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Interfaces in nanocarbon materials are highly important, as they determine the properties of carbon-based devices. In terms of carrier and thermal transport properties, the interfacial features are...

An impedance relationship was speculated from the automatic design of the high-efficiency RF-DC conversion circuit. By the measurement, it was found that each of the reactance of the operating impedance of the diode and the input filter are complex conjugates, and the method manufacturing high-efficiency RF-DC conversion circuit was clarified.

Recently, the magnetic coupling wireless power transfer technology has been attracting a lot of attention and is expected to have a wide range of applications in the electrical equipment around us. On the other hand, there have been reports on the application of metamaterials for the purpose of improving antenna gain and suppressing mutual coupling between antennas, and this study aim applying this technique to the magnetic coupling wireless power transfer system. In this paper, a magnetic wall by meta material suitable for a magnetic coupling wireless transfer system is proposed and its effect is demonstrated experimentally.

This paper proposes a far-field estimation system at 28 GHz that does not require a reference signal input to the Antenna Under Test (AUT) by measuring an antenna system in the near-field and in the time domain.

The design method of RF-DC conversion circuits for wireless power transmission is discussed. The extent to which circuit properties can be estimated using convolutional neural networks is discussed in this study. In order to use an automatic design method for circuit design, it is a problem that it takes time for electromagnetic field analysis. It is shown that the proposed method may make it possible to design circuits in a realistic time.

Reduction of solution search time of automatic design of an RF-DC conversion circuit by Genetic Algorithms (GA) is argued in this paper. Accelerating GA by Convolutional Neural Networks (CNN) is proposed. Already simulated circuits’ patterns are learned by CNN and electromagnetic simulation in GA is partially replaced by it. This approach reduces circuit generating time by 90% compared to the general GA design method to generate an RF-DC conversion circuit with the same conversion efficiency.

Microwave components, prototypes of 4×4 transmitting active integrated antenna array(AIAA) and 2×2 receiving array with direction of arrival function operating at the X-band were demonstrated in this paper. For the components of the satellite on-board tracking system, a wideband and high gain low noise amplifier (LNA) as well as the compact planar antenna were fabricated using thin substrates. High isolation between the transmitting signal and the receiving signal was achieved for the good satellite tracking system. Good agreement on measured antenna patterns with the theoretical ones was obtained.

We demonstrated optical imagings of AC magnetic fields. A digital micro-mirror device and a lock-in detection allowed obtaining sub-millimeter resolution images without using magnetic shields. Images of gradient field from a wire suggested its potential to apply for signal-source estimations.

In this paper, we propose a principal color component extraction method that is simply performed by linear color composition (transformation) of R, G, B colors, but its composite coefficients are calculated so as to obtain a noisy-texture-less principal component of RGB color images. Our method is related to principal component analysis (PCA) and edge preserving smoothing by total variation (TV) minimization. The resultant image becomes a principal color component image with the minimum total variation. We show this problem can be formulated as TV minimization on a spherical manifold for a whitened data matrix. Although this spherical constraint is non-convex, it can be solved by using alternating direction method of multipliers (ADMM). As its application, we show the results of text character extraction from ancient wooden tablets, and how our method extracts faint ink characters while reducing wood grain textures. Our method is unsupervised but has performance equivalent to a linear discriminant analysis (LDA) method with user-assisted information.

SUMMARY The lens effect of acoustic waves in a two-dimensional (2D) phononic crystal is studied by numerical simulation based on the finite-difference time-domain (FDTD) method. We calculate the phonon band structure of 2D phononic crystals, consisting of metal/ceramic cylinders placed periodically in water. The lens effect is observed for the far-field wave in phononic crystals with two-layered and graded-index structure. We compare the focal intensity and the energy transmission efficiency in these numerical experiments, and show that a novel energy-transmission device can be designed using phononic crystals. © 2013 Wiley Periodicals, Inc. Electron Comm Jpn, 97(1): 22–27, 2014; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/ecj.11491

In this paper, a transducer that is suitable for the ultrasonic wireless power transmission system is discussed. The transducer is designed based on Mason's equivalent circuit theory, basically. The transducer was developed using design parameters optimized by multiphysics analysis. As a result, it is confirmed that the transmission efficiency is drastically improved to more than 50%. This result suggests that wireless power transmission by acoustic wave is feasible. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 184(3): 27–35, 2013; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.22406

The trend of microwave circuits has been toward highly integrated systems. Most design tools for designing microwave circuits mounted the linear or the nonlinear devices adopt the fundamental circuit theory using the S matrix on the frequency domain. The harmonic balance method is also used to correspond to the nonlinear circuit. Therefore, the effect of the electromagnetic field, for example, a mutual coupling between sub-circuits through the space is almost disregarded. To calculate these circuits included its surrounding electromagnetic field, the finite difference time domain method combined with the equivalent circuit simulation had been presented as the lumped element FDTD (LE-FDTD) method. In general, even if an analytical target is a linear circuit, the FDTD method requires very long analytical time. In this paper, we propose an efficient LE-FDTD method to reduce the analytical time. We investigate its efficiency to compare with the conventional LE-FDTD method or measurements, consequently, it is confirmed that the proposal method requires only at analytical time of 1/10 compared with the conventional method. We also show that the proposal method is able to analyze characteristics of the active integrated antenna (AIA) which are practicably impossible to analyze by using the conventional method.

An examination is made of phased array operation, by injecting signals with different phases into both ends of a coupled microwave oscillator system and controlling that phase, as a system for an active phased array antenna using frequency locking. This system has multiple operating modes, but by causing a slight deviation of only the free-running frequency of the end oscillator from the frequency of the injection signal, mode jumps can be suppressed and the phase difference between the oscillators made large. The effectiveness of this method can be numerically confirmed by finding the conditions for single mode operation with an approximation analysis of the governing equation. Using an active integrated antenna constructed of a patch antenna and serial-feedback FET oscillators, an experiment was performed by scanning the radiation beams of two-, three-, and five-element antenna arrays to demonstrate that the scan range in the radiation direction was extended with single mode operation. © 2007 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 90(4): 34–45, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjb.20293

Active integrated antenna techniques have high potential for giving smaller size, lighter weight, lower cost and higher efficiency, in particular to millimeter-wave circuit-antenna systems. This paper gives a review of active integrated antenna techniques with emphasis on beam steering and retrodirective antenna arrays. Various beam steering operations of integrated antenna oscillator arrays using locking phenomena are presented. Beam steering arrays of such type have the feature that phase shifters are not necessary in the arrays. Arrays with higher harmonic output radiation can enlarge the beam steering range. Arrays of locked active antennas which operate as self-oscillating mixers can be beam controllable receiving antennas.

A technique of selective electroless plating onto PLA-ABS (Polylactic Acid-Acrylonitrile Butadiene Styrene) composite structures fabricated by three-dimensional (3D) printing is demonstrated to construct 3D microwave metamaterials. The reducing activity of the PLA surface is selectively enhanced by the chemical modification involving Sn2+ in a simple wet process, thereby forming a highly conductive Ag-plated membrane only onto the PLA surface. The fabricated metamaterial composed of Ag-plated PLA and non-plated ABS parts is characterized experimentally and numerically to demonstrate the important bi-anisotropic microwave responses arising from the 3D nature of metallodielectric structures. Our approach based on a simple wet chemical process allows for the creation of highly complex 3D metal-insulator structures, thus paving the way toward the sophisticated microwave applications of the 3D printing technology. Published by AIP Publishing.

We design and characterize a two-dimensional sonic crystal (SC) to manipulate the propagation of acoustic waves by numerical simulation based on the finite-difference time-domain (FDTD) method and by ultrasonic measurement. Two types of SC for an acoustic lens effect are studied. One is a homogeneous periodic structure exhibiting negative refraction, and the other has a hetero-structure. Negative refraction behavior in the simulation is good agreement with the experiment in the frequency range around 1.2MHz. We also observe a lens effect for far-field wave in the hetero-structured SC. These results indicate that a novel energy-transmission/harvesting device can be designed using SCs.

A Rectifying Antenna (Rectenna) is one of the most important components for a wireless power transmission. It has been developed for many applications such as Space Solar Power System (SSPS), and Radio Frequency Identification (RFID) etc. The Rectenna consisting of RF-DC conversion circuits and receiving antennas needs to be designed for high conversion efficiency to achieve efficient power transmission. we try to design the mw-Class RF-DC conversion circuit using half-and full-wave rectification. The measured conversion efficiencies is 59.3 % and 65.3 % athalf- and full-wave type, respectively. And the full-wave type has lower 2nd harmonic reflection coefficient.

We developed a fundamental testbed and investigated the suitable transducer for the wireless power transmission (WPT). We also reported experimental results of the transmission efficiency in water by using the commercial transducer (COM) which only designed to match to the acoustic impedance of water and the electric impedance of the transmitter and receiver. In this paper, we investigate the transducer for improving the efficiency based on the Mason's equivalent circuit. For deciding a structure and materials of the transducer, we used ANSYS well-known as the multi-physics simulator. In this result, it is confirmed that the transmission efficiency is drastically improved from less than 1% to 60%. In addition, we made designed transducer, and confirmed the systems' efficiency is about 50 %. This result suggests that the WPT by acoustic wave is practicable.

Recently, various wireless applications have hugely become popular. Especially, mobile terminals such as mobile phones are actively developed. In developments of mobile terminals, miniaturization and frequency multiband of antennas are very important issues. However, there are no rational design strategy in small antenna designs. So, antenna developments depends on electromagnetic simulators or capability of engineer. And many cut-and-try processes are necessary for achieving desired characteristic. This makes many problems such as prolongation of developments. Then, now, automatic design techniques of antenna using genetic algorithm (GA) are paid attention. In this paper, the new design strategy for miniaturization of antennas is proposed by operation of chromosome-length in GA. Proposed design technique provides a minimum area necessary for keeping characteristics of a antenna. And, efficient miniaturization of a antenna and removing many undesirable conductors in a design ares are possible. Removing undesirable conductors provides lower-cost designing of antennas. The new design method can become rational design strategy for antennas miniaturization.

In this paper, a radio frequency to direct current (RF-DC) conversion circuit composed of chip devices is proposed. This circuit has high conversion efficiency as high as the previously proposed circuit, and the circuit size does not depend on the operating frequency.

In this paper, it is shown that reflectivity of a CRLH TL can be completely dispersionless, which means phase responses independent of frequencies. Especially, pseudoperiodic configuration of CRLH transmission lines, proposed in this paper, makes dipersionless responses even in much smaller designs. If the phase of reflectivity (S11) observed at a certain point does not depend on frequency, the input impedance seen from the point also does not, leading to broadband impedance matching. The above electromagnetic property is expected to have effective applications such as microstrip filters, feed networks for antennas.

A Rectifying Antenna (Rectenna) is one of the most important components for a wireless power transmission. It has been developed for many applications such as Space Solar Power System (SSPS), Radio Frequency IDentification (RF-ID), and electric vehicle etc. The Rectenna consisting of RF-DC conversion circuits and receiving antennas needs to be designed for high conversion efficiency to achieve efficient power transmission. In this paper, we investigated the RF-DC conversion circuits by the theoretical analysis. And, we propose the theoretical formula for calculating the output DC voltage in giving the input voltage. The result that is calculated by the formula agreed with the simulator's result, so, we confirmed the validity of the formula we derived. The theory and the formula we derived are useful in order to know the basic operation of the RF-DC conversion circuit, and to design the circuit efficiently.

A Rectifying Antenna (Rectenna) is one of the most important components for a wireless power transmission. It has been developed for many applications such as Space Solar Power System (SSPS), and Radio Frequency Identification (RFID) etc. The Rectenna consisting of RF-DC conversion circuits and receiving antennas needs to be designed for high conversion efficiency to achieve efficient power transmission. In this paper, we try to design the mw-Class RF-DC conversion circuit using full-wave rectification.

By atomistic simulation, we investigate an acoustic wave at THz frequencies in nanoscale thin films of aluminum–nitride piezoelectric material. A mode analysis reveals that the thickness longitudinal mode along the [0001] direction exists stably at the atomic level. To control the acoustic wave, we introduce a phononic crystal (PC) structure in the films. We determine the band-gap frequency in the phonon dispersion of the PC structure and confirm via molecular dynamics simulation that the acoustic wave within the band-gap frequency can be confined by a waveguide structure with a PC. The possibility of designing and controlling a THz acoustic wave in a nanoscale thin film with a PC is thereby demonstrated.

The trend of microwave circuits has been toward highly integrated systems. Most design tools for circuits are based on the fundamental circuit theory using the S-matrix combined with the harmonic-balance method. Consequently, the electromagnetic effect is ignored or approximated at best. Therefore, the extended finite-difference time-domain (FDTD) method combined with the equivalent circuit simulation had been presented. However, it takes very long times to analyze any circuits. In this paper, we propose a novel extended FDTD method to reduce calculation resources. We investigate its efficiency to compare with the conventional extended FDTD method or measurements, consequently, it is confirmed that the proposal method is required calculation resources less than 10% compared with the conventional method. We also show that the proposal method is able to analyze characteristics of the active integrated antenna(AIA) which are practicably impossible to analyze by using the conventional method.

A rectenna is one of the most important components for a wireless power transmission. It has been developed for many applications such as Space Solar Power System (SSPS), and RFID etc. The rectenna consisting of RF-DC conversion circuits and receiving antennas needs to be designed for high conversion efficiency to achieve efficient power transmission. In this paper, the extended FDTD method is proposed as a method for calculating the RF-DC conversion circuit, and the availability of this method is confirmed. Furthermore, the output power from the circuit including the radiation power is investigated.

For applications of the microwave power transmission technology, it is necessary to realize high efficiency rectennas or rectification circuits. Especially, RF-ID's or ubiquitous power sources demand high RF-DC conversion efficiency for below mW microwave inputs. However, almost all past rectennas or rectification circuits were designed for over 100mW rectifying and the RF-DC conversion efficiencies were less than 20% at 1mW microwave input. In this paper, we investigate rectification circuits for developing mW-class rectennas. Discussing diode mount structures in order to increase the efficiency below 10mW microwave input, we succeeded in developing a rectification circuit whose efficiency is 62.8% for a 10mW microwave input. We also find that approximately 30% of the input microwave power is consumed by the diode in the rectification circuit.

In this paper, we conduct propagation measurements focusing on the radiation pattern and the polarization of base station antennas under the line of sight (LOS) and no LOS environments. We measured and investigated propagation characteristics inside them, and we confirmed that propagation characteristics inside passages depend on cross sectional shape and that attenuation coefficient is changed by the radiation pattern and the polarization of the base station antenna.