The Research Of System Detecting ECG Signal

ECG is one of the important signals which can reflect the physiological signals of patients. ECG can help a lot when doctors diagnose. So there're many requirements for the detection, saving, transmission and processing of ECG .For example, when we detect the ECG, the signal should not be disturbed, and should be transported to experts effectively and in time. When we save the ECG, the smaller the capacity is, the faster she ECG transports. It's very important that we can get back the original signal. So it requires the system is able to eliminate noise and repeat the signal. The wireless central monitoring system is one of the systems which can detect ECG, and it can satisfy the above conditions. In this paper, the multi-parametric monitoring system, different from traditional lineate system, can realize the wireless transmission of ECG in a certain range. This system uses wireless programmable micro-transceiver XE1201. For it can has the long distance of transmission ( about 70m), fast speed (64kB/s), a good capability avoiding disturbance, and low requirement for power supply, so we can then realize the wireless communication between bedside machine and the center system. Furthermore, it can continuously work for a long time by itself at real time.For signal processing, this paper offers a technique which is used to compress the data of ECG. Two methods are included: one is wavelet , the other is wavelet packet. The wavelet is to transform the signals by wavelet directly, and then make the transformed coefficients coded, thus the data are compressed. Wavelet packet is to search the optimal wavelet packet according to the entropy, then ECG is translated by wavelet theory, and the translated coefficients are coded, thus the data are also compressed. Wavelet packet and wavelet are new methods of transformation and analysis, they can show some characters of signals by transformation. ECG is a mutative signal. If we analyse it by traditional Fourier, the result is we obtain low ratio of compressing and the heavy loss of ECG . However, wavelet packet and wavelet has a very high ratio of compressing, and the loss of ECG is light. During the process of compressing, the choice of the threshold value is involved. In the former method, the threshold value is fixed, but in our method, threshold value is adaptive. Furthermore, we can eliminate noise by wavelet.With the development of modem micro-electronics technique, further researches and comprehensive applications will carry out in the wireless central monitoring system. For example, it can be employed in resource share of medicine message in wireless net, in field exploration and first aid and so on. Meanwhile, signals in the system can be processed better.