PC based Electroencephalogram system

In this study a prototype of high performance PC based Electroencephalogram (EEG) system was developed which integrates a hardware circuit design for initial signal conditioning and the digital signal processing design for further signal conditioning and analysis. Since EEG signals are very weak and is from a source with high output impedance, in addition to amplification of the signal and filtering, design of a differential pre-amplifier with high common-mode rejection ratio and high signal-to-noise ratio was very important. In order to minimize the requirements of the notch filters to remove power line interference, Driven Right Leg (DRL) technique was integrated in the analog design for reducing common mode voltage of the patient body. The instrumentation amplifier with DRL was followed by a high pass filter stage, two amplifier stages and a low pass filter stage. The Digital signal processing techniques were implemented in LabVIEW (National Instruments) with further filtering for power line noise, ability to identify the most significant EEG band present in acquired signal, and capability for further analysis of the signal. A high performance single channel EEG system with high input impedance, high signal to noise ratio, and high amplification range was achieved for the use under non shielded conditions. The performance of individual blocks as well as the integrated system was verified. Testing results showed that the performance of all parts of the EEG system satisfies the design specifications. The effectiveness of the design was verified by comparing to results from Great Lakes Neurotechnologies BioRadio 150 system as well as using EEG signals obtained during visual and motor tasks.