设计一个3阶低通切比雪夫滤波器，对信号发生器产生的频率为1KHZ的正弦信号进行实时滤波，将结果通过示波器显示，并与滤波前的波形进行对比。-Design a 3-order low-pass Chebyshev filter, the signal generator' s frequency sinusoidal signal 1KHZ real-time filtering, the results shown by the oscilloscope, and waveform with the filter before the comparison.