低通滤波器的设计，可以实现滤波前后的频率普和幅度谱的对比-Low-pass filter design, you can achieve before and after the filter frequency and amplitude of the spectrum comparison

通过给定的参数来设计无限长单位脉冲响应数字滤波器（IIRDF）和有限长单位脉冲响应数字滤波器(FIRDF)(Using some given parameters, an infinite unit pulse response digital filter (IIRDF) and a finite length unit pulse response digital filter (FIRDF) are designed.)