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- 2018
- GaN HEMTs
- Power amplifier
- Broadband power amplifier
- SC band
- Power combining
- concentrated capacitive load
- distribution of the complex current at the antenna
- broadband antenna
- standing wave voltage factor
- antenna gain factor
- Electronic Science and Technology
- Oles Honchar Dnipro National University
- University of Tehran
- Gdansk University of Technology
- V. N. Karazin Kharkiv National University
- Reykjavik University
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Broadband light harvesting for highly efficient hot-electron application based on conformal metallic nanorod arrays
摘要： The utilization of nonradiative decay of surface plasmons (SPs) in the form of hot electrons in metallic nanostructures has a great potential for applications in photovoltaics, photocatalysis, photodetection, and surface imaging. Unfortunately, the metallic nanostructures usually support only narrowband plasmon resonances; moreover, the hot-electron thermalization loss during the transport to Schottky interface and the confined momentum space for hot-electron injection into semiconductor together result in an inefficient internal quantum process. In this study, we propose and experimentally demonstrate a broadband super absorber based on the metallic nanorod arrays (NRs). Optically, the average absorption across the entire visible band is up to 0.8, which is over 16-fold enhancement of the planar reference. Electrically, the hot electrons are controlled to be preferentially generated near Schottky interface within the mean free path, relieving the severe hot-electron thermalization loss. Moreover, the three-dimensional Schottky junction provides much increased hot-electron momentum space for injection at the vertical surface. These optical and electrical benefits lead to over 30-fold enhancement in the IPCE (incident photon-to-electron conversion efficiency) relative to the reference. The IPCE can be up to 10.9% at Eph = 3.1 eV, which is close to the limit of the thick-film single-barrier hot-electron devices. The conformal NRs system provides a promising strategy to simultaneously improve the hot-electron generation, transport and collection efficiencies and could be an outstanding candidate for efficient hot-electron optoelectronic and photocatalysis systems.
关键词： hot electron,surface plasmons,nanorod arrays,broadband absorber
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) - Linear GFDM: A Low Out-of-band Emission Configuration for 5G Air Interface
摘要： This paper explores the ?exibility of generalized frequency division multiplexing (GFDM) for achieving the same performance as ?lter bank multicarrier (FBMC). We present a GFDM con?guration where the good spectral containment of FBMC is also achieved through a modi?cation in the GFDM transmission scheme. For evaluating the scheme’s performance, we estimate the bit error ratio (BER) under three channel models: i) pure additive Gaussian AWGN; ii) time-invariant frequency-selective; iii) time-variant frequency-selective (doubly dispersive). The spectral containment is measured through the power spectral density. Furthermore, the complementary cumulative distribution function (CCDF) of the peak-to-average power ratio (PAPR) is also estimated. The Linear GFDM waveform shows identical performance when compared to FBMC in the above test scenarios.
关键词： GFDM,wireless communications,FBMC,non-orthogonal waveforms,enhanced mobile broadband,5G
更新于2025-09-23 15:21:21
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Nonlinear Noise of Low Transmission Penalty Dual-Stage Discrete Raman Amplifier
摘要： We experimentally characterise the linear and nonlinear performance of a >70nm, dual-stage, 19.5dB average net gain discrete Raman amplifier using different nonlinear fibres in the second stage. We propose an architecture built with a combination of IDF and SMF, and compare its performance with amplifiers built with conventionally used nonlinear fibre types (IDF-IDF, IDF-DCF). The measured FWM product power shows the IDF-SMF architecture to generate less nonlinear interference when compared to other schemes. We test the amplifiers with 5x120Gb/s DP-QPSK WDM signals in a recirculating loop at 10 recirculations of 93.4km SMF fibre, where the power sweep shows up to 2dB optimum launch power difference, with the maximum Q2 factor varying by up to 1.6dB. Using the optimum transmission point we measure a Q2=8.8dB at 35 recirculations of 93.4km transmission (3269km) with the proposed IDF-SMF scheme, which is >460km further than the other tested architectures. All characterised schemes performed similarly in the linear noise regime.
关键词： Broadband Transmission,Discrete Raman Amplification,Nonlinearity Characterisation
更新于2025-09-23 15:21:21
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[IEEE 2018 IEEE MTT-S International Conference on Numerical Electromagnetic and Multiphysics Modeling and Optimization (NEMO) - Reykjavik, Iceland (2018.8.8-2018.8.10)] 2018 IEEE MTT-S International Conference on Numerical Electromagnetic and Multiphysics Modeling and Optimization (NEMO) - Low-Cost Simulation-Driven Design of Broadband Rectifiers for Ambient RF Energy Harvesting
摘要： A steady growth of ambient RF energy density associated with a rapid increase of the number of broadcasting devices stimulates the research on broadband harvesting circuits. Such circuits can be used as energy sources for low-power sensors or Internet-of-Things devices. On the other hand, dedicated design techniques for rectifiers are lacking which results in poor performance of existing circuits. Also, their design cost is high because it involves hybrid electromagnetic (EM) and harmonic balance (HB) simulations. In this work, we propose a novel design procedure for low-cost design of broadband rectifiers. The core component of the approach is a novel equivalent-circuit-based low-fidelity model which does not involve harmonic balance (HB) simulations. The model consists of a matching circuit loaded with the RF-to-DC converter block represented using the S-parameter matrix. The latter is obtained from a single HB simulation of the converter circuit. Inaccuracy of the model is reduced using appropriate correction techniques. At the first stage of the design process, the proposed model is optimized for minimization of the in-band reflection. At the second stage, a hybrid HB-EM-based tuning oriented towards maximization of the structure efficiency is carried out. The proposed approach is demonstrated using a novel broadband rectifier operating within 0.5 GHz to 3.5 GHz band. Numerical cost of the method is 80% lower compared to direct EM-HB- based optimization of the rectifier circuit.
关键词： broadband rectifiers,constrained optimization,simulation-driven design,surrogate-based optimization,equivalent circuit model
更新于2025-09-23 15:21:21
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An Optically Transparent Broadband Microwave Absorber using Interdigital Capacitance
摘要： In this paper, an optically transparent broadband microwave absorber has been developed. The proposed geometry is constructed of patterned resistive films of ITO on flexible substrates, structure exhibits broadband absorptivity (above 90%) from 4 to 17.20 GHz (covering C, X, and Ku bands). The novelty of the design lies in leveraging the properties of interdigital capacitance to achieve wide absorption (fractional bandwidth of 124.53%), angular stability, as well as optical transparency compared to the earlier reported broadband absorbers. Moreover, the structure has been extensively investigated through deriving an equivalent circuit model and studying surface current distributions. Experimental validation of the fabricated prototype has also confirmed the potential use of resistive film based broadband absorbers in several applications.
关键词： interdigital capacitance,optically transparent absorber,Circuit analog absorber,broadband absorber
更新于2025-09-23 15:21:21
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[IEEE 2018 9th International Conference on Ultrawideband and Ultrashort Impulse Signals (UWBUSIS) - Odessa, Ukraine (2018.9.4-2018.9.7)] 2018 9th International Conference on Ultrawideband and Ultrashort Impulse Signals (UWBUSIS) - Broadband Antennas with Reactive Loads
摘要： The results of a study on the expansion of the frequency range of vibrational curved whip and loop antennas are presented. Optimal designs of these antennas with concentrated reactive loads included in the shoulders are proposed. The study was carried out for a design that appears promising for use as a microstrip antenna. It is a Z-shaped antenna of orthogonal linear polarization and loop antenna, supplemented by concentrated capacitive loads. It is shown that in order to obtain in the Z-shaped antenna and loop antenna a regime of a current close to the traveling wave regime and to obtain broadband, it is sufficient to include no more than four capacitive loads of a certain value in the antenna arm. This makes the construction of a broadband antenna and to reduce the expenditure of time and resources for its development and fabrication in comparison with known works in which it was proposed to include in the arm of the antenna a much larger number of reactive loads.
关键词： concentrated capacitive load,distribution of the complex current at the antenna,broadband antenna,standing wave voltage factor,antenna gain factor
更新于2025-09-23 15:21:21
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Preparation of ultra-broadband antireflective coatings for amplifier blast shields by a sol–gel method
摘要： A type of λ/4–λ/4 ultra-broadband antire?ective coating has been developed using modi?ed low refractive silica and high refractive silica layers by a sol–gel dip coating method for ampli?er blast shields of the Shen Guang II high power laser facility (SG-II facility). Deposition of the ?rst layer (high refractive index silica) involves baking at 200 ?C in the post-treatment step. The second layer (low refractive index, n = 1.20) uses low refractive index silica sol modi?ed by acid catalysis. Thermal baking at temperatures no less than 500 ?C for 60 min offers chemical stability, ethanol scratch resistance, and resistance to washing with water. The average residual re?ection of dual-side-coated fused silica glass was less than 1% in the spectral range from 450 to 950 nm. Transmission gain has been evaluated by taking into account angular light, and the results show that the transmission gain increases with increasing light incidence. Even at 60?, the transmission spectrum of the broadband antire?ective coating effectively covered the main absorption peak of Nd:glass.
关键词： blast shields,ampli?er,ultra-broadband,sol–gel,antire?ective coating
更新于2025-09-23 15:21:21
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A broadband ultraviolet light source using GaN quantum dots formed on hexagonal truncated pyramid structures
摘要： Broadband ultraviolet (UV) emission has been achieved from the GaN quantum dots grown on different facets of hexagonal truncated pyramidal structures. The GaN-based structures include both semipolar and polar facets, on which the intrinsic piezoelectric fields and the growth rates are different. In addition, a strain is locally suppressed at the boundaries of the truncated pyramid structure. As a result, the emission wavelength of quantum dots on various facets and boundaries becomes quite different, rendering a solid-state broadband UV light source with homogenerous intensity in a wide wavelength range.
关键词： broadband ultraviolet emission,GaN quantum dots,solid-state broadband UV light source,hexagonal truncated pyramid structures
更新于2025-09-23 15:21:01
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Manipulating disordered plasmonic systems by external cavity with transition from broadband absorption to reconfigurable reflection
摘要： Disordered biostructures are ubiquitous in nature, usually generating white or black colours due to their broadband optical response and robustness to perturbations. Through judicious design, disordered nanostructures have been realised in artificial systems, with unique properties for light localisation, photon transportation and energy harvesting. On the other hand, the tunability of disordered systems with a broadband response has been scarcely explored. Here, we achieve the controlled manipulation of disordered plasmonic systems, realising the transition from broadband absorption to tunable reflection through deterministic control of the coupling to an external cavity. Starting from a generalised model, we realise disordered systems composed of plasmonic nanoclusters that either operate as a broadband absorber or with a reconfigurable reflection band throughout the visible. Not limited to its significance for the further understanding of the physics of disorder, our disordered plasmonic system provides a novel platform for various practical application such as structural colour patterning.
关键词： broadband absorption,external cavity,disordered plasmonic systems,tunable reflection,structural colour patterning
更新于2025-09-23 15:21:01
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[IEEE 2019 International Conference on Communication and Electronics Systems (ICCES) - Coimbatore, India (2019.7.17-2019.7.19)] 2019 International Conference on Communication and Electronics Systems (ICCES) - Design and performance analysis of WDM optical Communication system with EDFA-DCF and FBG for dispersion compensation using $8\mathrm{x}5$ Gbps data rate
摘要： The way in which electromagnetic ?elds are transmitted and received by ground penetrating radar (GPR) antennas is crucial to the performance of GPR systems. Simple antennas have been characterized by analyzing their radiation patterns and directivity. However, there have been limited studies that combine real GPR antennas with realistic environments, which is essential to capture the complex interactions between the antenna and surroundings. We have investigated the radiation characteristics and sensitivity of a GPR antenna in a range of lossy dielectric environments using both physical measurements and a three-dimensional (3-D) ?nite-difference time-domain (FDTD) model. Experimental data were from measured responses of a target positioned at intervals on the circumference of a circle surrounding the H-plane of the antenna. A series of oil-in-water emulsions as well as tap water were used to simulate homogeneous materials with different permittivities and with complex conductivities. Numerical radiation patterns were created utilizing a detailed 3-D FDTD model of the antenna. Good correlation was shown between the experimental results and modeled data with respect to the strength of the main lobe within the critical angle window. However, there are discrepancies in the strength of main lobe at shallow angles. In all the dielectrics, the main lobes are generally broad due to the near-?eld observation distance but, as expected, become narrower with increasing permittivity. These results provide con?dence for further use of the FDTD antenna model to investigate scenarios such as larger observation distances and heterogeneous environments that are dif?cult to study experimentally.
关键词： electromagnetic modeling,Antenna measurements,?nite-difference time-domain (FDTD),antenna radiation patterns,broadband antennas
更新于2025-09-23 15:21:01