A method based on a generalization of the well-known two-port error model and calibration procedure employed by commercially available network analysers is presented to routinely test and measure the scattering (S) matrices of the multijunctions that build up lower-hybrid (LH) antennae. It accounts for the systematic errors inherent to microwave (mW) measurements, which appear as error coefficients determined via calibration standards, and it allows for any number of ports and for the use of adaptors between the measuring system and the device under test. Once the calibration is completed, the whole S-matrix of a LH multijunction, considered as a multiple-port mW device, can be swiftly and reliably measured.