A hybrid probe-tip calibration for multiport vector network analyzers

This paper details the first commercial implementation [1] of a hybrid multiport vector network analyzer (VNA) calibration method suited to a probing environment. The new calibration method implements the enhanced Line-Reflect-Reflect-Match with automatic determination of load inductance [2]-[5] for a number of straight thru paths to fully determine all directivity, reflection tracking, and source and load match terms as well as the associated transmission tracking terms. The remaining transmission tracking terms are found from the use of an unknown but reciprocal thru structure using a process similar to that of the SOLR [6]-[7] calibration algorithm. Combining the LRRM and SOLR algorithms creates a robust, hybrid calibration method that is insensitive to the normal variation in one-port standard behavior associated with normal probe-placement variability [8]-[9]. The hybrid calibration is also insensitive to the inherently non-ideal thru behavior of coplanar waveguide bends or loop-back structures [10].