A High-Resolution Quasi Optical Spectrometer for Complex Permittivity and Loss Tangent Measurements at Millimeter Wavelengths

This paper presents for the first time a high power free space dielectric measurement technique to evaluate the complex dielectric permittivity and loss tangent of solid dielectric materials at millimeter waves. This new method enables us to obtain broad band high-resolution transmittance spectra at extended V-band (40 -90 GHz) using a quasi-optical free space spectrometer equipped with a new extended V-band backward-wave oscillator as a high power tunable source of coherent radiation. Due to the sufficiently strong energy throughput in the transmission and a very fine frequency sweep step of the measurement, this instrumentation is superior in obtaining reliable complex permittivity and loss tangent data with great stability and reproducibility over a much broader millimeter wave frequency range. Dielectric permittivity and loss tangent measurement results are reported for a variety of materials and compared with previously published data.