Jim Kelley wrote:
You do understand that interference is the result of the superposition
of waves traveling in the same direction, right?

Of course, there are two superposition terms in each direction
represented by the two S-parameter equations.

b1 = s11*a1 + s12*a2 toward the source

b2 = s21*a1 + s22*a2 toward the load

The two terms in the first equation interfere with each other
toward the source. The two terms in the second equation interfere
with each other toward the load. When b1=0, the system is matched,
and total destructive interference exists toward the source. In
that case, total constructive interference exists toward the load.

Actually, the fact that those equations appear in his book (as well as
just about any other optics book) does not convey any rights of
ownership or invention to the author. They were around a long time
before Dr. Hecht.

Didn't mean to imply that he owns them. "Hecht's equations" simply
means they appear in his book. They were around a long time before
anyone on this newsgroup called them "gobblegook". The interference
equations also appear in Chipman's 1968 "Transmission Lines".

You should show him your equation with all the power terms (P1-P4) in
it! You had some of the powers going one way, and the others going the
other way.

Nope, you are confused. All powers are going the same direction for any
individual equation in my article. Destructive interference energy in one
direction equals constructive interference energy in the opposite direction.
If you will wade through the transient buildup to steady-state of the recent
examples, you won't be confused anymore by direction. During the transient
buildup phase, when the first destructive interference occurs toward the source,
an equal amount of constructive interference energy flows toward the load -
same energy, just flowing in the opposite direction. If destructive
interference energy in one direction equals P3+P4, constructive interference
energy in the opposite direction equals P3+P4 to satisfy the conservation
of energy principle.

Perhaps you are remembering the equation (Pload = Pfor - Pref) where Pfor
and Pref are flowing in different directions. But that equation doesn't
appear in my article.
--
73, Cecil http://www.qsl.net/w5dxp

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