Cecil wrote,

I'm not entirely certain, but I believe the H-parameter analysis,
the Y-parameter analysis, and the Z-parameter analysis all use
the reflection model and are valid for impedance discontinuities
in transmission lines.
--
73, Cecil http://www.qsl.net/w5dxp



Those are all examples of two port parameters, good for your basic linear,
time invariant system. (While you're at it, don't forget the
transmission parameters, Cecil.) They'll work with any old lumped
or distributed system as long as it's linear, has two ports, and is
time invariant.

You can't really use S-parameters to prove reflections exist because
S-parameter theory assumes reflections exist even when they don't, as in the
case of
transistor characterization - much like calculating the VSWR in a
zero length transmission line. They're good for analysis, though, as long
as you don't get carried away and look on them as proving something about
God, the Universe and Everything.
73,
Tom Donaly, KA6RUH

Tdonaly wrote:
You can't really use S-parameters to prove reflections exist because
S-parameter theory assumes reflections exist even when they don't, ...

On the contrary, if one assumes same-cycle reflections, the reflection
model works perfectly. Why wouldn't a 50 ohm source looking into a 100
ohm resistor suffer an immediate reflection (energy rejection)? :-)
--
73, Cecil http://www.qsl.net/w5dxp



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Cecil wrote,
Message-id:

Tdonaly wrote:
You can't really use S-parameters to prove reflections exist because
S-parameter theory assumes reflections exist even when they don't, ...

On the contrary, if one assumes same-cycle reflections, the reflection
model works perfectly. Why wouldn't a 50 ohm source looking into a 100
ohm resistor suffer an immediate reflection (energy rejection)? :-)
--
73, Cecil http://www.qsl.net/w5dxp



Why wouldn't it, indeed.
73,
Tom Donaly, KA6RUH

"Tdonaly" wrote in message
...
Cecil wrote,
Message-id:

Tdonaly wrote:
You can't really use S-parameters to prove reflections exist because
S-parameter theory assumes reflections exist even when they don't,
....

On the contrary, if one assumes same-cycle reflections, the reflection
model works perfectly. Why wouldn't a 50 ohm source looking into a 100
ohm resistor suffer an immediate reflection (energy rejection)? :-)
--
73, Cecil http://www.qsl.net/w5dxp



Why wouldn't it, indeed.
73,
Tom Donaly, KA6RUH



if there are no components that introduce a time delay it would. so no
transmission lines allowed... hence no reflections. and you are back to a
simple lumped resistor problem.

Dave wrote:
"Tdonaly" wrote:

Cecil wrote,
On the contrary, if one assumes same-cycle reflections, the reflection
model works perfectly. Why wouldn't a 50 ohm source looking into a 100
ohm resistor suffer an immediate reflection (energy rejection)? :-)

Why wouldn't it, indeed.

if there are no components that introduce a time delay it would.

All real-world components introduce a time delay.

so no
transmission lines allowed... hence no reflections. and you are back to a
simple lumped resistor problem.

RF energy travels at the speed of light. For the length of time it
takes for the energy to reach the resistor and reflect back to the
source, the source sees 50 ohms. That length of time is not zero.
--
73, Cecil http://www.qsl.net/w5dxp



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Dave wrote,


if there are no components that introduce a time delay it would. so no
transmission lines allowed... hence no reflections. and you are back to a
simple lumped resistor problem.



Maybe, but don't tell that to the analytical types. Zero length transmission
lines are part of the stock in trade of some people who find the concept
useful.
73,
Tom Donaly, KA6RUH

Cecil wrote,

RF energy travels at the speed of light. For the length of time it
takes for the energy to reach the resistor and reflect back to the
source, the source sees 50 ohms. That length of time is not zero.
--
73, Cecil http://www.qsl.net/w5dxp



Even though the length of time is not zero, it's close enough
so that the theorems of network analysis work (at least
at the lower frequencies). Of course, if you want to do a reflection analysis
on a
couple of resistors, each of which is only a minute fraction of
a wavelength long, well, it's a free country. S-parameters assume
reflections and such, and are very useful to the people who use them,
but, as an intellectual tool, it doesn't matter whether there are any real
reflections or not as long as the answers come out right. They
don't really prove reflections in and of themselves, anyway, since it's hard to

prove something based on the assumption that it's true. (I assume it, therefore

it's true.)
73,
Tom Donaly, KA6RUH

Tdonaly wrote:
Dave wrote,
if there are no components that introduce a time delay it would. so no
transmission lines allowed... hence no reflections. and you are back to a
simple lumped resistor problem.

Maybe, but don't tell that to the analytical types. Zero length transmission
lines are part of the stock in trade of some people who find the concept
useful.

At 3 GHz, one inch of wire is close to 1/4WL. :-)
12*984'/3000 = 3.936"
--
73, Cecil http://www.qsl.net/w5dxp



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On Tue, 15 Jun 2004 06:15:16 -0500, Cecil Moore
wrote:
At 3 GHz, one inch of wire is close to 1/4WL
At 3 GHz nobody uses wire.

"Cecil Moore" wrote in message
...
Tdonaly wrote:
Dave wrote,
if there are no components that introduce a time delay it would. so no
transmission lines allowed... hence no reflections. and you are back to
a
simple lumped resistor problem.

Maybe, but don't tell that to the analytical types. Zero length
transmission
lines are part of the stock in trade of some people who find the concept
useful.

At 3 GHz, one inch of wire is close to 1/4WL. :-)
12*984'/3000 = 3.936"
--
73, Cecil http://www.qsl.net/w5dxp


Now I get it! (Cecil, that is) LOL

Just like the Civil Defense days... "This is a test. Had it been an actual
response, Cecil would have made an intelligent comment about the real
question". What a "tweeker", is Cecil. What a little devil. (:-)
I'm thinkn' it proves the old adage about the idle mind and a workshop....

73, Steve


P.S. Remember that sea of entropy we were supposed to drown in? Well, upon
closer examination, it turns out to be ignorance.

BTW... This is my comment on the general population, not any specifics
here...