信号处理的目的就是要得到不受干扰影响的真正信号。相应的处理系统称为滤波器。这里，我们只考虑加性噪声的影响。-The purpose of the signal processing is to obtain undisturbed affect the real signal. Corresponding to the processing system is called a filter. Here, we consider only the impact of the additive n