[SI-LIST] RMS jitter

Khalid,

I always considered the RMS value to be 1 sigma.   When going from RMS to 
p-p I have used 6 sigma (+/- 3 sigma).
You should be able to reverse this if you are coming from p-p to 
RMS.    You can get a good sampling with as little as 500 - 1000 
cycles.   We sometime look at the 3 sigma reading on the scope as it is 
taking its measurments and wait for it to register less than 100% (i.e. 
99.9%) and consider that enough for general measurements.

For a BER measurement of 10 ^-12 you would need 14.069 sigma.  That 
provides a p-p range that includes all of the samples minus 1 x 10^ -12 
times the number of samples.  Such a BER would be typical for fiber channel 
communication.  On the other hand a BER for 6 sigma will be 1.3 x 10^-3 
because less of the samples are included in the lower sigma.

Ed






At 02:28 PM 12/11/01 -0800, Khalid Ansari wrote:

>Hi all,
>
>I am not very clear on what exactly is the RMS jitter value when using a
>scope such
>as the Tek11801.  Also, the relation between RMS and pk-pk jitter
>values.  Looking
>at the eye for X amount of time is it possible to get the RMS value from
>the pk-pk value.
>The oscilloscope basically generates the pk-pk value from the time
>difference between
>the furthest points on the histogram which varies with the number of
>samples taken,
>not a very sensible measurement I guess.
>
>I remember multiplying the RMS value by 14 (7 sigma) to get the pk-pk value
>in the
>past because we were using BER tolerance of 10exp-12...what this means, I 
>don't
>exactly know.
>
>Any reference to documents on RMS jittter or any feedback will be very 
>helpful,
>
>Thanks in advance,
>Khalid
>
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