Free-space quasi-optical spectrometer for material characterization in the 50–500 GHz frequency range

A compact free-space setup is designed based on 90-degree off-axis parabolic mirrors and pyramidal horn antennas to cover a wide frequency range from 50 GHz to 500 GHz. A commercial VNA with frequency extenders is used to measure s-parameters and provide raw data to extract intrinsic material characteristics. The calibration process is simplified and a method is presented to extract both real and imaginary part of permittivity. Several materials were measured and the extracted parameters are presented.