[SI-LIST] Re: Rx Eye Mask width, BER, and Jitter

  • From: Marty Bewildered <martym777@xxxxxxxxx>
  • To: si-list@xxxxxxxxxxxxx
  • Date: Mon, 21 Jun 2010 13:11:50 -0700 (PDT)

My first comment is Rj is not a function of BER, Tj is ... or more directly 
Jrms ... is a function of BER

Second comment ... if your margin at 1e-12 is 0.2UI, you're in big trouble at 
1e-15.

Basically your Tj is getting bigger than 1UI ... so all the numbers don't make 
sense anymore.



----- Original Message ----
From: Conrad Herse <herse@xxxxxxxxxxxxxxxxxx>
To: si-list@xxxxxxxxxxxxx
Cc: herse@xxxxxxxxxxxxxxxxxx
Sent: Mon, June 21, 2010 12:40:13 PM
Subject: [SI-LIST] Rx Eye Mask width, BER, and Jitter

Hello experts,

I've been working on trying to scale receiver eye mask widths to 
different bit error rates. There is something which is puzzling me which 
I'm hoping someone can clear up for me.

I've been studying the dual-Dirac jitter model given by the formula:

Tj = Dj + 2Q * Jrms

where Q is a constant from the Complimentary Error function for a given 
BER (2Q*Jrms = Rj at a specific BER). So if I have a receiver with the 
following jitter tolerance spec:

Tj = 0.8 UI
Dj = 0.3 UI
Rj = 0.5 UI
BER = 1e-12

then, given 2Q = 14 for BER = 1e-12:

Jrms = 0.5 / 14 = 0.036 UI

The Rx eye mask width would be:

1 - 0.8 = 0.2 UI

If I want to scale the Rx eye mask width to BER=1e-15 I would expect I 
need to *grow* the eye mask width by Jrms.

Given that 2Q = 15.883 at BER = 1e-15, then my new eye mask width would be:

0.2 + (15.883 - 14) * 0.036 = 0.268 UI

So far so good, assuming I did this correctly. Here's what puzzles me, 
if I adjust my Rx jitter tolerance to accommodate the new Rx eye mask:

Tj = 1.0 - 0.268 = 0.732 UI
Dj = 0.3 UI
Rj = 0.732 - 0.3 = 0.432 UI
BER = 1e-15

and recalculate Jrms:

Jrms = 0.432 / 15.883 = 0.027 UI

The Jrms number has changed, I wouldn't expect this to happen simply 
because I'm extrapolating to a different BER. Can someone please 
straighten me out?

Thanks!

-- 
Conrad Herse

------------------------------------------------------------------
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:
//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:    
        //www.freelists.org/archives/si-list

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:
//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:     
                //www.freelists.org/archives/si-list
 
Old (prior to June 6, 2001) list archives are viewable at:
                http://www.qsl.net/wb6tpu

Other related posts:

  1. Home
  2. si-list
  3. Archive
  4. 06-2010