Mark,
you have the following options:
- HP (Agilent) E5052A/B or R&S FSUP Signal Source Analyzer (works for a
single DUT, though limited to 1 Hz offset, normally useful for 10 Hz up
to 40 MHz).
- Compare two identical DUT's with a HP 3048A or similar PN test system
and subtract 3 dB, assuming that the PN characteristic of both DUT's is
identical.
- Compare 3 similar DUT's with a HP 3048A and calculate the individual
PN using the three cornerd hat method.
- set up a cross correlation PN measurement system similar to the E5052A
and have fun. You will however need two - as good as possible, but
preferaby not more than 10 dB worse than what you want to measure -
VCXO's like HP 10811A's...
- you may build your own HP 3048A alike system, but be prepared to
invest serious money and time, and much more time than you thought in
the beginning... (if that is what you're after, you'll have the most fun
you can).
- find someone who has one of the above and talk him into measuring yours.
- search the web for published PN data of the model you have and take
these as a reference (give or take a few dB).
Btw. do not assume that the phase noise of a disciplined VCXO is the
same as the VCXO alone.
Also keep the power supply contribution into account that can be
surprisingly high.
And, the PN of most frequency standards is significantly lower than what
you can measure with any spectrum analyzer with PN measurement software
(except for the R&S FSUP of course).
Adrian
Grant Hodgson schrieb:
Mark
You've come to the right place - well, that is if you want to devote a
significant amount of your life in the pursuit of ever-more accurate
time and frequency measurements....
If you've only got one source then you need to use the frequency
discriminator method (aka delay line method) of phase noise
measurement. Basically you take the output of the source, split it in
two, delay one of the signals, re-combine the two and then measure the
resultant signal on a base-band spectrum analyser.
There are loads of references to this on the web, which describe the
method in more detail, including :-
The Art of phase noise measurement - Dieter Scherer
and
HP Application Note AN270-2
both available from John Miles web site
www.thegleam.com/ke5fx/gpib/pn.htm
The references at the end of these articles, especially the HP ones,
are particularly useful. The operating manual for the HP 11729B or
11729C Carrier Noise Test Set is also highly recommended.
Yes, there's some maths, you need to understand the relationship
between phase and frequency measurements, but you don't necessarily
need ALL the theory that most of the papers give - don't give up just
because of a few differential equations :)
The limitation of the frequency discriminator method is that the noise
floor of the measurement system is often worse than the DUT,
especially if your DUT is very good, and it's even worse if you're
trying to measure close-in noise. The Sherer article gives a good
graph illustrating this. If you're trying to measure the phase noise
of the oscillator inside a Tbolt then I don't think that a frequency
discriminator will be sensitive enough, although I might be wrong.
Despite what you said, you might want to consider buying an HP 10811
oscillator or similar which you could use in a phase detector
measurement system which is likely to give superior results.
Hope that helps
regards
Grant
Mark wrote :-
My new GPSDO leaves me with the question of "how do I measure the
phase noise of what is by far the best oscillator I own... without
buying a better one to compare it to". That question is what brought
me to time-nuts. I'm starting to read some papers on oscillator
characterization that are collected together in a technical note from
NIST that a co-worker pointed me towards, but some of them are giving
me a math-induced headache.
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