New Interference Technique for Determination of Low Loss Material Permittivity in the Extremely High Frequency Range

In this paper a new interference technique for material permittivity determination in the extremely high frequency range using a vector network analyzer is described. The novelty of this technique is the absence of a reference interference channel and there is no need to rotate the experimental sample that simplifies the measurement process and increases its accuracy. In order to approve this technique, the respective experimental setup was designed. The setup structure and theoretical background of interference fringe minimum formation were described. Based on the quasi-optical principle of the setup operation, the formula for the calculation of the material permittivity was derived. Two different dielectric materials were subjected to test measurements using the created experimental setup. Obtained average values of permittivity in the 50÷70 GHz range are ε = 10.67 ± 0.09 and ε = 2.35 ± 0.03 for sapphire and optical glass, respectively. For the purposes of result verification, the time-domain processing technique was also applied to calculate the permittivity of these materials. Besides, the obtained data are compared with those reported in the literature.