Ecg Monitoring System Based On Wireless Sensor Network Design

Wireless medical monitor, especially the electrocardiogram (ECG) monitor, plays an important role in improving the quality of humans'living and promoting the healthy and harmonious development of the society. Wireless medical monitor is an international hot spot of research which is developed swiftly in these years. This thesis introduces design for a wireless ECG monitoring system and mainly concentrates on the processing of ECG signals acquired by this system, including the design of pre-processing circuit and the software processing at terminal.In the design of pre-processing circuit, this thesis analyzes the character of ECG signal and possible noise. Then a relative processing circuit is designed and proved to be effective and feasible combining experiments. According to the character of ECG signals'being interfered easily, the circuit of rejecting interference is studied and designed in detail. The experiment of collecting humans'ECG signals proves that the circuit can effectively prevent the EMG signal, power line interference and the phenomenon of baseline drift. Particularly in the part of removing EMG, this thesis improves the maximally flat filter. The simulation result indicates that by introducing a pair of jω-axis zeros, a good performance on both the smoothness in the pass-band and attenuation in the stop-band can be obtained. The effect of removing the interference of EMG is highly superior to that of Butterworth filter of the same order.In the aspect of software processing at the system terminal, this thesis applies wavelet analysis to the processing of ECG signals, and discusses the effect that different threshold functions make for processing results. According to the Pseudo-Gibbs phenomenon existing with the soft threshold filtering and the previous impulse noise, this thesis combines the improved threshold function with translation-invariant de-noising. The results showed that Gibbs phenomenon is removed effectively. At the same time, the previous impulse noise is greatly filtered. In the end, the thesis introduces the theory of Bionic wavelet transform and discusses its application in the processing of ECG signal.