| dc.description.abstract | The signal, compositive changes produced by cerebration, is called electroencephalogram (EEG). Researchers are interested in EEG because EEG relates consciousness of human.
After going though the skull, EEG signal is very weak. Moreover, it is easily interfered with noise. Therefore, it is difficult to measure. Furthermore, because the brain wave is very feeble and electrode-skin impedance is high, the measurement system should have high impedance to reduce the loading effect.
Due to the uncertainties of electric elements, circuits are not ideal, especially the notch filter. This study designs an effective circuit only by adjusting a variable resistance of the circuit.
This study proposes a brain wave measure and amplifier circuit for a visual evoked potentials (VEPs) brain computer interface (BCI) system. The proposed brain wave measurement system includes a preamplifier, a three order low pass filter (LPF), a two order high pass filter (HPF), a notch filter and a wireless transmission module. The designed circuit has not only high gain but also high input impedance. The system can adjust variable resistance to overcome the non-ideal situation of the circuit. In addition, the circuit combination with a wireless transmission module and battery makes the proposed system being portable. | en_US |