Proposed S‑Parameter Method to Measure the Voltage Division Factor of a LISN

The voltage division factor (VDF) of a line impedance stabilization network (LISN) is also known as LISN insertion loss (LISNIL). LISNIL is defined differently than the usual RF insertion loss parameter; hence, VDF is measured using a unique setup with a three-port coaxial T-connector. We describe and propose an S-parameter-based method of measuring VDF. Using this method, VDF can be measured simultaneously with LISN input impedance by acquiring both forward S-parameters and performing a simple calculation. We derive model equations based on ideal instrumentation and show the equivalence of the two methods. Comparative measurements performed on representative LISNs experimentally confirm the mathematical equivalence. In the second article of this three-part series, we calculate the errors due to the actual, non-ideal adapters needed to perform the measurements, present measurement-based models of the input adapter, and analyze a significant phase-to-amplitude conversion error mechanism. In the third article, we derive complete model equations based on actual, non-ideal instrumentation, then compare errors and uncertainties. Here, we show that the T-connector method is redundant during LISN calibrations.