This paper focuses on underwater wireless power transfer with electric coupling. First, the maximum available efficiency is derived by using the S-parameters of the parallel plate coupler. The frequency which represents the maximal value of the efficiency is revealed. Further, the elevation in the efficiency in association with a reduction of the electrode size is found. It is clarified that the elevation depends on the characteristic of the water dielectric loss. From these results, the optimal electrode size that obtains the maximal value of the efficiency is provided. Finally, we fabricate the couplers by utilizing the optimal frequency and the electrode size. The efficiency of 75.8% under water is achieved.

Anisotropic dielectrics and ferromagnetic materials are widely used in dispersion-engineered metamaterials. For example, nonreciprocal magnetic photonic crystals (MPhCs) are periodic structures whose unit cell is composed of two misaligned anisotropic dielectric layers and one ferromagnetic layer and they have extraordinary characteristics such as wave slowdown and field amplitude increase. We develop an unconditionally stable complex-envelop alternating-direction-implicit finite-difference time-domain method (CE-ADI-FDTD) suitable for the transient analysis of anisotropic dielectrics and ferromagnetic materials. In the proposed algorithm, the perfectly-matched-layer (PML) is straightforwardly incorporated in Maxwell's curl equations. Numerical examples show that the proposed PML-CE-ADI-FDTD method can reduce the CPU time significantly for the transient analysis of anisotropic dielectrics and ferromagnetic materials while maintaining computational accuracy.

This study mainly involved examining a high-directivity radiation system with spherical dielectric resonator as pseudo multipole source. The method of spherical wave expansion is focused on wherein the plane wave that is infinitely spread can be radiated from or absorbed by multipoles at the origin. It is not possible to explain this phenomenon by Huygens' principle, which is a basic principle of aperture antenna theory. Thus, in the study, a high-directivity beam design is proposed by synthesizing spherical waves. The directivity of the synthesized spherical wave corresponds with the angular momentum and angle, which is an uncertainty relation different from that of the aperture source. The estimation of the effective aperture of the synthesized spherical wave indicates that the wave intrinsic source is assumed to exist at the surface of the cutoff region. Finally, the results reveal that a radiation system without a singular point can be composed using a spherical dielectric resonator. The study discusses the potential of a high-directivity radiation system constructed by a multi-mode degenerate spherical dielectric resonator as a pseudo multipole source.

A miniaturized and bandwidth-enhanced implantable antenna is designed for wireless biotelemetry in the medical implantable communications service (MICS) frequency band of 402-405MHz. To reduce the antenna size and enhance the available bandwidth with regard to the reflection coefficients, a meandered planar inverted-F antenna (PIFA) structure is adopted on a dielectric/ferrite substrate which is an artificial magneto-dielectric material. The potential of the proposed antenna for the intended applications is verified through prototype fabrication and measurement with a 2/3 human muscle phantom. Good agreement is observed between the simulation and measurement in terms of resonant characteristics and gain radiation patterns; the bandwidth is enhanced in comparison with that of the ferrite-removed antenna, and antenna gain of -27.7dB is obtained in the measurement. Allowances are made for probable fabrication inaccuracies and practical operating environments. An analysis of 1-g SAR distribution is conducted to confirm compliance with the specific absorption rate limitation (1.6W/kg) of the American National Standards Institute (ANSI).

A broadband approach to estimate the relative permittivity of dielectric cuboids has been proposed for materials of weak frequency dispersive characteristic. Our method involves a numerical iterative scheme with appropriate initial values carefully selected to solve for the relative permittivity in a wide range of frequencies. Good agreements between our method and references have been observed for nylon and acrylic samples. An applicable range relation between the minimal thickness, the frequency range and the dielectric property of the material has also been discussed.

Microwave heating is expected to increase the yield of product, to decrease the reaction time, and to discover the new reaction system. The Rolling Circle Amplification (RCA) is an enzymatic synthesis method of deoxyribonucleic acid (DNA) strands with repeated sequence of a circulate template-DNA. In previous study, controlled microwave heating accelerated the maximum 4-fold compared with the conventional condition. Further, we indicated that the selectively heat of some buffer components by microwave irradiation induced the acceleration of RCA. The purpose of this research is to clarify the relationship between the microwave heating and buffer components. The understanding of role of ion-containing buffer components under microwave will be able to control the microwave-assisted enzymatic reaction. We studied the relation between the microwave power loss and RCA components via dielectric measurements, cavity resonator feature measurement, and electromagnetic simulation. Electromagnetic simulation of the TM010 cavity showed that the sample tube was heated only by an electric field. The buffer containing ions of the RCA components was selectively heated via microwave irradiation in the TM010 cavity resonator.

In this paper, we have investigated a new structure which combines dielectric cylinders with air-hole cylinders array, and analyzed the guiding problem for periodically dielectric waveguides by arbitrary shape of dielectric constants in the middle layer. In the numerical analysis, we examined an influence of the dielectric circular cylinder along a middle layer by using the energy distribution and complex propagation constants at the first stop band region compared with hollow dielectric cylinder. In addition, we also investigated the influence of dielectric structure with equivalence cross section compared with dielectric cylinders, and clarified an influence of dielectric structures in the middle layer by energy distribution analysis for TE0 mode.

In this study, to obtain a more accurate analysis of the temperature in microwave coagulation therapy (MCT) for liver cancer, the water content ratios of dehydrated liver tissue and the dependencies of the dielectric and thermal constants of the tissue on the water content ratios were investigated in tissue heated at 2.45GHz. Swine liver tissues were heated and dehydrated under various conditions, and the water content ratios and dielectric and thermal constants were measured. The results indicated that the water content ratio of the tissue depended on the heating temperature and that the dielectric constants (relative permittivity and electrical conductivity) and thermal constants (specific heat and thermal conductivity) of the dehydrated tissues strongly depended on the water content ratio. Based on these results, numerical analyses of the electromagnetic field and temperature inside the liver tissue heated with a coaxial-slot antenna were conducted. Incorporating information on the water content ratio improved the accuracy of temperature calculations in MCT.

Ultra-wideband radar exhibits high range resolution, and excellent capability for penetrating dielectric media, especially when using lower frequency microwaves. Thus, it has a great potential for innovative non-destructive testing of aging roads or bridges or for non-invasive medical imaging applications. In this context, we have already proposed an accurate dielectric constant estimation method for a homogeneous dielectric medium, based on a geometrical optics (GO) approximation, where the dielectric boundary points and their normal vectors are directly reproduced using the range point migration (RPM) method. In addition, to compensate for the estimation error incurred by the GO approximation, a waveform compensation scheme employing the finite-difference time domain (FDTD) method was incorporated. This paper shows the experimental validation of this method, where a new approach for suppressing the creeping wave along the dielectric boundary is also introduced. The results from real observation data validate the effectiveness of the proposed method in terms of highly accurate dielectric constant estimation and embedded object boundary reconstruction.

A high frequency approximation method is proposed to obtain the scattering from rectangular dielectric cuboids. Our formulation is based on a Kirchhoff type aperture integration of the equivalent current sources over the surface of the scattering bodies. The derived formulae have been used to get the radar cross section of cuboids, and the results are compared with those by other methods, such as physical optics, geometrical theory of diffraction, the HFSS simulation and measurements. Good agreement has been observed to confirm the validity of our method.

Microwave ultra-wideband (UWB) radar systems are advantageous for their high-range resolution and ability to penetrate dielectric objects. Internal imaging of dielectric objects by UWB radar is a promising nondestructive method of testing aging roads and bridges and a noninvasive technique for human body examination. For these applications, we have already developed an accurate internal imaging approach based on the range points migration (RPM) method, combined with a method that efficiently estimates the dielectric constant. Although this approach accurately extracts the internal boundary, it is applicable only to highly conductive targets immersed in homogeneous dielectric media. It is not suitable for multi-layered dielectric structures such as human tissues or concrete objects. To remedy this limitation, we here propose a novel dielectric constant and boundary extraction method for double-layered materials. This new approach, which simply extends the Envelope method to boundary extraction of the inner layer, is evaluated in finite difference time domain (FDTD)-based simulations and laboratory experiments, assuming a double-layered concrete cylinder. These tests demonstrate that our proposed method accurately and simultaneously estimates the dielectric constants of both media and the layer boundaries.

A millimeter-wave radar receiver using a z-cut LiNbO3 optical modulator with orthogonal-gap-embedded patch-antennas on a low-k dielectric material is proposed. A millimeter-wave from a reflected radar signal can be received by the patch-antennas and converted directly to a lightwave through electro-optic modulation. A low-k dielectric material is used as a substrate for improving antenna gain. Additionally, an interaction length between millimeter-wave and lightwave electric fields becomes long. As a result, large modulation efficiency can be obtained, which is proportional to sensitivity of the millimeter-wave radar receiver. Optical millimeter-wave radar beam-forming can be obtained using the proposed device with meandering-gaps for controlling interaction between millimeter-wave and lightwave electric fields in electro-optic modulation. Analysis and experimentally demonstration of the proposed device are discussed and reported for 40GHz millimeter-wave bands. Optical millimeter-wave radar beam-forming in 2-D is also discussed.

This paper proposes reflection and transmission control panels using artificially designed materials. As the artificially designed material, finite- and infinite-length metal wire array sheets are used here. Laminated structures consisting of the metal wire array sheets and dielectric material are proposed. Reflection and transmission characteristics of these structures can be controlled by changing the metal wire parameters such as wire length, spacing gaps between the wires, and the dielectric material's thickness and relative permittivity. The reflection and transmission characteristics of the laminated structures are evaluated by measurements in free space and by transmission line theory.

The short-channel effect (SCE) in a MOSFET with an atomically thin MoS$_{2}$ channel was studied using a TCAD simulator. We derived the surface potential roll-up, drain-induced barrier lowering (DIBL), threshold voltage, and subthreshold swing (SS) as indexes of the SCE and analyzed their dependency on the channel thickness (number of atomic layers) and channel length. The minimum scalable channel length for a one-atomic-layer-thick MoS$_{2}$ MOSFET was determined from the threshold voltage roll-off to be 7.6,nm. The one-layer-thick device showed a small DIBL of 87,mV/V at a 20 nm gate length. By using high-k gate insulator, an SS lower than 70,mV/dec is achievable in sub-10-nm-scale devices.

In the scattering problem of dielectric gratings in conical mounting, we have considered and formulated scattering fields using transverse electric (TE) and transverse magnetic (TM) waves. This paper formulates scattering fields by superpositions of right-circularly (RC) and left-circularly (LC) polarized waves through the matrix eigenvalue method.

The effects of the gate dielectrics on ambipolar transport in top-gate-type polymer light-emitting transistors with single-layer and bilayer gate dielectrics are investigated. Hole field-effect mobility is dependent on the dielectric constant of the gate dielectric onto the active layer. Hole transport of devices is affected by the dipolar disorder in the first gate dielectric layer on the active layer. Electron threshold voltage tends to decrease with increasing the total stacked gate capacitance.

Underfill materials are used in a packaging of millimeter wave IC. However, there are few reports for dielectric properties of underfill materials in millimeter wave region. A cut-off circular waveguide method is one of a powerful technique to evaluate precisely complex permittivity in millimeter wave region. This method may be useful not only for low-loss materials, but also for mid-loss ones with loss tangent of 10$^{-2}$ order. In this paper, an evaluation technique based on the cut-off circular waveguide method is presented to measure mid-loss underfill materials. As a result, the relative permittivity $arepsilon_{r}$ and the loss tangent tan$delta$ are in the range of 2.8$sim $3.4 and (1.0$sim$1.6)$ imes10^{-2}$, respectively. Also, the measurement precision is 2.3% for $arepsilon_{r} approx 3$ and 40% for tan$delta approx 10^{-2}$.

In the shadow theory, a new description and a physical mean at a low grazing limit of incidence on gratings in the two dimensional scattering problem have been discussed. In this paper, by applying the shadow theory to the three dimensional problem of multilayered dielectric periodic gratings, we formulate the oblique primary excitation and introduce the scattering factors through our analytical method, by use of the matrix eigenvalues. In terms of the scattering factors, the diffraction efficiencies are defined for propagating and evanescent waves with linearly and circularly polarized incident waves. Numerical examples show that when an incident angle becomes low grazing, only specular reflection occurs with the reflection coefficient -1, regardless of the incident polarization. It is newly found that in a circularly polarized incidence case, the same circularly polarized wave as the incident wave is specularly reflected at a low grazing limit.

The equivalent circuit of aperture-coupled cavities filled with a lossy dielectric is considered by means of an eigenmode expansion technique founded on the segmentation concept. It is different from a series LCR resonant circuit, and the resistor which symbolizes the dielectric loss is connected to the capacitor in parallel. If the cavities are formed by a short-circuited oversize waveguide, then the input admittance can be represented by the product of a coupling factor to the connected waveguide port and the equivalent admittance of the short-circuited waveguide. The transmission line model is effective even if lossy wall effect and dielectric partially-loading effect are considered. As a result, three-dimensional eigenmode parameters, such as the resonant frequency and the Q-factor, become dispensable and the computational complexity for the cavity simulation in the field of microwave heating is dramatically reduced.

The 4 lowest Transverse-Electric modes of a cylindrical Dielectric Resonator Antenna were investigated using a commercially available simulation software. All 4 modes were shown to produce dipole or multi-pole radiation patterns, having Transverse-Electric polarization as opposed to Transverse-Magnetic as with conventional wire antennas. The even numbered modes were shown to be applicable to the niche application of small Unmanned Aerial Vehicles to ground station communications. A practical design for the lowest order even mode was prepared, and successfully demonstrated on a carbon fiber reinforced plastic ground plane. That design was then shown in simulation to have less adverse interaction when installed on a common small Unmanned Aerial Vehicle airframe at the new 5.05GHz telemetry band than an off-airframe dipole.