提出了采用线性插值的方法来实现直接数字频率合成器（DDFS）结构中相位到正弦曲线幅度之间的映射（简称“相幅映射”）。该方法使用具有分段连续性质的线性分段来近似正弦函数曲线的第一象限部分；然后根据正弦曲线的象限对称性，重构完整的正弦曲线。文中分析了基于线性插值技术的DDS的频谱特性；然后对基于该方法的DDS的“无杂散动态范围”进行了研究。最后，提出了线性插值系数选择的详细、系统的步骤，从而取得期望的SFDR。

This paper presents an approach based on linear interpolation to realize the mapping from phase to sinusoid amplitude(phase-to-amplitude) in the structure of direct digital frequency synthesizers(DDFS).For that approach,the first quadrant of the sine function is approximated with a number of linear segments,then the sine function is fully reconstructed by using its symmetry.This paper provides the analysis of spectrum in DDFS based on linear interpolation technology.Then the spurious free dynamic range(SFDR) is also studied for DDFS based on this approach.At last,a detailed and systematic procedure for the selection of linear segment coefficients to achieve a desired SFDR is provided.

TN957