(1)设计一个数字低通滤波器．设计指标如下：

　　通带内幅度衰减人大于1dB

　　阻带内幅度衰减大于15dB

　　(2)编制计算设计的数字滤波器幅度特性与相位特性程序，并进行实验验证；

　　(3)编制实现该数字滤波器程序并且模拟实现数字滤波

　　①分别让满足所设计滤波器的通带、过滤带、阻带频率特性的正弦波通过滤波器，验证滤波器性能。

　　②改变正弦抽样时间，验证数字低通滤波器的模拟截止频率是抽样时间的函数。-(1) Design a digital low-pass filter. Design specifications are as follows: pass-band attenuation range of people within a range greater than 1dB stopband attenuation greater than 15dB (2) the preparation of calculation and design of digital filter amplitude characteristics and phase characteristics of processes and experimental verification　(3) the preparation of implementation of the digital filter program and simulate digital filtering ① were designed to meet the pass-band filter, filter belt, stop-band frequency characteristics of the sine wave through the filter, verify the filter performance. ② change the sine sampling time, verify that the number of analog low-pass filter cutoff frequency is the sampling function of time.