Hi Charles,
Can you point us to where you saw this claim? Like David Kirby, I'm
skeptical, but I'd like to see the details of the argument. It is
true that, since noise factor is dimensionless, a purely ratiometric
measurement process is in principle possible. But details matter.
-- Cheers,
Tom
--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
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Hi, about 18 months ago I put the below on a Keysight forum
expecting some helpful replies. Sadly I have not had a single
reply as yet. (The concept of doing the measurement without the
ENR being known is to compare derivatives of things not absolute
values. This is the point where my mathematical cabilities
implode).
Measuring the ENR of a Noise
Source
Hi, I have read that it
is possible to accurately measure the noise figure of
a device without having a calibrated noise source.
This is done by including an extra amplifier and an
attenuator in the process. If the amplifier gain and
the attenuator loss are very accurately known then
knowing the exact ENR of the noise source is not
necessary. The?device noise figure can?be?then
determined as accurately as doing the normal Y-factor
method with a calibrated noise source.
?
If this is correct then
surely the next step would be to do the normal
Y-factor process and change the ENR of the
un-calibrated noise source in the calculation until
the result given is the same as in the above
procedure. So now the ENR of the un-calibrated noise
source is known.
?
So how accurate could
this result be? Could it be claimed that the
un-calibrated noise source is now calibrated or only
measured?
?
Would it be possible to
create a spreadsheet to calculate all this using only
the noise marker readings from something like an old
859xE or 856xE spectrum analyzer? (As an aside I don't
think this would work using an E440xB spectrum
analyzer would it?)?
?
My thought is that a
hobbyist could buy 3 of the small amplifier modules
seen on auction sites, the best being the ones that
use the SBB5089 MMIC, as it have the right gain and a
fairly flat frequency response. Also needed would be a
termination and 2 attenuators. On one of the
amplifiers the termination would be placed on the
input and one of the attenuators placed on the output.
This would be the un-calibrated noise source. The
other preamplifiers would be the one normally used on
the front end of the spectrum analyzer for a Y-factor
method? measurement and the last is the DUT to be
measured.
