A new open resonator method for the measurement of dielectric permittivity and loss tangent of low absorbing materials at 60 GHz

An open resonator system is constructed for the measurement of real and imaginary part of complex dielectric permittivity and the loss tangent of low absorbing materials at 60 GHz. A full cavity length variation technique was employed. The cavity length of the Fabry-Perot hemispherical open resonator was varied in small steps (20 nano meters) to record the resonance mode patterns for a number of modes. It is no longer necessary to have any expensive tunable frequency source as the fine frequency tunability is substituted with the cavity length variation in ultra fine steps. The cavity length variation method has an additional advantage since it provides less noise in the resonance interferogram as a function of the cavity length compared to the equivalent interferogram recorded as a function of fine frequency sweeping. The measurements are made on a number of fused silica and polymeric specimens and dielectric permittivity and loss tangent results are compared with other published results.