[time-nuts] Phase noise measurement (was - no subject)

Bob Camp lists at rtty.us
Fri Aug 20 15:30:30 UTC 2010


Hi

You can make a pretty good "front end" (mixer / amp / lock) for under $100. That will let you measure phase noise with an audio spectrum analyzer.

Bob



On Aug 20, 2010, at 10:40 AM, Adrian <rfnuts at arcor.de> wrote:

> 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.
>> 
>> _______________________________________________
>> time-nuts mailing list -- time-nuts at febo.com
>> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>> and follow the instructions there.
>> 
> 
> 
> _______________________________________________
> time-nuts mailing list -- time-nuts at febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
> 




More information about the Time-nuts_lists.febo.com mailing list