| 1. IntroductionHeart disease have graduated the main threaten to the human's life lately. Furthermore, the incidence of a disease increases year after year and the age of patient presents declining trend. But electrocardiogram signal is the main gist of heart disease diagnoses and the important target for the research of heart disease patient.It has an important value of application in diagnoses and research of medical clinic.Electrocardiogram signal is an extreme exactitude, regularity and quite complex faintness signal from hominine heart. Its extent is commonly between 10uV-5mV and frequency is between 0.05-100Hz.Outside interference and other factors make electrocardiogram signal more intricacy. The electrocardiogram technology applied to clinic by Einthoven in 1903 and up to present, it has been hundreds year. In this period, the persisted development of electrocardiogram technology have turned in tremendous contribute for human life and health, biology and clinic medicine and become indispensable and the most important general inspected technique of clinic.In the early sexagesimal ages,Caseres validated feasibility of general 12-conduction ECG signal analyse by computer,and emplodered programme of wave mode identifying which used gaining average parameter of ECG signal.In the upper septuagenary ages,the high development of microprocessor technology promoted research of ECG signal auto-analyse technology.In the 1965, the adaptive noise canceling system established in the Stanfu college.At the same time,It triumphantly applied to medicine and canceled the work frequency interference of ECG signal.In virtue of electrocardiogram analysis, we can no harmfully realize work status of heart transmitting system of patient and provide a simple and convenient means for diagnoses of patient's heart disease. Therefore, the disposal of valid filter for electrocardiogram signal and so on is a hotspot of research at present.Electrocardiogram signal is a faint no-calm signal. Adaptive signal processor has a wonderful developing foreground and gradually perfect. Adaptive system may real time change weight parameter according as the change of input signal. This character is out of other filters. At the same time, electrocardiogram signal very easily get interference from outside signal. So that, filter and inspecting of electrocardiogram signal with the changeability of adaptive signal processing weight parameter is relatively ideal method at present.2. Research ContentThis thesis discusses basic information of electrocardiogram and produce and characteristic of noise in electrocardiogram signal at first. And then, analyses common adaptive arithmetic base on adaptive noise canceling system theory, for example,LMS arithmetic, normalize LMS arithmetic and error normalize changing step LMS arithmetic. In adaptive filter arithmetic, the selecting of step parameter is very important. The speed of constringency of adaptive processing inverses to step parameter, the maladjustment directs to step parameter. When the step parameter has a larger value, the speed of constringency is rapid, but the maladjustment accordingly become great; when the step parameter has a smaller value, the maladjustment is little, but adaptive time is long. When the value of step parameter is over large, it may lead to transpire of adaptive process and make system not achieve stabilized state. Thereby bring on defeat of arithmetic.Therefore; the selecting of step parameter is the most important in order to achieve fast constringency process and little maladjustment at the same time. In the technique idea, this thesis bring forward changing step LMS arithmetic base on iterative time by error normalize changing step LMS arithmetic and integrate fitness step LMS arithmetic. The renewal of modulus formula: w( n + 1) = w( n ) + 1/( c * n ) e ( n ) x ( n)Besides, we compare the account of this arithmetic on the theory.2.1 Restraining of work frequency interference and base line excursionThe work frequency interference and base line excursion both are the most interference of diagnoses and analyses of electrocardiogram signal, and enormously depress Signal-to-Noise of ECG signal. Therefore, affect veracity of ECG signal inspecting. This thesis analyses current method of restraining the work frequency interference and base line excursion. With the adaptive noise canceling system, we respectively adopt LMS arithmetic, normalize LMS arithmetic and changing step LMS arithmetic base on iterative time and filter the work frequency interference and base line excursion of electrocardiogram signal, at last, make compare on Signal-to-Noise and convergence speed. The result of test indicates that changing step LMS arithmetic base on iterative time achieves maximal Signal-to-Noise and Signal-to-Noise improves 46.0149dB, and that normalize LMS arithmetic take second place and Signal-to-Noise improve 36.9235dB. However, in the calculative time, the calculative time of changing step LMS arithmetic base on iterative time is not the least compared with LMS arithmetic, because it adopts alter-step arithmetic. This also indicates that the account of LMS arithmetic is the least.But, the account of normalize LMS arithmetic is the most.This is consistent with anterior discussion on theory. The error convergence speed of changing step LMS arithmetic base on iterative time is the most fast by average square error learn curve, and normalize LMS arithmetic take second place. At the same time, this thesis gets electrocardiogram signal which include the work frequency interference and base line excursion across an adaptive noise canceling system, and one-off filter the noise of electrocardiogram signal by the combine of changing step LMS arithmetic base on iterative time and LMS arithmeitic. Above all, the result validates the validity of this arithmetic in the pretreatment of ECG signal.2.2 Inspecting of QRS waveThe key of electrocardiogram signal auto-analysis system is the pick-up of parameter and identifying of wave of electrocardiogram signal. Its veracity and reliability decide the effect of diagnosis and treatment, more over the succeeding and defeating of saving patient's life. QRS wave have large extent and take up narrow time. Therefore, the inspecting of QRS wave becomes the most pivotal matter of electrocardiogram signal. That fast truly inspect QRS wave is the premise of calculating correlative parameter and diagnosis and the base of electrocardiogram auto-analysis. In the accounting complication and the anti-jamming ability aspect, this thesis analyze several regular inspecting methods of QRS wave, and decide to inspect QRS wave which is the electrocardiogram signal of foregoing adaptive filter pretreatment by the difference threshold-value method.At last, we achieve inspecting and orientation of Q,R,S wave.3. ConclusionWith the adaptive noise canceling system, this thesis adopts several common LMS arithmetic and achieve availably filter of the work frequency interference and base line of electrocardiogram signal by computer emulator-test. The changing step LMS arithmetic base on iterative time has the best filter effect and Signal-to-Niose improves 46.0149dB and indicates the validity and advantage of changing step LMS arithmetic base on iterative time.At the same time,this thesis adopts an adaptive noise canceling system and one-off filter ECG signal which includes The work frequency interference and base line excursion and achieves simultaneity restraining of both interferance.At last,with the difference limiting value arithmetic,this thesis devises inspecting and orientation of Q,R,S wave of ECG signal by pretreatment. |
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