频率采样法：使所设计的FIR数字滤波器的频率特性在某些离散频率点上的值准确地等于所需滤波器在这些频率点处的值，在其他频率处的特性则有较好的逼近。 -Frequency sampling method：Make the FIR digital filters designed by the frequency characteristic in some discrete frequency is equal to the value accurately in these frequenc