[SI-LIST] Re: How is the jitter spec and BER number related to each other
- From: Samit Ashdhir <ashdhir@xxxxxxxxx>
- To: "Julia (Zhuyuan) Liu" <zliu@xxxxxxxxxx>
- Date: Wed, 10 Nov 2010 06:26:03 -0800
Hi Julia,
A BER bathtub curve provides the relationship between the jitter spec and BER.
The curve is the plot of BER vs. sample time from the left edge to the right
edge of a data eye. This plot resembles a “bathtub” and is also referred to as
a “BERT scan.”
BER measurements is across the regions where data transitions occur (the left
and right eye edges) and provide the necessary information to calculate TJ. TJ
is quantified by noting the points where the BER reduces to 1E-12 (or required
limit) at both eye edges. Subtracting that interval from the bit period
provides TJ. For example, if the data rate is 1.25 Gb/s, the corresponding bit
period is 800 ps. If a BER of 1E-12 occurs at 20 ps and 780 ps, then the total
jitter is 800 – (780 – 20), or 40 ps.
Agilent has some good papers explaining these more.
-samit
On Nov 9, 2010, at 5:08 PM, "Julia (Zhuyuan) Liu" <zliu@xxxxxxxxxx> wrote:
> Hi, Everyone
> XLAUI/ CAUI spec specifies the jitter tolerance in UI, assuming the BER is
> 1e-12 or 1e-15. Does anyone know how to calculate the jitter tolerance when
> the BER is given?
>
> For example, CAUI has the following note in the spec.
> NOTE-A transmitter capable of operating at TJ = 0.3 UI and DJ = 0.16 UI and
> receiver capable of operating at stress
> jitter tolerance of TJ = 0.64 UI and DJ= 0.41 UI would have sufficient margin
> for operation at approximately BER 10-15.
>
>
> Thanks,
> Julia
>
>
>
>
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