基于广义S变换的超声多普勒信号检测

发布时间：2019-05-09 22:14

【摘要】：超声多普勒回波信号是一种非线性、非平稳的信号,其瞬时频率随着时间的变化而变化。提取出多普勒回波信号的瞬时速度对运动目标的运动状态分析具有重要的意义,但由于其非平稳性的限制,一般的信号分析方法无法提供足够的时频聚焦性能。时频分析方法则能够展示出信号的频率随时间的变化规律,其形式有多种,包括短时傅立叶变换、Wigner-Ville分布以及小波变换等常用的时频分布方法。针对这几种时频分布方法存在不能提供足够的时频聚焦性能的问题,本文提出了基于广义S变换的超声多普勒信号瞬时速度提取方法,并进行了计算机仿真和实验验证。论文做了如下研究工作：1、本论文基于连续多普勒方法对运动物体进行测速,从理论上分析了超声多普勒信号处理中的几种时频方法。对比了这几种方法的时频聚焦性能,并提出将广义S变换引入到超声多普勒信号瞬时速度的提取上。2、在将广义S变换应用于多普勒信号的仿真中,我们设定超声波入射一个往复运动的质点得到了多普勒回波信号,计算机仿真表明了广义S变换在超声多普勒信号中运动目标的瞬时速度提取上的有效性。3、我们设计了一个往复运动的机械装置,构建了由FPGA和USB 2.0芯片组成的信号采集系统。在实验中,采用该系统对超声接收探头获得的多普勒信号进行采集,实时传输到PC并以文本格式存储在磁盘中。实现了高速数据采集和传输的功能,采集系统技术参数和功能符合超声多普勒测量系统要求。4、在对实测多普勒信号的瞬时速度提取的实验中,利用广义S变换信号处理程序对实际采集到的离散信号进行处理,提取出多普勒信号的瞬时频率,并计算得到运动目标的瞬时速度。通过对实测多普勒信号进行处理,表明了广义S变换在超声多普勒信号中运动目标的瞬时速度提取上的有效性。对超声多普勒信号瞬时速度的提取是医学超声工程的一个研究方向,本论文的研究工作对于超声多普勒血流瞬时速度的高精度提取具有一定的实际意义和应用价值。
[Abstract]:Ultrasonic Doppler echo signal is a nonlinear and non-stationary signal, and its instantaneous frequency varies with time. It is of great significance to extract the instantaneous velocity of Doppler echo signal for the motion state analysis of moving targets, but due to the limitation of its non-stationarity, the general signal analysis method can not provide enough time-frequency focusing performance. Time-frequency analysis method can show the variation of signal frequency with time, including short-time Fourier transform, Wigner-Ville distribution and wavelet transform and other commonly used time-frequency distribution methods. In order to solve the problem that these time-frequency distribution methods can not provide enough time-frequency focusing performance, a method of ultrasonic Doppler signal instantaneous velocity extraction based on generalized S transform is proposed in this paper, and the computer simulation and experimental verification are carried out. The following research work has been done in this paper: 1. In this paper, several time-frequency methods in ultrasonic Doppler signal processing are analyzed theoretically based on continuous Doppler method to measure the velocity of moving objects. The time-frequency focusing performance of these methods is compared, and the generalized S transform is introduced into the instantaneous velocity extraction of ultrasonic Doppler signal. 2, in the simulation of Doppler signal, the generalized S transform is applied to the simulation of Doppler signal. The Doppler echo signal is obtained by setting the ultrasonic incident particle of a reciprocating motion. The computer simulation shows the effectiveness of the generalized S transform in the instantaneous velocity extraction of the moving target in the ultrasonic Doppler signal. 3, We designed a reciprocating mechanical device and constructed a signal acquisition system composed of FPGA and USB 2.0 chips. In the experiment, the Doppler signal obtained by ultrasonic receiving probe is collected, transmitted to PC in real time and stored on disk in text format. The function of high speed data acquisition and transmission is realized, and the technical parameters and functions of the acquisition system meet the requirements of ultrasonic Doppler measurement system. 4. In the experiment of instantaneous velocity extraction of measured Doppler signal, The generalized S transform signal processing program is used to process the discrete signal collected in practice, the instantaneous frequency of Doppler signal is extracted, and the instantaneous velocity of moving target is calculated. By processing the measured Doppler signal, the effectiveness of the generalized S transform in the instantaneous velocity extraction of moving targets in ultrasonic Doppler signals is shown. The extraction of instantaneous velocity of ultrasonic Doppler signal is a research direction of medical ultrasonic engineering. The research work of this paper has certain practical significance and application value for the high precision extraction of instantaneous velocity of ultrasonic Doppler blood flow.
【学位授予单位】：合肥工业大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TB559

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