采用函数法设计一FIR低通数字滤波器 ，，采样频率,阻带衰减不小于-50dB。-The function design FIR low-pass digital filter, the sampling frequency, stop-band attenuation of not less than-50dB.

FIR直接卷积运算 加窗函数 hann采样频率128000 截止频率5-Hann FIR convolution operation directly add window function