[SI-LIST] Re: Jitter transfer vs. accumulation
- From: Scott McMorrow <scott@xxxxxxxxxxxxx>
- To: Vinu Arumugham <vinu@xxxxxxxxx>
- Date: Fri, 23 Mar 2007 12:59:04 -0400
Vinu
I would agree, and would claim that the RMS value is a scalar
representation of an unbounded phenomena (the 1-sigma value of the
statistics), when we view it w.r.t. a true Gaussian distribution. The
jitter itself is unbounded.
I suspect that we have a nomenclature issue. I would claim, however,
that the measured RMS jitter value (not the actual) will change over
time as additional samples are taken, and better statistical confidence
is obtained. The RMS jitter value is then a bounded number which
describes an unbounded process.
But I'm just a hack engineer. WTF do I know?
Scott
Scott McMorrow
Teraspeed Consulting Group LLC
121 North River Drive
Narragansett, RI 02882
(401) 284-1827 Business
(401) 284-1840 Fax
http://www.teraspeed.com
Teraspeed® is the registered service mark of
Teraspeed Consulting Group LLC
Vinu Arumugham wrote:
> May be we need to clear up the terminology/definitions.
>
> By RMS jitter I think George is referring to RJ rms or the 1-sigma
> value of the gaussian. This I think is bounded as George has
> repeatedly stated.
> The peak-peak RJ of course is unbounded and depends on the number of
> samples. I think George has referred to this as phase jitter.
>
> Comments from Steve and Alfred seemed to suggest that the RJ rms, the
> 1-sigma of the gaussian itself is unbounded.
> Steve, Alfred could you please clarify if that is what you meant/observe?
>
> Thanks,
> Vinu
>
>
>
> Scott McMorrow wrote:
>> George
>>
>> I have a quick question. You said:
>>
>> "The VCO RMS jitter is bounded, and so is the PLL RMS jitter. The RJ
>> distribution takes on a true Gaussian waveform."
>>
>> My meager understanding of this is that Rj is by definition unbounded. And
>> the presence of a true Gaussian distribution (when all other deterministic
>> components have been subtracted out) is an indication of this unboundedness.
>> And yes, theoretically it will approach infinity at infinite time. However,
>> because the random component is so low, it "seems" to be bounded within a
>> specific BER confidence level. Which is why we have repeatability in
>> measurements. My contention is that Rj is much smaller than most people
>> believe or are able to measure, and that it is low probability deterministic
>> noise components that dominate the jitter spectrum. Unfortunately, these can
>> also tend to have near-gaussian distributions, mucking up the measurement
>> apparatus.
>>
>> If what I say above is correct, then what you describe above is truly
>> unbounded jitter, taking on a Gaussian distribution.
>>
>> Do you agree?
>>
>>
>> best regards,
>>
>> Scott
>>
>>
>>
>>
>> Scott McMorrow
>> Teraspeed Consulting Group LLC
>> 121 North River Drive
>> Narragansett, RI 02882
>> (401) 284-1827 Business
>> (401) 284-1840 Fax
>>
>> http://www.teraspeed.com
>>
>> Teraspeed® is the registered service mark of
>> Teraspeed Consulting Group LLC
>>
>>
>>
>>>
>>>
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>
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