说明：  单频干扰陷波器源码。自适应陷波器,与一般陷波器比较，有两大优点：（1）能够自适应地准确跟踪干扰频率。 （2）容易控制带宽.
(Single-frequency notch filter interference source. Adaptive Notch Filter, Notch Filter with the general comparison, there are two main advantages: (1) can be adaptively tracking the exact frequency interference. (2) easy to control bandwidth.)