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AD9910 Phase Noise/Spurs

Question asked by madmike on May 30, 2017
Latest reply on May 31, 2017 by madmike

Hey EZ, i really hope you can help me out with this. I have the following issue:

 

i have an AD9910 at frequencies of 200-300 MHz to drive some acousto-optics for the lab. I detect a phase noise, not periodic, with a peak noise deviation of 0.005 pi radians. My question is now if that could be spur-related. The phase resolution of the AD9910 is about 0.1 milliradians, so thats 50 times less than what i can see on my signal. Could that be spur related?

 

Also, how does the AD9910 - or a DDS in general - handle the phase accumulator overflow? If, lets say, my phase increment is N and my 32-bit phase accu has a current value of 2^32 - N + 1 is the next increment then leading to an overflow and the accu starts at value 1 (would lead to some phase noise due to truncation) or does it start at 0? Is the carry handled in any particular way?

 

Best regards,

 

Mike

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