利用多项式拟合的方法消除交流信号中的趋势项，将原始信号和滤波信号时域图和频率图分别进行了对比，结果显示趋势项得到了很好的消除。(The polynomial fitting method is used to eliminate the trend items in the AC signals. The comparison between the original signal and the filtered signal time-domain and frequency charts