Broadband Permittivity Measurements up to 170-GHz Using Balanced-Type Circular-Disk Resonator Excited by 0.8-mm Coaxial Line

This paper describes the broadband permittivity measurements up to 170 GHz of plate samples by using a balanced-type circular-disk resonator (BCDR) excited by a 0.8-mm coaxial line. Because only the TM
_0m0
modes are selectively excited in the BCDR and their resonant frequencies largely change by changing the size of the circular disk that constitutes the resonator, the BCDR method provides permittivity measurements at an almost arbitrary frequency across a wideband. We have increased the maximum measurable frequency of the BCDR method to 170 GHz by developing a BCDR excited by a 0.8-mm coaxial line and by improving the analysis method. We demonstrated that highly stable and rather simple permittivity measurements up to 170 GHz can be realized by the BCDR method by confirming that the measured complex permittivities of a low-loss material from 11.3 to 167 GHz at 59 frequency points obtained with five circular disks of different radii are consistent within the uncertainties.