1）设计不同长度的单级CIC滤波器，并plot出阶数为2、5、7、8的CIC滤波器幅频特性 2）设计出5级CIC滤波器(1) design a single level CIC filter with different lengths, and the amplitude frequency characteristics of the plot order of 2, 5, 7, 8 of the CIC filter 2) a 5 level CIC filter is designe