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Old December 9th 03, 09:14 PM
Cecil Moore
 
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pez wrote:
Accordingly and as far as we are not in place
to reduce the number of "The Any Waves",
regardless of their more or less well established physical meaning,
in something less than infinity,
any further attempt to discuss about "what actually happens"
in the totality of the related practical applications
becomes redundant and worthless.

It seems that we have to content ourselves
with what it is already known...


Assuming an s-parameter analysis is one of the things already known ...

the equations b1 = s11*a1 + s12*a2 and b2 = s21*a1 + s22*a2

should be familiar. HP's AN 95-1 defines some powers. Assume an
impedance discontinuity in a transmission line, e.g. where 50 ohm
coax interfaces with 300 ohm twinlead aka G5RV style:

|a1|^2 is the power incident on the input of the network
|a2|^2 is the power incident on the output of the network
|b1|^2 is the power reflected from the input port
|b2|^2 is the power reflected from the output port

If we take the equation, b1 = s11*a1 + s12*a2 and square it
we get |b1|^2 = |s11*a1|^2 + |s12*a2|^2 + 2*s11*a1*s12*a2

This takes the form of Dr. Best's equation Ptot = P1 + P2 + 2[sqrt(P1)*sqrt(P2)]
in his QEX article which is also the form of Hecht's irradiance equation in _Optics_
which is: Itot = I1 + I2 + 2*sqrt(I1*I2)

In optics, 2*sqrt*I1*I2) is known as the "interference term". It's
pretty obvious that 2*s11*a1*s12*a2 is that same interference term
in an s-parameter analysis of RF waves. It follows that what happens
at a Z0-match point in a transmission line involves destructive and
constructive interference.

What?
--
73, Cecil http://www.qsl.net/w5dxp



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