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[Institution of Engineering and Technology 12th European Conference on Antennas and Propagation (EuCAP 2018) - London, UK (9-13 April 2018)] 12th European Conference on Antennas and Propagation (EuCAP 2018) - Accurate Determination of Radiation Patterns from Near-Field Measurements in Highly Reflective Environments
摘要： The radiation pattern of an antenna under test is determined from measurements in a highly reflective, fully metallic measurement environment similar to a reverberation chamber. The undesired influence of the reflecting walls is eliminated by processing the data obtained for a large number of frequencies and different probe locations in the chamber. The post-processing concept effectively combines temporal and spatial filtering of the measured signals in an innovative field synthesis concept. S-Band measurements show the effectiveness of the proposed processing concepts. The accuracy is comparable to anechoic measurements, however, for the cost of increased measurement and post-processing effort.
关键词： echo suppression,near-field far-field transformation,antenna measurement
更新于2025-09-23 15:23:52
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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) - Feasibility and Challenges of Over-The-Air Testing for 5G Millimeter Wave Devices
摘要： The evolution from 1G through 5G cellular technologies has been fueled mainly by the insatiable need for speed, lower latency, high reliability and enhanced flexibility of use across the wireless ecosystem. Using multiple antennas in conjunction with complex modulation schemes has rendered each generation of cellular technology an enhanced version over its former counterpart. 5G technology aims to exploit previously unchartered higher millimeter wave (mmWave) frequencies & larger bandwidths towards realizing the goal of greater data throughput, while simultaneously enhancing data reliability and reducing latency. The small wavelength of mmWave signals makes it possible to design 5G devices using several multi-element phased array antennas with small element-element spacing. However, unlike the antenna designs of 2G/3G/4G devices, 5G multi-element antennas would be integrated with the radio frequency integrated circuit (RFIC) board of the 5G device. The tight integration between antennas and RFIC renders the antenna port of the device under test (DUT) inaccessible for physical connections using cables/connectors to test equipment. Since conducted testing with cables is not feasible anymore, radiated over-the-air (OTA) testing becomes mandatory for 5G mmWave device verification. This paper aims to assess the feasibility of candidate OTA test methods for 5G mmWave test requirements. The challenges of testing 5G mmWave devices over-the-air have been elucidated and alternative OTA test solutions for overcoming these challenges have also been discussed.
关键词： multi-probe anechoic chamber (MPAC),Multiple-input multiple-output (MIMO),compact antenna test range (CATR),far-field,near-field,antenna arrays
更新于2025-09-23 15:21:01
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Plasmonic Fano Resonance in Homotactic Aluminum Nanorod Trimer: the Key Role of Coupling Gap
摘要： Recently, the Fano effect of aluminum nanostructures has attracted a lot of attentions in several detector and sensor applications, but the role of coupling gap in it remains unintuitive. In this paper, a homotactic aluminum rod trimer (HART) is designed to form the plasmonic Fano resonances and visualize the important role of coupling gap size. The plasmon hybridization model and far field images were used to qualitatively describe the formation mechanism of Fano resonance. The simulation results intuitively show that the Fano dip of HART with a smaller coupling gap size has a higher red-shift speed when increasing the refractive index of surrounding environment or the length of HART with a fixed axial ratio (LS/LL = 0.6). Our study provides the insights to the key role of coupling gap in the performance of Fano structures.
关键词： Fano resonance,Aluminum nanorods,Far field,Plasmon,Coupling gap
更新于2025-09-23 15:19:57
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Substrate-modulated directional far field scattering behavior of individual plasmonic nanorods
摘要： Steering the energy of the incident light into the specific directions by using plasmonic nanostructures plays a key role for future micro-nano photonic integration and optical imaging systems, but the influence of the dielectric substrate on the full-space far-field scattering image of metal nanostructures remains unintuitive. In this paper, the influence of dielectric substrate on the far-field scattering behavior of surface plasmon resonance mode is systematically investigated. By using a simple model, we found that the dielectric substrate could suppress the backscattering energy of plasmon mode. The forward scattering energy of plasmon mode will be concentrated as the refractive index of the substrate increased. We also realized a directional forward scattering of plasmon mode energy by combining the dielectric substrate and dielectric/metal structures. Our research provides a new strategy for the directional control of the incident light energy in a dielectric substrate.
关键词： Lossless dielectric substrate,Surface plasmon resonance,Far field pattern,Directional radiation,Nanorod
更新于2025-09-23 15:19:57
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An antipodal Vivaldi antenna for improved far-field properties and polarization manipulation of broadband terahertz quantum cascade lasers
摘要： We present an antipodal Vivaldi antenna for broadband double metal waveguide terahertz quantum cascade lasers and frequency combs. Its exponentially curved flare profile results in an adiabatic in-plane mode expansion, producing an improved far-field with a single-lobed beam of (23° × 19°) full width half maximum with an octave-spanning bandwidth. The antenna also acts as a wave retarder, rotating the polarization from vertical toward horizontal polarization by a frequency-dependent angle. The laser’s emission spectrum and current–voltage characteristics are not affected, as well as frequency comb operation. Measurements agree well with numerical simulations, and the proposed antenna covers a broad spectral range (1.5–4.5 THz).
关键词： antipodal Vivaldi antenna,broadband,polarization manipulation,far-field properties,terahertz quantum cascade lasers
更新于2025-09-23 15:19:57
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Uniqueness and Direct Imaging Method for Inverse Scattering by Locally Rough Surfaces with Phaseless Near-Field Data
摘要： This paper is concerned with inverse scattering of plane waves by a locally perturbed infinite plane (which is called a locally rough surface) with the modulus of the total-field data (also called the phaseless near-field data) at a fixed frequency in two dimensions. We consider the case where a Dirichlet boundary condition is imposed on the locally rough surface. This problem models inverse scattering of plane acoustic waves by a one-dimensional sound-soft, locally rough surface; it also models inverse scattering of plane electromagnetic waves by a locally perturbed, perfectly reflecting, infinite plane in the transverse electric polarization case. We prove that the locally rough surface is uniquely determined by the phaseless near-field data generated by a countably infinite number of plane waves and measured on an open domain above the locally rough surface. Further, a direct imaging method is proposed to reconstruct the locally rough surface from the phaseless near-field data generated by plane waves and measured on the upper part of the circle with a sufficiently large radius. Theoretical analysis of the imaging algorithm is derived by making use of properties of the scattering solution and results from the theory of oscillatory integrals (especially the method of stationary phase). Moreover, as a by-product of the theoretical analysis, a similar direct imaging method with full far-field data is also proposed to reconstruct the locally rough surface. Finally, numerical experiments are carried out to demonstrate that the imaging algorithms with phaseless near-field data and full far-field data are fast, accurate, and very robust with respect to noise in the data.
关键词： Dirichlet boundary condition,phaseless near-field data,inverse scattering,full far-field data,locally rough surface
更新于2025-09-19 17:15:36
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A study on the effects and visibility of low-order aberrations on laser beams with orbital angular momentum
摘要： Laguerre–Gaussian-like laser beams have been proposed for driving experiments with high-intensity lasers. They carry orbital angular momentum and exhibit a ring-shaped intensity distribution in the far field which make them particularly attractive for various applications. We show experimentally and numerically that this donut-like shape is extremely sensitive to off-axis wavefront deformations. To support our claim, we generate a Laguerre–Gaussian-like laser beam and apply a selection of common low-order wavefront aberrations. We investigate the visibility of those wavefront deformations in the far field. Under use of established tolerance criteria, we determine the thresholds for the applied aberration and compare the findings with simulations for verification.
关键词： tolerance criteria,Laguerre–Gaussian-like laser beams,orbital angular momentum,far field,wavefront aberrations
更新于2025-09-19 17:13:59
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High-performance blue perovskite light-emitting diodes based on the a??far-field plasmonic effecta?? of gold nanoparticles
摘要： Metal halide perovskites have become the next-generation electroluminescent materials due to their excellent optoelectronic properties. In the last several years, there has been tremendous progress in the performance of red and green-light perovskite electroluminescent devices (PeLEDs) with external quantum efficiencies (EQE) exceeding 14% and 21%, respectively. In contrast, blue PeLEDs are still in infancy stage, due to EQEs below 1%. Therefore, development of blue PeLEDs is sorely needed since blue light plays a vital role in achieving full-color and white-light emission. In order to improve the efficiency of blue PeLEDs, herein we introduce gold nanoparticles (Au NPs) into poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) hole transport layer (HTL) to achieve a high performance blue PeLEDs with an emission wavelength ~475 nm. By introducing Au NPs, the optical properties of poly(ethylene oxide) (PEO):PEA2(CsPbBrxCl3?x)n?1PbBr4 perovskite films have been significantly improved leading to 3.8 times enhancement in fluorescence intensity. Based on this improvement, the blue PeLEDs record a maximum luminance and EQE of ~1110 cd/m2 and 1.64%, respectively performing among the best reported so far. Finally, the PeLED performance improvement is attributed to the far-field surface plasmonic effect of Au NPs. This effect is originated from the interference between the original chromophores emission and the mirror-reflected emission of mirror-type substrates. This study not only reveals the function of Au NPs in development of blue PeLEDs, but also offers new insights into the fundamental physics underlying the effect of surface plasmon resonance of Au NPs on perovskite light emitting devices.
关键词： gold nanoparticles,blue PeLEDs,Metal halide perovskites,far-field plasmonic effect,external quantum efficiency
更新于2025-09-19 17:13:59
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Color speckle measurement of white laser beam emitted from fiber output of RGB laser modules
摘要： Color speckle metrics of an RGB-combined white laser beam emitted from an optical fiber output of two types of RGB laser module are measured. A new method for eliminating the effects of a fiber far field pattern from the measured 2D speckle data is employed to calculate the speckle metrics with a statistical accuracy. In this method, unspeckled 2D data of the far field pattern can be directly measured by opening the iris of the speckle measurement equipment. As a result, white photometric speckle contrast and color speckle distribution in CIE1931 chromaticity diagram are, for the first time, successfully obtained by eliminating the far field pattern effects.
关键词： Optical fiber,Color speckle,Far field pattern,Laser module,Speckle
更新于2025-09-16 10:30:52
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[IEEE 2019 Antenna Measurement Techniques Association Symposium (AMTA) - San Diego, CA, USA (2019.10.6-2019.10.11)] 2019 Antenna Measurement Techniques Association Symposium (AMTA) - Waveguide-integrated Rydberg Atom-based RF Field Detector for Near-field Antenna Measurements
摘要： We demonstrate simultaneous amplitude and phase measurements of a radio-frequency (RF) ?eld through the use of a Rydberg atom-based sensor embedded inside a waveguiding structure. This measurement uses the Rydberg atom-based sensor in a mixer con?guration, which requires the presence of a local oscillator (LO) RF ?eld. The waveguiding structure supplies the LO ?eld. The combined waveguide and Rydberg atom system is used to measure phase and amplitude in the near-?eld of a horn antenna to extract the far-?eld pattern.
关键词： far-field pattern,near-field antenna measurements,waveguide,Rydberg atom-based sensor,RF field measurements
更新于2025-09-12 10:27:22