Wang Ching-Sung
Department of Electronic Engineering, Oriental Institute of Technology, 58, Section 2, Szechwan Road, Banciao, New Taipei 220, Taiwan.
J Biomed Biotechnol. 2012;2012:274939. doi: 10.1155/2012/274939. Epub 2012 Jun 21.
This study integrates the hardware circuit design and the development support of the software interface to achieve a 32-channel EEG system for BCI applications. Since the EEG signals of human bodies are generally very weak, in addition to preventing noise interference, it also requires avoiding the waveform distortion as well as waveform offset and so on; therefore, the design of a preamplifier with high common-mode rejection ratio and high signal-to-noise ratio is very important. Moreover, the friction between the electrode pads and the skin as well as the design of dual power supply will generate DC bias which affects the measurement signals. For this reason, this study specially designs an improved single-power AC-coupled circuit, which effectively reduces the DC bias and improves the error caused by the effects of part errors. At the same time, the digital way is applied to design the adjustable amplification and filter function, which can design for different EEG frequency bands. For the analog circuit, a frequency band will be taken out through the filtering circuit and then the digital filtering design will be used to adjust the extracted frequency band for the target frequency band, combining with MATLAB to design man-machine interface for displaying brain wave. Finally the measured signals are compared to the traditional 32-channel EEG signals. In addition to meeting the IFCN standards, the system design also conducted measurement verification in the standard EEG isolation room in order to demonstrate the accuracy and reliability of this system design.
本研究集成了硬件电路设计和软件接口的开发支持，以实现用于脑机接口应用的32通道脑电图（EEG）系统。由于人体的脑电信号通常非常微弱，除了要防止噪声干扰外，还需要避免波形失真以及波形偏移等情况；因此，设计具有高共模抑制比和高信噪比的前置放大器非常重要。此外，电极垫与皮肤之间的摩擦以及双电源的设计会产生影响测量信号的直流偏置。为此，本研究专门设计了一种改进的单电源交流耦合电路，有效降低了直流偏置并改善了由部分误差影响所导致的误差。同时，采用数字方式设计可调放大和滤波功能，可针对不同的脑电频段进行设计。对于模拟电路，通过滤波电路取出一个频段，然后采用数字滤波设计将提取的频段调整为目标频段，并结合MATLAB设计人机界面以显示脑电波。最后将测量信号与传统的32通道脑电信号进行比较。该系统设计除了满足国际临床神经生理联合会（IFCN）标准外，还在标准脑电隔离室进行了测量验证，以证明该系统设计的准确性和可靠性。
