数字下变频器的原理与实现方法

Principle and implementing of DDC

阐述了数字下变频器(Digital Down Conversion,DDC)的原理.DDC主要由数字控制振荡器、混频器、低通滤波器等部分组成,DDC是将中频信号与数字控制振荡器产生的载波信号进行混频,再经过低通滤波器得到基带信号,实现了下变频功能.分别介绍了用查表法、坐标旋转数值计算机算法和MVR CORDIC)算法3种方法实现DDC的过程.基于这3种方法设计的DDC应用广泛,同时也适合用于FPGA器件实现.

The principle of DDC （Digital Down Conversion） is clarified in this paper. DDC is made up of NCO （ Numeral control oscillation） , mixer and lowpass filter. The singal of intermediate frequency and the singal of carrier wave are mixed up in the DDC, then the singal passes through lowpass filter, the function of down conversion is implemented. The implementing of DDC based on looking up table, CORDIC algorithmic and MVR CORDIC algorithmic are introduced in this paper. DDC based on these means are used diffusely, and are implemented compatibly using in FPGA.