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OCXO + DDS  vs. TCXO

Question asked by xubing on Aug 16, 2016
Latest reply on Aug 17, 2016 by xubing

Hi, everyone!

 

Here I have a question about the direct digital synthesis, such as AD9951, AD9959.

 

As we know, the DDS usually has an option of external reference. We can use a high performance oscillator (e.g. OCXO) as the external reference, so as to get a synthesized frequency of high performance. But, is necessarily the performance of the synthesized frequency better than that of a TCXO?

 

For example, I want a frequency of 16.368MHz, which is not a common frequeny point of OCXO. If I use  a 25MHz OCXO as the external reference of AD9951 to generate 16.368MHz, and use a TCXO of 16.368MHz to directly output this frequency, which one is better in terms of the short term frequency stability (allan variance) or the frequency stability vs. temperature?

 

Thank you very much!

 

Best regards!

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