[SI-LIST] Re: Simulationsof a connector

  • From: Robert Haller <rhaller@xxxxxxxxxx>
  • To: michael.kurten@xxxxxxxxxxxxxxx
  • Date: Tue, 21 Jan 2003 08:04:10 -0500

Michael,
        The problem that you may be encountering is, when utilizing connector 
models that were created with a field solver that generates models with 
partial inductance. (The descriptions/discussions of partial versus loop 
inductance have already been covered in detail on this list).

The issue is if you tie BOTH sides of the connector to IDEAL gnd (i.e. 
node 0) you are violating assumptions the field solver utilized to 
generate the model in the first place. Your results (in this case) may 
vary from OK to unrealistic.

There are at  least 2 ways to solve the problem.
1. Their is one paper I know of that documents how to convert partial 
inductances into loop inductances.

2. Tie one side of your connector to ideal ground (i.e. node 0). Tie the 
other side of your connector to module_gnd (contrived node name). Then 
place the appropriate capacitance between Module_gnd and ideal ground. 
If you have power in the connector you need to decouple that also.

Regards,
Bob
  --
Robert J. Haller (rhaller@xxxxxxxxxx)
Principal Consultant
Signal Integrity Software Inc.
6 Clock Tower Place, Suite 250
Maynard, MA 01754
Phone: (978) 461-0449, ext 15



Michael Kurten wrote:
> I'm simulating a connector (6x6 coupled spice model) with HSPICE to
> determine the crosstalk caused by the connector. The connector is connected
> to one active line, 14 quiet lines, and the remaining 21 pins are grounded.
> 
> *  topology of the active line
> *
> * source  50Ohm          50Ohm         50Ohm         50Ohm       50ohm
> *     |>--/\/\/----=========----{CONNECTOR}-------=========---/\/\/--|gnd_a
> *                             |             |  |
> *                             =             =  \ 1e6Ohm
> *                             |             |  /
> *                            gnd            |  |
> *                                           | gnd
> *                                                       |
> *                                         gnd_a
> *  topology of the quiet lines
> *
> *     gnd 50Ohm      50Ohm         50Ohm         50Ohm     50Ohm
> *     |---/\/\/----=========----{CONNECTOR}----=========---/\/\/--|gnd_a
> *                             |             |
> *                             =             =
> *                             |             |
>                              gnd          gnd_a
> 
> The active line is excited by a single rising edge with a rise time of
> 500ps.
> The transmission lines are all 50 Ohm T-element
> The capacitors at the left and right side of the connector have a value of
> 1.0pF
> The grounded pins are connected directly to ground via a 1m resistor in
> parallel with a 1.0pF capacitor
> 
> The results on the quiet lines show the crosstalk followed by an
> establishing sine function which decays very slowly. The frequency of the
> sine function is in the 4-5 GHz range.
> 
> I'm trying to understand where this behavior comes from. I tried a couple of
> arrangements to get rid of this sine function but none of them changed the
> behavior significantly. E.g. option gshunt and cshunt, connecting gnd and
> gnd_a via a high impedance resistor and a small capacitor.
> 
> Any help is highly appreciated.
> 
> Regards
> Michael
> 
> 
> 
> 
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