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[IEEE 2018 IEEE Asia-Pacific Conference on Antennas and Propagation (APCAP) - Auckland (2018.8.5-2018.8.8)] 2018 IEEE Asia-Pacific Conference on Antennas and Propagation (APCAP) - A High-Efficiency 35GHz Rectenna with compact structure for rectenna arrays
摘要： A 35GHz rectenna with high efficiency and compact structure is proposed in this paper. A patch antenna fed by the coupling slot is employed to receive power from free space. The structure of designed rectifier is compact and printed on the bottom side of the antenna. The input low-pass or band-pass filter of the rectifier is removed. Instead, a short ended microstrip line is introduced as a band stop structure to block the harmonics and match the impendence. This circuit configuration highly simplifies the total topology and is suitable for rectenna arrays applications. Furthermore, removing the input filters reduced the insertion loss and thus improved the microwave-to-dc (MW-DC) conversion efficiency. The rectenna is designed, fabricated and measured, a maximum MW-DC efficiency of 53.2% is achieved for a power density of 51.2 mW/cm2 with the dc load 250 Ω at 35 GHz.
关键词： compact structure,millimeter-wave rectenna,high conversion efficiency,WPT
更新于2025-09-23 15:22:29
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[IEEE 2018 28th International Telecommunication Networks and Applications Conference (ITNAC) - Sydney, Australia (2018.11.21-2018.11.23)] 2018 28th International Telecommunication Networks and Applications Conference (ITNAC) - CamThings: IoT Camera with Energy-Efficient Communication by Edge Computing based on Deep Learning
摘要： In recent years, the demand for IoT cameras has increased due to the high demand for image data. However, the image sensor is unsuitable as an energy-constrained edge device for IoT due to its high-power consumption. Therefore, periodic on–off scheduling of IoT cameras is a promising approach since video recording using image sensors is energy-intensive. Due to the constrained computing performance of edge devices, IoT is still based on cloud computing with energy leaks by transmitting all the data of edge devices to cloud. In this paper, we proposed energy-efficient communication via edge computing based on deep learning, which reduces power consumption by transmitting only images of interest classified using edge computing. We also designed and implemented CamThings, which is an energy-efficient IoT camera with periodic on–off scheduling and the proposed energy-efficient communication. To analyze and evaluate the efficiency of the proposed communication scheme, we implemented a power consumption model for CamThings. In an environment with a low interest ratio, the proposed CamThings is superior to the baseline method with only periodic on–off scheduling in terms of power consumption and lifetime. When the scheduling period T is 5s and the interest ratio is 0.1, the proposed method consumed 41% less power than the baseline method. As a result, CamThings has a lifetime of more than one month.
关键词： Wireless Communication,Energy Efficiency,Edge Computing,IoT Camera,Deep Learning
更新于2025-09-23 15:22:29
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Efficient and stable emission of warm-white light from lead-free halide double perovskites
摘要： Lighting accounts for one-fifth of global electricity consumption1. Single materials with efficient and stable white-light emission are ideal for lighting applications, but photon emission covering the entire visible spectrum is difficult to achieve using a single material. Metal halide perovskites have outstanding emission properties2,3; however, the best-performing materials of this type contain lead and have unsatisfactory stability. Here we report a lead-free double perovskite that exhibits efficient and stable white-light emission via self-trapped excitons that originate from the Jahn–Teller distortion of the AgCl6 octahedron in the excited state. By alloying sodium cations into Cs2AgInCl6, we break the dark transition (the inversion-symmetry-induced parity-forbidden transition) by manipulating the parity of the wavefunction of the self-trapped exciton and reduce the electronic dimensionality of the semiconductor4. This leads to an increase in photoluminescence efficiency by three orders of magnitude compared to pure Cs2AgInCl6. The optimally alloyed Cs2(Ag0.60Na0.40)InCl6 with 0.04 per cent bismuth doping emits warm-white light with 86 ± 5 per cent quantum efficiency and works for over 1,000 hours. We anticipate that these results will stimulate research on single-emitter-based white-light-emitting phosphors and diodes for next-generation lighting and display technologies.
关键词： lead-free halide double perovskites,self-trapped excitons,white-light emission,photoluminescence efficiency,Jahn–Teller distortion
更新于2025-09-23 15:21:21
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Increased luminescent efficiency of perovskite light emitting diodes based on modified two-step deposition method providing gradient concentration
摘要： We increased the luminescent efficiency of perovskite light-emitting diodes (PeLEDs) by using a modified two-step deposition method combined with an interdiffusion process without additional solvent engineering or additive molecules. Methylammonium lead bromide (MAPbBr3) polycrystalline films with nanosized grains and low electronic disorder were fabricated by a modified two-step deposition process. The as-fabricated MAPbBr3 films showed gradient concentration characteristics as a result of a gradient distribution of the MABr. Also, the MABr-gradient concentration structure was intensified by the interdiffusion process, showing improved performance of MAPbBr3 PeLEDs with maximum current efficiency CEmax = 0.861 cd A?1 and maximum luminance = 604 cd m?2 with very narrow electroluminescence spectral width. This is the highest CEmax among MAPbBr3-based PeLEDs deposited by the two-step deposition method.
关键词： two-step deposition method,perovskite light-emitting diodes,luminescent efficiency,gradient concentration,interdiffusion process
更新于2025-09-23 15:21:21
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Tuning phosphors for better white light
摘要： Light-emitting diodes (LEDs) that produce white light are about to take over the lighting world. The U.S. market share of these super-long-lasting, cool-to-the-touch lights, which use less than a quarter of the energy of conventional incandescent bulbs, sits around 10%. Industry watchers predict that number will exceed 80% by 2030, reducing power consumption in the U.S. by 40%. Chemists are taking a leading role in this technology, which underpins general lighting and electronic displays, by customizing the emission spectrum, stability, and other properties of inorganic phosphors in the LEDs that help produce finely tuned white light.
关键词： energy efficiency,inorganic phosphors,color rendering index,LEDs,white light
更新于2025-09-23 15:21:21
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Thin Films
摘要： We demonstrate how to extract the material-dependent spin-torque efficiency (ξ) and asymmetry (λ) from the field-current nucleation boundaries of magnetic droplet solitons in orthogonal nano-contact spin-torque oscillators with Cox(Ni80Fe20)1?x, (x = 0 ? 1), fixed layers. As the perpendicular component of the fixed-layer magnetization plays a central role in governing droplet nucleation, the nucleation boundaries exhibit monotonic shifts towards higher perpendicular magnetic fields when the fixed-layer magnetization μ0Ms,p is tuned from 1.04 to 1.7 T. We then extract ξ and λ from fits to the nucleation boundaries and find that while ξ does not vary with composition, λ increases from 1.5 to 3 with increasing Co content. The analysis of droplet nucleation boundaries is hence a useful tool for the systematic study of both ξ and λ as functions of material composition.
关键词： Cox(Ni80Fe20)1?x,magnetic droplet solitons,spin-torque asymmetry,spin-torque efficiency,nano-contact spin-torque oscillators
更新于2025-09-23 15:21:21
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[IEEE 2018 IEEE 5G World Forum (5GWF) - Silicon Valley, CA, USA (2018.7.9-2018.7.11)] 2018 IEEE 5G World Forum (5GWF) - 5G-NR Bandwidth Efficient Modulation Options for Efficient Link Operation that are Compatible with mmW Transistor Nonlinearities
摘要： The 5G network has a goal to significantly increase its energy efficiency with respect to the energy draw of the LTE network. The decision to use OFDM-based modulation for 5G-NR forces a low-valued ceiling on achievable energy efficiency from any linear power amplifier. This ceiling is lowest for amplifiers operating at frequencies near and above 30 GHz: the millimeter-wave bands. Transistors behave differently at these high frequencies, and the modulation used must change to match to these different characteristics. Ring oriented constellations with polar filtering meet these changed conditions.
关键词： transmitter,millimeter wave,efficiency,5G,new radio
更新于2025-09-23 15:21:21
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Improving satellite-based modelling of gross primary production in deciduous broadleaf forests by accounting for seasonality in light use efficiency
摘要： Vegetation gross primary production (GPP), the photosynthetic yields by green plants per unit area per unit time, is a key metric of carbon flux in understanding the land–atmosphere interactions and terrestrial carbon cycles. Satellite-based light use efficiency (LUE) models are valuable methods to retrieve large-scale terrestrial GPP using remote sensing data. As studies have reported that maximum light use efficiency, a key parameter that is often assumed to be constant in the LUE models, there is a need to explore the effects of LUE seasonality on GPP simulation and ways for correction. This study proposes a method based on leaf area index to account for LUE seasonality and applies it to four different light use efficiency models (i.e., the MOD17 algorithm, the vegetation photosynthesis model, the radiation partitioning model, and the vegetation index model) for comparisons. Based on 59 site-years flux tower data from deciduous broadleaf forest sites in the United States, the results show that all models could simulate daily GPP time series well and explain more than 85.0% variance of tower-based GPP. There is, however, a tendency to overestimate GPP during the non-growing season but underestimate GPP during the growing season. By applying the correction function, GPP simulation using the LUE models improved in all experiments as indicated by increased correlation coefficients, the index of agreement and decreased root-mean-square errors. Among all models, the radiation partitioning model achieves the highest correlation coefficients between modelled and observed daily GPP likely because it considers the influences of direct and diffuse radiation partitioning on daily canopy photosynthesis. Our study indicates that satellite-based light use efficiency models could be successfully applied for deriving daily vegetation GPP and potentially producing daily routine satellite products, while considering the effects of LUE seasonality on canopy could help improve significantly the simulation accuracy of daily GPP in phenology.
关键词： seasonality,light use efficiency,satellite-based modelling,gross primary production,deciduous broadleaf forests
更新于2025-09-23 15:21:21
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Detection of damage of a filter by visualization of filtration process
摘要： This paper deals with testing of filters on the basis of visualization of filtration process. A filtration material can be damaged by flow of the filtered medium, high pressure drop and long-term adverse conditions. These negative effects can cause extensive damage of the filtration textile and filtration efficiency decreases. The filter can be also fractured during manufacturing, processing or by improper manipulation. A testing of a purposely damaged filtration textile is described in the article. Experiments were performed on the filtration setup which permits an optical entrance to the position where a sample of filter is placed. A laser sheet is directed into this place. Scattered light from seeding particles in front of and behind the filter is captured by a digital camera. Images from the camera are analyzed and the filtration efficiency versus time and also versus position can be obtained. Measuring chain including light scattering theory and measuring of light intensity by a digital camera are also discussed in the article.
关键词： damage detection,optical measurement,filtration,visualization,filtration efficiency
更新于2025-09-23 15:21:21
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Design of a Compact GaN MMIC Doherty Power Amplifier and System Level Analysis With X-Parameters for 5G Communications
摘要： This paper presents a monolithic microwave integrated circuit Doherty power amplifier (DPA) operating at sub-6 GHz for 5G communication applications by a 0.25-μm gallium nitride high-electron mobility transistor process. A compact impedance inverter and output matching of the DPA are achieved using a transmission line network and shunt capacitors. Also, the size ratio of power cells in the main and auxiliary amplifiers is optimized for a high efficiency at output power backoff (OPBO). The measured peak output power (Pout) and the 1-dB compression point (P1 dB) are 38.7 and 32.1 dBm, respectively, at 5.9 GHz. The power-added efficiency at 6-dB OPBO is up to 49.5%. Without digital predistortion (DPD), the DPA can deliver an average Pout of 23.5 dBm with error vector magnitude (EVM) <?28 dB and 21.5 dBm with EVM <?32 dB for 64-quadrature amplitude modulation (QAM) and 256-QAM signals, respectively. The measured X-parameters are employed to further investigate the DPA nonlinear characteristics and verify the accuracy of conventionally used power amplifier characterization/measurement methods for system-level design and testing applications. The simulated results based on the X-parameters also indicate that the average output power can be enhanced up to 25.7 dBm with DPD for 256-QAM.
关键词： 5G communication,monolithic microwave integrated circuit (MMIC),X-parameters,power-added efficiency (PAE),power amplifier (PA),Doherty,gallium nitride (GaN)
更新于2025-09-23 15:21:21