LMX2820: 1MHz Spur in18.5GHz signal

how can i add image here

Greetings,

You should be able to drag-and-drop or copy-and-paste images and files into the E2E post editor and they will automatically be uploaded. If that doesn't work, you can use the toolbar at the bottom of the post to Insert -> Image/Video/File:

Can you also upload your configuration file or register settings? It will be helpful for debugging.

A few other things to check:

• Is there a similar spur on your reference input?
• Does the 1MHz spur persist through different power supplies.

As for PFD leakage, this can sometimes be improved with changes to the PFD gain (generally lower is better, but you pay for it with increased in-band PLL noise) or with changes to the PFD delay. You can manually configure PFD delay, but this is more of an art than a science; in theory we have already selected the best values automatically, but you may find certain values better for spurs or leakage.

Regards,

Derek Payne

Thank you for reply.This is my setting and output.....

I ll check once with different power supply....yes there is multiple of refrence also as you can see in the plot...I'll check with different PFD_DLY

I am able to see 1 MHz leakage in Eval board also....but i'll check once with different supply

Hi CS,

According to your configuration, there should be no 1MHz spurs. 

BTW, 1st order MASH is seldom use as spurs will be big with this MASH. Please use 2nd or 3rd order MASH for a fraction channel.