*From*: "Steve Waldstein" <swldstn@xxxxxxxxxxxx>*To*: <si-list@xxxxxxxxxxxxx>*Date*: Fri, 23 Mar 2007 19:59:52 -0400

To all, Sorry if this is not what other think but I agree with Scott that the Random Jitter is unbounded and that the RMS measurement represents a way to describe its distribution if it is and only if it is Gaussian. Random jitter does not have to be Gaussian but to simplify a lot of problems we assume it is. In the past people had tried to find a way to map RMS to Peak-to-Peak and The rule of thumb developed was +/- 7 sigma. In reality this is only true if you assume that your are concerned with an error rate of ~ 10e-12. If, as in most modern systems you are looking for a error rate of > than 10e-12 the conversion from RMS to peak-to-peak changes. Maxim and other have Some great app notes on converting from RMS to a error rate. If it bounded than we assume it can be described by some deterministic phenomena (even if we don't understand it). In this case we tend to put it into two buckets, correlated (to something) or uncorrelated (meaning we can't figure it out). In the past we assumed that the deterministic jitter was only caused by duty cycle distortion (DCDj), or periodic jitter (Pj) or even a more specific Pj called Sj (sinusoidal jitter). If it came down a link or contained data we would also try to partition it into ISI (inter symbol interference) or data dependant jitter (DDj). All of these are ether correlated or uncorrelated with something but they were all bounded because no matter how long we measured it it would not change. Random jitter by definition will continue to "accumulate" the longer we look assuming the probability of the event happening (no matter how low) is still > zero. That's my two cents. Steve Waldstein Tundra Semiconductor -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of Mark Randol Sent: Friday, March 23, 2007 1:18 PM To: si-list@xxxxxxxxxxxxx Subject: [SI-LIST] Re: Jitter transfer vs. accumulation Time to get out the dictionaries. According to mine (the before mentioned MJSQ): "3.5.45 jitter, random, RJ: Jitter that is characterized by a Gaussian distribution and is unbounded." "Because random jitter is practically measured as an RMS value (the same as the standard deviation for a Gaussian distribution), a seemingly small amount of RMS random jitter corresponds to a large peak to peak value. The RMS value for random jitter is multiplied by approximately 14 to result in a peak to peak random jitter value that corresponds to a 10-12 bit error ratio;..." To sum up, RJ is unbounded as the number of edges (aka samples, BER, etc) increases, because the Gaussian distribution is unbounded at an infinite number of samples. =20 In reality RJ is bounded because in a real system, at the grossest level, there's not infinite time nor bandwidth. There are other reasons too, but those are adequate to make the point. This makes the math messy though, so being good engineers we 'ignore' that inconvenient fact. But that's not what I understood the discussion to be about. Awaiting the deluge of 'Out of the Office' messages, -- Mark Randol, RF Evaluation & Application Engineer ON Semiconductor ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: http://www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List technical documents are available at: http://www.si-list.net List archives are viewable at: http://www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: http://www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List technical documents are available at: http://www.si-list.net List archives are viewable at: http://www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu

**References**:**[SI-LIST] Re: Jitter transfer vs. accumulation***From:*Mark Randol

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