Study on spurious suppression method of high accuracy DDS

摘要

The traditional Direct Digital Synthesis (DDS) is based on the method of ROM look-up table for phase-amplitude conversion, and the signal quality does not meet the high accuracy requirements in the condition of high frequency resolution, because of phase truncation causing the serious signal deterioration of spectral properties. For the problem, the key research is the application of coordinate rotation digital computer (CORDIC) algorithm to DDS signal source, and to propose an improved algorithm to reduce ROM consuming and iterations, especially in favor of hardware implementation. The design of novel DDS signal source is based on the improved CORDIC algorithm and the phase accumulator without frequency error. The simulation results show the signal source has advantages of relatively pure frequency spectrum, high SNR and obvious spurious suppression. Accordingly, the new DDS signal source is able to meet high frequency resolution and accuracy requirements simultaneously. The DDS signal source based on the spurious suppression method is easy to implement on FPGA, so it has important practical significance to the design of DDS signal source.