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This study demonstrates a novel low-loss dielectric measurement technique that utilizes reflections at the backside of a probe in the millimeterwave frequency range up to 300 GHz. The accuracy of measurement was investigated by evaluating the measurement uncertainty contributors individually. Further, the dielectric dispersion of alumina was calculated from a phonon model. The evaluated dielectric constant and dielectric loss tangent corresponded with values in the accuracy range generated by the phonon model, which was constructed from Fourier transform infrared spectroscopy (FT-IR). These results validated the accuracy of the proposed method in the millimeter-wave frequencies. The measurement technique is expected to be useful for the evaluation of dielectric properties of circuit substrates used in "Beyond 5G" communication technologies.

This paper proposes a breakthrough in-situ dielectric permittivity measurement technique for a circuit substrate with various planar circuits on the substrate. The proposed technique uses a quasi-resonator at the backside of an RF probe, which is contacted at the middle of the feed line of the planar circuits. Dielectric permittivity is calculated using the difference between the resonance frequencies of two measurements with different probe-contact positions. The proposed technique can be used for the feed lines of a matched-transmission line and an attenuator. Therefore, it can be used for the evaluation of circuit substrates with various devices. The proposed technique can realize the in-situ dielectric measurement of circuit substrates, and it is expected to be a powerful tool for the investigation of the defects in practical RF devices because it does not require any resonator for a device under test.

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In this study, we demonstrate the temperature dependence of the dielectric properties of Al 2 O 3 and Ba 2 Ti 9 O 20 ceramics, using a probe-backside reflection (PBR) method, at frequencies range up to 320 GHz. The impact of transmission loss on the dielectric properties was first eliminated from the measured S-parameter values using the original S-parameter values of a transmission line. Although the temperature coefficient of dielectric permittivity was uncertain owing to limitations in the measurement repeatability of the PBR method, those of loss tangents of Al 2 O 3 and Ba 2 Ti 9 O 20 ceramics were calculated as 2.8 × 10 −5 K −1 and 1.1 × 10 −4 K −1 , respectively, for frequencies up to 125 GHz. Furthermore, the temperature coefficient of the dielectric permittivity of Al 2 O 3 was calculated as 691 ppm K −1 at 255 GHz, while those of the dielectric loss tangent at 235 GHz and 275 GHz was calculated as 1.2 × 10 −5 K −1 and 1.5 × 10 −5 K −1 , respectively.

This paper is the first report on transmission loss of screenprinted metallization of transmission lines at frequencies ranging up to 340 GHz. We observed that the printed transmission lines exhibited significantly reduced transmission losses when compared to conventional lines on the commercialized impedance standard substrate (ISS). The conductivity of Ag metallization was considered the reason for this reduced loss. Though degradation of the loss was observed in transmission lines approximately 3 years post fabrication, the printed line retains a smaller loss than conventional lines on the ISS. Further, despite the printed line having inferior production reproducibility, the screen-printed technology was considered to be an improved solution for the fabrication of millimeter-wave circuits, even in the 300 GHz band.