Accurate phase measurement of passive non-reciprocal quasi-optical components

A method for accurate measurement of the phase of passive non-reciprocal quasi-optical components is presented. The measurements are performed using a two-port free-space measurement system that is composed of two horn-fed axially aligned lenses calibrated using a through-reflect-match (TRM) technique. The proposed method for accurate phase measurement consists in measuring the component twice, i.e. once facing the first port and then facing the second port. A simple relationship is derived between the phase at the desired location, recorded phase values and the phase due to the thickness of the sample. The method was verified by measuring two different structures at Ka band, i.e. a polarisation-sensitive frequency-selective surface (FSS) and a multilayer isotropic dielectric sample. Another method requiring two identical components is used to measure the phase of the reflection coefficient based on a Fabry–Perot interferometer (FPI) architecture. Neither time-domain gating nor data smoothing were applied to the results. The S-parameter magnitude and phase results are in good agreement with simulations.