说明：  一些数学处理函数，包括：用频域最小误差平方方法设计线性相位FIR低通数字滤波器、最小均方(LMS)算法的自适应数字滤波、离散小波变化函数
(Deal with some mathematical functions, including: use of frequency domain methods of design of the smallest square error linear phase FIR low-pass digital filter, least mean square (LMS) algorithm for adaptive digital filtering, discrete wavelet function changes)