According to Figure 2-2, it can be analyzed that the Butterworth filter has a smooth frequency response, and the frequency response decreases monotonously outside the cut-off frequency. The steepness of the transition zone is directly proportional to the order of the filter. After comparing the square amplitude response of the high-order Butterworth filter with the N=20-order filter, it is proved that the high-order Butterworth filter is better The amplitude characteristic of is closer to an ideal low-pass filter.