Designing For The Broadband EEG Acquisition System And Its Preliminary Application

EEG acquisition system, which is easy to operate, is non-invasive device, and the experiment cost is very low. The system can get EEG signal from human-being scalp. The signal can reflect related information of brain nervous system. So EEG acquisition system is one of the most useful tools for studying brain.Because of DC offset voltage in the experiment and limited understanding of brain, sampling bandwidth of many commercial EEG acquisition systems is relatively narrow. These systems couldn’t acquire some new EEG signal with lower frequency or higher frequency. In order to solve the issue, we would design a broadband EEG amplifier with high performance using some technologies and methods, such as dynamic DC correction technique. Besides that, we also design a software system with openness and compatibility. EEG amplifier combined with software system would be applied to different research area. The purpose is enhancing value of EEG acquisition system.The main works and innovations of the paper are described as follows:1. Based on characteristics of EEG signals, A 32 channels of broadband EEG amplifier with high-precision would be designed in the paper. The sampling band is between DC to 1000 Hz, and sampling rate is 5000 Hz. In order to acquire signal of DC~0.5Hz which were discarded by traditional EEG acquisition system, dynamic DC suppression technique was used in EEG amplifier. The technique could compensate DC offset voltage introduced into EEG amplifier. After debugging and passing EEG amplifier, we tested performance parameter of EEG amplifier in accordance with the relevant national testing standards. We discussed and analyzed problems in the circuit according to tested results. Then a satisfactory EEG amplifier with high performance was designed. Microsoft foundation class MFC was used as a graphical interface development tools for designing software system. The system connected with EEG amplifier can be used as integrated EEG acquisition system.2.Acquiring EEG signal using our amplifier during fMRI experiment, to solve the problems of EEG signal with low spatial resolution and MRI image with low temporal resolution, and get information of brain with high temporal-spatial resolution. In the paper, we tested three typical electrodes, three typical electrode gel and combination of them respectively. While we also analyze reason of MRI image impacted by electrode. Then, electrode and electrode gel were placed on phantom and head of rat respectively, to teste whether there was a safety hazard for people in MRI. At last, appropriate electrode and electrode gel which could be used in EEG-fMRI recording were found. We also tested if EEG amplifier connected with electrode could acquire EEG signal in MRI.3. In the application of brain Computer Interface(BCI), online test results might become inaccuracy due to the less number of samples. We enhanced method of Z-LDA(Z-score Linear Discriminant Analysis). Then, data of simulation and real EEG signal which were acquired by our EEG acquisition system were used to test result of training less number of samples by Enhanced Z-LDA(EZ-LDA).4. Blink Electro-Oculogram(EOG) could be acquired by our EEG amplifier. Then, three algorithms including digital morphological filtering algorithm, dynamic threshold detection algorithm and normalization algorithm were added in software system to deal with EOG. The signal detected by three algorithms was used to import character in graphical interfaces.5. Surface electromyography(SEMG) could be acquired by our EEG amplifier. Then, some algorithms including feature extraction, pattern recognition and so on were added in software system to deal with SEMG. The signal detected by algorithms was translated to computer instructions to control manipulator.6. Analyzing the problems in acquiring Laplacian signal directly, and discussing shortcoming in obtaining Laplacian signal indirectly. And then, we proposed a possible plan based on our EEG amplifier for acquiring Laplacian signal directly.In a word, a broadband EEG acquision system was designed. It can not only enhance bandwith of collected signgal, but also can be used for acquiring EOG or SEMG to improve the value of EEG acquision system.