While reading articles and application notes regarding DACs and their output spectrum, I stumbled across aliasing of higher harmonics to the first Nyquist band. For example, when generating a single test tone with a DAC, harmonics of the fundemental frequency appear due to DAC nonlinearity, and if their frequency is higher than the Nyquist frequency (half of the sample rate), they fold down (alias) to the first Nyquist band.

I know what is aliasing and how it affects the spectrum when sampling with an ADC, but I can't figure out how and why this happens when reconstructing the waveforms with a DAC.

This is an example taken from Tektronix High-Speed DACs application note (https://download.tek.com/document/76W_30631_0_HR_Letter.pdf)

DAC aliasing of harmonics

Could someone expain this to me or at least point me to where I could read more about this?


  • 3
    \$\begingroup\$ I think you're misunderstanding this. The diagram shows what you would see if you sampled the DAC output with an ADC. The actual 3rd and above harmonics generated by the DAC are shown as the grey spurs above Fs/2; all but the 2nd are aliased into the in-band region. \$\endgroup\$ – Finbarr Jun 9 '20 at 12:37
  • \$\begingroup\$ That makes sense. I found this harmonic "aliasing" in different places with an explanation that the DAC is a "sampled" system, but I couldn't think of a reason why this would happen. \$\endgroup\$ – t_nogic Jun 9 '20 at 15:36

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