[time-nuts] Realistic Tbolt phase noise

life speed life_speed at yahoo.com
Tue Mar 9 20:07:42 UTC 2010


> From: "Bob Camp" <lists at rtty.us>
> Subject: Re: [time-nuts] Realistic Tbolt phase noise

> Hi

> I think you will find that the noise floor of the ADF4107 (dividers and
> phase detector) is a bit higher than -150 at 100 Hz offset at 10 MHz. It
> should get you past the -120 level though. That's still much better than you
> are seeing. 

> Indeed -120 is not what figure 15 on page 8 of the specification would
> imply. I'm sure that the figure is technically correct. It's just not
> showing the complete picture.

> Bob

I have found the Analog Devices chips to have a very poor phase comparator noise floor close-in.  If you do the math based on their published figure of merit, it won't add up.

I believe the issue is 1/F noise due to the low-current CMOS process they use.  They are cheap, jelly-bean chips that have their uses.  Definitely not high performance.  Bipolar is they way to go.

Clay


      



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