Cecil Moore wrote:

How does a wave know whether to
carry energy or not depending upon its future fate?

Does a laser beam reflected from an ideal mirror carry any
less energy than the forward beam just because it has been
reflected?

What can be said other than; these questions appear to have been posed
by someone who is struggling to understand some pretty simple concepts.

In a one second long lossless transmission line, watts
equal joules. A forward wave of 200 watts contains 200
joules of energy. A reflected wave of 100 watts contains
100 joules of energy. Under such conditions, the source
has supplied exactly 300 joules more than has been
delivered to the load, no more and no less.

Is your claim that the above describes the system with, or without,
the circulator load?


Yes, in both cases the voltage reflection coefficient
at the load is 0.707 making the power reflection
coefficient = 0.5, i.e. half the power incident upon
the load is reflected.

But, is the latter really more than a mathematical convenience? (You
may recall that 'power' isn't something which actually moves in
physical systems. And being a scalar, it can be tricky to do a proper
vector analysis.) How energy moves is dependent upon factors
throughout the entire system - not just at the load.

The system with the circulator load at the signal
generator has the signal generator supplying 200
watts and the circulator load resistor dissipating 100
watts. 'SGCR' stands for a signal generator equipped with
a circulator and circulator load resistor equal to the
Z0 of the feedline. There's 300 joules of energy in the
feedline during steady-state. 100 watts is dissipated
in the load.

200W SGCR-----one second long feedline-------load
Pfor=200W-- --Pref=100W

The system without the circulator and load consists of
a 100 watt source feeding an ideal autotuner tied to
the transmission line. In this case all reflected energy
is re-reflected by the Z0-matched autotuner. 'SGAT' stands
for a signal generator equipped with an ideal autotuner.
There's 300 joules of energy in the feedline during
steady-state. 100 watts is dissipated in the load.

100W SGAT-----one second long feedline-------load
Pfor=200W-- --Pref=100W

Very inventive. The question was posed without a load on the
circulator, not without a circulator. You still haven't answered that
question. Perhaps you wouldn't mind just considering one system at a
time. No sense changing the variables just to make the solution come
out the way we want. Don't they teach you that you're not supposed to
change horses in the middle of a stream out there in Texas? ;-)

So, since we've obviously been talking about the steady state, what's
with all the weird questions about 'how the wave knows' what's going
to happen in the future?

73, ac6xg