Design and calibration of a compact quasi-optical system for material characterization in millimeter/sub-millimeter wave domain

A compact spectrometer setup based on conventional rectangular horn antennas and two symmetrical parabolic mirrors is designed to provide a plane wave on the material-under-test. A commercial Vector Network Analyzer (VNA) and waveguide frequency extension units are used to measure the scattering parameters. A simple practical calibration process is used to determine the S-parameters on the material surface without need of high-cost micrometer positioners. Several materials are measured and the complex permittivity is presented.