0
\$\begingroup\$

I have a question about the FFT spectrum of an ADC output enter image description here

I understand SFDR you can measure the difference between the fundamental and the next biggest spur/harmonic.

But how do you find SNDR from the plot? Can I simply just measure the fundamental to noise-floor differene? Similarly, how do I find SNR?

\$\endgroup\$
1
  • \$\begingroup\$ One piece of information missing : the number of FFT bins (or conversely, the width of each one). You can see there's "about" -70dB energy per bin ... you need to sum that across all bins. (Or convert to voltage/rtHz, and intecrate across 90MHz, etc) \$\endgroup\$
    – user16324
    Jan 12, 2020 at 14:42

1 Answer 1

1
\$\begingroup\$

with no obvious spurs, how to proceed?

I'd expect 2*input - Fsample.

Thus 2*76 - fsample of 180 === 152 -180 = 28MHz.

Yet at 28MHz, there is a big dip

\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.