Maximum Transmission Efficiency Research Articles

Reconfigurable Wireless Power Transmission in Fully-Enclosed Space Using Antenna Array

This paper studies employing antenna array to reconfigure wireless power transmission in fully-enclosed space (that is, environments enclosed by conducting walls, such as spacecrafts and engine compartments). Because strong coupling may appear among array elements, conventional phased array is not the best approach. We find parasitic array, which includes one driver element and multiple parasitic elements, an excellent candidate to achieve high power transmission efficiency in fully-enclosed space. Phased array and parasitic array are analyzed and compared with each other; closed-form expressions of maximum power transmission efficiency are derived when the array includes two elements. With the theoretical analysis as guideline, some experiments are conducted in a cubic box with size of 1 cubic meter and with aluminum walls. Experimental results demonstrate that, parasitic array offers higher power transmission efficiency than phased array in most of the scenarios. To be more specific, the power transmission efficiency could always reach 90% when a parasitic array includes 4 elements (i.e., 1 driver element and 3 parasitic elements) and when the receiver changes its location in a 60 cm by 60 cm region.

A Full-Freedom Wireless Power Transfer for Spheroid Joints

A full-freedom wireless power transfer for spheroid joints is proposed to solve the problem of power transmission between the caput-articularis and the acetabulum in a spheroid joint. According to the characteristics of the spheroid joint, a hemispherical coil and a spherical coil are designed having no effect on the performance of the joint. Hemispherical and spherical magnetic cores are used to optimize the magnetic field distribution of the transmitter and receiver coils to reduce the electromagnetic influence on the external environment of the acetabulum and the internal environment of the caput-articularis during the power transmission process. Practical results obtained from a hardware prototype are included. They confirm that the maximum transmission efficiency of the designed system is 91%, and the transmission efficiency is always higher than 80% when the caput-articularis rotates freely.

Novel analytical model for nano-coupler between metal–insulator–metal plasmonic and dielectric slab waveguides

We propose a new analytical model for nano-coupler between metal–insulator–metal (MIM) plasmonic and dielectric slab waveguides. By using the boundary conditions and mode matching technique, the analytical expression for transmission coefficient can be achieved at the plasmonic–dielectric junction. The theoretical results are compared with the simulation results of COMSOL software. A good agreement between the simulation and theoretical results is observed which validates our analytical model. The maximum transmission efficiency of the coupler can be obtained by changing the width of the dielectric (Wd) and air (Wa) layers. For the nano-coupler with Wd = 300 nm at the wavelength 1.55 μm, the results show that maximum transmission efficiency of 75% can be achieved at the width of 63 nm (Wa= 63 nm). Our analytical model is accurate and can calculate the modal properties of the proposed coupler.

Distributed Laser Charging: A Wireless Power Transfer Approach

Wireless power transfer (WPT) is a promising solution to provide convenient and perpetual energy supplies to electronics. Traditional WPT technologies face the challenge of providing Watt-level power over meter-level distance for Internet of Things (IoT) and mobile devices, such as sensors, controllers, smart-phones, laptops, etc.. Distributed laser charging (DLC), a new WPT alternative, has the potential to solve these problems and enable WPT with the similar experience as WiFi communications. In this paper, we present a multi-module DLC system model, in order to illustrate its physical fundamentals and mathematical formula. This analytical modeling enables the evaluation of power conversion or transmission for each individual module, considering the impacts of laser wavelength, transmission attenuation and photovoltaic-cell (PV-cell) temperature. Based on the linear approximation of electricity-to-laser and laser-to-electricity power conversion validated by measurement and simulation, we derive the maximum power transmission efficiency in closed-form. Thus, we demonstrate the variation of the maximum power transmission efficiency depending on the supply power at the transmitter, laser wavelength, transmission distance, and PV-cell temperature. Similar to the maximization of information transmission capacity in wireless information transfer (WIT), the maximization of the power transmission efficiency is equally important in WPT. Therefore, this work not only provides the insight of DLC in theory, but also offers the guideline of DLC system design in practice.

A new design of a photonic crystal ring resonator based on Kerr effect for all-optical logic gates

All optical photonic crystal based logic gates are believed to be essential components for compact photonic integrated circuits and Wavelength Division Multiplexing (WDM) systems. One of the promising designs for a logic gate is based on the photonic crystal ring resonators (PhCRR). In this paper, we carried out a performance analysis of a new simple shape of a PhCRR as a function of the nonlinear rods emplacement to pick up the best case offering the maximum transmission efficiency. Then, the optimal case is used for the design of ultra fast all optical gates (OR, AND, NAND). In our work, the novelty lies in the design of a new simple nonlinear ring based on the combination of GaAs/In0.53Ga0.47As materials that can be used, with the minimum required power (0.733 KW/µm2), to ensure different logic gates’ functionalities. Simulations performed by Numerical methods such as plane wave expansion (PWE) and finite difference time domain (FDTD) demonstrate that the proposed PhCRR has a high quality factor (Q) of about 1719 and a high transmission efficiency of 100%. Moreover, designed logic gates are characterized by its low energy consumption, its ultrafast response, its compactness and its simplicity of integration.

High-Efficiency Output Pressure Performance Using Capacitive Micromachined Ultrasonic Transducers with Substrate-Embedded Springs.

Capacitive micromachined ultrasonic transducers (CMUTs) with substrate-embedded springs offer highly efficient output pressure performance over conventional CMUTs, owing to their nonflexural parallel plate movement. The embedded silicon springs support thick Si piston plates, creating a large nonflexural average volume displacement efficiency in the operating frequency range from 1–3 MHz. Static and dynamic volume displacements of the nonflexural parallel plates were examined using white light interferometry and laser Doppler vibrometry. In addition, an output pressure measurement in immersion was performed using a hydrophone. The device showed a maximum transmission efficiency of 21 kPa/V, and an average volume displacement efficiency of 1.1 nm/V at 1.85 MHz with a low DC bias voltage of 55 V. The device element outperformed the lead zirconate titanate (PZT) ceramic HD3203, in the maximum transmission efficiency or the average volume displacement efficiency by 1.35 times. Furthermore, its average volume displacement efficiency reached almost 80% of the ideal state-of-the-art single-crystal relaxor ferroelectric materials PMN-0.33PT. Additionally, we confirmed that high-efficiency output pressure could be generated from the CMUT device, by quantitatively comparing the hydrophone measurement of a commercial PZT transducer.

Wireless charging with textiles through harvesting and storing energy from body movement

This paper presents a wireless charging method based on textiles through harvesting and storing energy from human movement. The proposed method uses resonant coils made of a conductive yarn and a flexible printed circuit board. The conductive yarn consists of polyurethane-coated copper and polyester filaments. The transmission characteristics of the resonant coils, which were worn on the arm of a human body, were evaluated using simulation and measurement tools. It was determined that the change in the resonant frequency of the conductive-yarn resonant coils can be obtained from the coil length, stitch intervals, and fabric thickness using equations. The measured resonant frequencies of the sending and receiving coils were designed to achieve a resonant frequency of 13.56 MHz when the coils are worn. The resonant coils were worn on the arm of a subject, who moved at various speeds, and the transmission efficiency was measured using an alternating current–direct current converter. The measurement results showed a maximum transmission efficiency of 55.1%, even though the resonant coils were worn around the arm and not the leg, and an average transmission efficiency of 52.1% when the subject was moving at a speed of 6 km/h.

Optimization of a more efficient protocol for mechanical inoculation for watermelon bud necrosis orthotospovirus and its validation with different watermelon genotypes

Watermelon bud necrosis orthotospovirus (WBNV) is one of the emerging and most serious pathogens affecting watermelon cultivation in India. In the present study, the effect of different inoculation methods and buffer formulation on virus transmission was studied and validated in 17 watermelon genotypes. Among various inoculation methods used, maximum transmission efficiency 60–100% was obtained in 4–10 days post-inoculation (DPI) with pin-pricking and rubbing together, followed by rubbing (85–100%; 20–25 DPI) and pin-pricking (10–32%; 10–25 DPI) alone with the sodium buffer (PBS) having pH 7.0 supplemented with sodium sulfite (SS) and 2-mercaptoethanol (2-ME). Similarly, among the various abrasives used, maximum transmission efficiency 82–100% was obtained at 10–35 DPI with Celite and Carborundum together, followed by Celite (64–100%; 10–20 DPI) and Carborundum (72–100%; 20–40 DPI) alone. Among various additives used, maximum transmission efficiency 82–100% was obtained in 10 DPI with PBS supplemented with SS and 2-ME followed by PBS supplemented with SS alone (85–100%; 20–40 DPI) and PBS with no additive (76–85%; 20–35 DPI). The 15–20 days old watermelon plants were found suitable for the efficient mechanical transmission (100%) and to obtain maximum virus titre (Absorbance at 405 nm) i.e. 1.52–2.50 at 8–25 DPI. The 21–60% and 100% transmission was obtained at 4 and 10 DPI, respectively using the same buffer composition as mentioned above. For validation of optimized sap inoculation protocol for WBNV, 17 watermelon genotypes were inoculated under glasshouse conditions and the percent transmission ranged from 80 to 100%. Besides symptomatology, virus transmission was further confirmed by DAC-ELISA, RT-PCR and sequencing of the partial N gene. The O. D. at 405 nm ranged from 0.38 to 0.9 in naturally infected watermelon plants whereas in the glasshouse inoculated watermelon plants it was ranged from 0.30 to 0.73 at 15 DPI. This is the first effort on optimization of more efficient sap inoculation protocol for WBNV and it validated to 17 watermelon genotypes.

Dynamic impedance compensation for wireless power transfer using conjugate power

Wireless power transfer (WPT) via coupled magnetic resonances has been in development for over a decade. However, the frequency splitting phenomenon occurs in the over-coupled region. Thus, the output power of the two-coil system achieves the maximum output power at the two splitting angular frequencies, and not at the natural resonant angular frequency. According to the maximum power transfer theorem, the impedance compensation method was adopted in many WPT projects. However, it remains a challenge to achieve the maximum output power and transmission efficiency in a fixed-frequency mode. In this study, dynamic impedance compensation for WPT was presented by utilizing the compensator within a virtual three-coil WPT system. First, the circuit model was established and transfer characteristics of a system were studied by utilizing circuit theories. Second, the power superposition of the WPT system was carefully researched. When a pair of compensating coils was inserted into the transmitter loop, the conjugate power of the compensator loop was created via magnetic coupling of the two compensating coils that insert into the transmitter loop. The mechanism for dynamic impedance compensation for wireless power transfer was then provided by investigating a virtual three-coil WPT system. Finally, the experimental circuit of a virtual three-coil WPT system was designed, and experimental results are consistent with the theoretical analysis, which achieves the maximum output power and transmission efficiency.

Femtosecond Optical Kerr Gate With Double Gate Pulses

We proposed an improved femtosecond optical Kerr gate with double gate pulses (DOKG) using a femtosecond laser, in which an ultrashort switching time can be realized even when a relatively slow response optical Kerr medium of carbon disulfide was used. The results showed that when the time delay and the light intensity ratio of the two pump pulses were adjusted to be about 140 fs and 1:0.9, the switching time and the maximum transmission efficiency of the DOKG could be optimized to be about 130 fs and 37%. The DOKG is convenient to be built and offers a good choice for applications based on ultrafast optical switch.

Optimal design of antenna array for multiple targets microwave power transmission with precise power division ratio control

A novel method used to design multiple targets microwave power transmission antenna array that could transmit power wirelessly to discrete targets with different power division ratios is introduced in this study. The maximal transmission efficiency and the precise power division ratio could be achieved simultaneously by utilising the basis functions, which are optimised for high-transmission efficiency, and the power division ratio is achieved precisely by investigating the transmission coefficients related to each basis function carefully. Two antenna arrays working at 2.45 GHz are designed and fabricated to verify the method. The power division ratios of array 1 and array 2 are designed to be 1:1 and 1:2 when the transmission distance is 10 cm, and the measured results are 1:1 and 1:2.1, respectively.

Optimum Design of Low-Cost Dual-Mode Beam-Steerable Arrays for Customer-Premises Equipment Applications

Two novel designs of dual-mode beam-steerable array antennas are proposed for customer-premises equipment applications. To obtain the optimal distribution of excitations for the arrays, the gain and front-back ratio of the array systems are optimized by using the method of maximum power transmission efficiency. The first design operates at 2.45 GHz and uses four folded monopoles of height <1/10 wavelength and a sleeve of height of 1/4 wavelength underneath the monopoles. The peak gain and the front-to-back ratio are 6.7 dBi and 7.8 dB respectively. The second design operates at 830MHz and uses four Yagi monopoles as elements with a common reflector and four directors. The peak gain and the front-to-back ratio for the second design are 6.0 dBi and 16.8 dB respectively. The proposed antennas have advantages including: low cost and compact size; dual-mode operation including the modes of omnidirectional radiation and directional radiation; and in the mode of directional radiation, the beam can be electronically steered to achieve the full coverage of the azimuthal plane. It achieves higher gain than the traditional electronically steerable passive array radiator antenna.

Current vector control of wireless power transfer system with 2D transmitting coils

Current vector control of a resonant-type wireless power transfer system with 2D transmitting (Tx) coils is presented. The equivalent circuit model between two Tx and one receiving coils is derived in d–q coordinates. The control method to obtain the maximum power transmission efficiency is proposed. The experimental results are provided to verify the proposed control method.

Wireless Power Transmission to Implantable Monitoring Devices for Gastroesophageal Reflux Disease

This paper proposes a wireless energy transmission system for implanted devices for monitoring gastroesophageal reflux disease. One of the wireless energy transmission systems is transcutaneous energy transmission system (TETS). We developed a wireless power transmission system that uses a planar-type transmitting coil to send power to a planar-type receiving coil implanted deep inside the body. To obtain higher transmission efficiency, the transmission frequency and number of turns of the receiving and transmitting coils were modified. The relative performance of two methods of wireless power transmission, i.e., series compensated transmitting and receiving (SS method) and series compensated transmitting and parallel compensated receiving (SP method), was analyzed. The calculation result revealed that the maximum transmission efficiency of SP method was 0.8%, when the number of turns of receiving coil was 15 and that of transmitting coil was 22 at 0.9 MHz.

Electron Gun and Output Coupling System for a 220-/251.5-GHz, 2-MW Triangular Corrugated Coaxial Cavity Gyrotron

In this paper, design studies of a common electron gun and output coupling system for the dual regime operation of a 2-MW coaxial cavity gyrotron are presented. The operating frequencies (220/251.5 GHz) are selected, such that the proposed gyrotron can be used for plasma heating applications in the future experimental fusion reactors. A coaxial magnetron injection gun (MIG) is designed for the generation of hollow electron beam with the desired parameters. Initial geometry of the electron gun is determined through our in-house code Gyrotron Design Suite version 4.1 2016 (GDSv4.1 2016). The MIG is further optimized and simulated through the beam trajectory code ESRAY. A nonlinear taper (NLT) is designed with maximum transmission efficiency at both the operating frequencies. A quasi-optical launcher (QOL) is designed and numerically optimized through the commercial software, launcher optimization tool. The designed launcher efficiently converts both the operating modes into Gaussian-like mode. A single-disk RF window is designed for the extraction of high-power output beam from the gyrotron at their respective operating frequencies. The design of the NLT and the RF window are carried out through GDSv4.1 2016.

Feasibility study of microwave wireless powered flight for micro air vehicles

New small unmanned air vehicles designated as micro air vehicles (MAVs) are increasingly attractive for research, environmental observation, and commercial purposes. As described herein, the feasibility of a system for wireless power transmission via microwaves for MAVs was investigated. For its light weight and flexibility, a textile-based rectenna was proposed for microwave wireless power transmission of MAVs. To investigate bending effects on radiation performance, a microstrip patch antenna with a 5.8 GHz left-hand circular polarization was developed on a textile substrate. The antenna return loss, 20 dB, increased slightly with the antenna bending angle. An axial ratio &lt;3 dB was maintained when the antenna bend angle was &lt;30°. A rectification circuit was formed on the back side felt with sandwiched copper foil as a ground plate. Its weight per unit area was 0.08 g/m2, with maximum rectification efficiency of 58% with 100 Ω load at 63 mW input power. The average and maximum total transmission efficiency using the 5.8 GHz multiple rectenna with a 2.45 GHz retrodirective system were, respectively, 0.44 and 0.60%. The possibility and feasibility of microwave power transmission system using the textile-based rectenna were evaluated.

Magnetic shielding structure optimization design for wireless power transmission coil

In order to improve the performance of the wireless power transmission (WPT) system, a novel design scheme with magnetic shielding structure on the WPT coil is presented in this paper. This new type of shielding structure has great advantages on magnetic flux leakage reduction and magnetic field concentration. On the basis of theoretical calculation of coil magnetic flux linkage and characteristic analysis as well as practical application feasibility consideration, a complete magnetic shielding structure was designed and the whole design procedure was represented in detail. The simulation results show that the coil with the designed shielding structure has the maximum energy transmission efficiency. Compared with the traditional shielding structure, the weight of the new design is significantly decreased by about 41%. Finally, according to the designed shielding structure, the corresponding experiment platform is built to verify the correctness and superiority of the proposed scheme.

Novel Cranial Implants of Yttria-Stabilized Zirconia as Acoustic Windows for Ultrasonic Brain Therapy.

Therapeutic ultrasound can induce changes in tissues by means of thermal and nonthermal effects. It is proposed for treatment of some brain pathologies such as Alzheimer's, Parkinson's, Huntington's diseases, and cancer. However, cranium highly absorbs ultrasound reducing transmission efficiency. There are clinical applications of transcranial focused ultrasound and implantable ultrasound transducers proposed to address this problem. In this paper, biocompatible materials are proposed for replacing part of the cranium (cranial implants) based on low porosity polycrystalline 8 mol% yttria-stabilized-zirconia (8YSZ) ceramics as acoustic windows for brain therapy. In order to assess the viability of 8YSZ implants to effectively transmit ultrasound, various 8YSZ ceramics with different porosity are tested; their acoustic properties are measured; and the results are validated using finite element models simulating wave propagation to brain tissue through 8YSZ windows. The ultrasound attenuation is found to be linearly dependent on ceramics' porosity. Results for the nearly pore-free case indicate that 8YSZ is highly effective in transmitting ultrasound, with overall maximum transmission efficiency of ≈81%, compared to near total absorption of cranial bone. These results suggest that 8YSZ polycrystals could be suitable acoustic windows for ultrasound brain therapy at 1 MHz.

Design of a broadband reciprocal optical diode in a silicon waveguide assisted by silver surface plasmonic splitter.

In this paper, we propose a new scheme for a reciprocal optical diode integrated in a multimode silicon waveguide. The compact 4μm long functional region consists of a tapered coupler, a narrow single-mode waveguide, and a half-elliptical silver surface plasmonic splitter with refractive index modification of silicon. This spatial asymmetric design achieves even-to-odd mode conversion in the forward direction and blocks propagation of the even mode in the backward direction. The maximum contrast ratio and forward transmission efficiency reach approximately 0.99 and 87% while the values respectively keep higher than 0.96 and 80% within a 100nm operational bandwidth in a two-dimensional design. Both freestanding and SOI-based three-dimensional devices are simulated and at least a 0.94 contrast ratio is observed. Moreover, the robustness is demonstrated by introducing deviations to the surface plasmonic splitter. The proposed scheme brings together advantages including a high contrast ratio (>0.94), a large operational bandwidth (100nm) and a small footprint (4μm long).

Freestanding dielectric nanohole array metasurface for mid-infrared wavelength applications.

We designed and simulated freestanding dielectric optical metasurfaces based on arrays of etched nanoholes in a silicon membrane. We showed 2π phase control and high forward transmission at mid-infrared (mid-IR) wavelengths around 4.2μm by tuning the dimensions of the holes. We also identified the mechanisms responsible for high forward scattering efficiency and showed that these conditions are connected with the well-known Kerker conditions already proposed for isolated scatterers. A beam deflector was designed and optimized through sequential particle swarm and gradient descent optimization to maximize transmission efficiency and reduce unwanted grating orders. Such freestanding silicon nanohole array metasurfaces are promising for the realization of silicon-based mid-IR optical elements.