Research On A Novel Wideband Current Source For Bioelectrical Impedance Spectroscopy Measurement

The function of the excitation source in the BIS(Bioelectrical Impedance spectroscopy)measurement system is to provide a current or voltage excitation signal that directly acts on biological tissues,and its accuracy and stability play a decisive role in the performance of the entire measurement system.In order to ensure accurate measurement of BIS,a current source is used as the excitation signal,which requires a wide frequency range of the current source,high output impedance,and stable output current.The upper limit of the BIS measurement band has been increased to 1 MHz or higher.Scholars have found that more physiological information is included in the high-frequency range with the growth of wideband bioimpedance applications.The upper limit of the BIS measurement band has been increased to 1 MHz or higher.In the current BIS measurement system,when the current source frequency reaches BIS the upper frequency limit of the system near 1 MHz,the output impedance decreases rapidly,the output current amplitude is unstable,and the phase changes.The main purpose of this thesis is to develop a novel wideband current source for bioelectrical impedance spectroscopy,mainly including the following content.Firstly,the principle of bioelectrical impedance spectroscopy and the research status of wideband current sources.Next,A novel wideband mirrored current source based on a differential difference amplifier,analyzes in detail the working principle of the novel wideband current source.analyzes the working principle of the novel wideband current source and the components of the current source in detail,mainly including the novel wideband based on a differential differential amplifier.Current source design,signal pre-processing circuit design,and derive the output current expression.In addition,a new type of wideband mirrored current source based on differential differential amplifier is proposed.The working principle of the novel wideband current source and the components of the current source are analyzed in detail,including the new type based on a differential differential amplifier.Design of wideband current source,signal pre-processing circuit,and deduce the output current expression of novel wideband current source.Combined with a novel wideband current source equivalent model,analyze the output impedance evaluation method of wideband current source.It is planned to use the mutation particle swarm optimization(PSO)algorithm to solve the equivalent model parameters,which can effectively improve the accuracy and fit of the model parameters.Then,the effectiveness of the algorithm is verified through simulation experiments.Finally,the effects of different signal-to-noise ratios of white noise and parameter mismatch on current sources are compared.At last,complete the hardware circuit design of the novel wideband current source system,and verify the superiority of the proposed novel wideband current source.First,the overall scheme of the hardware circuit of the novel wideband current source system is given,and then the output impedance of the current source is estimated using the variation PSO algorithm according to the experimental data,and the performance test of the novel wideband current source is performed to test the current stability of the current source,Output characteristics,evaluate its output impedance.Simulation and experimental results show that the novel wideband current source designed in thisthesis has better output current stability and higher output impedance than the other types of current sources.The equivalent model of the wideband current source is within the frequency range of 1 k Hz ～ 1 MHz and the load range of 0.1 ～ 1.5 k?,the parameter accuracy and the fitting degree is very high,obviously superior to the traditional current source equivalent model.Compared with the method of solving equivalent model parameters based on mathematical analytical formulas,This algorithm is suitable for general constant current source design analysis.It is of great significance to improve the measurement accuracy of BIS.This algorithm is suitable for general constant current source design analysis.It is of great significance to improve the measurement accuracy of BIS.