In my vision, there are two different concepts that should not be confused or mixed (but can be combined, as we will see):
a) The meaning of the term immitance, in reference to a magnitude that can be impedance or admittance. It is used for example in these situations:
- the NIC (negative immittance converter), a circuit that transforms an impedance Z into -Z*Kz, conversely an ammittance Y into -Y*Ky
- working with Smith charts, the chart can be used as an impedance or an admittance chart. The case depends whether you have parallel or serial components, and the change between one and the other is immediate.
b) Normalized impedances or admittances, that are dimensionless because they are referred to a specific reference value.
My conclusion about immitance: "Immitance" is a wildcard that can replace both "impedance" and "admittance". It is a useful and nonambiguous concept.
The original post combines the two aspects, a) and b), in "normalized immitance".
Regards
Z