一个基于扫频与混频相结合的多频EIT数据采集系统

采用多频率组合与扫频技术相结合的方式,建立了一个32电极多频电阻抗断层成像数据采集系统,该系统具有四种工作模式,在程序控制下,最多步采集四种频率下的组织阻抗信息,工作频率可在1．6KHZ到380KHZ间程控选择。为从含多种频率分量的测量信号中解调出各频率下的组织阻抗,我们设计了一种新的具有高速和高精度特点的解调方法,正交序列数字解调法,对含有n个频率分别的信号,若对其每周期采样N点,则总运算量可降低到2nN次乘法和2n(N-1)次加法运算,信号的信噪比可提高（N／2）^-0．5倍。

A Data Acquisition System for Multi-frequency EIT based on Frequency Mixing and Sweeping Technique

A new 32-electrode data acquisition system for multi-frequency EIT has been designed. In this system, sweeping frequency combined with mixing frequency technique is employed. With its four working modes and control programs, it can collect impedance information at four different frequencies simultaneously from 1.6kHz to 380kHz. In order to demodulate the signal with more than one frequency in a single set of measurement, a new digital demodulation method, which has the advantages of high calculation speed and high precision, has been developed and named by us as "orthogonal sequential digital demodulation". For a signal with 'n' components of frequencies and sampling N points per period, using this method.the total needed operations is 2nN multiplication and 2n(N-1) addition operations, and the signal-to-noise ratio can be improved by (N/2)0.5 times.