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This paper proposes a design method of a circular patch array absorber for oblique incidence by using an equivalent circuit with a transformer. In the equivalent circuit with the transformer, a matching angle of the absorber can be determined by using the winding ratio of the transformer. Hence, a calculation model for obtaining an arbitrary winding ratio of the transformer by using an arrangement period (winding ratio model) is developed. The winding ratio calculated by using the developed model is agreement in with that of simulated by using an electromagnetic (EM) simulator. The absorbers for 30 $^\circ$ and 45 $^\circ$ at 5 GHz are designed by using the developed model, and the incident angle characteristics of the designed absorbers are measured. As the result, the measured and the simulated matching angle are agreed within 5 $^\circ$. Therefore, the validity of the proposed method is indicated. [ABSTRACT FROM AUTHOR]

A small package suitable for the mobile terminals of the 60-GHz wireless personal area network is proposed. Two antennas for Tx and Rx are integrated in the package. The antenna provides the end-fire radiation from the side face of the substrate. The package is mounted on the edge of a printed circuit board by using the ball grid array assembly. The antenna is composed of a post-wall waveguide and a slab waveguide with metal sidewalls. The gain and beamwidth are determined by the size of the slab waveguide. The sidewalls are for the design of the beamwidth in the H-plane and for realizing the high isolation between Tx and Rx antennas. The beamwidths of the fabricated antenna were measured to be 47° and 46° in the E- and H-plane at 60 GHz, respectively. The gain more than 7.8 dBi was measured in the frequency range from 59 to 66 GHz. The package was fabricated for the evaluation of the isolation. The measured average isolation level between Tx and Rx antenna was 46.0 dB in the frequency range above. The antenna characteristics and isolation level are sufficient for the 60-GHz WPAN system. [ABSTRACT FROM AUTHOR]

This paper proposes a cost-effective antenna package suitable for the mobile terminal of the wireless file-transfer system. The antenna package provides the end-fire radiation from the open-ended post-wall waveguide built into the side of the package. The antenna package, in which a 60-GHz CMOS chip is attached, is mounted on the edge of a printed circuit board by the ball-grid-array assembly. The fabricated antenna, to be built in the package, had the size of \ 4.8 mm\times \ \ 6.4 mm\times \ \ 1.0 mm. The beamwidths of 120^\circ (E-plane) and 72^\circ (H-plane) and the gain of 2.2 dBi were measured at 60 GHz. The cost-effective antenna package with two antennas for the transmitter (Tx) and the receiver (Rx) was fabricated. The isolation between the Tx and Rx antenna was measured to be greater than 36 dB in the frequency range of 59–66 GHz. Moreover, the antenna with higher gain required from the system was fabricated. The gain of 6 dBi in the range of 58–68 GHz was measured. The beamwidth of 60^\circ (E-plane) and 30^\circ (H-plane) at 60 GHz were measured, respectively. [ABSTRACT FROM AUTHOR]

When foods are sterilized by heating in the industrial microwave oven, uneven heating takes place inside the heated foods. This causes inadequate sterilization and deterioration of foods. In this paper, we analyzed temperature distribution of a food inside the industrial microwave oven. Parallel finite-difference time-domain method and heat transfer equation are applied to the temperature analysis. As a result, the trend of the temperature distribution inside the food is explained. And, it is confirmed that temperature rise at the edge of the cup is reduced by arranging water film around the food. Basic data for uniform heating of foods is provided. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 518–521, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22177 [ABSTRACT FROM AUTHOR]

Abstract: This paper presents estimation technique using the Kalman filter finite-element method (KF-FEM). The Kalman filter is employed frequently for the solution of time series analysis including the observation and the system noises. The finite-element method (FEM) approximates the physical phenomena by the differential equations. KF-FEM is the combination method of the Kalman filter and the finite-element method and is capable of estimating not only in time but also in space. The Onjuku coast is analyzed to obtain the performance of the present method. [Copyright &y& Elsevier]

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. [ABSTRACT FROM AUTHOR]

In this study, the relative complex permittivity of an epoxy resinous material is measured under changes in temperature. The temperature distribution of a single-layer radiowave absorber is analyzed using the FDTD-HTE method with measured relative complex permittivity, and then the irradiation electric power's temperature change inside the absorber is calculated. As a result, it is observed that the temperature inside the absorber increases rapidly, so that the irradiation electric power is high, and that the temperature of the absorber increases to 170°C after the irradiation during 120 min under the irradiation electric power with 1000 W/m². It is found that the absorption characteristics of the absorber vary rapidly when they are calculated using the abovementioned analytical result. [ABSTRACT FROM AUTHOR]

The radiation properties of a graphene‐based optically transparent half‐wavelength dipole antenna in microwave bands was investigated. The resonance frequencies of a reference Au antenna and a graphene antenna having the same antenna structures were 9.5 and 21.6 GHz, respectively, owing to the difference in conductivity. Despite the low conductivity of graphene, the gain of the graphene antenna was 1 dB higher than that of the Au antenna. We also showed the feasibility of using graphene‐based optically transparent antenna through the measurements of transmission characteristics between two graphene antenna. [ABSTRACT FROM AUTHOR]

Graphene has been investigated as a transparent conductive film for use in a variety of devices, and in recent years it has shown promise for use in millimeter-wave devices as 5G technology. In this study, we applied single-layer (SL), triple-layer (3L), and P-type doped 3L graphene to coplanar waveguide (CPW) transmission lines and obtained transmission characteristics (S21) from 1 to 50 GHz, which covered the 5G band. Furthermore, an equivalent circuit model of the CPW used in the measurements was constructed and simulations were performed, which showed good agreement with the measured results. The results validated the transmission properties of the graphene and the contact impedance at the interface between electrodes and the graphene in CPW circuits, which are necessary parameters for designing antennas using graphene. In addition, by comparing the transmission loss of three types of graphene, the parameters for improving the transmission characteristics were clarified. [ABSTRACT FROM AUTHOR]

A semisolid human-body phantom for simulating the steady-state temperature elevation at the skin surface due to exposure to millimeter waves (MMWs) and quasi-MMWs was developed in this article. The phantom was designed by optimizing the electric constants of a mixed material consisting mainly of water and glycerin. First, the empirical equation of the complex permittivity of the phantom with respect to the composition and frequency was derived from dielectric measurements of phantoms. Then, the phantom composition used to obtain the temperature elevation equivalent to skin exposure were optimized using a computational approach. Here, the phantom composition was optimized at frequencies ranging from 10 to 100 GHz. In addition, we found that a single composition can be used for frequencies from 20 to 100 GHz. This phantom can simulate the temperature elevation due to skin exposure within the variation of the temperature elevation due to the individual differences in human tissue thickness. The developed phantom was validated by thermographic measurement using a horn antenna and an array antenna at 28 and 60 GHz, respectively. The developed phantoms are applicable to the thermal assessment of skin exposure to electromagnetic fields at MMW and quasi-MMW frequencies. [ABSTRACT FROM AUTHOR]

We fabricated an optically transparent monopole antenna using graphene film and investigated the feasibility of the film as an electrode material for antennas. A low sheet resistance (80 Ω/sq) was attained by stacking the graphene films and carrier doping with an ionic liquid. The optical transmittance of the carrier-doped three-layer stacked graphene film was greater than 90%, enabling it to be embedded in highly transparent objects without altering their landscape. Using the monopole antenna structure with a metal ground plane, we measured the reflection and radiation characteristics of the graphene monopole antenna, excluding the contribution from the power feeding components. The radiation efficiency of the graphene monopole antenna, which was measured by the Wheeler cap method, was determined to be 52.5% at 9.8 GHz. Through the measurements of the graphene monopole antenna, we demonstrated that the carrier-doped three-layer stacked graphene film can be used as an electrode material for optically transparent antennas. [ABSTRACT FROM AUTHOR]