Evaluation of Measurement Uncertainties Caused by Common and Cross Modes in Differential Measurements Using Baluns

Two-port vector network analyzers can be used for measuring differential circuits by integrating baluns. However, due to the imperfection of the baluns, measurement uncertainties occur even under the most accurate calibration conditions. These uncertainties are caused by the common and cross modes of the baluns and the device-under-test. This paper proposes a new algorithm, which evaluates these measurement uncertainties, by using a few sets of assumptions that can approximately correspond to the worst conditions in which the common and cross modes maximally affect the measurements. The proposed algorithm can be used in post measurement processes by which the users can be informed of their measurements´ uncertainties.