Design Of EP/EMG System And Research Of Signal Extraction Algorithm Of Auditory Evoked Potentials

EP/EMG system is a clinical medical equipment of detecting EMG and Evoked Potential signals. EMG and Evoked Potential signals are strongly nonlinear, coupling, weak human electrophysiological signals. EMG signals description manifested electrical characteristics of human muscle activity status, it is a complex integrated results of muscle activity under the epidermis in time and space; Evoked potentials describe the electrical characteristics of integrated presented in the specialized parts and time, when the human nervous system stimulation by external. EP/EMG widely used in the field of human nervous system, clinical diagnosis, medical rehabilitation engineering, information transmission, and it has become a hotspot of research in related fields.The EP/EMG signal in this paper detected by the host computer module, control module, signal acquisition module and to stimulation module. Stimulation module can generate three kinds of stimulation which are current, sound and image and stimulate the human body. Signal acquisition module amplified and filtered EMG signals or stimuli evoked potential signals. The master module conversion electrophysiological signals of amplified through the high-speed AD. And sends the data to the host computer by high speed USB communication interface, the host computer complete waveform display in real-time, measuring and information management.Signal acquisition module is mainly composed of Preamplifier circuit,31-80000multiplier adjustable gain of the main amplifier circuit, third-order Butterworth low-pass filter and the analog-to-digital conversion circuit. The nV level auditory evoked potential signal extremely easy submerged by the external environment. Therefore, this paper presents a novel differential amplifier circuit scheme based on the common-mode signal drive power to address the problem. The new method is that using of common-mode signal as a power supply drive signal makes the floating to track the common-mode signal in order to suppression frequency interference indirectly, and the traditional method is using of labor-frequency notch filter to direct inhibition of frequency interference, so that both suppress common mode interference and effective retention characteristics of the signal at that frequency. The Auditory Evoked potential signals that obtained by the signal acquisition module exists ambient noise, interference EEG, EMG interference, ECG interference, etc. There need for the extraction algorithm of the nV class Auditory Evoked Potential signal. Thesis analyzes superposition average algorithm of tradition and pointed out the limitations of the algorithm, the problems about that the residual interference noise and the incubation period of disturbance, proposes a superposition averaging algorithm based on the arc tangent function of the IIR filter. First, use the superposition average method to improve the signal-to-noise ratio, then smooth the signal by IIR filters based on the arctangent. The use of the algorithm to extract the data of the four test brainstem auditory evoked potential signal, the test results show that the algorithm is practical and effective, meeting the requirements of clinical detection.