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@febo.com [mailto:time-nuts-bounces@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 >

The relationship between phase noise and Allan variance is a complex one and was described in papers at FCS in 1976 and 1978 by my previous manager Mike Fischer (then of HP). I think these papers come closest to answering your question. Rick Karlquist Jeff Mock wrote: > 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@febo.com [mailto:time-nuts-bounces@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 >> > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > >

Richard (Rick) Karlquist wrote: > The relationship between phase noise and Allan variance is > a complex one and was described in papers at FCS in 1976 > and 1978 by my previous manager Mike Fischer (then of HP). > I think these papers come closest to answering your question. > > Rick Karlquist > > Essentially the mapping from phase noise to Allan variance isnt 1 to 1. AVAR formula Whilst it is possible to calculate the Allan variance from the phase noise spectrum using the above formula or a variant thereof, the reverse isnt an unambiguous process as it is possible for different phase noise spectra to have the same Allan variance. In practice the Allan Variance low pass filter frequency response isnt necessarily rectangular as assumed in the above formula. Bruce

Missing formula attached bruce

From: "Richard (Rick) Karlquist" <richard@karlquist.com> Subject: Re: [time-nuts] Close-in phase noise measurements Date: Sun, 30 Mar 2008 21:05:50 -0700 Message-ID: <47F0631E.7020802@karlquist.com> > The relationship between phase noise and Allan variance is > a complex one and was described in papers at FCS in 1976 > and 1978 by my previous manager Mike Fischer (then of HP). > I think these papers come closest to answering your question. Add to that the added complexity that you would like to have a window function before you DFT/FFT. Turning a FFT into Allan deviation or the reverse is among the lost causes. Also, there is only a small overlap of interest mostly, so I think they are best handled separatly, except when analysing spikes in the Allan deviation. Cheers, Magnus