[ibis-macro] What P370 say about S-Parameter referencing

From: Walter Katz <wkatz@xxxxxxxxxx>
To: "'IBIS-Interconnect'" <ibis-interconn@xxxxxxxxxxxxx>, "IBIS-ATM" <ibis-macro@xxxxxxxxxxxxx>
Date: Fri, 27 Apr 2018 12:35:40 -0400 (EDT)

All,

The following comes from the currently unapproved draft of:

P370T/D2
Draft Standard for Electrical Characterization of High-Frequency
Interconnects at Bandwidths up to 50 GHZ

I point out the following lines from the statement below:

1.      Current flowing in the signal terminal is equal to current flowing
out of the reference terminal at each port.
2.      "the local references can be different for different ports of a
multiport, but they have to coincide with the local reference terminals of
another multiport to be connected."

The key point is that if two s-parameters are connected, then each
s-parameter measurement (or extraction from a layout data base) must use
the same reference at each port that is connected. This is a fundamental
part of using s-parameter data. It could be on a "ground" net or a power
rail net, just needs to be the same. Since they are connected, and the
flow in and out of both of the s-parameters are the same, then there is no
net current flowing from the connected s-parameters. So for simulation
purposes, the actual "reference node" connected to the S element is
academic. I see no reason to challenge what the P370 committee is stating,
since the committee members are a Who's Who of signal integrity and
s-parameter experts.

Figure B.1  Multiport currents and voltages definition

Ports are numbered from 1 to N. Each port has two terminals. One terminal
is the signal and another terminal is local reference or local ground
terminal. Current flowing in the signal terminal is equal to current
flowing out of the reference terminal at each port. Connection of
multiports requires that the definition of the terminals on both sides of
the connection is the same. It means that the local references can be
different for different ports of a multiport, but they have to coincide
with the local reference terminals of another multiport to be connected.
Some groups of ports may share the reference terminals. The currents and
voltages at ports are either actual measurable values or effective
voltages and currents as in microwave theory.  In frequency domain, the
currents and voltages are complex variables and can be united into vectors
with N complex elements:

Walter

Walter Katz

<mailto:wkatz@xxxxxxxxxx> wkatz@xxxxxxxxxx

978.461-0449 x 133

Mobile 303.335-6156

Follow-Ups:
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  - From: Muranyi, Arpad

[ibis-macro] What P370 say about S-Parameter referencing

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