We can show that the reflectance and transmittance of the yielding termination are power complementary. That is, the reflected and transmitted signal-power sum to yield the incident signal-power.
The average power incident at the bridge at frequency
can be
expressed in the frequency domain as
.
The reflected power is then
. Removing the minus sign, which can be
associated with reversed direction of travel, we obtain that the
power reflection frequency response is
, which
generalizes by analytic continuation to
. The power
transmittance is given by
which generalizes to the
Finally, we see that adding up the reflected and transmitted power yields the incident power: