- 标题
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- 实验方案
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Dimming Control Systems Based on Low-PAPR SCFDM for Visible Light Communications
摘要： In this paper, the efficient dimming control systems based on single-carrier frequency-division multiplexing (SCFDM) are proposed for visible light communications (VLC). By virtue of the strengths of the low peak-to-average power ratio and the inherent resistance to high-frequency distortion, the proposed SCFDM-based dimming control schemes are adaptive to the bandwidth-limited and linearity-limited VLC system, thus supporting the wide dimming range for different illumination requirements. Two SCFDM-based VLC systems with dimming control including asymmetrical hybrid optical SCFDM (AHO-SCFDM) and DC-biased optical SCFDM (DCO-SCFDM) are proposed. For AHO-SCFDM with spectral efficiency of 1.75 bit/s/Hz and DCO-SCFDM with spectral efficiency of 2 bit/s/Hz, the 20% wider dimming range can be achieved than their orthogonal frequency-division multiplexing (OFDM) based counterparts, respectively. Meanwhile, the two proposed schemes can also achieve 24.8% and 31.3% gains of average spectral efficiency under the same dimming range compared with their counterparts, respectively. For an overall analysis, SCFDM shows the feasibility and superiority for dimming control systems.
关键词： light emitting diode,Visible light communication,single-carrier frequency-division multiplexing,dimming control,orthogonal frequency-division multiplexing
更新于2025-09-23 15:21:21
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Distance-Resolving Raman Radar Based on a Time-Correlated CMOS Single-Photon Avalanche Diode Line Sensor
摘要： Remote Raman spectroscopy is widely used to detect minerals, explosives and air pollution, for example. One of its main problems, however, is background radiation that is caused by ambient light and sample fluorescence. We present here, to the best of our knowledge, the first time a distance-resolving Raman radar device that is based on an adjustable, time-correlated complementary metal-oxide-semiconductor (CMOS) single-photon avalanche diode line sensor which can measure the location of the target sample simultaneously with the normal stand-off spectrometer operation and suppress the background radiation dramatically by means of sub-nanosecond time gating. A distance resolution of 3.75 cm could be verified simultaneously during normal spectrometer operation and Raman spectra of titanium dioxide were distinguished by this system at distances of 250 cm and 100 cm with illumination intensities of the background of 250 lux and 7600 lux, respectively. In addition, the major Raman peaks of olive oil, which has a fluorescence-to-Raman signal ratio of 33 and a fluorescence lifetime of 2.5 ns, were distinguished at a distance of 30 cm with a 250 lux background illumination intensity. We believe that this kind of time-correlated CMOS single-photon avalanche diode sensor could pave the way for new compact distance-resolving Raman radars for application where distance information within a range of several metres is needed at the same time as a Raman spectrum.
关键词： time-correlated single photon counting (TCSPC),remote Raman spectroscopy,CMOS single-photon avalanche diode (SPAD),time interval measurement,distance-resolving Raman radar,stand-off Raman spectrometer
更新于2025-09-23 15:21:21
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[IEEE 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - Kyoto, Japan (2018.7.9-2018.7.13)] 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - Electron sources based on diamond pin-diodes
摘要： Efficient electron sources are of ongoing interest in particular for space and terrestrial power telecommunications and radar applications. With conventional cathode technology based on thermionic- and field electron emission a novel approach for direct electron emission is realized through a diamond pin diode. Electrons injected into the conduction band of the intrinsic layer of the diode can be released into vacuum with a negative electron affinity surface of the i-layer. The diamond pin diodes were prepared on boron doped (p-type) substrates with (111) surface orientation. A high purity intrinsic and a phosphorus doped diamond layer (n-type, ~400nm thickness) were deposited in dedicated PECVD systems, respectively. An additional contact layer comprised of nanostructured carbon was grown in a dedicated PECVD. The layered device was processed by lithography utilizing an aluminum hard mask to etch mesa structures with diameters ranging from 50μm to 200μm. The final devices were treated in a pure hydrogen plasma to induce the negative electron affinity properties of the i-layer. After an annealing step in high vacuum individual pin diodes were biased in forward current and voltages up to 20V. The observation of light from the diode was attributed to the UV exciton state and indicated bipolar transport. At a diode current of about 80mA an electron emission current of 25μA was observed from a single 200μm diameter diode.
关键词： Diamond,solid state electronics,doping,phosphorus,electron emission,plasma-enhanced chemical vapor deposition,nanostructured carbon,pin diode,single crystal
更新于2025-09-23 15:21:21
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Indoor Localization Using K-Pairwise Light Emitting Diode Image-Sensor-Based Visible Light Positioning
摘要： A great deal of research has been devoted to studying indoor localization schemes for the development of location-based services. This study investigated an indoor localization system, including subsystems of non-line-of-sight (NLOS) image-sensor-based visible light communications (IS-VLC) and the proposed ??-pairwise light emitting diode (LED) image-sensor-based visible light positioning (IS-VLP), in a unified lighting environment. A smartphone received multiple LED identifiers through the designed NLOS IS-VLC and successfully performed the proposed ??-pairwise LED IS-VLP with ?? = 3 to achieve localization, with maximum localization errors of 2.92 cm and 3.54 cm being obtained for ceiling heights of 100 cm and 150 cm, respectively.
关键词： visible light communications (VLC),Image-sensor-based visible light positioning (VLP),light emitting diode (LED)
更新于2025-09-23 15:21:21
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[IEEE 2018 VII. Lighting Conference of the Visegrad Countries (Lumen V4) - Trebic, Czech Republic (2018.9.18-2018.9.20)] 2018 VII. Lighting Conference of the Visegrad Countries (Lumen V4) - Evaluation of Lighting Parameters at the Workplace with the use Replacements for Incandescent Lamps
摘要： The article evaluates the possibility of using halogen lamps, compact fluorescent lamps and LED lamps as direct substitutes of traditional 100 W incandescent lamps for selected residential lighting applications. A single halogen lamp, six compact fluorescent lamps and six LED light sources were examined. A traditional light bulb was also examined for comparison. All lamps operated in three luminaires. The basic evaluation criterion was the illuminance, uniformity and glare limitation in the place of work. It was found that not all light sources can be considered substitutes of traditional light bulbs. In the case of a luminaire made from a translucent material and one luminaire with a reflector, not all lamps allowed to obtain at least the same lighting parameters in the place where visual work was performed, as when a traditional light bulb was used.
关键词： light-emitting diode (LED),bulb's replacement,lighting parameters at the workplace,light sources for household
更新于2025-09-23 15:21:21
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Improving performance of thermally activated delayed fluorescence emitter by extending its LUMO distribution; 通过扩展LUMO分布提高热激活延迟荧光材料的性能;
摘要： An optimized compound 9-(9,9-dimethylacridin-10(9H)-yl)-6H-benzo[c]ch-romen-6-one (MAB) was designed and synthesized based on our previously reported TADF emitter 6-(9,9-dimethylacridin-10(9H)-yl)-3-methyl-1H-isochromen-1-one (MAC) to further improve the performance of thermally activated delayed fluorescence (TADF) emitters. With the additional phenyl in coumarin-contained plane, MAB possesses an extended distribution of the lowest unoccupied molecular orbitals (LUMO), and thus realizes reduced electron exchange between the frontier molecular orbitals and a stretched molecular dipole moment compared with MAC. MAB based organic light-emitting diode (OLED) exhibits a remarkable maximum external quantum efficiency (EQE) of 21.7%, which is much better than the maximum EQE of MAC-based OLED with a value of 12.8%. Our work proves that extending the distribution of LUMO is a simple but effective method to improve the efficiency of TADF emitter.
关键词： lumo distribution,external quantum efficiency,thermally activated delayed fluorescence,organic light-emitting diode
更新于2025-09-23 15:21:21
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[ASME ASME 2018 International Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Microsystems - San Francisco, California, USA (Monday 27 August 2018)] ASME 2018 International Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Microsystems - Analysis of Thermal Properties of Power Multifinger HEMT Devices
摘要： In this paper, several methods suitable for real time on-chip temperature measurements of power AlGaN/GaN based high-electron mobility transistor (HEMT) grown on SiC substrate are presented. The measurement of temperature distribution on HEMT surface using Raman spectroscopy is presented. We have deployed a temperature measurement approach utilizing electrical I-V characteristics of the neighboring Schottky diode under different dissipated power of the transistor heat source. These methods are verified by measurements with micro thermistors. The results show that these methods have a potential for HEMT analysis in thermal management. The features and limitations of the proposed methods are discussed. The thermal parameters of materials used in the device are extracted from temperature distribution in the structure with the support of 3-D device thermal simulation. The thermal analysis of the multifinger power HEMT is performed. The effects of the structure design and fabrication processes from semiconductor layers, metallization, and packaging up to cooling solutions are investigated. The analysis of thermal behavior can help during design and optimization of power HEMT.
关键词： thermal properties,Raman spectroscopy,thermal management,Schottky diode,power HEMT devices
更新于2025-09-23 15:21:21
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Exploiting lateral current flow due to doped layers in semiconductor devices having crossbar electrodes
摘要： Organic electronic devices such as light-emitting diodes, solar cells or rectifying diodes normally have a sandwich layer architecture stacked between the electrodes in a crossbar layout. Often however, the side effects of operating the devices in such an arrangement are either ignored or give rise to misinterpretations regarding the device performance or layer quality. For the sake of simplicity, device currents are typically assumed to exclusively flow in the direction vertical to the substrate, even though the conductivity of doped organic layers is high and gives rise to significant lateral current flows. Here, we study the vertical and lateral charge up along the n-doped and the p-doped layers as well as the resulting capacitance increase of charging the intrinsic layer outside the active area. We observe that controlling such lateral charging by structuring the doped layers can reduce the leakage current dramatically. We employ impedance spectroscopy to investigate the lateral charging responsibility for the capacitance increase at low frequencies. Modeling of the devices by a distributed RC circuit model yields information about the thickness, the conductivity, and the corresponding activation energy of both, the n-doped and the p-doped layers, simultaneously. We demonstrate that the capacitive effects from lateral charging can easily be misinterpreted as trap states in capacitance frequency characteristics. However, correct analysis with the proposed model actually yields rich and detailed post-fabrication information which can be utilized in device failure and degradation tests. Moreover, our results will aid the design and characterization of new electronic devices where lateral charge flow is part of the device concept.
关键词： Parasitic current,Leakage current,Impedance spectroscopy,Crossbar electrodes,Lateral current flow,Organic light-emitting diode,Capacitance,Organic solar cell,Structuring
更新于2025-09-23 15:21:21
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Mechanism of Liquid-Phase Reductive Thin-Film Deposition under Quasiballistic Electron Incidence
摘要： Highly reducing activity of quasiballistic hot electrons emitted from a nanocrystalline silicon (nc-Si) diode is veri?ed in terms of liquid-phase thin ?lm deposition. Incident electrons reduce positive ions in salt solutions coated on a target substrate, and then result in deposition of thin metal (Cu) and semiconducting (Si, Ge, and SiGe) ?lms. This mechanism is investigated here throughout the process from electron incidence to thin ?lm deposition. Thermodynamic criterion deduced from classical nucleation theory suggests that the output electron energy of the nc-Si emitter is suitable for promoting preferential reduction of target ions in solutions leading to the nuclei formation. In accordance with mass-transport analyses on generated nanoclusters, the most primary factor of thin ?lm growth is the dose of incident electron. The formulated deposition rate rapidly increases and reaches a stationary value within 0.1 s after electron incidence. The theoretical dependency of the thin ?lm thickness on the electron incidence time is consistent with the experimental results. Speci?c features of this scheme as an alternative approach for thin ?lm deposition are discussed in comparison with the conventional dry and wet processes.
关键词： nanocrystalline silicon diode,quasiballistic hot electrons,mass-transport analyses,thermodynamic criterion,liquid-phase thin film deposition
更新于2025-09-23 15:21:21
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A Lifetime Performance Analysis of LED Luminaires Under Real-Operation Profiles
摘要： Light-emitting diode (LED)-based lighting is the most dominant lighting solution in the current era since it is energy-efficient and long-lasting. Hence, performance analysis of the LEDs throughout its lifetime is of prime importance. The work presented in this article provides insight on degradation analysis of the LED luminaire inclusive of the LED driver in real operating ambient conditions and investigates the performance of both LED light engine and LED driver throughout the period of its lifetime. To represent the practical scenario of LED lighting system usage in commercial applications, analysis of switching cycles on the performance of LED luminaires is also studied. The outcome of this article suggests that LED luminaire under study tends to fail due to lumen degradation, followed by color shift represented by Duv and then lastly by driver failure. Scanning electron microscope and energy-dispersive spectroscopy (SEM-EDS) analysis suggests the corrosion of Ag mirror resulting in lumen output reduction and, thus, is the main reason for the failure of LED luminaire. This provides an insight into the LED manufacturing companies to have better estimate on lifetime of LED luminaires and also the necessity to improve the LEDs’ performance such that luminaires will have longer lifetime as claimed.
关键词： Life estimation,operating cycles,light-emitting diode (LED) luminaire,lumen degradation
更新于2025-09-23 15:21:01