Michael
Define "described". What is the purpose of the black box measurements?
Any 2-wire, 4-terminal black box can be modeled with a measured s-parameter.
The question regarding the purpose is important, as it helps to define the
measurement needed.
Assume, for example, two wires in Free space. We can measure them in 2 ways. We
can use differential and common mode probing to create e black box. Or we can
create a virtual ground reference between the conductors, one in each end and
measure single ended s parameters.
In either case, the measurements are valid and identical. N ports are required.
However, unless the two wires are placed inside a Faraday cage the measurements
will be noisy, since they include the electromagnetic environment of the
universe. Instead, we use shorter sections that we measure, and then
extrapolate then out to one mile long.
I have no comment regarding the bird.
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From: Mirmak, Michael
Sent: Monday, February 26, 7:36 PM
Subject: [ibis-macro] S-parameter thought experiment
To: IBIS-Interconnect (ibis-interconn@xxxxxxxxxxxxx), IBIS-ATM
(ibis-macro@xxxxxxxxxxxxx)
(apologies if you have heard something like this before – I have discussed it
privately in a couple of contexts)
Imagine that I have a physical interconnect, consisting of a differential pair
of wires not particularly strongly coupled to each other. I want to model the
interconnect using an S-parameter set of at least 4 (four) ports: two inputs P
&N and two outputs P’ & N’.
The problem: the physical pair of wires is approximately one mile in length
from P & N to P’ & N’.
My questions:
1) Can this structure be correctly and unambiguously described using a
circuit with N terminals and an N+1 reference terminal? If not, how many
additional terminals are required?
2) Does the current BIRD189 draft, as written, enable correct and
unambiguous description(s) of this structure?
3) Does BIRD158.7, as written, enable correct and unambiguous
description(s) of this structure?
Thank you!
- MM
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