应用matlab 软件设计了下变频器中的CIC、HB、FIR滤波器等核心模块，并将各模块融为一体从软件实现的角度完成了对系统的搭建和功能仿真。-About such key algorithms as CIC, HB, FIR of each module in down- conversion, discussion, abstraction and summarization are given in this paper. Using the MATLAB software, we design such core modules as CIC filter, HB filter and FIR filter of the digital down converter.