Some people with motor disabilities, such as amyotrophic lateral sclerosis (ALS), spinal cord injury, stroke and cerebral paralysis , couldn’t live independently. They need to have the ability to interact with the outside world. Brain Computer Interface (BCI), a channel aiming to establish the communication between human brain and outside environment directly without the participation of muscles and bones. This technology can help those people to live a better life. It covers various applications and signal processing methods. A complete BCI system typically includes four parts: signal acquisition, signal processing, operation protocols and output devices . In the signal acquisition section, EEG which records brain activities from scalp is always introduced in the laboratory and some practical application among diverse monitoring method.
Among varieties of applications, Steady State Visually Evoked Potentials (SSVEP) BCI which is based on EEG was investigated. SSVEP which is caused by visual stimulus frequency over 6Hz in Electroencephalogram (EEG) has been widely applied due to its high information transmission rate, short training time and easy-to-extract features. In SSVEP BCI, an optical stimulus is presented to the subject whose brain events are recorded on EEG. The processing and analysis of it enables us to have a better understanding of what the subject observed. Common analytical approaches such as Power Spectrum Density Analysis (PSDA) and Canonical Correlation Analysis (CCA) were widely used. CCA is a new and more effective method to process the brainwave .
To be more practical and more serviceable, in the current paper, a BCI system based on SSVEP, in which a portable, effective and blinking stimulator and three-channel EEG amplifier was designed. It was implemented to enhance its performance especially in stimulation effect, flexibility and portability.