# 超声成像检测系统声波信号激励与处理技术Acoustic Signal Excitation and Processing Technology in Ultrasonic Imaging Detection System

DOI: 10.12677/JSTA.2020.81001, PDF, HTML, XML, 下载: 361  浏览: 975  科研立项经费支持

Abstract: In a process tomography system, the accuracy of projection data directly determines the imaging resolution. MAX038 chip with high working frequency is used as the signal generator in the ultra-sonic transmitting circuit, according to the sound field requirements of imaging detection. At the front-end of receiving circuit, a passive RC band-pass filter and a voltage follower with high input resistance integrated op-amp were used. The results show that the transmitted ultrasonic wave amplitude and power are stable; electromagnetic interference in the received signal is effectively eliminated, and piezoelectric charge leakage at the front-end of the receiving circuit is avoided.

1. 引言

2. 超声波激励电路的设计

2.1. 脉冲发生器电路设计

MAX038芯片输出信号幅频精度高、波形易于变换，外加少许外围电路就能够方便地输出方波、矩形波、正弦波、三角波或锯齿波。当频率调节引脚FADJ接地时，MAX038输出信号的频率 ${ƒ}_{o}$ 与电流IIN、COSC引脚外接电容Cf之间的关系为

${ƒ}_{o}=2.5V/\left[\left({R}_{W11}+{R}_{12}\right){C}_{f}\right]$ (1)

2.2. 功率放大电路设计

Figure 1. Oscillation circuit for rectangular wave

Figure 2. Power amplifier circuit

${U}_{1}/{U}_{2}={N}_{1}/{N}_{2}=1/2$ (2)

${N}_{1}=\frac{{U}_{1}}{4fA×{B}_{m}}$ (3)

${Z}_{1}={\left({N}_{1}/{N}_{2}\right)}^{2}R$ (4)

Figure 3. Excitation voltage waveform

3. 信号接收电路的设计

Figure 5. Diagram of signal receiving circuit

3.1. 信号预处理电路设计

Figure 6. RC band-pass filter

RC带通滤波器的传递函数(放大倍数)为输出、输入电压之比。低通滤波器的传递函数为

${\stackrel{˙}{A}}_{u}=\frac{{\stackrel{˙}{U}}_{o}}{{\stackrel{˙}{U}}_{i}}=\frac{\frac{1}{j\omega {C}_{1}}}{{R}_{1}+\frac{1}{j\omega {C}_{1}}}=\frac{1}{1+j\omega {R}_{1}{C}_{1}}$ (5)

${\stackrel{˙}{A}}_{u}=\frac{1}{1+j\frac{f}{{f}_{p}}}$ (6)

${\stackrel{˙}{A}}_{u}$ 的模为

$|{\stackrel{˙}{A}}_{u}|=\frac{1}{\sqrt{1+{\left(\frac{f}{{f}_{p}}\right)}^{2}}}$ (7)

$|{\stackrel{˙}{A}}_{u}|=\frac{\frac{f}{{{f}^{\prime }}_{p}}}{\sqrt{1+{\left(\frac{f}{{{f}^{\prime }}_{p}}\right)}^{2}}}$ (8)

Figure 7. Signal waveform after RC filtering

3.2. 电压跟随器设计

${\stackrel{˙}{A}}_{us}=\frac{{R}_{i}}{{R}_{s}+{R}_{i}}{\stackrel{˙}{A}}_{u}$ (9)

3.3. 工频陷波器设计

Figure 8. Double T power frequency trap

$A=1+\frac{{R}_{5}}{{R}_{4}}$ (10)

3.4. 有源带通滤波器设计

Figure 9. Active band-pass filter circuit

3.5. 程控放大电路设计

Figure 10. Programmable cascade amplifier circuit

PGA放大电路是信号处理电路中唯有的数字部分，为避免外部元件引起增益、CMR等方面的误差，在电路板设计时采用了“一点接地法”。

3.6. 检波电路设计

Figure 11. Detection circuit

Figure 12. Voltage waveform of detection circuit

4. 超声成像投影数据测量测量

Figure 13. Schematic diagram of projection data measuring device

Table 1. The projection data

5. 结论

NOTES

*通讯作者。

 [1] 马平, 周晓宁, 田沛. 过程层析成像技术的发展及应用[J]. 化工自动化及仪表, 2009, 36(1): 1-5. [2] 杜运成. 基于电容层析成像技术的气液两相流特性分析[D]. 天津: 天津大学, 2011. [3] 李楠, 徐昆, 刘逵. 基于超声层析成像技术的气/液两相流检测仿真[J]. 北京工业大学学报, 2018, 44(5):735-742. [4] 杨键刚, 吴运新, 龚海, 李伟, 韩雷. 基于LabVIEW的电磁超声热态金属在线缺陷检测系统[J]. 传感技术学报, 2018, 31(5): 809-814. [5] 陈文会, 丁晓鸿, 陈江宁, 刘小民. 超声波测距信号小波阈值去噪参数的选定方法[J]. 传感技术学报, 2017, 30(3): 407-410. [6] 刘宇舜, 程登峰, 夏令志, 李森林, 程洋. 基于单通道盲源分离算法的局部放电特高频信号去噪方法[J]. 电工技术学报, 2018, 33(23): 5625-5635. [7] 赵彩凤, 于志, 王智勇. 高频功率脉冲变压器的设计[J]. 变压器, 2003, 40(10): 6-7.