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Multi-frequency Excitation Source and Quadrature Demodulation Technique in Digitized EIT System

Author: WuYou
Tutor: RenChaoShi；ShaHong；ZhaoDeChun
School: Peking Union Medical College , China
Course: Biomedical Engineering
Keywords: Electrical impedance tomography Complex impedance Multi-frequency excitation source The digital quadrature demodulation
CLC: R310
Type: Master's thesis
Year: 2010
Downloads: 73
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Abstract

Electrical impedance tomography (Electrical Impedance Tomography, EIT) is a new generation of medical imaging technology after following the morphological , structural imaging . Functional imaging , without injury and medical image guardianship three outstanding advantages . Physiological and pathological conditions of the human body , through the organization of the electrical characteristics of the expression , and the biological changes occur in molecular and cell level linked . Based on the nature of the complex impedance of the human tissue , extract the imaginary part of the tissue impedance or phase information , given early or forward-looking results that occur at the cellular level , is an important task of the EIT technology . This study focuses on the analysis at home and abroad the EIT the development of dynamic , technology status and key technological advances based on a number of multi-frequency complex impedance EIT system for application goals , focus on multi-frequency excitation source and digital quadrature demodulation method . The complete FPGA platform based on the multi-frequency sequence of constant current excitation source and digitized quadrature demodulation module design , construction and experimental validation . The key findings include : 1 , based on the needs of multi- frequency EIT measurements to study the DDS and FPGA - based sinusoidal excitation signal generating programs ; complete circuit design ; satisfaction multi-frequency sinusoidal signal . 2 , the Howland circuit solution based on the improved design of the voltage - controlled current source module ; build a high output impedance constant current source . The constant current source output impedance of not less than 190 kΩ in the range of 1 MHz , 1 MHz to 1.6 MHz , not less than 75 kΩ . 3 , in the analysis of analog, digital demodulation method characteristics on the basis of proposed orthogonal sequence FPGA-based digital demodulation scheme ; research demodulation process ; tested the performance of the research demodulation module , and given lower error possible way . The completion of the paper work for the digitized EIT system and laid the technical foundation , but also to create the conditions for the next target for some applications EIT applied research .

Multi-frequency Excitation Source and Quadrature Demodulation Technique in Digitized EIT System

Abstract

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