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Questions about AD9957 configuration for QPSK generation

Question asked by David-M on Jan 30, 2015
Latest reply on Feb 3, 2015 by David-M

Hello, I am an RF and MW engineer trying to figure out how to configure AD9957 to obtain a 1 MHz bandwidth QPSK signal at fc = 70 MHz. My conclusions up to now are that I should use the following values:

Fsysclk = 176 MHz

R = 44

FTW = 1,708,225,629 (not exactly 70 MHz of output frequency, but near enough)

Is that correct?

I also have some doubts on how to generate a QPSK. I mean in that kind of modulation I transmit 2 bits per symbol, but I should provide 18 bits per path (I or Q) to AD9957 parallel data input. How do I translate my 2 bits to all those bits I should put at data input?

 

Probably all those questions are quite simple to someone who is used to work with baseband, but it is a bit out of my scope, so I would appreciate any clarification. It also would help any advice or reminder of important facts that I should keep in mind to generate my signals.

 

Thanks for your support!

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