Keith Dysart wrote:
Can you make this all work for a pulse, or a step
function?

Please reference a good book on optical EM waves
for a complete answer. It is *not me* making it work.
It is a body of physics knowledge that has existed
since long before you were born. It should have
been covered in your Physics 201 class. That you
are apparently unaware of such is a display of
basic ignorance of the science of EM waves.

The basic theory applies specifically to coherent
waves (which are the only EM waves capable of truly
interfering). CW RF waves are close enough to ideal
coherency that the theory works well. It would no
doubt work for a coherent Fourier series as well
but I don't want to spend the time necessary
to prove that assertion.

How do you compute
Ptot = Ps + Pr + 2*SQRT(Ps*Pr)cos(A)
for a pulse or a step?

The above equation applies to coherent signals.
It is known not to work when the signals are not
coherent because the angle 'A' never reaches
a fixed steady-state value.

Or is your approach limited to sinusoids?

Again, it is not *my* approach and is described in any
textbook on "Optics" including Hecht and Born & Wolf.
--
73, Cecil http://www.w5dxp.com