Design Of An Active Electrode For High Quality Bioelectric Signal Measurement

Measuring the Bioelectric signal of the human body is a convenient and quick way to know the health status of the body,and the quality of the electrodes used in the measurement greatly affects the quality of recorded signal.By introducing active electrodes,interference can be effectively reduced and the quality of signal can be improved.However,the current active electrode design is mostly a first-order filtering model,there are the disadvantages of too long transition band and too slow attenuation in the stop band,so this paper proposes an active electrode using second-order filtering model which can effectively overcome the above shortcomings,then makes the systematic investigation in the paper.The second chapter of the paper describes the design scheme of the active electrode of the second-order high-pass filtering model,makes a theoretical analysis of its circuit model,including the transfer function,input impedance and noise,then draws the conclusion that the input impedance can be effectively improved by properly taking values from the component.In order to find the exact component value,the solution of nonlinear programming is used,the output noise is used as the target function,and the input impedance is used as the constraint,to find out the value of each component.Finally,using the software to simulate the resulting solution,and comparing with the theory to confirm its correctness.The third chapter of the paper is the hardware realization of the active electrode designed,the corresponding circuit board is made according to the circuit design,and combining three boards to be one is used to make the electrode in order to meet the shielding demand.After the electrode production is completed,the ECG measurement experiment is used to verify the working ability of the electrode,comparing it with the traditional passive electrode.The fourth chapter of the paper makes a detailed measurement of the performance index,which includes amplitude response,output noise,input impedance and output impedance.By building auxiliary circuits and running the corresponding program,the performance index of electrode is accurately measured to prove that the finished electrode can meet the design expectations.The fifth chapter of the paper is a summary of the work,and puts forward the prospect of the next step.