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AD9833 Eval Board weird output problem

Question asked by coburn on May 2, 2011
Latest reply on May 4, 2011 by coburn

Hey everyone,

 

I recently purchased the evaluation board for the AD9833 DDS. The objective is to produce a clock at 12MHz which can be varied by 3% either side.

My current issue is the DDS is producing a quite strange output that is hard to explain. I have attached 3 pictures which hopefully can show what the problem is.

 

It's like there are two frequencies and one is moving through the other one, so in the pictures you can see in between successive peaks how it is moving up and down.

 

I have implemented a LP and HP filter separately and they don't seem to change anything.

 

The output frequency was chosen to be 10MHz.

 

So just wondering if anyone else has seen a similar sort of thing with their DDS?

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