| Portable EEG equipment has a wide range of research and applications in medical rehabilitation,sleep monitoring,fatigue detection,and brain-computer interface.In the environment of the unshielded room,EEG signals usually face many problems,such as power frequency interference,motion artifact,and so on.These problems will have a negative impact on the quality of EEG signals and the popularization of EEG application,and EEG electrode is a key factor to solve the signal problem.In this thesis,a flexible active dry electrode and a portable EEG amplifier are designed and fabricated.Then,the performance of the active dry electrode proposed in this thesis is compared with that of the mainstream dry electrode and the wet electrode on the same portable EEG amplifier.The performance test mainly includes signal similarity test,signal stability test,contact noise test,and power frequency interference suppression ability test.The performance test results show that the closed eye resting EEG signals of the active dry electrode proposed in the thesis and the wet electrode are highly similar,and the correlation coefficient is as high as 0.9.Compared with the dry electrode,the active dry electrode has a stronger anti-power frequency interference ability.In the unshielded environment,the power spectral density of the active dry electrode subjected to power frequency interference is about 1/7 of that of the dry electrode.In terms of stability and contact noise test,the performance of the active dry electrode is better than the performance of the dry electrode and wet electrode.The active dry electrode can effectively reduce the influence of cable motion interference and contact noise interference on EEG signals.Finally,10 healthy subjects participated in the application experiment with active dry electrodes,including an eye closure resting experiment,steady-state visual evoked potentials（SSVEP）experiment,and event-related potentials（ERPs）experiment based on the useful field of view.Calculate and analyze the collected EEG signals,including the calculation of eye closed resting EEG α Wave power spectral density value,and use power spectral density analysis（PSDA）to analyze the SSVEP signal.Draw ERPs component wave induced by the useful field of view,and make statistics of ERPs component wave time window.The experimental results show that the active dry electrode can collect αwaves;The average accuracy of SSVEP signals of 10 participants at 7.5 Hz,10 Hz,12 Hz,and 15 Hz stimulation frequencies were 93%,100%,81%,and 79% respectively;The active dry electrode can effectively measure ERPs signals,including N1,P2,N2,and P3.The results of the performance test and application experiment show that the active dry electrode has good signal quality and strong anti-noise ability,which can meet the common needs of EEG experiments.Active dry electrodes can be used in EEG experiments under low-intensity activities and in unshielded environments.Which have important application value in portable monitoring,wearable medical care,and so on. |
