On the Exact S-Parameter Measurement of Active Devices

The accuracy of the S-parameter measurements have been analyzed in several publications based on the assumption that the errors can be represented by a 4-port connected between the ideal test set and the device to be measured. Conditions are given under which the 4-port representation is justified. It is shown that for active device measurements both reciprocal and nonreciprocal calibrating elements may be necessary. Further conditions are formulated for the practical case when only reciprocal calibrating elements are available. Based on the theoretical results a calibration and error correction algorithm is presented.