On Jun 12, 2:05*pm, walt wrote:
So I now ask you, am I correct in saying that the reflection
coefficient in this situation is 1.0? *I'm holding my breath for your
answers.

Walt, some of us have previously discussed the difference between a
one-port s11 (reflection coefficient) and a two-port s11 and I think
that difference is what you are seeing. The one-port s11 (rho) is a
virtual reflection coefficient based on the available system
information. In that case, rho is 1.0. However, if we use the two-port
parameters, I believe s11 (rho) will be 0.5. The matching stub
complicates the analysis so maybe we can reduce the complexity using a
slightly different example about which you can ask the same question
and the answer will be a little easier.

--50 ohm--+--1/2WL 150 ohm--50 ohm load

It's essentially the same problem without the complexity of the stub.
There is a 50 ohm Z0-match at point '+'. The one-port s11 (rho)
looking into the Z0-match point from the source side is 0.0 because
there are no reflections. The one-port analysis is blind to any
interference that might be recognized if we were using the two-port
analysis.

The one-port s11 (rho) looking back into the Z0-match from the load is
1.0, same as your virtual open/short. The one-port analysis used for
your virtual open/short concept is unaware of the interference that is
visible in a two-port analysis. A one-port analysis cannot tell the
difference between an actual reflection and a redistribution of energy
associated with superposition interference.

However, the two-port s11 (rho) looking into the Z0-match from the
source side is 0.5, i.e. (150-50)/(150+50). Interference is not
invisible in the two-port analysis. In fact, when the voltage
reflected toward the source is zero, there is total destructive
interference in the direction of the source.

b1 = s11*a1 + s12*a2 = 0

where all math is phasor math. The two terms cancel destructively to
zero. The ExH energy components in those two terms are redistributed
back toward the load.

In a two-port analysis, the reflection coefficient looking back into
the Z0-match from the load is called s22. The matching equation is:

b2 = s21*a1 + s22*a2

All of the destructive interference energy involved toward the source
is redistributed back toward the load as constructive interference.
But such is invisible in a one-port analysis such as your virtual open/
short circuit.

There is nothing wrong with your one-port virtual open/short circuit
analysis. There is also nothing wrong with the more in-depth two-port
analysis. It is simply that more information is available during the
two-port analysis.

Over on another newsgroup, some reported using a one-port analysis
almost all of the time. Tell your critics that you are using a one-
port analysis where the interference information is simply not
available during the analysis.

What is the one-port reflection coefficient looking into a Z0-match
from the source side? 0.0
What is the one-port reflection coefficient looking into a Z0-match
from the load side? plus or minus 1.0

That is what you are doing with your virtual open/short and there's
nothing wrong with a one-port analysis.
--
73, Cecil, w5dxp.com