[SI-LIST] Re: [SI-List]: S parameters for Multi-point Topology
- From: "Dmitriev-Zdorov, Vladimir" <vladimir_dmitriev-zdorov@xxxxxxxxxx>
- To: vinod ah <ah.vinod@xxxxxxxxx>
- Date: Mon, 23 Nov 2015 03:35:36 +0000
Hi Vinod,
Only thing i am not still clear is why is that i am seeing difference in
behavior in S5P as compared to S2P
This is expected. The difference is caused by termination that is different
from the normalization conditions used for the eliminated ports. You exclude
some ports by assuming them not connected to anything or equivalently, applying
very large termination resistance to those ports (much larger than e.g. 50Ohm).
By doing this, you change the amount of reflected energy visible at the
remaining ports. Similar things happen if you short some of the ports to ground.
The only case when the remaining dependencies don't change is when you assume
the eliminated ports be terminated on their normalization impedance (e.g. 50
Ohm). Then, port elimination can be made by simply removing some rows and
columns of the S-parameter matrix.
Vladimir
________________________________
From: vinod ah [ah.vinod@xxxxxxxxx]
Sent: Sunday, November 22, 2015 7:56 PM
To: Dmitriev-Zdorov, Vladimir
Cc: si-list@xxxxxxxxxxxxx
Subject: Re: [SI-LIST] Re: [SI-List]: S parameters for Multi-point Topology
Hi All,
One common question which came up to me was, which tool is being used. Ansys
Siwave is used for extraction.
Thanks Vladimir for the suggestion. What i see is when i convert the extracted
S5P file to 4 S2P files using Hyperlynx touchstone viewer, i don't see the
gain, instead i see loss which is what expected.
Only thing i am not still clear is why is that i am seeing difference in
behaviour in S5P as compared to S2P.
Regards
Vinod A H
On Fri, Nov 20, 2015 at 12:17 PM, Dmitriev-Zdorov, Vladimir
<vladimir_dmitriev-zdorov@xxxxxxxxxx<
mailto:vladimir_dmitriev-zdorov@xxxxxxxxxx>>
wrote:
Hi Hermann,
Regarding the tools, it would be convenient to use Hyperlynx Touchstone Viewer.
To see how the signal propagates from port 1 to 2, you can exclude ports 3-5 by
letting them be "non-connected". No circuit simulation is needed. In the
resulting s2p file you'll get the "usual" insertion loss, with resonances
caused by the stubs to existing but already invisible ports 3-5. Then, repeat
this operation by eliminating ports 2, 4 and 5 as "not connected" and so on. If
needed, you can also re-normalize the remaining ports to any convenient
impedance value, or let them be 50 Ohm.
We have used to think about connectors in terms of "insertion loss". However,
this logic works only when you have a conductor that connected two ports, and
other ports being relatively isolated (e.g. with their respective conductor
coupled to the first). If we add more ports at either side of the conductor, or
even split any port into several connected to each other, all the dependencies
in S-parameter matrix are drastically affected and the "insertion loss"
thinking doesn't apply.
Perhaps, this is what caused difficulty in interpretation.
Of course, passivity and causality should be in any case, regardless of the
port number.
Vladimir
HI Scott,
yes, this is an option, but I think very cumbersome.
I setup this once in ADS with automatic switching .. but also this
requires a lot of effort.
I would still hope that tool vendors would see this as important task
and bring in some automatism for this ..
Hermann
EKH - EyeKnowHow
Signal Quality - Made in Bavaria
Hermann Ruckerbauer
www.EyeKnowHow.de<http://www.EyeKnowHow.de>
Hermann.Ruckerbauer@xxxxxxxxxxxxx
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