[time-nuts] Close-in phase noise measurements

Jeff Mock jeff at mock.com
Wed Mar 26 19:34:22 UTC 2008


This is a half-baked idea I've thinking about for awhile.  I wonder if 
it might be possible to create a single measurement to combine allan 
variance and phase noise in the same plot.  Allan variance usually plots 
tau in seconds on the x-axis.  Instead, you might plot 1/s or frequency 
on the x-axis.  This way, allan variance looks more like very close-in 
phase noise.

For example, a point where tau=1000s becomes the phase noise at 1mHz 
(milli-hertz) from the carrier.  Combining this with more typical phase 
noise measurements, you can create a single log-log graph covering 
micro-hertz to hundreds of kilo-hertz.  The advantage of combining the 
measurements into a single entity is that you get most of the 
characterization parameters for a timebase in a single graph.

Would this work?  Half-baked, I know...
jeff


Shane wrote:
> Do you know much about the R&S FSUP50?
> 
> http://www2.rohde-schwarz.com/en/products/test_and_measurement/product_categ
> ories/spectrum_analysis/FSUP-%7C-Key_Facts-%7C-4-%7C-966.html
> 
> 
> -----Original Message-----
> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
> Behalf Of Bruce Griffiths
> Sent: Tuesday, March 25, 2008 8:22 PM
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] Close-in phase noise measurements
> 
> Shane wrote:
>> Wenzel has a setup you can purchase at low cost.  
>>
>> http://www.wenzel.com/pdffiles1/PNTS%201000/BP-1000-SC.pdf
>>
>> Phase noise test sets can be pricey... $200K
>>   
> Shane
> 
> Their calibration method is somewhat problematic at the low frequency 
> end where the effect of the PLL and the audio amplifier low frequency 
> cutoff may be significant.
> The NIST calibration technique: 
> http://tf.nist.gov/timefreq/general/pdf/1000.pdf is far superior.
> 
> Bruce
> 





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