Physically, the reflection coefficient seen at port is due to an
impedance step from
, that of the port interface, to a new
impedance consisting of the parallel combination of all other
port impedances meeting at the junction. Let
Let's check this ``physical'' derivation against the formal definition
Eq. (N.20) leading to
in Eq. (N.22).
Toward this goal, let
and the result is verified.