Comparison of Three Methods for the Measurement of the Differential Impedance of a Balanced Device [Measurements Corner]

Three methods for the measurement of the differential impedance of a balanced device are evaluated: 1) the S-parameter method, 2) the balun method, and 3) the mixed-mode S-parameter method. An emphasis is given to the choice of combinations of five two-port standards for the balun method. Each of these methods was used to measure the known differential impedance of a broadband balanced load, and the unknown differential impedance of a narrowband balanced microstrip patch antenna. These methods and the obtained experimental results are discussed.