper. It includes cross-correlation method, high-order statistical moment delay estimation algorithm, matched filter time delay estimation algorithm, channel model-based time delay estimation algorithm and fractional Fourier transform based time delay estimation algorithm. This paper focuses on the time-delay estimation algorithm based on windowed frequency domain and time-domain coherent time-delay estimation algorithm. Both algorithms are aimed at LFM signals. At the same time, we compare and analyze the performance of the two algorithms under different simulation environments, such as different signal-to-noise ratio (SNR) and different number of multipath. At the end of this paper, using the time-delay estimation algorithm based on frequency-domain windowing and time-domain coherent time-delay estimation algorithm, the experimental team built a complete liquid detection system. Used to judge different liquid media. Different liquids have unwanted propagation rates and amplitude attenuation coefficients, so, The propagation velocity and amplitude attenuation coefficient can be obtained by time delay estimation algorithm. The sound parameters such as propagation velocity and amplitude attenuation coefficient can be estimated. Is the important content of ultrasonic imaging technology. For our application, the team built their own hardware and software system. In this paper, the liquid detection system based on LFM signal is described in detail. The experimental results show that the two delay estimation algorithms discussed in this paper are effective.
【学位授予单位】：华南理工大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TN911.23

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