An automated 60 GHz open resonator system for precision measurement of loss tangent and permittivity

A Fabry-Perot hemispherical open resonator system has been designed and constructed for precision measurement of loss tangent and dielectric permittivity of low absorbing materials at 60 GHz. The resonator system uses a cavity made with optically polished copper spherical and flat mirrors, highly stabilized synthesized phase-locked Gunn oscillator sources, and a superheterodyne receiver to enable measurement of loss tangent values as low as 10 mu rad. Using this system, the real part of the dielectric permittivity can be measured with an accuracy almost as high as that achieved with dispersive Fourier transform spectroscopy. A block diagram of the complete measurement system is presented.<>