Choy T T, Leung P M
Department of Electronics, Chinese University of Hong Kong, Shatin, New Territories.
J Biomed Eng. 1988 May;10(3):285-8. doi: 10.1016/0141-5425(88)90013-1.
High performance analogue notch filters are difficult to realize in practice. Their real time digital counterparts, when implemented on an inexpensive microprocessor with no additional hardware, also have limitations of their own. To overcome these limitations, we have developed a new type of 50 Hz notch filter with its poles close to the zero of the transfer function 1 + Z-N. This new type of digital notch filter can be used for suppression of 50 Hz noise in the ECG. The filter is simple to design and easy to implement on most 8-bit microprocessors. It has a high execution speed, low analogue to digital noise, low recursive noise and good frequency response with no overshoot or ringing. It is capable of suppressing 50 Hz noise by at least 40 db. Its finite bandwidth of 4 Hz causes about 2% attenuation on the QRS peak, which is acceptable for almost all practical applications. One possible drawback is that multiple notches occur at higher frequencies. However, this has hardly any effect on the ECG because of the limited notch bandwidth.
高性能模拟陷波滤波器在实际中难以实现。它们的实时数字对应物，当在没有额外硬件的廉价微处理器上实现时，也有其自身的局限性。为了克服这些局限性，我们开发了一种新型的50Hz陷波滤波器，其极点靠近传递函数1 + Z - N的零点。这种新型数字陷波滤波器可用于抑制心电图中的50Hz噪声。该滤波器设计简单，易于在大多数8位微处理器上实现。它具有高执行速度、低模数噪声、低递归噪声和良好的频率响应，无过冲或振铃。它能够抑制50Hz噪声至少40dB。其4Hz的有限带宽在QRS波峰处引起约2%的衰减，这对于几乎所有实际应用来说都是可以接受的。一个可能的缺点是在较高频率处会出现多个陷波。然而，由于陷波带宽有限，这对心电图几乎没有任何影响。
