Multiline TRL revealed

Abstract

We reveal the techniques underlying actual implementation of the NIST MultiCal software, an evolved, automated implementation of the Multiline TRL (Thru-Reflect-Line) calibration method for vector network analyzers (VNAs). We describe the sequence of events in MultiCal for the Multiline TRL calibration and show how the program operates more like a state-machine than a solver of simultaneous equations. Our report details the steps used in estimating the transmission-line propagation-constant and the VNA correction coefficients.