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[IEEE 2018 International Conference on Microwave and Millimeter Wave Technology (ICMMT) - Chengdu, China (2018.5.7-2018.5.11)] 2018 International Conference on Microwave and Millimeter Wave Technology (ICMMT) - A Sub-Wavelength Reflectarray Element Based on Minkowski Fractal Loop
摘要： A novel reflectarray element consists of one Minkowski fractal loop in combination of a square loop is proposed. The size of the element is two fifth of a wavelength of the working frequency of 5.8 GHz. The proposed element offers a slope value of 20°/mm, while the phase range is in excess of 411°. Utilizing the proposed element, a 10 × 10 reflectarray antenna is simulated. Simulation results show that the antenna gain is 18.9 dBi at its working frequency 5.8 GHz, and has an impedance bandwidth (|S11| < -10 dB) of 3% (5.73 ~ 5.9 GHz).
关键词： Minkowski fractal loop,reflectarray element,antenna gain,square loop,phase range
更新于2025-09-04 15:30:14
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[IEEE 2018 13th European Microwave Integrated Circuits Conference (EuMIC) - Madrid, Spain (2018.9.23-2018.9.25)] 2018 13th European Microwave Integrated Circuits Conference (EuMIC) - GaAs Balanced Amplifier for Ka-Band Space Communications System
摘要： The paper deals with the development of a state-of-the-art medium level amplifier able to combine good noise performance with a high P1dB compression point. The MMIC is realized with a balanced structure and making use of the PH25 GaAs pHEMT process provided by UMS. The balanced structure allows to achieve a gain of 19 dB with a P1dB compression point greater than 15 dBm and a noise figure of about 3 dB in a large bandwidth spanning from 26.5 GHz to 31.5 GHz. The chip has a single bias pad; the input and output bond wires are directly matched on chip, so easingenhancing the mechanical integration in the front-end.
关键词： Ka-band,GaAs technology,Balanced amplifier,Space technology,dynamic range
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) - Error Analysis of Target Angle and Angular Velocity in a PLL-based FMCW Radar Measurement
摘要： This paper analyzes the error in a real-time measurement of the angular velocity of a moving target. The angular velocity is deduced from two successive FMCW radar measurements using two homodyne radar systems with fast frequency ramps. We analyze the effect of phase noise in the phase-locked loop (PLL) driving the radar system on the rms error of the measured angular velocity. For fast frequency ramps, this error is given as a function of target distance, sweep bandwidth and VCO phase noise. The proposed method can support collision avoidance in automotive applications.
关键词： angular velocity,PLL,phase noise,FMCW radar,collision avoidance,range precision
更新于2025-09-04 15:30:14
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The effect of the medium-range configuration on the atomistic fracture behaviour of vitreous silica
摘要： Using molecular dynamics simulations, we prepare vitreous silica by quenching molten silica to ambient temperature. Varying the quenching rate, we show that the latter barely influences the short-range order, whereas the medium-range configuration is significantly affected. We subject the prepared silica specimens to tension until fracture occurs and demonstrate the effect on the material behaviour. We evaluate the medium-range configuration in terms of the ring statistics of the glass network structure. Linking the ring statistics with the deformation and fracture behaviour of vitreous silica, we provide a topologically motivated explanation of the material behaviour.
关键词： quenching rate,fracture behaviour,vitreous silica,medium-range configuration,molecular dynamics
更新于2025-09-04 15:30:14
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Design and engineering of dispersion and loss in photonic crystal fiber 1?×?4 power splitter (PCFPS) based on hole size alteration and optofluidic infiltration
摘要： We have presented a technique based on optofluidic infiltration and air-holes diameter variation together to design a 1 × 4 photonic crystal fiber power splitter (PCFPS) which have very low dispersion (D): (0 ≤ D ≤ 2.5 (ps/nm/km) and very low loss (L): 0 ≤ L ≤ 0.025(dB/cm) in a wide range of wavelengths (1100–1700 nm). This approach allows us to control the dispersion of the fundamental mode in a PCF beam splitter by choosing appropriate refractive indices for liquids and suitable diameters for air-holes in PCF power splitter. In fact, the techniques, used in this paper are complementary of each other and give us more excellent results which are better than other reported results in researchers’ works so far. In this work, a new design of 1 × 4 photonic crystal fiber power splitter is proposed by using beam propagation method. An optical Gaussian signal at a wavelength of third communication window range (1550 nm) is inserted into the central core and equally is divided into four core (25% of the total input power interred to each core). In addition, the physical behavior of coupling characteristics is obtained by using coupled mode analysis. Numerical simulations show that input optical signal can be equally divided in photonic crystal fiber structure with low dispersion and low loss. The total size of proposed PCFPS is 30 μm × 30 μm × 1.2 mm, too.
关键词： Third communication window range,Optofluidic infiltration,Air-holes diameter variation,PCFPS
更新于2025-09-04 15:30:14
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Reference Module in Materials Science and Materials Engineering || Photoelectron Diffraction
摘要： Surface structural information can be derived from a great variety of methods, but most quantitative data are based on elastic scattering of X-rays, electrons, or ions by the near-surface atoms. While the best-known methods based on electron (and X-ray) scattering are conventional diffraction methods, reliant on long-range order, the technique of photoelectron diffraction is a local scattering technique that thus provides local structural information not dependent on long-range periodicity. In this short article the physical principles of photoelectron diffraction are described, highlighting at least two fundamentally distinct versions of the technique. The main areas of utilization of the method are illustrated.
关键词： local scattering technique,long-range order,surface structural information,photoelectron diffraction,X-rays,electrons,elastic scattering,ions
更新于2025-09-04 15:30:14
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Superwide-Range Fiber Bragg Grating Displacement Sensor Based on an Eccentric Gear: Principles and Experiments
摘要： Aiming at the large displacement monitoring needs of slope, road, and bridge engineering, a new method concerning the superwide-range fiber Bragg grating (FBG) displacement sensor based on eccentric gear was investigated. The structure of the sensor was designed and the formula for the wavelength-displacement relationship was established via waveform fitting from calibration tests. The lateral displacement of a first-story shear wall was successfully monitored in a hysteresis test of a steel frame–reinforced concrete infill wall. A FBG relative displacement sensor was developed refitting a superwide-range fiber Bragg grating displacement sensor based on eccentric gear. The refitted sensor was applied in a self-repairing performance test of a shape memory alloy (SMA) strengthened concrete beam. The monitoring results of the crack were compared with the results of an integrated test instrument, and the results showed that the sensor exhibited very good accuracy. The innovative FBG displacement sensor has a low influence on the structure, strong practicability, and good prospects for engineering applications.
关键词： Crack measurement,Fiber Bragg grating (FBG),Superwide-range displacement monitoring,Eccentric gear,Displacement sensor
更新于2025-09-04 15:30:14
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Range- and Aperture-dependent Motion Compensation based on Precise Frequency Division and Chirp Scaling for Synthetic Aperture Radar
摘要： The complicated vibrations of the radar sensor, referred to as motion error, generally produce extra range cell migration (RCM) along range direction as well as spectral replicas along azimuth direction, which severely impairs the quality of a focused synthetic aperture radar (SAR) image. This paper concerns the compensation of motion error which is deemed to be range- and aperture-dependent. To this end two pairs of relations: shift-range and angle-frequency, are analyzed. Based on the derived relations, we propose a chirp scaling based range envelope correction (CS-REC) to cope with the range-dependent position shifts (i.e., RCM) and a precise frequency division (PFD) approach to account for the residual aperture-dependent motion error. The proposed algorithm can compensate bulk and complicated motion error completely before range cell migration correction and ensure the focusing-quality of a SAR image without autofocus. Both simulated and real data experiments validate the effectiveness of the proposed algorithm.
关键词： chirp scaling,synthetic aperture radar,Range- and aperture-dependent motion compensation,precise frequency division
更新于2025-09-04 15:30:14
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Ionization-Excitation of Helium-Like Ions at Compton Scattering
摘要： Ionization of helium-like ions with simultaneous excitation of the ns-states due to photon scattering is considered. The differential and total cross sections of the process are calculated to leading order of perturbation theory with respect to the electron–electron interaction. The formulas obtained are applicable in the nonrelativistic energy range far beyond the ionization threshold.
关键词： Nonrelativistic energy range,Excitation,Helium-like ions,Ionization,Compton scattering
更新于2025-09-04 15:30:14
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A Cyclic Vernier Two-Step TDC for High Input Range Time-of-Flight Sensor Using Startup Time Correction Technique
摘要： Herein, we present a low-power cyclic Vernier two-step time-to-digital converter (TDC) that achieves a wide input range with good linearity. Since traditional approaches require a large area or high power to achieve an input range >300 ns, we solve this problem by proposing a simple yet efficient TDC suitable for time-of-flight (TOF) sensors. In previous studies using the cyclic structure, the effect of startup time on the linearity of the TDC is not described. Thus, the achievable linearity has been limited when the TDC is used for applications requiring a high input range. We solve this problem by using a simple yet effective technique to compensate. The proposed technique is realized using (1) digitally-controlled oscillators (DCOs) that have dual frequency control and matched startup time; (2) an alignment detector that performs startup time correction by proper timing control; and (3) a fully symmetric arbiter that precisely detects the instant of edge alignment. To achieve a fine resolution for the cyclic Vernier TDC, we design two closely-matched DCOs with dual frequency control. The alignment detector performs the critical task of cancelling startup time via timing control. The detector is delay-compensated by using a dummy to provide matched loading for the two DCOs. To enhance the detection speed under low power, a current-reuse approach is employed for the arbiter. The TDC is fabricated using a 0.18 μm complementary metal–oxide–semiconductor (CMOS) process in a compact chip area of 0.028 mm2. Measured results show a dynamic range of 355 ns and a resolution of 377 ps. When the result is applied for TOF sensing, it corresponds to a distance range of 53.2 m and a resolution of 5.65 cm. Over a relatively large input range, good linearity is achieved, which is indicated by a DNL of 0.28 LSBrms and an INL of 0.96 LSBrms. The result corresponds to root mean square (RMS) error distance of 5.42 cm. The result is achieved by consuming a relatively low power of 0.65 mW.
关键词： Vernier,time-to-digital converter,startup time,cyclic,input range,digitally controlled oscillator,time-of-flight
更新于2025-09-04 15:30:14