Bob Camp wrote:
Hi
The noise spectrum is composed equally of AM and PM noise. Together they add
to -174.
Bob
-----Original Message-----
From: [email protected] [mailto:[email protected]] On
Behalf Of Graham / KE9H
Sent: Tuesday, January 15, 2013 3:46 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Thermal noise contribution to phase noise
Bruce:
The last time I looked, the thermal noise floor was still -174 dBm/Hz
(at 300 Kelvin).
http://en.wikipedia.org/wiki/Thermal_noise
Are you saying Boltzmann's constant is off by 3 dB, or are we mixing
apples and oranges here?
Is there a 3 dB adjustment between noise floor (at room temperature) and
the "single side band" phase noise measurement, which only looks at half
the noise, since it only looks on one side of the reference signal?
The upper and lower sidebansd are coherent so their combined power level
is 6dB higher when translated to baseband as is done in a traditional
analog diode mixer based phase noise measurement system.
Bruce
--- Graham / KE9H
==
On 1/15/2013 1:38 PM, Bruce Griffiths wrote:
I've noticed a disturbing tendency to quote the thermal noise
contribution to phase noise as -174dBm/Hz instead of the corrent value
of -177dBm/Hz as verified by measurement by NIST:
http://tf.nist.gov/phase/noisemeas.html
This error occurs in papers from Spectrum Microwave, Wenzel Associates
and others.
Blindly propagating the results quoted in the early literature isnt
particularly helpful given that the definition of SSB phase noise has
changed in the intervening decades.
Bruce
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