基于multisine激励与整周期采样的多频电阻抗成像系统设计

本文从周期信号的整周期采样无频谱泄露这一原理出发,提出基于multisine信号的整周期采样理论,从理论上推导出满足multisine整周期采样的采样率设置条件,构建了基于FPGA+数模转换器+模数转换器的整周期采样实现方法,研制了一种基于multisine激励和整周期采样的新型多频电阻抗成像(mfEIT)系统;设计了胡萝卜棒+黄瓜棒的双目标成像模型,并进行了多频时差成像和频差成像实验.实验表明,本mfEIT系统能够在一个基波周期(1 ms)内实现20个频率点(2—997 kHz)多目标组织边界的全频阻抗测量,成像结果可区分具有不同电特性生物组织的结构与位置.本文提出的基于multisine信号的整周期采样理论及其实现方法,只需一个multisine基波周期即可完成一次全频阻抗测量,为研制高速mfEIT系统奠定了理论和技术基础.

Design of multi-frequency electrical impedance tomography system based on multisine excitation and integer-period sampling

Starting from the principle that the integer-period sampling(IPS)of periodic signals is free of spectrum leakage,in this paper we propose the multisine-IPS theory,deduce theoretically the sampling rate setting formula of multisine-IPS condition for the first time,and build its realization method based on fieldprogrammable gate array(FPGA)plus digital-to-analog converter(DAC)plus analog-to-digital converter(ADC).A new multi-frequency electrical impedance tomography(mfEIT)system based on multisine excitation and its IPS theory is developed,and a dual-target imaging model including a carrot stick and a cucumber stick is designed.The experiments of multi-frequency time-difference imaging and frequency-difference imaging are carried out on the mfEIT system.The experimental results show that the newly-designed mfEIT system can achieve full-band impedance measurements on multiple objective tissue boundary at 20 frequency points(2–997 kHz)within one fundamental period(1 ms),and the structure and position of biological tissues with different electrical properties can also be distinguished from the resulting images.The proposed multisine-IPS theory and its implementation method can complete a full-band impedance measurement within one multisine fundamental period,which lays a theoretical and technical foundation for developing high-speed mfEIT system.