[SI-LIST] How do two Random (Gaussian) Jitter specs add?

  • From: "tom_cip_11551" <tom_cip_11551@xxxxxxxxxxx>
  • To: si-list@xxxxxxxxxxxxx
  • Date: Fri, 14 Apr 2006 15:08:21 -0000

Hi to sll signal integrity experts.

I am just a little rusty on "probability and random variables". 

Lets say that I had a system with two or more elements that 
generated Gaussian distribution or, random jitter, or random jitter. 
Random jitter tends to be specifed in terms of the standard 
deviation of the distribution. Each generator would therefore have 
a "sigma", which is also an RMS value. If I knew the sigma of each 
of the distributions coming from the generators, then I could 
convert these sigma values to a peak to peak number by arbitrarily 
assigning a desired bit error rate. The peak to peak values, as far 
as I know, will add, linearly.

However, if I wanted to stay in the statistical world, how could I 
add the two sigma values for the two jitter generators? In my way of 
thinking, they can not add linearly (sigma 1 plus sigma 2). Is this 
wrong?

Thank You
Tom




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