Two-Tier Multiline TRL for Calibration of Low-Cost Network Analyzers

We compare calibrations for use on three-sampler vector network analyzers (VNAs), which do not allow the direct application of some advanced error-correction schemes such as TRL (thru-reflect-line). Here we compare various alternatives, including an approximate version of TRL that has been introduced commercially and two-tier multiline TRL using external software. We consider both coaxial and coplanar open-short-load -thru (OSLT) calibrations for the first tier, showing that the latter can lead to inaccuracies. Finally, we investigate the stability of the load reflection terms to show that the first tier calibration need not be frequently repeated.