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[IEEE 2018 15th European Radar Conference (EuRAD) - Madrid, Spain (2018.9.26-2018.9.28)] 2018 15th European Radar Conference (EuRAD) - Design and demonstration of Linearly-Polarized Transmit-Arrays in X-band
摘要： This paper describes the design and demonstration of planar transmit-arrays operating in X-band with 1-bit phase quantization and based on wideband high efficiency unit cells. The unit cell consists of two identical square patch antennas loaded by C-loop slots and interconnected in their centers by a metalized via hole. The proposed transmit-array achieves a maximum directivity of 25.1 dBi and a gain of 22.8 dBi. Radiation efficiency of 56.3% is also obtained with a 1-dB gain bandwidth of up to 9.2% around 9.85 GHz and very low cross-polarization levels. The beam-steering up to 30° is achieved by tilting the focal source.
关键词： Patch antenna,slot loaded patch,Transmit-array,Antenna arrays,X-band,Unit cell,beam-steering
更新于2025-09-04 15:30:14
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[IEEE 2018 15th European Radar Conference (EuRAD) - Madrid, Spain (2018.9.26-2018.9.28)] 2018 15th European Radar Conference (EuRAD) - E-band Impulse Radio Transceiver with 2-bit Pulse-Position Modulation
摘要： This paper presents a novel radio transceiver based on a 2-bit pulse-position modulation (PPM) system for E-band wireless communication systems. We propose a time-based modulation architecture for a wireless transceiver. This is a promising architecture for deep-submicron and nanoscale CMOS technology. The performance of the wireless transceiver can be enhanced as the speed of the CMOS circuit increases. The transmitter is composed of four circuit blocks: a pulse-position modulator, impulse generator, millimeter-wave bandpass filter, and power amplifier. The receiver is comprised of a conventional quadrature demodulator. The transmitter and receiver chipset is fabricated in 55-nm standard CMOS technology. In transceiver loop-back tests, a data rate of 7.0 Gb/s with repetition data and 4.6 Gb/s with pseudo-random bit sequence (PRBS) data are demonstrated.
关键词： point-to-point communications,wireless transceiver,E-band,pulse-position modulation,impulse radio
更新于2025-09-04 15:30:14
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MULTI-BAND CYLINDRICAL DIELECTRIC RESONATOR ANTENNA USING PERMITTIVITY VARIATION IN AZIMUTH DIRECTION
摘要： A novel multi-band cylindrical dielectric resonator antenna (CDRA) using microwave laminates with permittivity variation in azimuth direction fed by coaxial probe is proposed in this paper. The proposed structures are constructed using di?erent materials having di?erent permittivities in azimuth direction in cylindrical dielectric resonator (DR). In order to determine the performance of various design parameters on resonance frequency and bandwidth, parametric studies have been performed. The operating band can be scaled up or down by adjusting the design parameters. Dual-band and triple-band CDRAs have been fabricated using commercially available microwave laminates to validate the simulation results. For each case, the input re?ection coe?cient, radiation pattern and antenna gain are simulated and measured. Good agreement between simulated and measured results has been observed. The proposed antennas may be suitable for WLAN applications.
关键词： WLAN applications,coaxial probe,multi-band,azimuth direction,permittivity variation,cylindrical dielectric resonator antenna
更新于2025-09-04 15:30:14
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Online weld pool contour extraction and seam width prediction based on mixing spectral vision
摘要： In this paper, based on gas–metal–arc welding (GMAW), we used a passive vision sensing system and proposed a double-path imaging method to capture weld pool images, and empirically and theoretically demonstrated the optimal bands. According to the mixed spectra of self-emitted radiation of the weld pool and the arc spectra, we selected 660-nm narrowband and 850-nm long-pass as the system’s working bands. Two cameras with 660-nm narrowband filter and 850-nm long-pass filter were used to capture weld pool images at the background level through a synchronous acquisition equation and weld pool images with high signal-to-noise ratio were obtained. After image registration, we used Gradient and Gray-based Neighbor Superpixel Merging (GNSM) method to extract the contour of weld pool image. Comparing with other algorithms, the proposed algorithm can obtain an effective and accurate contour of the weld pool image. Then we proposed an online seam width prediction method before seam formation which is based on the contour of the weld pool image. We used Gaussian distribution to fit the pixel width of the contour and the corresponding seam width measured by three-dimensional reconstruction. By comparatively analyzing the fitting deviation and the actual measurement results, we concluded that the deviation of weld seam width prediction was within 0.20 mm.
关键词： Three-dimensional reconstruction,Superpixel segmentation,Seam width prediction,Vision sensing system,Double-band imaging,Contour of weld pool
更新于2025-09-04 15:30:14
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Bandgap Renormalization, Carrier Multiplication and Stark Broadening in Photoexcited Black Phosphorous
摘要： We investigate black phosphorous by time and angle resolved photoelectron spectroscopy. The electrons excited by 1.57 eV photons, relax down to conduction band minimum within 1 ps. Despite the low bandgap value, no relevant amount of carrier multiplication could be detected at excitation density 3 ? 6 × 1019 cm?3. In the thermalized state, the bandgap renormalization is negligible up to a photoexcitation density that fills the conduction band by 150 meV. Astonishingly, a Stark broadening of the valence band takes place at an early delay time. We argue that electrons and holes with high excess energy lead to inhomogeneous screening of near surface fields. As a consequence the chemical potential is no longer pinned in a narrow impurity band.
关键词： Stark,ARPES,Ultrafast,Black Phosphorous,Band-Gap-Renormalization
更新于2025-09-04 15:30:14
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Electronic band structure of InAs/InAsSb type-II superlattice for HOT LWIR detectors
摘要： The InAs/InAs1?xSbx type-II superlattices (T2SLs) grown on GaSb bu?er layer and GaAs substrates have recently been applied for detectors for long wavelength infrared (LWIR) range and high operating temperature (HOT) conditions. The detailed modeling of T2SLs minibands structure required for detector’s design optimization process relies on accurate knowledge of the InAs1?xSbx bandgap and band edge position. The k?p (8 × 8 method) was used to analyze the valence band o?set (VBO) between InAs and InAs1?xSbx, and hence the InAs1?xSbx band edge position at required xSb composition. An increase of the VBO leads to the structure transformation from type-IIb to type-II superlattices. The required energy bandgap can be reached by changing the conduction band o?set (CBO) and the energy bandgap bowing parameter. The temperature dependence of the experimental results of InAs/InAs1?xSbx T2SLs energy bandgap was found to be comparable with theoretical one when energy bandgap bowing parameter is dependent on temperature. The proper ?tting of theoretically calculated and experimentally measured spectral response characteristics was shown.
关键词： Energy-band o?set,InAs/InAs1?xSbx type-II superlattice,T2SLs,LWIR,Infrared detectors
更新于2025-09-04 15:30:14
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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) - Compact Quadruple Band MIMO Antenna for 5G Mobile Applications
摘要： A design of compact quadruple band MIMO antenna for 5G mobile applications is proposed. The MIMO antenna consists of 8 antenna elements, each two of them are symmetrically placed on the orthogonal frame corners of the substrate, closely located to each other and connected by a short neutral line. Each antenna element consists of two feeding ports which operate at different frequencies. One feeding port operates at 3.5-3.9 GHz and the other feeding port operates at three bands, which are 2.3-2.5 GHz, 3.3-3.5 GHz and 4.25-4.45 GHz. The radiation efficiencies of all four bands are above 50% and ECC of the antenna elements are below 0.2, the calculated ergodic channel capacities with a 20 dB SNR at four bands reach to 87% of the ideal case at 3.6 GHz, 87.5% at 2.4 GHz, 82.7% at 3.4 GHz and 83.2% at 4.3 GHz, respectively, which are close to the ideal case of 8×8 MIMO system.
关键词： quadruple band antenna,5G mobile communication,channel capacity,mobile antennas,MIMO antenna
更新于2025-09-04 15:30:14
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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) - Compact Dual-band Bow-tie MIMO Antennas with Fragment-type Isolation Structure
摘要： Compact dual-band bow-tie MIMO antennas with fragment-type isolation structure are presented. The proposed bow-tie MIMO antennas include both canonical structures defining the radiators and fragment structures isolator. In the design, MOEA/D-DE for defining the optimization of canonical structures and MOEA/D-GO for optimization of fragment structures are combined and iterated. After the compound optimization, both simulation and measurement show that the return loss is higher than 10dB and isolation is higher than 25dB in the dual bands of 2.45-2.75GHz and 3.35-3.9GHz. Based on the overall performance, the proposed array can be employed for MIMO wireless communication systems like WiMAX.
关键词： fragment-type isolation,dual-band antennas,multi-objective optimization
更新于2025-09-04 15:30:14
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Energy Band Gap Modulation in Nd-doped BiFeO <sub/>3</sub> /SrRuO <sub/>3</sub> Heteroepitaxial for Visible Light Photoelectrochemical Activity
摘要： The ability of band offsets at multiferroic/metal and multiferroic/electrolyte interfaces in controlling charge transfer, and thus alters the photoactivity performance has sparked significant attention in solar energy conversion applications. Here, we demonstrate that the band offsets of the two interfaces play the key role in determining charge transport direction in a downward self-polarized BFO film. Electrons tend to move to BFO/electrolyte interface for water reduction. Our experimental and first-principles calculations reveal that the presence of neodymium (Nd) dopants in BFO enhances the photoelectrochemical performance by reduction of the local electron-hole pair recombination sites and modulation of the band gap to improve the visible light absorption. This opens a promising route to the heterostructure design by modulating the band gap to promote efficient charge transfer.
关键词： density functional theory (DFT),heterojunction band offsets,charge transfer,Nd-doped BiFeO3,photoelectrochemical (PEC)
更新于2025-09-04 15:30:14
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Electronic structure of the polymer-cathode interface of an organic electroluminescent device investigated using operando hard x-ray photoelectron spectroscopy
摘要： The electronic structure of a polymer-cathode interface of an operating organic light-emitting diode (OLED) was directly investigated using hard X-ray photoelectron spectroscopy (HAXPES). The potential distribution pro?le of the light-emitting copolymer layer as a function of the depth under the Al/Ba cathode layer in the OLED depended on the bias voltage. We found that band bending occurred in the copolymer of 9,9-dioctyl?uorene (50%) and N-(4-(2-butyl)-phenyl)diphenylamine (F8-PFB) layer near the cathode at 0 V bias, while a linear potential distribution formed in the F8-PFB when a bias voltage was applied to the OLED. Direct observation of the built-in potential and that band bending formed in the F8-PFB layer in the operating OLED suggested that charges moved in the F8-PFB layer before electron injection from the cathode.
关键词： polymer-cathode interface,band bending,organic light-emitting diode,electronic structure,hard X-ray photoelectron spectroscopy
更新于2025-09-04 15:30:14