Roy Lewallen wrote:
Although it's not really relevant to the discussion at hand, I believe a
valid argument could be made that if a2 isn't equal to zero, then S11
isn't a reflection coefficient at all. It surely isn't the reflection
coefficient at port 1, anyway.

Actually, it is, Roy. s11 is the *physical* reflection coefficient.
For instance, in the following two-port network:

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

s11 is *defined* as the input reflection coefficient with the output
port terminated by a matched load (ZL=150 ohms sets a2=0). s11
continues to be *defined* as 0.5 even when a2 is not zero.

s11 = (150-50)/(150+50) = 0.5

Since a Z0-match exists at '+', the reflection coefficient on the
50 ohm feedline is zero. rho = Sqrt(Pref/Pfwd)

For a two-port network with a2 not equal to zero, the reflection
coefficient 's11' is NOT equal to the reflection coefficient 'rho'.

The energy analysis on my web page deals only with physical reflection
coefficients. If 'rho' is not a physical reflection coefficient, then
it is the END RESULT of a mathematical calculation and is not the
CAUSE of anything. If a source doesn't "see" a physical impedance
discontinuity, it doesn't "see" anything except forward and reflected
waves. Coherent waves traveling in opposite directions are "unaware" of
each other. Coherent waves traveling in the same direction merge, lose
their separate identies, and become indistinguishable from one another.
--
73, Cecil http://www.qsl.net/w5dxp



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