Research On Bioimpedance Spectroscopy Fast Measurement Method Based On System Correlation Identification

Bioelectrical impedance spectrum(BIS),which is developed from the initial single-frequency measurement method to the multiple-frequency measurement,has been greatly improved in accuracy,efficency and scope of BIS measurement.But the research on dynamic characterstics(such as breathing,heartbeat,etc.)of physiological system puts forward higher requirements for BIS measurement speed and anti-interference ability.Consequently,this paper proposes a BIS fast measurement method based on system correlation identification.The main research contents are shown as follows:1.Firstly,the basic properties of m sequerncy is studied.Based on the generation principle of m sequence,fundamental propertries(periodic properties,binary properties,balancing properties),autocorrelation function,power spectrum,anti-interference ability and other characteristics are discussed in this article to prove that m sequence can be used as a good excitation signal in BIS measurement.2.The fundamental principle and transformation methods of correlation identification are researched,and the calculating method of impulse function in general system is deduced based on the input and output signal.In addition,fast m sequence transform is introduced.3.Considering features of bio-impedance measurement system,a BIS measurement method based on m sequence excitation and correlation identification is proposed,which improve the calculateing accuracy on the basis of over sampling;In order to reduce unecessary spectrum calculation,Chirp Z transformation is adopted to complete more data and less spectrum output calculation.Meanwhile,the verification of previous theory is fulfilled by using Matlab to simulate the algorithm and work out the error under different condition(sequency length,sampling rate).4.A BIS measurment hardware platform based on system correlation idenfication is designed,including the FPGA+ARM as core module,excitation signal,VCCS,analog front end,dual channel synchronization sampling,and cache module.The signal generation,acquistion,storage and processing can be completed by this hardware system,to fulfill the fast BIS measurement.5.The experiment on bio-impedance model(three component RC)is conducted by using this hardware system under different condition.The error analysis of measuring data is completed by correction system,keeping the measuring error within 4% of resistance,2% of phase.The features of m sequence pseudo random signal is taken full use to design and fulfill a BIS measurement instrument based on system correlation identification.The advantage of measuring 1023 frequence points within 1ms proposes a new thought for BIS fast measurement,which is in great significance.