AD9915 Spurious Output Question

Hi Alan,

We did a verification regarding your setup and the attached files contain the spectrum of it. However we do not see any spurs that you are seeing. Kindly check the signal purity of your clock and power sources, it might be the spurs were created due to the spurs which are present on those sources.

Best Regards

Louijie

Hello LouijieC,

Thank you for your response and the screen shots. Would it be possible to get the screen shots redone with the span set to 50 or 100 MHz instead of 1.25 GHz?

We have tried three different sources as the RefCLK signal without having an impact on the spurs mentioned.  We have also changed our power supplies to old analog type that don't use any digital controls.

Is it possible that the AD9915 is generating these spurs?Please advise.

Hi Alan,

Here are the snapshots of the spectrum of  which you wanted to have. In these snapshots, there are no spurs that are in the order of magnitude of which you are expecting.

Best regards

Louijie

Hello Louiji,

Thank you for the new information.  These new screen shots only display +/-2.5MHz.  That is not enough bandwidth to display the spurs that I have reported.  The spurs are located at +/- 5 MHz, +/-10 MHz and +/- 20 MHz.  That is why I asked for the span to be 50 MHz or 100 MHz.

For diagnosing the source of these spurs, have you read AN-927:  http://www.analog.com/media/en/technical-documentation/application-notes/131351807AN_927.pdf?

I don't think these are harmonics based on the frequencies you called out, is there anything in your system running at 5 or 10 MHz that might be injecting the noise?