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Bio- impedance measurement technology (Bio-Impedance Measuring Technology, BIMT) is the use of the electrical properties of biological tissues and organs ( impedance , admittance , dielectric constant ) and its changes , extraction and human physiology , pathology related information of a non-invasive detection technology. It has a unique ability to identify the blood , gas , body fluids and different tissue components , noninvasive , inexpensive , safe , simple operation , information-rich features , and therefore with a wide range of applications in clinical diagnostics , health testing . In this thesis , the author completed the following aspects : 1 , according to the principle of bio - impedance measurement , bio - impedance measurement system based on virtual instrument digitized mixer , and the problems of signal acquisition and digital demodulation system be optimized , and the realization of the system within a wider band of dynamic measurement of the body impedance . The application of the active electrode and the cable -driven technology , improve the signal-to-noise ratio of the measurement system and the anti - stray capacitance capability , simultaneous analysis of the causes of error of the measurement system , and the error compensation to improve the measurement accuracy of the system . Study , DFT-based the mixer signal demodulation method , through simulation , analysis the DFT energy leakage and fence effect of sinusoidal signal measurements , respectively, using the interpolated DFT method , virtual reference vector method , interpolation DFT and virtual the reference vector combination method to compensate the measurement results , and analysis of simulation results , the compensation effect of the virtual reference vector method is verified by experiment . 4 , according to the characteristics of the bio - impedance measurement signal , application binary wavelet transform method for processing of bio- impedance signal on human blood gas impedance signal separation , time-frequency characteristics of signal extraction . Combined medical background , design the experiment of human pulmonary function testing , proposed bio - impedance signal energy analysis method based on wavelet transform lungs impedance of blood gas than on the human body in different physiological states . Finally, for the shortcomings of the system , and made ??some suggestions .
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