说明：  主要研究了利用重叠滤波理论进行全相位数字滤波器设计。 首先介绍了设计 FIR 滤波器的常规方法及其优缺点，然后借助重叠理论提 出全相位的概念，继而给出频域全相位数字滤波器(简记为 APFF)结构图并 理论推导得到与其等效的其他三种系统。
(Research the use of overlapping full-phase digital filter theory, filter design. First introduced the conventional FIR filter design methods and their advantages and disadvantages, and then overlap with the theory put The whole concept of phase, frequency domain and then give the whole phase digital filter (abbreviated as APFF) Structure and Theoretical analysis to be equivalent with the other three systems. )