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Problem with  burst modulation of the evaluation board EV-ADF4159EB1Z

Question asked by aidos on Oct 11, 2017

Hello,
I’m using the evaluation board EV-ADF4159EB1Z to understand how the ADF4159component works and how to program it. I use software ADF4158-59 dated 28.01.2016.
Using the default parameters of this software and disabling all modulation I can to shift the carrier signal from 10.6GHz to 13GHz.If I set 12GHz carrier, I have the VTUNE output fixed continuous voltage of 5V . If I set 13GHz carrier, I have the VTUNE output fixed continuous voltage of 13,66 Vdc. I noticed that setting the MUXOUT to have in output DIGITAL LOCK DETECT the led D1 is on .

Question1: I noticed that for each carrier the spectrum presents a sort of burst modulation as shown in the attachment figure and highlighted with the red arrow.

Having not set any modulation, it is incorrect to have this burst modulation.

To capture the attachment figure  I used  the spectrum analyzer ANRITSU MS2725C in burst mode acquisition. 

What should I do to remove this burst modulation?

 Can anyone to answer to my questions?

Thanks.

Regards

Pier Giorgio

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