The main frequency range of the ECG signal is 0.05"100Hz, the amplitude is about 0"4mV, and the signal is very weak. Because the ECG signal is usually mixed with other biological signals, and the electromagnetic field interference mainly based on 500Hz power frequency in vitro, the background of ECG noise is strong, and the measurement conditions are more complicated, which brings certain difficulties for medical research, treatment and teaching. Based on the analysis of the characteristics of ECG signals, this paper proposes a simulation method based on MATLAB/SIMULINK for ECG signals. The rapid prototyping technology is used to convert the virtual simulation signals into actual physical electrical signals through the input/output card, and the actual hardware circuit. Connected to form a semi-physical simulation model of the ECG signal.
Fundamental
ECG signal
A typical ECG signal is shown in Figure 1. It consists of P wave, Q wave, R wave, S wave and T wave. It can be based on the interval amplitude of these characteristic waves and PR interval, ST interval and QT in the diagnosis process. Intervals determine the patient's condition.
Fourier series
If a function satisfies the Dirich's condition, it can be expanded into the form of a Fourier series. The trigonometric form of the Fourier series is defined as follows:
Dirichli conditions are sufficient:
(1) The function is continuous in any finite interval, or only a finite number of first-class discontinuities (when t moves from left or right to this discontinuity, the function has a finite left and right limit);
(2) In a cycle, the function has a finite number of maxima or minima.
ECG signal simulation and result analysis
ECG signal simulation
In this design scheme, the ECG signal is regarded as a combination of each triangular wave signal and a sinusoidal signal, and each characteristic wave sequence is obtained by calculation, and then the waves are synthesized into a final simulation signal. The specific implementation method is as follows:
(1) The QRS, Q, and S waves of the ECG signal are realized by triangular waves.
(2) The P wave, T wave and U wave of the ECG signal are realized with a sine wave.
Mathematical model of triangular wave
The triangular wave mathematical model is established as follows:
To facilitate calculations, expand this function into the form of a Fourier series:
In the formula,
Sine wave mathematical model establishment
The sine wave is modeled as follows:
To facilitate calculations, expand this function into the form of a Fourier series:
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