[time-nuts] Low Additive Phase Noise 10 MHz Amps

Bill bill at hsmicrowave.com
Mon Nov 24 12:48:54 EST 2014

Hi Rick,

Thanks for your response and comments. 

Although the term additive and residual phase noise have been used interchangeably in the literature to this day, I agree with you that they shouldn't, but with my following interpretation.

To me residual phase noise applies to the "measurement" of a single device whereas additive phase noise refers to the noise "added" from one device to another, i.e. at least two.
So when I used the term low additive noise I was referring to the end result of adding one noise source to another. Naturally it follows that a device with a low measured residual phase noise will contribute lower additive noise to another device. I think additive phase is a more apt description of the noise within a system being used, rather than reference to the measurement system of a single device.

Oh boy, I hope I didn't open up a can of worms.


-----Original Message-----
From: time-nuts [mailto:time-nuts-bounces at febo.com] On Behalf Of Richard (Rick) Karlquist
Sent: Sunday, November 23, 2014 9:54 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Low Additive Phase Noise 10 MHz Amps

I did some checking around for low noise buffer amps earlier this year.  They needed to have 200 MHz bandwidth, so this isn't directly applicable to 10 MHz.  I also needed isolation.
About the only information in print is from the usual suspects at NIST.  They wrote a series of papers taking a fairly classic discrete design and refining it.  Check FCS proceedings.  My idea was to take ideas from 10 MHz and extend them to 200 MHz.
I didn't see any really profound ideas in the NIST papers.
There is a reproducibility problem because the original discrete devices may not be available, or NIST might have used special hand picked devices.

BTW, I cringe when I see the term "additive phase noise".
Phase noise, as all time nuts know, is NOT ADDITIVE NOISE, as in AWGN.  It is multiplicative.  The correct term, IMHO, is "residual phase noise".  What additive noise refers to is the classic noise figure type noise involving small signals.
Again, as all time nuts know, low NF is necessary but not sufficient for low phase noise.

Rick Karlquist N6RK
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