FreeLists / si-list / [SI-LIST] Re: Isolation

[Hassan Ali <hali@xxxxxxxxxxxxxx>]

Hi Mick,

If all what you want is to see how much voltage couples into a victim
diff-pair as a result of a signal (of particular rise-time and frequency)
running on an aggressor diff-pair, then you can do that:

1. by HSPICE simulation:

Create a W-element model of a four-conductor (two diff-pairs) coupled
transmission line representing your victim-aggressor configuration. Create
an HSPICE netlist corresponding to your configuration especially the length
of the transmission line. 

Connect a differential source of your interest to one end of the aggressor
diff-pair and terminate the other end with a suitable differential
termination (usually 100 ohms). Terminate both ends of the victim diff-pair
with suitable differential terminations (usually 100 ohms). By definition,
isolation, is the ratio of the voltage on the near-end victim termination to
the source voltage. In SI terms, this is the near-end (or backward)
crosstalk (expressed as a ratio).

2. by measurement:

Design a PCB with differential traces of interest. Provide for a way to
drive the aggressor line with a source of interest and also to measure the
near-end induced voltage on the victim diff-pair. An oscilloscope can serve
as a termination on the measured end. You may have to terminate the other
ends with suitable terminations.

Good luck.

Hassan.



> -----Original Message-----
> From: Zhou, Xingling (Xingling) [mailto:xlzhou@xxxxxxxxx]
> Sent: Thursday, September 06, 2001 5:17 PM
> To: 'si-list@xxxxxxxxxxxxx'
> Subject: [SI-LIST] Isolation
> 
> 
> 
> Hi,
> 
> Is there any information on characterizing isolation between 
> differential
> pairs 'quantitatively' ?
> 
> Thanks.
> 
> Mick
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