The measurement of arbitrary linear microwave two-ports

The measurement of the scattering parameters of linear but otherwise arbitrary two-ports (active, lossless or dissipative, and reciprocal or non-reciprocal) by means of an interference bridge is described. Since the measured data form circular loci from which the parameters are then derived, known precision curve-fitting techniques are applicable. The various methods available for distinguishing the proper locus from its inverse are discussed. Various methods of balancing the bridge and many of the errors associated with bridge balancing are given. Finally, the deliberate use of bridge imbalance for increasing measurement accuracy is considered.