[SI-LIST] Re: [SI-List]: S parameters for Multi-point Topology

  • From: Hermann Ruckerbauer <Hermann.Ruckerbauer@xxxxxxxxxxxxx>
  • To: scott@xxxxxxxxxxxxx, erdinih@xxxxxxxxx
  • Date: Thu, 19 Nov 2015 22:09:22 +0100

Hello,

I agree with Scott, that this is possible.
I find it difficult to understand the result just looking to the data in
Frequendy domain, but causality and passivity should be no problem.
Usually I work here with ADS ..

Hermann

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Am 19.11.2015 um 20:32 schrieb Scott McMorrow:

Vinod
it is possible to extract and simulate with a multi-point s-parameter
model. It absolutely should be a passive and causal model. You either have
a setup problem, or a solver problem. We do these sorts of extractions all
the time with Ansys SIwave and Ansys HFSS.

Scott







Scott McMorrow
R&D Consultant
Teraspeed Consulting - A Division of Samtec
16 Stormy Brook Rd
Falmouth, ME 04105
(401) 284-1827 Business
http://www.teraspeed.com

On Thu, Nov 19, 2015 at 2:26 PM, Ihsan Erdin <erdinih@xxxxxxxxx> wrote:

Vinod,
The transmission parameters like S51 and S13 are the bellwether of your
s-parameter data. There will be additional resonances because of junctions
and multiple port effects (if not matched well to the reference
terminations at ports) but eventually the magnitude of those parameters
should decay with frequency because any passive structure is a low-pass
filter. If, instead, they increase as you described your data sound like
total garbage. It is possible that you may have made a mistake in port
numbering etc. In your simulations you should also make sure that the
reference connections of all ports are the same signal.

Regards.

Ihsan Erdin

On Thu, Nov 19, 2015 at 7:28 AM, vinod ah <ah.vinod@xxxxxxxxx> wrote:

Hi All,
I am extracting S parameters of multi-point topology where a traces
starts
from controller and branches out to 4 loads/devices in T-shape i.e. one
trace going to 4 loads.

Trace length from controller to each device is ~5 inches. The branching
to
4 loads happens at ~ 4 inches from controller. Trace is microstrip on
FR4.
I have assigned ports at the controller and the devices. Port 1 is at
controller, Port 2,3,4,5 is at device. S parameter is extracted from 1MHz
to 3GHz with spacing of 1MHz using 2.5D solver.

I am seeing the extracted S5P model is non-causal and also when i plot
S31
or S51, i see the plot rising with respect to frequency instead of a
falling graph i.e. gain is seen, while loss is expected.

When i try to convert this S5P file to Broadband spice model, In rational
model fitting there is no convergence.

Are these problems related to multi-point topology? Is it a standard
practice to extract S parameter for this topology or just go with
transient
simulation?

Regards
Vinod A H


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