Tom wrote, "The directional effect can be analyzed using wave theory or
simple
circuit theory. The results are the same."

Of course, "the directional effect" depends completely on having the
sampler calibrated to the impedance of the line into which it's
inserted. Otherwise, it's just resolving "forward" and "reverse"
_as_if_ the signal is in a line that has a characterisitc impedance
equal to the sampler's calibration impedance.

To the extent the samples are accurate for instantaneous currents and
voltages, the sampler does NOT depend on sinusoidal excitation. The
result is accurate for the current and voltage that exist at each
instant in time. Some directional couplers are very broadband; others
are not. We made the ones in the 8753 that Tom uses to be accurate
over a wide frequency range. And of course, if you don't just rectify
the output, you can extract phase information from it as well as
amplitude.

Cheers,
Tom