根据过渡带宽及阻带衰减要求，选择窗函数的类型并估计窗口长度N（或阶数M=N-1），窗函数类型可根据最小阻带衰减As独立选择-According to the transition bandwidth and stopband attenuation requirements, select the type of window function and estimate the window length N (or the order of M = N-1), type of window f