AD9767用DDS输出1.1M的正弦波时（时钟为100MHz），为什么在频谱仪上看到2.2M的谐波附近有对称的杂散？

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Hi 王508 ,

Thank you for using the AD9767. I hope I correctly understood and translated your question into English, and that the information provided addresses your concerns.

When generating a 1.1 MHz sine output using a DDS clocked at 100 MHz, the DAC (AD9767) produces harmonic images and alias products due to sampling theory.  The 2.2 MHz tone is simply the 2nd harmonic (2 × 1.1 MHz).  What you are seeing—symmetrical spurs around this harmonic come from DAC image aliasing, DDS quantization/truncation artifacts, and clock–output mixing products. These effects are normal in DDS + high‑speed DAC systems.

For further understanding, you may review the application notes, technical tutorials, and related EngineerZone discussions listed below.

• AN‑927 Determining if a Spur is Related to the DDS/DAC or to Some Other Source
• A Technical Tutorial on Digital Signal Synthesis
• MT-085 Fundamentals of Direct Digital Synthesis (DDS)
• EZ DAC Spurs

Thanks and kind regards,

Alex