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As i read, IQ sample doesn't need nyquist criteria. What is the mathematical representation of this result? Why IQ sample doesn't need nyquist frequency? I know that can be set to nyquist frequency but i want to know why not equal nyquist frequency at least.

Thanks for answers..

Ahmet Serdar
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    Your question is based on a misunderstanding. It does require Nyquist rate sampling. – Marcus Müller Jan 22 '21 at 07:54
  • Nyquist rate means twice of max frequency component. As i read IQ sample doesn't require nyquist frequency, also recommended IQRate=1.25*fmax. Why? – Ahmet Serdar Jan 22 '21 at 09:57
  • "Nyquist rate means twice of max frequency component" the answer you've gotten explains why that is wrong for complex sampling. – Marcus Müller Jan 22 '21 at 09:58
  • Please ckeck the answer dear: https://knowledge.ni.com/KnowledgeArticleDetails?id=kA00Z000000kIpTSAU&l=en-TR – Ahmet Serdar Jan 22 '21 at 09:59
  • I did. It doesn't contradict what I said. Again, the answer you've gotten addresses your misunderstanding about Nyquist rate for complex sampling. – Marcus Müller Jan 22 '21 at 10:06
  • Do you have any document that is explain to Nyquist criteria for IQ signal in therotical? – Ahmet Serdar Jan 22 '21 at 12:49
  • hm, my signals and systems textbook did in university. Where do you know Nyquist from? Other than that, Oppenheim's standard "Discrete-time signal processing" book introduces Nyquist for real-valued signals first, but makes the explanation super graphical so that someone understanding complex signals don't have symmetric spectra sees the factor of 2 disappears. – Marcus Müller Jan 22 '21 at 12:54
  • I saw it during my university years but not complex signal. Complex signal sampling confused me, actually i know very well what is nyquist(For not aliasing due to negative frequencies) but i don't understand why IQ signals don't have negative frequencies.Also my english is not good ,sorry:) – Ahmet Serdar Jan 22 '21 at 13:02
  • They have negative frequencies. They can just represent separate things on negative and positive frequencies, which real signals can't. – Marcus Müller Jan 22 '21 at 13:08
  • I will work on this issue, thank you dear. – Ahmet Serdar Jan 22 '21 at 13:11

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As Marcus commented, it certainly does follow the Nyquist criterion. However you just need to keep in mind that I/q sampling is complex so each complex sample can be considered 2 real independent samples and Nyquist will still apply. Also take a look at this answer "Complex sampling" can break Nyquist?

user67081
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