磁感应成像系统中相位检测方法研究

Study on technique of phase detection in magnetic induction tomography

在磁感应成像(MIT)系统中,组织电导率和激励信号与检测信号之间的相位差成正比。为了能对组织电导率分布进行成像,要求系统具有高精度的相位差检测功能。着重研究数字鉴相,包括FFT法、相关法和经典法,并与硬件鉴相方法进行比较。实验结果表明,FFT法和相关法能够较好地区分0.1°水平的相位差,具有误差小、线性度高的优点。数字鉴相为MIT系统鉴相提供了一种更理想的方法。

In the magnetic induction tomography （MIT） system, the electrical conductivity of biological tissue is direct proportion to the phase difference between the excitation signal and the detection signal. To obtain the image of the contribution of tissue＇s electrical conductivity, the system must have the function of phase detection with high accuracy. The paper focuses on the means of digital phase detection, including FFT method, the correlation method and the classic method, which are ultimately compared with analogue phase detection method. The experimental results show that FFT method and the correlation method, with low error level and high linearity, can better detect the phase difference with the level of 0.1% The digital phase difference detection provides a kind of effective method for MIT system.