Naoki Shinohara

• Doctor of Engineering
• Professor at Kyoto University

This study presents a novel technique to improve axial ratio (AR) of wide-angle scanning phased array. This technique can be applied to phased arrays of reconfigurable dual-polarized circular patch antennas: each antenna element has two feeding channels, with separate variable gain amplifier and phase shifter for each channel. In the proposed techn...

In this paper, a novel pattern and beamwidth reconfigurable cylindrical dielectric resonator antenna (CDRA) is proposed. The pattern reconfigurable structure is achieved by a pair of 3D-printed arc-shaped parasitic metal panels, which are capable of high-gain beam scanning with ±24° in the H-plane and ±18° in the E-plane radiation, respectively, wi...

This study proposes a design method for rectennas that provide high RF–dc conversion efficiency and enhanced second harmonic reradiation levels by employing source-pull simulation with harmonics. Reusing a harmonic generated by a rectenna is an advantageous retrodirective system, because harmonic reradiation can be used as a battery-less pilot sign...

A high gain filtering quasi-Yagi antenna based on compressed third-order mode dipole is presented in this paper. The meander line structure is employed on the dipole to realize the compressed dipole. The current distributions on the meander structure are equal amplitude and out-of-phase to cancel the far-field radiation to realize sidelobes suppres...

The inappropriate power allocation among multiple targets may lead to low power transmission efficiency and thus the waste of available power sources in multi-target wireless power transmission (WPT) system. This letter proposes an efficient method, called the weighted and constrained method of the maximum power transmission efficiency, for the opt...

In this paper, a dual-band polarization-independent terahertz (THz) metamaterial absorber (MA) based on metal-insulator-metal (MIM) configuration is proposed and measured. The flexible material polyimide is chosen as the substrate. The periodic metal array cell on the top surface is fabricated utilizing four F-shaped metal strips, and due to the hi...

This study presents a novel waveguide slot array with a code-division multiplexing function for single RF chain digital beamforming. The proposed antenna is comprised of a rectangular metallic waveguide's bottom part and a multilayer printed circuit board (PCB) with the rectangular waveguide's top wall and slot apertures. Multiple pairs of two symm...

A high-efficiency power-combining method for four-way 5.8-GHz magnetrons based on the external injection-locking technique is presented in this article. The method uses a nonisolated, lossless five-port hybrid waveguide combiner for power combining. Meanwhile, the injection-locking technology has been applied to magnetrons for achieving coherent po...

We introduce an all-dielectric 3-D-printed multifocusing truncated Gutman lens integrated with a high-efficient MMIC class-F load GaAs rectenna for mm-Wave Battery-free IoT applications at 24 GHz in this article. We conduct a detailed analysis of the multifocusing performance of the proposed lens structure using full-wave simulation, revealing the...

We introduce an all-dielectric 3D-printed multi-focusing truncated Gutman lens integrated with a high-efficient MMIC class-F load GaAs rectenna for mm-Wave Battery-free IoT applications at 24GHz in this paper. We conduct a detailed analysis of the multi-focusing performance of the proposed lens structure using full-wave simulation, revealing the va...

A low-cost electrically-switched focused beam charging system based on a reconfigurable phase-change cascaded feed network is introduced for wireless power transfer application. To realize the reconfigurable feed network, we theoretically decomposed the dynamic focusing phase distribution into two independent terms: a linear phase shift and a quadr...

A self-packaged air-filled substrate-integrated waveguide (AFSIW) filtering power divider (FPD) operating at Ka-band with the characteristics of low loss, broadband, high in-band isolation, and sharp roll-off skirt is proposed in this letter. The filtering network is dexterously integrated into the branches of the T-junction, which is simple and co...

This study introduces a novel single-diode rectenna, enhancing the rf-dc conversion efficiency using harmonic control of the antenna impedance. We employ source-pull simulations encompassing the fundamental frequency and the harmonics to achieve a highly efficient rectenna. The results of the source-pull simulations delineate the sourceimpedance ra...

We propose microwave heating via electromagnetic coupling using zeroth-order resonators (ZORs) to extend the uniform heating area. ZORs can generate resonant modes with a wavenumber of 0, which corresponds to an infinite guide wavelength. Under this condition, uniform heating is expected because the resulting standing waves would not have nodes or...

This study investigates the counterintuitive behaviors of a microwave‐induced atmospheric pressure plasma jet (APPJ) under the influence of an external electrostatic field applied by one or a pair of parallel electrode plates subjected to DC voltages. The findings demonstrate that the plasma jet consistently deflects toward the electrode plate with...

This article presents the design and realization of a compact size high-efficiency complementary metal-oxide- semiconductor rectifier with resonance control technique employing the concept of parallel rectifier. The methodology involves the integration of two rectifiers, where one is main rectifier, specifically designated for rectification purpose...

In this paper, we demonstrated a self-bending beam with over-obstacle focusing characteristic by using a single phase-modulated dielectric plate at 28GHz. Unlike conventional near-field focusing, this self-bending over-obstacle focusing offers a promising solution to enhance the efficiency and reliability of WPT systems, particularly in scenarios w...

https://search.ieice.org/bin/summary.php?id=j103-b_11_559

With the advancement in the understanding of plasma discontinuous structures and the progress of related research, numerical methods for simulating plasmas based on continuous medium approach have encountered significant challenges. In this paper, a numerical model is presented to simulate the motion trajectory of an atmospheric pressure plasma jet...

Borrowing the idea of graded-index (GRIN) fiber, we propose an all-dielectric porous structure with unique surface focusing feature to improve the performance of rectenna for mm-Wave WPT applications in this paper. The on- and off-axis focusing properties of proposed structure is analyzed by the full-wave electromagnetic simulation. Moreover, benef...

In recent years, microwave wireless power transmission (MWPT) has emerged as a promising technology for supplying energy by receiving radiative power without wires and converting it into DC power. A high transmission efficiency is crucial for improving the performance of MWPT systems. To address the challenge of propagation loss, beam synthesis usi...

Radio frequency (RF) energy harvesting and wireless power transmission (WPT) technologies —both near-field and far-field—have attracted significant interest for wireless applications and RFID systems. We already utilize near-field WPT products in our life and it is expected that RF EH and far-field WPT systems can drive the future low-power wireles...

In this letter, we propose a reconfigurable series-fed phase-shifting structure with movable metal plate for active millimeter wave beam-scanning application. The proposed phase-shifting structure can be equivalent to a certain number of phase shifters in the series-fed network. It can be easily controlled with only one meta l plate, which further...

Providing energy to Internet of Things (IoT) apparatuses is ever more challenging. Humans are increasingly invested in the revolutionary new scenario that experts call Industry 4.0 , where billions of electronic devices are interconnected with one another. The operations of battery charging or battery replacement for these devices will soon becom...

In this paper, we present the design and implementation methods of quarter-wavelength resonators accommodating Beltrami standing waves with parallel electric and magnetic (E‖H) fields. The resonator is bounded by the quarter-wavelength longitudinal electromagnetic conductor (LEMC), the circumferential electromagnetic conductor (CMEC), and the radia...

In this paper, we introduce a phase modulated zone plate to generate the circular symmetric Airy beam (CSAB) with abruptly autofocusing characteristic at 30GHz. This phase modulated zone plate is a phase combination form of a radial phase plate and a lens, which would make the conventional generation system of CSAB more compact. Based on full wave...

Far-field wireless power transfer (WPT) has gained significant attention due to its potential to provide convenient and efficient power transmission overextended distances. In this study, we propose a far-field WPT system that only utilizes a transistor and a diode. A single transistor is used to create a high-power oscillator as the transmitter, w...

Drones have been attractive for many kinds of industries, but limited power supply from batteries has impeded drones from being operated for longer hours. Microwave power transmission (MPT) is one of the most prospective technologies to release them from the limitation. Since, among several types of drones, micro-drone has shorter available flight...

This study theoretically and experimentally indicates that a charge pump rectifier for low-power rectifiers such as RF-ID can be applied to high-power rectifiers and can attain the same level of RF-dc conversion efficiency and twice as high power rectification as the single-shunt rectifiers. A high-power rectifier is primarily a single-shunt rectif...

This study proposes a new structure of a single-shunt rectifier circuit that can reduce circuit loss and improve efficiency over the conventional structure. The proposed structure can provide impedance matching to the measurement system (or receiving antenna) without the use of conventional matching circuits, such as stubs and tapers. The proposed...

In this paper, we propose a novel radial line planar phased array in which helical antenna elements are individually rotated by their respective connected micromotors to realize dynamic beam-scanning. To our knowledge, this is the first radial line planar array (RLPA) that has antenna elements electromechanically rotated by their individual micromo...

In this paper, we present novel cylindrical cavity resonators accommodating spatially and temporally zero Poynting vector Beltrami standing waves with the parallel electric and magnetic fields (E∥H). We introduce the special boundary conditions, i.e., longitudinal electromagnetic conductor (LEMC) on which zero longitudinal electromagnetic component...

This paper presents a novel dual-band substrate integrated waveguide (SIW) sensor that is designed to measure the complex permittivities of liquids or solid powders at two industrial, scientific, and medical (ISM) frequencies simultaneously. Resonant frequencies and quality factors are obtained from S-parameter measurements with the proposed SIW se...

Power beaming is one of the core technologies for microwave power transmission (MPT) systems. Effective plane-to-plane power beaming requires not only high point-to-point efficiency but also appropriately-shaped beam to extract the best performance of receivers (rectennas). Flat-top beam plays an important role in plane-to-plane power beaming for d...

In this paper, we propose novel retrodirective systems to improve the efficiency and safety of microwave power transmission (MPT) systems in multipath environments. The retrodirective system consists of an array antenna with phased conjugation circuits and it sends back the phase-conjugate signal toward the pilot signal transmitted from the receive...

Recently, microwave power transfer (MPT) for Internet-of-Things (IoT) devices has been actively studied. The distributed microwave power transfer (DMPT) can supply power efficiently by cooperating multiple transmit antenna arranged distributed in a relatively wide area. In this article, the advantages of DMPT are shown by using ray-trace-based Mont...

This article used image recognition and beam forming technology to build a phased array with target tracking and transmitting the microwaves with a focused beam. The coordinate position of the target is obtained from the image recognition module and converted into phase information for the phased array. This system was constructed by a 1 $\times$...

We built a phased array system for high-power simultaneous wireless information and power transfer (SWIPT) using four 5.8-GHz injection-locked magnetrons. In the magnetron injection-locked state, the transmission efficiency was measured at different modulation rates. The fluctuation in the transmission efficiency was not more than 0.5%. We observed...

Modern optical fibers are capable of transmitting multiple wavelengths simultaneously using the wavelength division multiplexing (WDM) method for multiple–input multiple–output (MIMO) communication systems. They have been put to practical use by increasing the communication speed. This letter proposes a new WDM circuit that transmits and separates...

To meet the increasing power demands of microwave industries and scientific innovations, a dual-way magnetron (MGT) power-combining system based on an asymmetric H-plane tee combined with closed-loop phase compensation (CLPC) was developed and tested. Only one external injection was used, which could lock both frequencies of the two MGTs via the po...

Rectifiers are essential for microwave wireless power transfer (MWPT). RF-DC conversion efficiency must be improved for the practical use of MWPT. The focus of this research is related to single shunt rectifiers. Former research explained the operations of single shunt rectifiers in the frequency domain. Currently, we are using a harmonic balance m...

Wireless power transfer (WPT) technology gained wide recognition over a decade ago following a resonance coupling WPT study conducted by a group at the Massachusetts Institute of Technology (MIT) [1]. WPT was originally proposed by Nicola Tesla at the end of the 19th century [2] based on a study of near-field inductive-coupling WPT and far-field WP...

Power beaming is the efficient point-to-point transfer of electrical energy across free space by a directive electromagnetic beam. This paper clarifies the basic principles of power beaming in simple terms, and proposes a benchmarking methodology for improving the comparative assessment of power beaming systems and technology. An in-depth historica...

Wireless power transfer (WPT) has a long history of over 100 years since the first experiment conducted by Nicola Tesla. However, the most interesting innovation of WPT was born in the 21 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">st</sup> century. In this decade, near-field WPT commercialization...

This article proposes a circular sector subarray to equalize input power to rectifiers and an eight-port radial line slot antenna (RLSA) with the circular sector subarray. Rectifiers are nonlinear components and have the optimum input power. To maximize RF-DC conversion efficiency, the input power to the rectifiers should be the uniform and optimum...

In this article, an array optimization method for maximizing beam collection efficiency (BCE) to an arbitrary receiving plane in the near field is proposed. The proposed method considers each element pattern in an array; thus, optimization with mutual coupling is possible by using active element patterns. Besides, the proposed method can consider t...

To achieve a high-efficiency microwave wireless power transfer system, a high conversion efficiency rectifier is necessary. Brown (1974) designed rectifiers with approximately 3-W input power achieved 90% conversion efficiency for 2.45 GHz, and it maintains the record for maximum conversion efficiency. In this study, to design a high-efficiency and...

Data monitoring with updated information is important and necessary in today’s era of digital technology. This study proposes a smart water quality monitoring (SWQM) system of aquaculture ponds that uses a Wireless Sensor Network (WSN) at a radio frequency band of 900 MHz in an Internet of Things (IoT) platform. The proposed system provides solutio...

To increase the power level and energy utilization rate of injection-locked magnetron sources, a dual-way 1-kW ${S}$ -band magnetron microwave power combining system with high combining efficiency was proposed and validated. A waveguide magic-Tee was used to achieve power combining and to provide a pathway for the reference signal. This system ut...

In this article, we investigate the performance of an injection-locked 5.8-GHz continuous-wave magnetron with various load reflection levels. The load reflection is introduced to an equivalent magnetron model to theoretically evaluate the system performance. The effects of different load reflection levels on the magnetron's output are numerically a...

We build a phased array system with four power-variable phase-controlled magnetrons (PCMs) by applying the injection-locking method and phase-locked-loop method. To reduce the cost and ensure the durability of the phased array, a waveguide slot array antenna was designed and used for the output antenna of power-variable PCMs. The slot antenna has a...

This study proposes a dual-circularly polarized Reduced-Surface-Wave (RSW) antenna which has a compact and simple structure by the integration of a via-loaded annular-ring (VLAR)-RSW antenna with a branch-line coupler. The fundamental characteristics of a VLAR-RSW antenna are analyzed through simulations in detail. In general, stronger mutual coupl...