- 标题
- 摘要
- 关键词
- 实验方案
- 产品
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Two-Dimensional Imaging Based on Near-Field Focused Array Antenna
摘要： In this letter, a near-field focused array antenna is applied to two-dimensional (2-D) microwave imaging, which steers its focus on the designed focal plane by changing the operating frequency and by phase control in two directions, respectively. The imaging system is composed of this array and two microstrip antennas, as receiver and transmitters, respectively. Simulations and measurements have proved the feasibility of the image reconstruction approach. The proposed method has a high imaging speed due to fast electrical beam scan, and thanks to the frequency scan performance of the array in one dimension, it also shows low-cost property against the fully phased method.
关键词： near-field focused beams,Microwave imaging,phased arrays,reconstruction algorithm
更新于2025-09-23 15:23:52
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[IEEE 2018 IEEE Asian Solid-State Circuits Conference (A-SSCC) - Tainan, Taiwan (2018.11.5-2018.11.7)] 2018 IEEE Asian Solid-State Circuits Conference (A-SSCC) - A Sub-Picosecond Hybrid DLL for Large-Scale Phased Array Synchronization
摘要： A large-scale timing synchronization scheme for scalable phased arrays is presented. This approach utilizes a DLL co-designed with a subsequent 2.5GHz PLL. The DLL employs a low noise, fine/coarse delay tuning to reduce the in-band rms jitter to 323fs, an order of magnitude improvement over previous works at similar frequencies. The DLL was fabricated in a 65nm bulk CMOS process and was characterized from 27MHz to 270MHz. It consumes up to 3.3mW from a 1V power supply and has a small footprint of 0.036mm2.
关键词： phase noise,tracking loops,CMOS integrated circuits,radio frequency,phase locked loops,phased-arrays,delay-lines
更新于2025-09-23 15:22:29
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Angle-of-Arrival Measurement System Using Double RF Modulation Technique
摘要： A new technique for determining the angle of arrival (AoA) of an RF signal is presented. It is based on a cascaded modulator structure, where continuous wave light from an optical source is modulated by an incoming RF signal twice. The AoA of an RF signal can be determined by the system output RF signal power. The proposed structure is capable for measuring the AoA of both narrow and broadband RF signals. This overcomes the limitation in all previously reported photonics-based AoA measurement systems, which are applicable to either a single-frequency RF signal or a broadband RF signal. It also does not involve electrical components and high extinction ratio modulators, which are required in reported structures. Experimental results are presented that show an AoA measurement range of 0° to over 65° with errors of less than 1.9° for a microwave signal at 2.65 and 12.62 GHz. Results also show that the system is capable to measure the AoA of a pseudorandom binary sequence signal at a microwave frequency.
关键词： notch filters,Direction-of-arrival estimation,phased arrays,microwave photonics
更新于2025-09-23 15:22:29
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A Wideband Planar Aperture Array Using Interconnected Crossed Rings
摘要： A 5:1 frequency bandwidth aperture array antenna based on a new planar structure is reported. Dual polarization is implemented with high cross-polarization discrimination over ±45? scan angle from zenith. It is a low-loss cost effective approach using minimum dielectric materials. In the proposed planar antenna array design, a mutual coupled interconnected ring structure is used which extends the operational frequency band to the region where the element separation can be considerably greater than half a wavelength, unlike the previously reported interconnected array structures. Hence the total number of elements can be reduced for a speci?ed aperture size. The dual polarization have coincident-phase centers and in the implemen-tation reported here two low noise ampli?ers on the same board are integrated with a pair of dual polarized elements to form an active array. A 10 by 10 element array prototype of the design has been manufactured and the measured results con?rm it as a low cost, high performance front-end solution.
关键词： Aperture antennas,Phased arrays,Planar arrays,Radio astronomy
更新于2025-09-23 15:21:21
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DIAMAGNETO-DIELECTRIC ANISOTROPIC WIDE ANGLE IMPEDANCE MATCHING LAYERS FOR ACTIVE PHASED ARRAYS
摘要： In this paper, we present the full process of designing anisotropic metamaterial (MM) wide angle impedance matching (WAIM) layers. These layers are used to reduce the scan losses that occur in active phased arrays for large scanning angles. Numerical results are provided to show the improvement in performances that such layers can ensure. The proposed anisotropic MM-WAIM layers achieve an improvement of about 1 dB of more radiated power at θ = 70? from broadside, in a 13% of fractional bandwidth on the azimuthal plane φ = 90?. Weaker improvements are obtained in the other azimuthal planes, however keeping the active re?ection coe?cient below ?9 dB for all azimuthal planes up to θ = 60? and up to θ = 70? o?-axis for planes φ = 45?, 90? in the whole operational band.
关键词： scan losses,wide angle impedance matching,anisotropic metamaterial,active phased arrays,impedance matching
更新于2025-09-23 15:21:21
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Brazing, Laser, and Electron-Beam Welding of Additively Manufactured GRCop-84 Copper for Phased Array Lower Hybrid Launchers
摘要： Recent advances in selective laser melting 3-D printing technology allow additive manufacturing of lower hybrid current drive (LHCD) RF launchers from a new material, Glenn Research Copper 84 (GRCop-84), a Cr2Nb (8 at. % Cr, 4 at. % Nb) precipitation hardened alloy, in configurations unachievable by conventional machining. Cr2Nb crystals pin grain boundaries within the copper matrix resulting in high tensile strength and resistance to annealing at elevated temperatures. Brazing, laser, and electron-beam welding (EBW) techniques are explored for joining a thin-walled GRCop-84 waveguide with zero porosity and minimal internal surface roughness. GRCop-84 wets well with the silver solder, CuSil, and Cusil-ABA brazes, once the durable surface oxide is mechanically removed. GRCop-84 melt pool size and flow during EBW is reduced compared to oxygen-free copper (OFC). Pulsed laser and e-beam welding maintains the Cr2Nb precipitate size; precipitate coarsening occurs in conduction mode e-beam welding.
关键词： joining processes,fusion reactor design,magnetic confinement,Annealing,tokamaks,copper alloys,melt processing,materials processing,phased arrays,waveguide
更新于2025-09-23 15:21:01
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Space PV Concentrators for Outer Planet and Near-Sun Missions, Using Ultra-Light Fresnel Lenses Made with Vanishing Tools
摘要： The Kilpisj?rvi Atmospheric Imaging Receiver Array (KAIRA) is a dual array of omnidirectional VHF radio antennas located near Kilpisj?rvi, Finland. It is operated by the Sodankyl? Geophysical Observatory. It makes extensive use of the proven LOFAR antenna and digital signal-processing hardware, and can act as a stand-alone passive receiver, as a receiver for the European Incoherent Scatter (EISCAT) very high frequency (VHF) incoherent scatter radar in Troms?, or for use in conjunction with other Fenno-Scandinavian VHF experiments. In addition to being a powerful observing instrument in its own right, KAIRA will act as a pathfinder for technologies to be used in the planned EISCAT_3-D phased-array incoherent scatter radar system and participate in very long baseline interferometry experiments. This paper gives an overview of KAIRA, its principal hardware and software components, and its main science objectives. We demonstrate the applicability of the radio astronomy technology to our geoscience application. Furthermore, we present a selection of results from the commissioning phase of this new radio observatory.
关键词： receiving antennas,radio astronomy,radar antennas,Antenna arrays,phased arrays
更新于2025-09-23 15:19:57
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[IEEE 2019 IEEE 19th International Conference on Nanotechnology (IEEE-NANO) - Macao (2019.7.22-2019.7.26)] 2019 IEEE 19th International Conference on Nanotechnology (IEEE-NANO) - Direct Transfer Printing of Dielectric Nanoparticle Assembled Superlens Array for Super-resolution Imaging <sup>*</sup>
摘要： We describe a novel iterative methodology for computing a set of low-sidelobe beamforming weights for an airborne, electronically-steered phased-array radar using an in-flight stochastic optimization routine performed over a number of coherent processing intervals (CPIs). The proposed approach is notable in that it does not rely upon a good antenna calibration and only requires digitization of the radar’s sum beam. By observing the radar ground clutter, the algorithm iteratively adjusts the beamformer. Furthermore, it is computationally inexpensive and scales favorably to radars comprising very large numbers of antenna elements and requiring extremely low sidelobes.
关键词： radar,clutter,iterative,Calibration,stochastic optimization,phased arrays
更新于2025-09-23 15:19:57
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[IEEE 2019 IEEE International Symposium on Phased Array System & Technology (PAST) - Waltham, MA, USA (2019.10.15-2019.10.18)] 2019 IEEE International Symposium on Phased Array System & Technology (PAST) - An Additively Manufactured, All-metallic Frequency-scaled Ultra-wide Spectrum Element (AM-FUSE) Active Electronically Scanned Array (AESA) for Space-borne Applications
摘要： A new breed of the Frequency-scaled, Ultra-wide Spectrum Element (FUSE) is built entirely from a single piece of metal using direct metal laser sintering (DMLS) for space-borne missions. An active electronically scanned array (AESA) was built that includes an 8x4 linearly polarized aperture and low-profile feed circuitry that has eight true-time delay units (TDU) to fit inside a 3U CubeSat. This AESA operates over 1.5 GHz – 6 GHz, scanning +/- 45 degrees in azimuth with a very low active voltage standing wave ratio (active VSWR). The weight of the array with its combiner and beamforming boards is less than 3 lbs.
关键词： wideband,tapered-slot,CubeSat,additive manufacturing,AESA,connector-less,phased arrays,Vivaldi,FUSE,Antennas,space missions
更新于2025-09-23 15:19:57
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Wideband Wide-Scanning Phased Array in Triangular Lattice with Electromagnetic Band-Gap Structures
摘要： A phased array in triangular lattice, with a large element spacing, wide band and wide scan angle, is investigated in this paper. The array is designed based on a connected backed-cavity antenna element. Scan blindness is observed for this triangular lattice array when the beam scans in the E plane due to large element spacing which provides a suitable propagation condition for the leaky surface waves in the array aperture. Therefore, compact electromagnetic band-gap (EBG) structures are loaded in the array element to suppress the leaky surface waves and then remove the E-plane scan blindness for the largest impedance bandwidth. The bandwidths close to the theoretical values are achieved as the beam is scanned in the E and H planes, for the given element spacing. The validity of design is verified by fabricating a 13×5 prototype, the measured results are in good agreements with the full-wave simulations.
关键词： scan blindness,phased arrays,wide scanning,Electromagnetic band-gap (EBG) structures,triangular lattice
更新于2025-09-19 17:15:36