基于m序列的生物电阻抗快速测量方法研究毕业论文

摘要

论文题目：基于m序列的生物电阻抗快速测量方法研究

摘要

生物电阻抗频谱（BIS）是指在生物组织中表现出的电阻抗特性(包含阻性和容性)随着加载电信号频率的改变而发生变化的特性。它是一种频域的测量方法，能够测得频域较宽的阻抗谱来研究生物组织的生理特征。生物电阻抗的测量要求创伤小或者无创伤、测量快速、精度高。本文选用了一种用电流源激励的无创伤的四电极法测量生物电阻抗的方法，设计了一套高速采集系统，对采集数据进行了算法处理，得出电阻抗值。全文主要包括以下几个部分：

1.本文首先研究和分析了m序列的性质。由于m序列的自相关函数接近于冲击函数、功率谱离散、抗干扰能力强、带宽调节方便、二值函数便于实现，所以伪随机信号m序列被选择为电流源激励模型，并用FPGA芯片实现。用m序列作为生物电阻抗模型的激励源时，可以通过求相关函数知道系统的冲击响应，方便求出阻抗谱。

2.为了实现快速测量，本文设计了一套基于FPGA+ARM的快速测量系统。系统以FPGA逻辑可编程芯片和STM32微处理器为核心，主要设计了电源模块、激励信号源模块、模数转换模块、数据缓存模块、FPGA前端控制模块和STM32后端控制模块。本系统实现了对m序列激励信号和响应信号的同步采样,完成了对实验数据的正确采集。

3.本文研究了一套基于快速相关算法和全相位FFT求阻抗值的算法，利用循环卷积与FFT之间的对应关系，通过序列补零加长的方法，设计FFT的快速求相关函数的检测算法，求取激励电流与响应电压信号之间的互相关，即被测阻抗的时域冲激响应。为了得到阻抗频谱值，采用全相位频谱分析方法，求取被测阻抗的频率响应，从而实现对电阻抗模型的多频率同步快速测量。

4.本文用电阻抗模型对构建的测量系统和研究的算法做测量实验，并对整个测量系统进行标定，分析测量结果的误差。

本文的研究实现了生物电阻抗多频率同步测量,为生物电阻抗快速测量研究提供了一种可行的方法。

关键词：m序列；生物电阻抗；同步采样；全相位

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西安理工大学硕士学位论文II

Abstract

Title：Research of Bioelectrical Impedance Fast Measurement Method Based on m Sequence

Major：Precision Instrument and Mechanism

Name：Wei LIU Signature: Supervisor：Associate Prof. Yuxiang YANG Signature:

Abstract

Bioelectrical impedance spectrum (BIS) indicates a character that reflects electrical impedance character (including resistance and capacitance) performing in biological tissue varies with the change of loading signal frequency. It is a frequency domain measurement method to measure a relatively wide frequency domain impedance spectrum in researching the physiological feature of biological tissues. Bioelectrical impedance measurement has the requirement that of tiny wound or wound absence, rapid measuring and high accuracy. This thesis employs a four-electrode method adopting current source excitation to measure bioelectrical impedance. It designs a high-speed acquisition system and afterwards processes data to acquire impedance value with a set of algorithm. The main research content is as follows:

1. The thesis firstly research and analyze properties of m sequence. Due to autocorrelation function of m sequence possesses the merits, such as close to impulse function, discrete power spectrum, strong anti-interference ability, convenient bandwidth adjustment and binary function is easy to realize, and the m sequence pseudo random signal is chosen as the current source excitation model and is implemented on FPGA platform. When using m sequence as bioelectricity impedance model excitation source, it can obtain system impact response through solving correlation function. Therefore, impedance spectrum is convenient to be acquired.

2. It designs the high-speed acquisition system that based on FPGA and ARM in order to achieve rapid measurement. The system use with FPGA logic programmable chip and STM32 microprocessor as a core, it designs several modules, such as power supply module, excitation signal source module, analog-to-digital converter module, data buffer module, FPGA front control module and STM32 backend control module. It realizes synchronous sampling about m sequence excitation and response signal, and achieves correct sampling about experimental data.

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