Cecil Moore wrote:

If I understand correctly, Roy's argument is that since
the source is not supplying any steady-state energy to
the lossless stub, there is no energy in the reflected
wave within the stub.

That sounds right... if the reflection coefficient is 1 then there's no
net power flux into/through the line in steady state, and this can be
described if you like by counterpropagating waves each carrying the
same amount of energy.

The problem is, in your other example where you say 200 joules in the
forward wave + 100 joules in the reflected wave = 300 joules in the
line total, you're neglecting the vector character of the power flux.

Yes, the waves carry energy, but they carry it in different directions.
The net power flux in the line with 200W forward power and 100W
reflected power is 100W net power flowing to the load from the source.
The real part of the Poynting vector of the reflected wave opposes that
of the forward wave, as long as I got all the signs right.

I don't think we can neglect the imaginary part of the Poynting vector,
though. It's not zero and I think it represents the flow of the power
in the stored fields in the line, and if we want to get the total
energy in the line, we have to include the stored fields.


Dan