Improvement of LISN Measurement Accuracy Based on Calculable Adapters

The line impedance stabilization network (LISN) is mostly used in electromagnetic compatibility (EMC) for conducted and radiated radio frequency emission and susceptibility tests. The input impedance is one of the most important parameters in LISN calibration. To measure the input impedance, an adapter is required to connect the vector network analyzer to the equipment under test port of the LISN. For EMC test laboratories, it is of best interest to perform this calibration with high accuracy. Until now, the impact of the adapter used has not been clearly demonstrated theoretically. This paper explains the magnitude and phase impedance errors caused by the adapter. Theoretical and practical methods for the elimination of generated error are given. We present the design of two sets of adapters and their associated modeling, a method for removing their impact from the measurement, the theoretical error on magnitude and phase input impedance, and the uncertainties related to the impedance measurement.