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AD9914 phase offset in profile mode

Question asked by RHITteam04 on Jan 20, 2014
Latest reply on Feb 7, 2014 by sitti

Hello,

 

We are novices at the AD9914 and are using the evaluation board and eval board software to control it.

 

We are attempting to do 8 PSK modulation using the eight profile registers, but are having difficulty interpreting the waveform we are receiving. We are triggering off the trigger port on the evaluation board, but the oscilloscope is not able to track the DAC output. When we stop and restart the oscilloscope measurements (as shown by the two scope captures in the attached document) we see the phase is different every time; it appears that the phase is changing, but we are not changing the profile, so we would expect the phase to remain constant.  We wondered what was causing this and if it had to do with the phase accumulator. Or is it's something else perhaps someone can point us in the right direction.

 

Thanks for any help you can provide.

 

-team04

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