- 标题
- 摘要
- 关键词
- 实验方案
- 产品
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High-speed Optical-beam Scanning by an Optical Phased Array using Electro-optic Polymer Waveguides
摘要： Optical phased arrays (OPAs), which manipulate an optical beam by controlling the phase of light, are optical devices characterized by high speed, small size, light weight, and high reliability that make various applications possible. In this study, an eight-channel-waveguide OPA using an electro-optic (EO) polymer for phase control was fabricated. Very high-speed optical beam scanning with a frequency of 2 MHz was demonstrated by applying a driving waveform superimposing sinusoidal and rectangular-wave voltages. Furthermore, the EO polymer OPA can be operated with a low total-operation power consumption of 0.38 mW at a scanning speed of 500 kHz.
关键词： Optical phased array,electro-optic polymer,optical waveguides
更新于2025-09-23 15:21:01
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ultra-fine tuning
摘要： Researchers from Xi’an University of Technology in China, alongside researchers from the ENSEIRB and the IERF in France, propose an auto-tuning network for a phased-array high intensity focused ultrasound (HIFU) system based on a variable synchronous switched capacitor. The novel system is capable of automatically compensating for the reactive power and impedance drifts, caused by temperature fluctuations and manufacturing errors, in circuit transducers and complies with magnetic resonance imaging (MRI) compatibility regulations.
关键词： phased-array,variable synchronous switched capacitor,high-intensity focused ultrasound,HIFU,Auto-tuning network,MRI compatibility
更新于2025-09-23 15:21:01
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[IEEE 2019 9th International Electric Drives Production Conference (EDPC) - Esslingen, Germany (2019.12.3-2019.12.4)] 2019 9th International Electric Drives Production Conference (EDPC) - Evaluation of Soft Magnetic Ferrosilicon FeSi 6.5 for Laser Beam Melting
摘要： Planar or cylindrical phased arrays are two candidate antennas for future polarimetric weather radar. These two candidate antennas have distinctly different attributes when used to make quantitative measurements of the polarimetric properties of precipitation. Of critical concern is meeting the required polarimetric performance for all directions of the electronically steered beam. The copolar and cross-polar radiation patterns and polarimetric parameter estimation performances of these two phased array antennas are studied and compared with that obtained using a dual-polarized parabolic reflector antenna. Results obtained from simulation show that the planar polarimetric phased array radar has unacceptable polarimetric parameter biases that require beam to beam correction, whereas biases obtained with the cylindrical polarimetric phased array radar are much lower and comparable to that obtained using the parabolic reflector antenna.
关键词： radiation patterns,phased array radar,cylindrical array,Antenna,polarimetry,planar array,remote sensing,weather measurement
更新于2025-09-23 15:19:57
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Fully noncontact measurement of inner cracks in thick specimen with fiber-phased-array laser ultrasonic technique
摘要： To realize a fully noncontact ultrasonic testing method for inner cracks inspection in thick metal specimen, a phased array laser ultrasonic testing system with using a compact optic fiber array bundle and a laser interferometer is developed in this study. The focusing and steering of the shear wave and longitudinal wave generated with seven fiber-phased-array laser sources in thermoelastic regime is investigated by a numerical simulation and validated by the experiment. A non-contact measurement of the inner-surface cracks by both the angle-beam testing method and time-of-flight diffraction method with the fiber-phased-array laser ultrasonic technique have been studied.
关键词： Fiber bundle,Laser ultrasonic testing,Phased array,Inner cracks
更新于2025-09-23 15:19:57
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[IEEE 2019 IEEE Asia-Pacific Microwave Conference (APMC) - Singapore, Singapore (2019.12.10-2019.12.13)] 2019 IEEE Asia-Pacific Microwave Conference (APMC) - Two-Dimensional Electronically Controlled Scanning Phased Array Antenna Based on Liquid Crystal Material
摘要： In this paper, a two-dimensional electronically controlled scanning phased array antenna based on liquid crystal material is introduced. The structure consists of a 2×2 microstrip patch antenna array, a continuously variable helical folded delay line phase shifter, a RF feed and a bias network. The suspended stripline power divider, ground coplanar waveguide-suspended stripline transition structure and broadband patch antenna are studied respectively. The Ka-band LC passive phased array is developed by cascading the above circuits. The simulation results show that by tuning the excitation phases of each unit, the two-dimensional phase scan of the array is realized, the scanning angle is greater than ±30°, and the -10dB bandwidth of the array is larger than that of 4GHz.
关键词： Phased array,electronic scanning,liquid crystal
更新于2025-09-23 15:19:57
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - High Performance Ultrafast Thulium-Doped Fiber Lasers
摘要： The temporal variations (diurnal and annual) in arboreal (εTree) and bare soil (εSoil) dielectric constants and their correlation with precipitation were examined for several trees in Japan. A significant (1 σ (standard deviation) and 2 σ) εTree increase is observed after rainfall at 89.8% and 90.5% probability. However, rainfall does not always induce significant εTree increases. Rainfall of more than 5 mm/day can induce 1 σ εTree increase at a 59.6% probability. In order to examine whether the increase in εTree affects the L-band σ0 variation in a forest, the four-year temporal variation of the L-band backscattering coefficient (σ0) was estimated from observations by the Advanced Land Observing Satellite Phased Array type L-band Synthetic Aperture Radar. Observed maximum absolute deviations from the mean over the forest area were 1.0 and 1.2 dB for σ0 HV, respectively, and 4.0 and 3.0 dB over open land. σ0 and rainfall correlations show that εTree and σ0 Forest are proportional to precipitation integrated over seven or eight days; εSoil and σ0 Open land are proportional to precipitation integrated over three days. This finding indicates that εTree variations influence σ0 Forest areas. A stronger correlation between σ0 HV and precipitation is observed in several sites with low σ0 HV, where less biomass is expected, and several sites with high σ0 HV, where more biomass is expected. A weaker correlation between σ0 HV and precipitation is observed for several sites with high σ0 HV. These differences may be explained by the different contributions of double bounce scattering and potential transpiration, which is a measure of the ability of the atmosphere to remove water from the surface through the processes of transpiration. The two other results were as follows: 1) The functional relation between aboveground biomass and σ0 showed dependence on precipitation data, this being an effect connected with seasonal changes of the εTree. This experiment reinforces the fact that the dry season is preferable for retrieval of woody biomass from inversion of the functional dependence of SAR backscatter and for avoiding the influence of rainfall. 2) The complex dielectric constant for a tree trunk, which is measured between 0.2 and 6 GHz, indicates that free water is dominant in the measured tree.
关键词： Biomass,temporal variation,forest,dielectric constant,Phased Array type L-band Synthetic Aperture Radar (PALSAR)
更新于2025-09-23 15:19:57
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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) - Compensation of Radome Effects in Small Airborne Monopulse Arrays by Convex Optimization
摘要： The quality of small array antennas in airborne monopulse systems can be significantly reduced by the radome. We therefore present a convex optimization approach to minimize radome effects in monopulse arrays. This is achieved by using active element patterns in the optimization to determine the excitation weights. Simulation results for a BoR array with 48 elements and an extended hemispherical radome are presented. We demonstrate that it is possible to reduce the side-lobe level by 3.5 dB by taking radome effects into account in the optimization. This approach also results in an increased gain, particularly at large scan angles. Furthermore, the presented approach allows the monopulse slope to be indirectly specified as a design parameter. It is shown that the trade-off between the monopulse slope coefficient and the side-lobe level is approximately linear.
关键词： radomes,airborne ESM,monopulse DOA estimation,convex optimization,phased array antennas
更新于2025-09-23 15:19:57
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Wide-angle scanning circular polarization phased array based on polarization rotation technology
摘要： A wide-beam circular polarization (CP) antenna and a wide-angle scanning phased array based on novel polarization rotation reflective surface (PRRS) are proposed. The CP wide-beam pattern is obtained by the combination of the radiation wave from the patch antenna and the orthogonal reflected wave from the PRRS with a 90(cid:1) phase difference. The proposed CP wide-beam antenna obtains the patterns with the 3-dB beamwidth more than 136(cid:1) and the axial ratio (AR) beamwidth more than 132(cid:1) in the xoz-plane. Furthermore, an eight-element phased array based on the wide-beam CP antenna element is also developed. The measured results show that the main beam of the array can scan from ?65(cid:1) to 65(cid:1) with a gain fluctuation less than 3 dB and the ARs at every scanning angle less than 3 dB.
关键词： polarization rotation,phased array,wide-beam,circular polarization,wide-angle scanning
更新于2025-09-19 17:15:36
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[IEEE 2019 6th Asia-Pacific Conference on Synthetic Aperture Radar (APSAR) - Xiamen, China (2019.11.26-2019.11.29)] 2019 6th Asia-Pacific Conference on Synthetic Aperture Radar (APSAR) - A Ku-band Broadband Single-Ridge Waveguide Slot Antenna Array for UAV SAR Application
摘要： a Ku-band broadband waveguide wide side longitudinal slot antenna array for unmanned aerial vehicle (UAV) SAR application is designed. A single-ridge is employed to reduce the sectional size of the waveguide, and to achieve wide scanning ability. The bandwidth of the antenna is expanded by the single-ridge and subarea feeding of the slots. The active admittance of the waveguide slot is extracted based on the simulation using the HFSS software, in order to determine the size parameters of the waveguide slots. The simulation mode is built and the size parameters of the waveguide slots are modified and optimized by the aperture distribution re-deducing method. This design method has high efficiency and high veracity. An antenna array of 72 waveguide slot antenna lines is designed and manufactured. The measured results show that the relative bandwidth of VSWR smaller than 2 is 15%. The measured patterns show that the side lobe is smaller than -21.5dB, the cross polarization is better than -40dB, and the scanning angle is ±60° in azimuth direction. This waveguide slot antenna array has many advantages such as wide band, wide scanning, low side lobe and compact structure, and is suitable for UAV SAR application.
关键词： phased array antenna,single-ridge waveguide,waveguide slot antenna,broadband
更新于2025-09-19 17:13:59
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[IEEE 2019 IEEE Conference on Power Electronics and Renewable Energy (CPERE) - Aswan City, Egypt (2019.10.23-2019.10.25)] 2019 IEEE Conference on Power Electronics and Renewable Energy (CPERE) - Integrated Single Output Sensor Distributed MPPT for Photovoltaic Systems: A Novel Per-Cell Approach
摘要： The temporal variations (diurnal and annual) in arboreal (εTree) and bare soil (εSoil) dielectric constants and their correlation with precipitation were examined for several trees in Japan. A significant (1 σ (standard deviation) and 2 σ) εTree increase is observed after rainfall at 89.8% and 90.5% probability. However, rainfall does not always induce significant εTree increases. Rainfall of more than 5 mm/day can induce 1 σ εTree increase at a 59.6% probability. In order to examine whether the increase in εTree affects the L-band σ0 variation in a forest, the four-year temporal variation of the L-band backscattering coefficient (σ0) was estimated from observations by the Advanced Land Observing Satellite Phased Array type L-band Synthetic Aperture Radar. Observed maximum absolute deviations from the mean over the forest area were 1.0 and 1.2 dB for σ0 HV, respectively, and 4.0 and 3.0 dB over open land. σ0 and σ0 and rainfall correlations show that εTree and σ0 Forest are proportional to precipitation integrated over seven or eight days; εSoil and σ0 Open land are proportional to precipitation integrated over three days. This finding indicates that εTree variations influence σ0 Forest areas. A stronger correlation between σ0 HV and precipitation is observed in several sites with low σ0 HV, where less biomass is expected, and several sites with high σ0 HV, where more biomass is expected. A weaker correlation between σ0 HV and precipitation is observed for several sites with high σ0 HV. These differences may be explained by the different contributions of double bounce scattering and potential transpiration, which is a measure of the ability of the atmosphere to remove water from the surface through the processes of transpiration. The two other results were as follows: 1) The functional relation between aboveground biomass and σ0 showed dependence on precipitation data, this being an effect connected with seasonal changes of the εTree. This experiment reinforces the fact that the dry season is preferable for retrieval of woody biomass from inversion of the functional dependence of SAR backscatter and for avoiding the influence of rainfall. 2) The complex dielectric constant for a tree trunk, which is measured between 0.2 and 6 GHz, indicates that free water is dominant in the measured tree.
关键词： forest,temporal variation,dielectric constant,Biomass,Phased Array type L-band Synthetic Aperture Radar (PALSAR)
更新于2025-09-19 17:13:59