A triple-through method for characterizing test fixtures

Test fixtures for evaluating microwave components usually consist of two unmeasurable sections, each having, for example, one coaxial and one microstrip terminal. A method is proposed for evaluating the S -parameters of these sections through three conventional reflection/transmission measurements. The method is based on the use of an auxiliary two-port. A microstrip standard is not needed, except for a load which is necessary if the SWR (standing wave ratio) of the auxiliary two-port is not low enough. Only one reflection measurement with a load has to be performed on the auxiliary two-port, and even this may be cancelled if the two-port is a transition with low SWR. The method is broadband, frequency-insensitive, and extendable to other media such as waveguide and finline