用matlab实现FIR滤波器，包括其幅频特性，然后让单位取样函数，周期方波序列和周期三角波序列通过滤波器，验证滤波器的特性-FIR filters using matlab implementation, including its amplitude-frequency characteristics, and then let the unit sample function, sequence and cycle-cycle square wave triangle wave sequence through the filters to verify the characteristics of filter