相位码补偿法实现DDS无相位截断杂散的研究

摘要

介绍了存在相位截断的直接频率合成(DDS)系统的原理,通过分析正弦波形相位幅度映射关系的方式阐述了相位截断杂散的来源.推导了在高频率分辨率和正弦波形无损压缩的条件下截断后相位码长最佳值,并提出了在相位截断之前对相位码进行补偿以消除误差的方法实现无相位截断杂散DDS系统,最后利用MATLAB仿真和FPGA硬件电路验证了该方法的有效性.%This paper introduces the principle of Direct Digital Synthesizer(DDS)system with phase truncation, and ex-patiates on the source of phase truncation spur by analyzing the mapping from phase to sine-amplitude. On this basis, the paper analyses the optimization calculation length of truncated phase code founded on high frequency resolution and loss-less compression of sine-wave, and a method of compensating error of phase code before phase truncated is proposed to implement DDS system without phase truncation spur. The validity of method is verified through simulation by MATLAB and implementation on a FPGA chip.