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导言来自局部60Hz的电力线的电干扰能使象心电图(ECG)一类的生物电信号不纯而产生杂波。截止频率低于60Hz的低通滤波器虽能消除这种类型的干扰,但同时也使信号的带宽显著减小。60Hz的陷波滤波器可以消除或畸变相关频段的频率成分。数字滤波器以60Hz正弦波为基础,可以维持信号频带的,但不能消除出现在某些干扰波形中的60Hz高次谐波。我们研制成一种滤波器,可以通过先识别一个周期的噪音波形,然后将其从信号中减去,以消除电力线上的噪音干扰。滤波器算法由于滤波器装在一个小的微型机数据采集系统上,其算法可分为两步进行。首先,滤波器在一个60Hz的时间间隔内通过采样
Introduction Electrical interference from a local 60 Hz power line can cause clutter of impure bioelectrical signals such as electrocardiograms (ECGs). A low-pass filter with a cut-off frequency below 60 Hz eliminates this type of interference but at the same time significantly reduces the bandwidth of the signal. The 60Hz notch filter eliminates or distorts the frequency components of the associated frequency band. The digital filter, based on a 60 Hz sine wave, maintains the signal band but does not eliminate the 60 Hz higher harmonics that appear in some interference waveforms. We developed a filter that eliminates noise on the power line by first identifying the noise waveform for a cycle and then subtracting it from the signal. Filter Algorithm Since the filter is mounted on a small microcomputer data acquisition system, the algorithm can be divided into two steps. First, the filter passes the sample at a 60 Hz time interval