In this paper, we demonstrated a quasi-optical method for extracting electromagnetic parameters of materials in free space. This contactless and non-destructive method shows the great value and significance in detecting the materials that is hard to process. The system contains a high-precision vector network analyzer and a quasi-optical system, a pair of high-gain corrugated horn antennas and an off-axis parabolic mirror system for beam shaping and focus controlling of transmitting and receiving electromagnetic waves. The measurement frequency can reach the range of 220GHz~325GHz as the frequency conversion module ZVA-Z325 matches with the vector network analyzer. The scattering parameter matrix of Teflon and a porous ceramics are measured. Fourier transform of the measured signal and time domain gating are used to eliminate multiple reflections and diffraction interference. The complex permittivity of the materials, including the complex permeability and complex refractive index, are derived from classical Fresnel formula. The differences between the results in this experiment and classical THz-TDS measurements in the same frequency range are compared to analyze the errors and make further explanations.

Date Published: 18 November 2019
PDF: 6 pages
Proc. SPIE 11196, Infrared, Millimeter-Wave, and Terahertz Technologies VI, 111961F (18 November 2019); doi: 10.1117/12.2537707

Published in SPIE Proceedings Vol. 11196:
Infrared, Millimeter-Wave, and Terahertz Technologies VI
Cunlin Zhang; Xi-Cheng Zhang; Masahiko Tani, Editor(s)