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.(F.17) leading to
in Eq.(F.19).
Toward this goal, let
denote the parallel combination of all admittances connected to the junction. Then by Eq.(F.21), we have
and the result is verified.