This paper presents a method of generating a class of equivalent

-port networks for which the open-circuit impedance matrix

remains completely invariant. The networks are generated from an initial network by a congruence transformation of the nodal admittance matrix

of the

-node network from which the

-ports are extracted. The transformation method, the invariance of

, and a method of computing

from

are then used to formulate an efficient iterative procedure for synthesizing resistive networks exactly on a

-tree port structure.