Understanding the residual waveguide interface variations on millimeter wave calibration

Calibration is essential in obtaining accurate Vector Network Analyzer (VNA) measurements. Often, it is taken for granted that millimeter wave waveguide calibration is a simple, straightforward process as those in the RF & microwave waveguide calibration or in the coaxial calibration. This paper provides a better understanding of the “residual” or “non-ideal” waveguide aperture interface that often obfuscates a valid, repeatable, Thru-Reft-Line (TRL) and/or Line-Reft-Line (LRL) calibration of a two-port waveguide millimeter wave VNA system. WR05 and WR03 waveguide band data are presented.