模拟滤波器带以50Hz限制ECG信号。 模数转换器（ADC）以200个样本/秒的速率对ECG进行采样。 得到的数字信号连续通过一系列处理步骤，包括用软件实现的三个线性数字滤波器。 首先是由级联低通和高通滤波器组成的整数系数带通滤波器。 它的功能是噪音抑制。 接下来是近似于导数的滤波器。 在幅度平方处理之后，信号通过移动窗口积分器。 然后，自适应阈值区分QRS复合波的位置。
Bandpass Filter
带通滤波器可降低肌电噪声，60 Hz干扰，基线漂移和T波干扰的影响。 最大化QRS能量的理想通带约为5-15 Hz [10]。
Low-Pass Filter
high-Pass Filter
Derivative
After filtering, the signal is differentiated to provide the QRScomplex slope information. We use a five-point derivative with the transfer function
Squaring Function
This makes all data points positive and does nonlinear amplification of the output of the derivative emphasizing the higher frequencies (i.e., predominantly the ECG frequencies).
Moving-Window Integration
The purpose of moving-window integration is to obtain waveform feature information in addition to the slope of the R wave. It is calculated from
Fiducial Mark
The QRS complex corresponds to the rising edge of the integration waveform. The time duration of the rising edge is equal to the width of the QRS complex. A fiducial mark for the temporal location of the QRS complex can be determined from this rising edge according to the desired waveform feature to be marked such as the maximal slope or the peak oftheR wave.
Adjusting the Thresholds
The thresholds are automatically adjusted to float over the noise. Low thresholds are possible because of the improvement of the signal-to-noise ratio by the bandpass filter.
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