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Now showing items 1 - 14 of 14

  • A 1.12 GHz TO 2 GHz wide-tuning-range VCO with dynamic coupling structures

    Xiang, Yong-Bo   Wang, Guang-Ming   Zhang, Xu-Chun   Liang, Jiangang  

    This paper presents a continuous wide-tuning-range VCO with 56.4% frequency tuning ratio (FTR). Both a dynamic coupling resonator structure and a dynamic feedback amplifying circuit are proposed to maintain the wide-tuning range for the VCO. The dynamic coupling promises stable loaded Q factor and wider tuning range, while the dynamic feedback amplifying circuit assured the oscillating condition across the large frequency tuning range. There are three voltage tunable structures in the proposed, all of which are controlled by the same tuning voltage, so it is easy to be controlled and can be phase locked by a phase-lock-loop (PLL). The VCO results in a tuning range from 1.12 GHz to 2.00 GHz at 0 approximate to +5 V tuning voltage. The measured output power is 4.0 approximate to 6.37 dBm within the tuning range. The measured phase noise is -94.24 approximate to -98.66 dBc/Hz at 100 kHz frequency offset and -118.07 approximate to -123.41 dBc/Hz at 1 MHz frequency offset respectively within the tuning range. (c) 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:1525-1529, 2016
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  • Broadband Antenna Employing Simplified MTLs for WLAN/WiMAX Applications

    Zhou, Cheng   Wang, Guangming   Liang, Jiangang   Wang, Yawei   Zong, Binfeng  

    A broadband electrically small antenna (ESA) based on simplified metamaterial transmission lines (SMTLs) is proposed in this letter. The antenna consists of two different-sized SMTL unit cells of different resonance frequencies. A dispersion analysis of the SMTL reveals that an increase in series of the interdigital capacitance would decrease the 1st-order mode resonance frequency, thus reducing the electrical size of the proposed antenna. A matching wideband antenna is enabled when the two resonance frequencies suitably merge. A fabricated prototype for WLAN/WiMAX applications has been designed and presented. The prototype measurements are 49.6% for bandwidth (10 dB) and 96.5% for radiation efficiency. Simulation and experimental results are used to verify the theoretical prediction.
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  • Dual-Band Low-Scattering Metasurface Based on Combination of Diffusion and Absorption

    Zhuang, Yaqiang   Wang, Guangming   Liang, Jiangang   Zhang, Qingfeng  

    In this letter, a low-scattering metasurface with dual-band, wide-angle, and polarization-insensitive features is proposed and validated by measurement. The metasurface converts incident electromagnetic wave into heat at S-band frequency, and disperses it into various reflected directions across X-and Ku-band frequencies. Furthermore, each operational mode works independently. The agreement between simulated and measured results demonstrates that more than 8 dB radar cross-section reduction can be realized over 3.9-4 and 7.7-19 GHz under different polarized wave incidences. The dual-band and wideband characteristics are also well maintained within 0 degrees-45 degrees oblique incidence.
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  • Single-Layer Focusing Gradient Metasurface for Ultrathin Planar Lens Antenna Application

    Li, Haipeng   Wang, Guangming   Liang, Jiangang   Gao, Xiangjun   Hou, Haisheng   Jia, Xinyan  

    A single-layer focusing gradient metasurface (MS) built by one element-group is proposed. The element-group is designed by well connecting the phase shift range of two similar single-layer elements under the condition of transmitting efficiencies over 0.7. The proposed MS can focus the propagating plane wave on a point and a patch antenna is placed at its focus to build a high-gain planar lens antenna. This lens antenna achieves pencil-shaped far-field radiation pattern with a simulation peak gain of 16.7 dB at 10 GHz. The single-layer structure makes it easy to fabricate the MS with low profile and satisfying performances. Finally, the MS and the patch antenna are fabricated, assembled, and measured. The measured results are in good agreement with the simulations.
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  • High-performance broadband vortex beam generator based on double-layered reflective metasurface

    Ran, Yuzhou   Liang, Jiangang   Cai, Tong   Ji, Wenye   Wang, Guangming  

    Wavefront manipulation is of great importance in the development of science and technology, and the generation of vortex beam is one of the most effective methods to improve the channel capacity and communication accuracy. However, current available vortex beam generators suffer from complex structure, large size, especially narrow bandwidth. To solve these issues, we propose a general strategy to enhance the bandwidth of the vortex beam generator by using double-layered reflective metasurface. The well-optimized double-layered reflective element possesses dual resonance, which realizes complete phase coverage (larger than 360 degrees) and a flat slope of the reflection phase, resulting in a broad bandwidth (8.5-11.5GHz). A compact and low-profile vortex-beam generator is proposed by combining the parabolic phase and the spiral phase plate phase. Both near field and far field experiments are performed to demonstrate the predesigned effects. A pure vortex beam is observed clearly with a topological charge of m=3D1 in a wide frequency window of 3 GHz (8.5-11.5GHz). More importantly, the working efficiency of the vortex beam is better than 90% at center frequency 10 GHz. The findings in this paper motivate the realization of high-performance reflective metasurfaces and other functional metadevices. (C) 2018 Author(s).
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  • High-performance broadband vortex beam generator using reflective Pancharatnam-Berry metasurface

    Ran, Yuzhou   Liang, Jiangang   Cai, Tong   Li, Haipeng  

    Vortex beam generators, especially for broadband working ones, are essential in recent communication systems, since it is believed to be a key to improve the channel capacity efficiently. However, available vortex beam generators surfer from narrow bands, low efficiencies as well as complex configurations. In this paper, we propose an ultra-broadband reflective Pancharatnam-Berry metasurface to generate the vortex beams within 12-18 GHz. The metasurface consists of 20x20 single-layered rotated reflective elements A Ku-band Archimedes spiral antenna is placed at the focal point of the PB metasurface as a feed source which is used to emit a right-handed circularly polarized wave. Then, the metasurface is fabricated, simulated, and measured. Numerical and experimental results coincided well, indicating that the proposed vortex beam generator demonstrated several improvements, including wideband working (12-18 GHz), high efficiency (75.76%), and simple fabrication. Our findings open up a new avenue for the design of high-performance broadband vortex beam generators.
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  • Compact Dual-band ACS-fed Monopole Omnidirectional Antenna for 2.4/5.2/5.8 GHz WLAN Applications

    Niu, Xuebin   Liang, Jiangang   Wu, Guo-cheng   Lin, Yongfan  

    A compact dual-band asymmetric coplanar strip (ACS) fed printed monopole omnidirectional antenna with three radiating structures for 2.4/5 GHz WLAN/Bluetooth applications is presented. The designed antenna comprises of a simple ACS-fed (Asymmetric Coplanar Strip) monopole and three different strip radiating elements. It occupies a very compact overall size of 15 x 24 mm(2) including the ground plane, which is only about 0.12 lambda x 0.20 lambda (lambda is the wavelength at the frequency of 2.45 GHz in free space). So, it has the characteristics of miniaturization. A resonant mode at 2.45 GHz is created by adding a inverted-L branch, and the resonant mode at 5.62 GHz is co-produced by the horizontal strip and vertical strip including an element which is like a Chinese Tai Chi fish. Dual desired resonant frequencies achieved, and each of them can be tuned independently. Both the simulated and measured results show reasonable agreement, and the measured dates show that the antenna has an impedance bandwidth of 90 MHz (2.4-2.49 GHz) and 810 MHz (5.07-5.88 GHz), and a reflection coefficient of less than -10 dB, it is suitable for WLAN 2.4/5.2/5.8 GHz applications and 2.4 GHz Bluetooth bands.
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  • PI and Repetitive Control for Single Phase Inverter Based on Virtual Rotating Coordinate System

    Li, Mengqi   Tong, Yibin   Jiang, Jiuchun   Liang, Jiangang  

    Microgrid technology developed rapidly and nonlinear loads were connected increasingly. A new control strategy was proposed for single phase inverter when connected nonlinear loads under island condition. Pl. and repetitive compound controller was realized under synchronous rotating coordinate system and acquired high quality sinusoidal voltage output without voltage spike when loads step changed. Validity and correctness were verified by simulation using MATLAB/Simulink.
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  • Circularly Polarized Fabry-Perot Antenna Employing a Receiver-Transmitter Polarization Conversion Metasurface

    Xie, Peng   Wang, Guangming   Li, Haipeng   Liang, Jiangang   Gao, Xiangjun  

    This study presents a linear-to-circular polarization conversion metasurface (PCM) based on a novel unit cell for a circularly polarized (CP) Fabry-Perot (FP) antenna. The unit cell consists of a bottom linear-polarization patch and a top circular-polarization patch, which are separated by a metalized plane and connected by a metalized via. The bottom patch receives the power and transfers it to the top layer through the metalized via; the top layer then transmits the power into space. The metasurface is designed to have high reflectivity and an appropriate reflection phase to compose a resonate cavity with the ground plane. The capability of linear to circular polarization conversion is provided to the PCM by adjustment of the transmission magnitude and phase. A slot coupled patch antenna is used as the feeder due to its stable broadside radiation. The linearly polarized wave emitting from the feeder resonates in the cavity and then is converted into a CP wave when it comes out of the cavity. A prototype antenna is fabricated and measured. The measurement results show that the antenna has good circular polarization performance within the band of 9.8-10.2 GHz. The maximum gain of the antenna reaches 17.8 dBic at 10 GHz, with an aperture efficiency of 53%. The proposed antenna outperforms most of the previously reported CP FP antennas due to its low profile, high gain, and relatively high efficiency.
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  • Bifunctional circularly-polarized lenses with simultaneous geometrical and propagating phase control metasurfaces

    Li, Haipeng   Wang, GuangMing   Cai, Tong   Liang, JianGang   Hou, Haisheng  

    Achieving different and arbitrary phase distributions for left-handed (LH) and right-handed (RH) circularly polarized (CP) waves, especially in transmission cases, is very important in designing CP lenses. Here, a strategy to control the propagating and geometrical phases simultaneously and independently is proposed by using a four-layered element. The element is a perfect transparent half wavelength plate, which controls the propagating phase by changing the structural size at both orthogonal polarizations and geometrical phase via rotating the structures. To verify the effectiveness of the modulation, we design three linear deflectors by manipulating only propagating phases, only geometrical phases and mix of them to achieve identical, symmetry and asymmetric refractions, respectively. Finally, we simulate and measure lens1 with refractions in different planes and lens2 with pencil-shape and vortex-shape beams. Our findings break the fixed relations of orthogonal CP waves for sole geometrical or propagating metasurface and then offer an effective strategy to achieve arbitrary bifunctional CP devices.
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  • Random Combinatorial Gradient Metasurface for Broadband,Wide-Angle and Polarization-Independent Diffusion Scattering

    Zhuang, Yaqiang   Wang, Guangming   Liang, Jiangang   Cai, Tong   Tang, Xiao-Lan   Guo, Tongfeng   Zhang, Qingfeng  

    This paper proposes an easy, efficient strategy for designing broadband, wide-angle and polarization-independent diffusion metasurface for radar cross section (RCS) reduction. A dual-resonance unit cell, composed of a cross wire and cross loop (CWCL), is employed to enhance the phase bandwidth covering the 2 pi range. Both oblique-gradient and horizontal-gradient phase supercells are designed for illustration. The numerical results agree well with the theoretical ones. To significantly reduce backward scattering, the random combinatorial gradient metasurface (RCGM) is subsequently constructed by collecting eight supercells with randomly distributed gradient directions. The proposed metasurface features an enhanced specular RCS reduction performance and less design complexity compared to other candidates. Both simulated and measured results show that the proposed RCGM can significantly suppress RCS and exhibits broadband, wide-angle and polarization independence features.
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  • A Dual-Polarized Two-Dimensional Beam-Steering Fabry-Perot Cavity Antenna With a Reconfigurable Partially Reflecting Surface

    Xie, Peng   Wang, Guangming   Li, Haipeng   Liang, Jiangang  

    A dual-polarized two-dimensional beam-steering Fabry-Perot cavity antenna with a reconfigurable partially reflecting surface (PRS) is proposed. A polarization-reconfigurable aperture-coupled patch antenna, which can work in two different linear polarizations, is adopted as the exciter. By controlling the PIN diodes, the PRS can have different reflection phase distributions, giving the antenna different beam tilted states in eight azimuthal directions. The PRS has the same function on different linear polarization waves, so the antenna can realize polarization reconfiguration and beam steering simultaneously. Aprototype antenna is fabricated and measured. The measured results show that, beam angles greater than 8 degrees were obtained for each azimuthal direction at 5.5 GHz. Good agreement between the simulated and measured results was achieved, which confirms the correctness of the design principle.
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  • Photobiomodulation by low-power laser irradiation attenuates A beta-induced cell apoptosis through the Akt/GSK3 beta/beta-catenin pathway

    Liang, Jiangang   Liu, Lei   Xing, Da  

    Apoptosis induced by amyloid beta peptide (A beta) is thought to associate with the pathogenesis of Alzheimer disease (AD). Accumulating evidence shows that low-power laser irradiation (LPLI) is capable of reducing A beta-induced apoptosis. However, the underlying mechanisms remain unclear. In this study, we report a novel molecular mechanism by which LPLI attenuates A beta(25-35)-induced apoptosis through the Akt/GSK3 beta/beta-catenin pathway. We found that Akt activated by LPLI interacted with GSK3 beta and phosphorylated it on Ser9 in the presence of A beta(25-35), which resulted in the inhibition of GSK3 beta. Furthermore, LPLI increased the nuclear translocation of beta-catenin and enhanced its T cell factor/lymphocyte enhancer factor-dependent transcriptional activity via the Akt/GSK3 beta pathway to promote cell survival upon treatment with A beta(25-35). Our data demonstrate that LPLI has a prosurvival effect on A beta-induced apoptosis and may be an effective therapeutic strategy in treating AD by targeting GSK3 beta. (C) 2012 Elsevier Inc. All rights reserved.
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  • A Compact UWB Diversity Antenna

    Zhao, Hui   Zhang, Fushun   Wang, Chunyang   Liang, Jiangang  

    A compact printed ultrawideband (UWB) diversity antenna with a size of 30 mm x 36 mm operating at a frequency range of 3.1-10.6 GHz is proposed. The antenna is composed of two semielliptical monopoles fed by two microstrip lines. Two semicircular slots, two rectangular slots, and one stub are introduced in the ground plane to adjust the impedance bandwidth of the antenna and improve the isolation between two feeding ports. The simulated and measured results show that impedance bandwidth of the proposed antenna can cover the whole UWB band with a good isolation of < -15 dB. The radiation patterns, peak antenna gain, and envelope correlation coefficient are also measured and discussed. The measured results show that the proposed antenna can be a good candidate for some portable MIMO/diversity UWB applications.
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