摘要
本文讨论了文氏电桥陷波器的品质因素Q和陷波深度D之间的关系,并从参数灵敏度的角度分析了元件的制造容差对电路D、Q特性的影响情况。在此基础上,介绍了一种性能优越的陷波电路。该电路能够达到的陷波深度及品质因素取决于有源器件的开环增益。
One of the major problems encounted in recording physiological signal(such as ECG, EEG,CPT,PCG, etc.) is the apperance of unwanted 50 Hz or 60Hz interference in the output. This disturbance comes into the signal path by means magnetic induction or displacement currents into the body. An often used method to remove the interference from signal is to insert a 50Hz (or 60Hz) notch filter into the path of the signal. The most popular used notch filter is the Wien bridge circuit and the twin-tee filter. Many discussions have been made on their charicteristics. But the effect on the circuit performance caused by component tolerence is lack of quantitative analysis. There are two important parameters for a notch filter, one is the quality factor(or the sharpness of the null) Q, the other is the depth of the notch at the rejection frequency D. In this paper, the relationship between D and Q is first disscussed. It was proven that the depth of the notch D degrades rapidly when Q went high. Therefore,there was an optimal point of K for which D and Q were both obtained. By means of sensitivity analyzing, several sets of curves were obtained which showed. the influence of component tolerenceon the ciriuit parameters D and Q, and which gave the possible values. of D and Q the circuit could reach for certain component precision. The effect on D become more prominent with a higher Q. The other problem for the twin-tee and Wien bridge notch filter is that they easily oscillate when Q goes high An example was given to show how this would happen and how it was connected to the component drift Finally, a new type of notch filter circuit with better performance was introduced. The quality factor Q and the notch depth D of this circuit depended mainly upon the open loop gain of the op amp used.
出处
《生物医学工程学杂志》
EI
CAS
CSCD
北大核心
1990年第3期238-242,共5页
Journal of Biomedical Engineering
关键词
陷波器
生理信号
检测
Notch filter
rejection filter
50Hz interference.
