数字下变频中基于CORDIC算法的NCO设计  

Design of NCO Based on CORDIC Algorithm in Digital Down-conversion

作　　者：刘刚[1] 蒋伟进[2] 董胡[1] 钟新跃 

机构地区：[1]长沙师范学院信息与工程系,湖南长沙410100 [2]湖南商学院计算机与信息工程学院,湖南长沙410205

出　　处：《无线电工程》2017年第12期71-74,共4页Radio Engineering

基　　金：国家自然科学基金资助项目(61472136;61772196);湖南省教育厅科学研究一般项目(15C0103);湖南省大学生研究性学习和创新性实验项目(601)

摘　　要：在数字下变频中传统数字控制振荡器(Numerically Controlled Oscillator,NCO)模块都是基于查找表结构的,该结构在FPGA内部实现需要占用大量ROM资源,针对这一问题,提出采用坐标旋转数字计算(Coordinate Rotation Digital Computer,CORDIC)算法进行NCO设计,相比传统的NCO设计,该方法具有输出信号频谱纯度高、能够直接混频而不需要乘法器等优点。设计中采用变象限映射方法解决CORDIC算法无法全周期覆盖的问题,采用流水线技术解决串行迭代带来难以实时输出的问题。经过Modelsim仿真分析,实际输出值与理论值之间的相对误差在10-4~10-5数量级范围内,满足数字下变频中NCO的性能需要。bIn digital down conversion,the traditional NCO module is based on look-up table structure,which takes up a large amount of ROM resources in FPGA.In order to solve this problem,this paper uses the Coordinate Rotation Digital Computer（ CORDIC）algorithm for NCO design.Compared to the traditional NCO design,this method has high spectral purity,can be directly mixing without multiplier.In the design,a variable quadrant mapping method is adopted to solve the problem that CORDIC algorithm can not be covered by full cycle.The pipeline technology is used to solve the problem that the serial iteration is difficult to output in real time.The results of Modelsim simulation analysis show that the relative error between the actual output value and the theoretical value is 10-4-10-5,which satisfies the performance requirement of NCO in digital down-conversion.

关 键 词：数字下变频 坐标旋转数字计算方法 流水线 数字控制振荡器 现场可编程门阵列 

分 类 号：TN911[电子电信—通信与信息系统]