Class of inductive two-ports that includes two-winding coupled inductors

A rigorous and complete analysis of the inductive two-ports that are linear lumped time-invariant, duly-controlled and non-trivial, reciprocally coupled and passive is carried out. It is based on the use of the flux/current transmission matrix, which permits pursuing a straightforward unified investigation. It clarifies some important features concerning the perfect coupling mode of operation, and shows the existence of another mode of operation that in some sense is the counterpart of the perfect coupling one.