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9. Graphene transparent antennas

Author

Koh, Shinji, primary, Kosuga, Shohei, additional, Suga, Ryosuke, additional, Nagata, Shunichiro, additional, Kuromatsu, Sho, additional, Watanabe, Takeshi, additional, and Hashimoto, Osamu, additional

Published
2023
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18. Analytical study on change of temperature and absorption characteristics of a single-layer radiowave absorber under irradiation electric power

Author

Suga, Ryosuke, Hashimoto, Osamu, Pokharel, Ramesh K., Wada, Kouji, and Watanabe, Shinya

Subjects
Radio waves -- Analysis, Electric waves, Electromagnetic radiation, Electromagnetic waves, Business, Computers, Electronics, Electronics and electrical industries
Abstract

Radiowave absorbers are frequently used in high power applications, such as radar sites, and the rise of temperature of the absorber has often become a matter of concern. In this paper, the finite-difference time-domain (FDTD) method combined with the heat transport equation (HTE), also known as the FDTD-HTE method, which has been widely used in the analysis of microwave heating or temperature increase in the human head due to portable phones, is used in the analysis of the wave absorption characteristics of a single-layer wave absorber. The complex permittivity of a sample made of epoxy resin, measured by a cavity-resonator method when the sample is irradiated by a high power field for different irradiation times, is used in the analysis, and the wave absorption characteristics of the absorber under investigation highly depend on the input power and irradiation time of the high power field. Index Terms--Electromagnetic heating, finite-difference time-domain heat transport equation (FDTD-HTE) method, relative permittivity measurement, temperature rise, wave absorber.

Published
2005

28. Characterization of contact properties at interface between metal and graphene up to 15 GHz.

Author

Kosuga, Shohei, Suga, Ryosuke, Watanabe, Takeshi, Hashimoto, Osamu, and Koh, Shinji

Abstract

The contact properties between metal and monolayer chemical vapor deposition (CVD) graphene were investigated. Coplanar waveguides (CPWs) composed of CVD graphene‐based signal lines and Au‐based ground lines were fabricated. The S‐parameters of the CPWs were experimentally measured from 1 to 15 GHz. The contact properties were analyzed using a lumped component‐based equivalent circuit model, which consists of the experimentally determined parallel contact resistance and the parallel contact capacitance. The calculated S‐parameters of the model roughly agreed with the measured ones, which indicated that the model was suitable for analyzing the contact properties between metal and graphene up to 15 GHz. Because the impedance of the contact capacitance (4.8 × 10−3 Ω) was four orders of magnitude lower than that of the contact resistance (50 Ω) at 15 GHz, the current flow was more capacitive and efficient than that in the DC band. The ratio of power consumption and power storage in the microwave band to the total power consumption in the DC band decreased with increasing frequency and increasing contact capacitance. Therefore, higher contact capacitance is preferable in designing microwave devices with a metal/graphene‐based feeding structure, such as antennas and transmission lines. [ABSTRACT FROM AUTHOR]

Published
2021
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