Cecil Moore wrote:
K7ITM wrote:
No, it's about practicality. Convince me that calculations based
primarily on power (or energy) rather than on voltage and current
offer me something useful, with respect to TEM lines, and I might have
a closer look at them.

Assume you are dealing with light waves in free space
instead of RF waves in a transmission line. Would you
then find intensity (power density) calculations useful?
That's why optical physicists find them so useful.

Tom, are you familiar with an s-parameter analysis?

If so, it seems to me that b1 = s11(a1) + s12(a2) = 0
represent two wave components that immediately cancel
to zero when superposed at the impedance discontinuity.
Would you care to comment?

Cecil,

Most serious calculations by optical physicists are done through
Maxwell's Equations solvers. Intensity calculations are utterly
inadequate for exploring the details of high resolution imaging, for
example.

73,
Gene
W4SZ

Gene Fuller wrote:
Most serious calculations by optical physicists are done through
Maxwell's Equations solvers. Intensity calculations are utterly
inadequate for exploring the details of high resolution imaging, for
example.

All that may be true, Gene. But don't Maxwell's
equations obey the superposition principle?
What does Maxwell say happens when we superpose
two EM waves out of phase such that destructive
interference occurs? What does Maxwell say
about the energy "lost" to destructive
interference? Where did it go?

Are intensity calculations utterly inadequate
for exploring the details of low resolution
transmission lines? :-) If the intensity
(power) calculations enumerated in the s-
parameter analysis description are utterly
inadequate, why are they used so often?
--
73, Cecil http://www.w5dxp.com

Cecil Moore wrote:
Gene Fuller wrote:
Most serious calculations by optical physicists are done through
Maxwell's Equations solvers. Intensity calculations are utterly
inadequate for exploring the details of high resolution imaging, for
example.

All that may be true, Gene. But don't Maxwell's
equations obey the superposition principle?
What does Maxwell say happens when we superpose
two EM waves out of phase such that destructive
interference occurs? What does Maxwell say
about the energy "lost" to destructive
interference? Where did it go?

Are intensity calculations utterly inadequate
for exploring the details of low resolution
transmission lines? :-) If the intensity
(power) calculations enumerated in the s-
parameter analysis description are utterly
inadequate, why are they used so often?

Cecil,

Changing the topic again? So soon?

You made a claim about optical physicists. I pointed out that your claim
is simply not correct. You then start babbling about low resolution
transmission lines. What a surprise!

You seem to be going back and forth about the utility of bringing optics
into the discussion on antennas and transmission lines. I doubt that
many here would expect different physical principles to apply to the two
wavelength regimes. I wonder if there might be a practical reason why
the preferred computational techniques are somewhat different?

The physics does not change, but the mathematical convenience does
change. Yes, that seems to be a recurring theme from me.

8-)

73,
Gene
W4SZ

Gene Fuller wrote:
Changing the topic again? So soon?

No, just asking questions, Gene, like any grasshopper
worshiping at the feet of a guru is supposed to.
Please stop avoiding the questions with non-technical
diversions.

Do Maxwell's laws abide by the superposition principle?
It is a question with a simple yes/no answer. If they
do abide by the superposition principle, the forward
wave and reflected wave can be analyzed separately
and then superposed. Every individual wave component,
e.g. s11(a1), s12(a2), s21(a2), and s22(a2) can be
analyzed separately and then superposed. What do you get
when you apply Maxwell's equations to s11(a1)? Hopefully,
the same voltage, current, and energy as any other valid
analysis. If not, there's a distinct problem that needs
to be solved.

You made a claim about optical physicists. I pointed out that your claim
is simply not correct.

And I asked you to explain why it is not correct and
you very carefully avoided answering. One wonders why.

I doubt that
many here would expect different physical principles to apply to the two
wavelength regimes.

My point exactly, Gene. The two fields should agree in
every way (except lingo). If you switch from voltage and
current to EM fields, nothing should change. But when you
admit that, you are forced to admit that voltages and
currents associated with EM waves are bound by a set of
restrictions, one of them being that they must at all
times, travel at c(VF) and cannot, by definition, stand
still as long as they exist as EM waves.

Intensity, irradiance, and Poynting vectors are just
different names for the same physical phenomenon. To
assert that power density in a transmission line doesn't
obey the same rules as light intensity is just nonsense.
The energy content of component waves has been known for
decades in the field of optics and it applies just as
well to RF waves as it does to light waves.

The physics does not change, but the mathematical convenience does
change.

My point exactly! No matter what the mathematical convenience,
(except for the lingo) the two fields should agree in every way.
When they appear to disagree, there is a contradiction somewhere.
Seems to me, in the quest to fit EM waves into the voltage and
current mold, some have forgotten that EM waves are not DC.
--
73, Cecil http://www.w5dxp.com