分别使用矩形窗和汉明窗函数设计一个线性相位FIR低通滤波器，使其逼近理想低通滤波器的频率特性。采用频率抽样法设计FIR数字低通滤波器滤波器。-Using rectangular window and hamming window function to design a linear phase FIR low-pass filter, the frequency characteristics of the ideal low-pass filter. Frequency sampling method is used to design FIR digital filter based on low-pass filter.