[SI-LIST] Re: Jitter transfer vs. accumulation

FYI, for others who is interested in the reference.

1.      Jitter in ring oscillators
McNeill, J.A.;
Solid-State Circuits, IEEE Journal of
Volume 32,  Issue 6,  June 1997 Page(s):870 - 879

2.    Ali Hajimiri, S. Limotyrakis, and Thomas H. Lee,
"Jitter and Phase Noise in Ring Oscillators," IEEE
Journal of Solid-State Circuits, June 1999, p.
790-804. [Paper]

3. T. H. Lee and A. Hajimiri, ?Phase Noise in
Oscillators, A Tutorial,? Invited Paper, IEEE Journal
of Solid-State Circuits, vol. 34, no. 3, pp. 326-336,
March 2000


Cheers,

Yafei

--- "Tang, George" <George.Tang@xxxxxxx> wrote:

> Alfred,=20
> 
> See comments in [[[[[ ]]]]]. =20
> 
> George=20
> 
> 
> -----Original Message-----
> From: Alfred P. Neves
> [mailto:al.neves@xxxxxxxxxxx]=20
> Sent: Wednesday, March 21, 2007 11:07 PM
> To: weirsi@xxxxxxxxxx; Tang, George;
> si-list@xxxxxxxxxxxxx
> Subject: RE: [SI-LIST] Re: Jitter transfer vs.
> accumulation
> 
> George,
> 
> 
> >{{{{{Alfred made the initial postulate that
> open-loop VCO has rms=20
> >jitter governed by his funny equation Y=3DmX + b,
> where Y is the rms=20
> >jitter, X is the time duration of measurement, and
> m > 0.  This shows=20
> >that as time goes to infinity, the rms jitter of
> the open-loop VCO also
> 
> >goes to infinity.
> 
> No George, this is not what I said.  It is the
> autocorrelation record of
> the VCO that increases linearly on a log-log plot,
> where the axis are
> log(RMS jitter) and log(time interval length), where
> this is not to be
> confused with an RMS jitter or whether it is bounded
> or not. =20
> 
> [[[[[Amazing.  If your autocorrelation record for
> the open-loop VCO
> looks like Y=3DmX + b, you have either invented a
> random-noise-free
> environment (congratulations to you,) or your
> environment is so bad that
> it is completely dominated by deterministic
> modulation so you cannot
> take clean measurements at all.  My guess is that
> the latter case is the
> truth.  ]]]]]]]=20
> 
> 
> I already
> provided numerous references regarding this and can
> also provide
> numerous measurements for several VCO's to
> illustrate VCO RMS jitter
> characteristics versus measurement interval.  We
> have used this analysis
> 100's of times for closed (and open loop) PLL
> analysis to determine the
> PLL loop bandwidth and peaking in the PLL loop
> response. =20
> 
> [[[[[Like I said before, we do not see this problem
> in our measurements.
> The VCO RMS jitter is bounded, and so is the PLL RMS
> jitter.  The RJ
> distribution takes on a true Gaussian waveform.  In
> addition to that, we
> test our communication channels (including TX, RX,
> &PLL) for weeks with
> no errors.  All our measurements fairly closely
> match up with the system
> BER predicted by the model simulation.  We do not
> see the problems that
> you are fighting with.  ]]]]]=20
> 
> 
> You can also
> use this analysis to analyze jitter problems like
> spurious response due
> to charge pump leakage, power supply junk like
> switching noise or HF
> digital, XTALK in the substrate, SSO, and jitter
> multiplication from PLL
> to PLL.  The basis for this analysis is work by John
> McNeil in
> collaboration with Analog Devices in the mid 90's -
> have you read the
> reference already provided, I can send you a copy if
> need be?   I didn't
> originate the concept, just use the practical
> elements to analyze PLL's
> and VCO's.  Before you belittle this, become
> dismissive, or make any
> more personally targeted comments it may behoove you
> to do a bit of
> homework.   And once again, you are asked to
> significantly raise the
> level of your professionalism in your
> communications.  =20
> 
> > He further claimed that with the feedback loop
> of=20
> >the PLL, the rms jitter became bounded.  You don't
> think Alfred was=20
> >crazy enough to make the mistake of comparing phase
> jitter of VCO to=20
> >the RMS jitter of the PLL, do you?  That will be
> comparing apples to=20
> >bananas, let alone oranges
> 
> No, I did not say this either.  The reference was
> regarding the
> autocorrelation record, NOT any comment regarding
> characteristics of VCO
> RMS jitter.  A VCO has certain properties:   It has
> poor frequency
> stability, it is temperature sensitive, it is not
> WSS (wide sense
> stationary), it has a LOT of low frequency jitter
> due to numerous 1/f
> noise sources, it also has unbounded RMS jitter, but
> the estimate of the
> RMS jitter is difficult to measure since:   Measure
> the RMS of a VCO
> over a certain time T, remeasure the RMS jitter
> later over the same time
> interval and you will arrive at a different RMS
> number since it is not a
> stationary process.   Sample size really has little
> to do with this.
> BTW, do you have data on "stable" VCO's in terms of
> PPM frequency drift
> versus time, after you claim the temperature
> stabilizes in 1-2 hours.
> 
> [[[[[If the RMS RJ of the VCO is unbounded, the
> closed-loop PLL will
> never be fully stable since the feedback has finite
> correction
> capability.  The only way the PLL can be fully
> stable is that the RMS
> jitter of the VCO HAS TO BE BOUNDED.  We measure the
> PLL for say 20
> minutes on day one and another 20 minutes on day 2
> and day 3, and the
> Peak-to-Peak jitter and RMS jitter for each day
> matches the results of
> the other days down to 0.1ps range.  To say that the
> VCO and/or the PLL
> has unbounded RMS jitter will be a tough tough sell,
> since you will
> never be able to get this kind of repeatability
> otherwise.  ]]]]]]=20
> 
> 
> NOW, place the VCO into a PLL loop that is locked on
> a stable input
> signal, the VCO accumulated phase jitter  is shaped
> by the PLL loop
> response.  The RMS RJ jitter measured (using some
> RJ-DJ extraction) will
> be unbounded  - by definition.   =20
> 
> [[[[[Why?  What equipment do you use to give you
> such results? ]]]]]
> 
> The resulting PLL accumulated jitter,
> phase jitter, or autocorrelation record will not
> continue to increase
> past a value related to the PLL loops bandwidth,
> however (assuming the
> loop is stable).  =20
> 
> 
> [[[[[Phase jitter is bounded??  What equipment shows
> that! ]]]]]]
> 
> This is due to the intrinsic PLL loop gain. =20
> 
> [[[[[No, you are wrong, again.  Even when the PLL is
> in the locked
> operation, the feedback can only correct the VCO
> jitter within the loop
> bandwidth.  Beyond that, the feedback cannot do
> anything, period.  When
> the overall PLL output RMS jitter is measured to be
> bounded across all
> frequencies, then the VCO RMS jitter *must also be
> bounded across all
> frequencies*. =20
> 
> On the other hand, phase jitter for a locked PLL is
> unbounded due to
> probability of random events.  ]]]]]
> 
> 
> My point is that the way to deal with both VCO's and
> the VCO-PLL
> 
=== message truncated ===



 
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