The Discrete Fourier Transform of Direct Digital Synthesis in the presence of phase truncation

This paper introduces an accurate and simple method by using Discrete Fourier Transform (DFT) to calculate the spectrum of Direct Digital Synthesis (DDS) in the presence of phase truncation. The analysis results show the relationships between spectrums of different output signals and different Frequency Control Words (FCW). By obtaining the spurious spectrum location and the spurious amplitude we can compute the Spurious Free Dynamic Range (SFDR) directly. This method greatly reduces the amount of computation and has the guiding significance in the practical application.