一种改进超四算法的DDS设计

为了提升直接数字频率合成器(Direct Digital Synthesizer,DDS)的性能,针对DDS的相幅转换器进行了改进。基于坐标旋转数字计算算法(Coordinate Rotation Digital Computer Algorithm,CORDIC),利用三角函数角度近似的性质和相位寻址位与旋转角度的转换关系对超四算法改进,得到了仅需一次单向旋转的改进算法,并给出了该算法实现的电路结构。通过Matlab仿真分析,该电路无杂散动态范围值可以达到-119. 1 dBc,输出误差小于1. 05×10-5。基于Xilinx的FPGA平台进行仿真实验,结果表明该电路结构的输出延时不超过21 ns,相比其他类型的CORDIC算法提升了近48!的速度,同时面积资源也明显减少。该设计可以为雷达、通信等系统优化提供新的思路。

A DDS design of improving excessfours algorithm

In order to improve the performance of direct digital synthesizer(DDS),the phase-to-space converter for DDS is improved.Based on the coordinate rotation digital computer algorithm(CORDIC),the properties of the angle approximation of the trigonometric function and the conversion relationship between the phase addressing bit and the rotation angle are used to improve the Excessfours algorithm.An improved algorithm with only one unidirectional rotation is obtained,and the circuit structure realized by the algorithm is given.Through Matlab simulation analysis,the spurious free dynamic range(SFDR) value of the circuit can reach -119.1 dBc,and the output error is less than 1.05×10-5.Simulation experiments based on Xilinx FPGA platform show that the output delay of the circuit structure does not exceed 21 ns,which is nearly 48% faster than that of other types of CORDIC algorithms,and the area resources are also significantly reduced.This design can provide new ideas for system optimization such as radar and communication.