基于同步检波的单通道磁感应成像技术研究

Study on single-channel magnetic induction tomography technique based on synchronous detection

磁感应成像在医学领域的应用,由于生物组织的电导率非常小,需要一种测量相位精度高的系统才能满足应用需要。描述了一种基于同步检波的单通道磁感应测量系统,来测量微小相位变化。系统使用模拟开关代替模拟乘法电路,减少直流漂移,增加电路的动态范围。电路中引入了模拟的相移电路,使参考信号和与检测信号相位正交,提高相位测量的灵敏度。研究了单通道系统的稳定度和灵敏度,通过实测电路,该测量系统在1 min内的相位漂移0.001 5°,在1 h内的相位漂移0.006°;并给出电导率变化相应相位变化关系。

Because the conductivity of biological tissues is very small in biomedical applications,a high accuracy phase measurement system is needed to meet the requirement of the applications.This paper describes a single-channel magnetic induction tomography system,which is based on synchronous detection to measure the small phase change.The system uses analog switch to replace analog multiplication circuit to reduce the DC drift and increase the dynamic range of the circuit.An analog phase shift circuit is introduced in the circuit,which makes the reference signal and detection signal as two quadrature signals,and improves the sensitivity of phase measurement.This paper studies the sensitivity and stability of single channel system;Actual circuit measurement indicates that the phase shift is 0.006° in 1 hour,and 0.001 5° in 1 minute,and the phase change corresponding to conductivity change is also given.