Phased Array Feed (PAF) is a small two-dimensional phased array antenna, playing a role as the multi-beam feed for the reflector antenna. The prominent capability of large continuous Field-of-View (FoV) coverage and f...Phased Array Feed (PAF) is a small two-dimensional phased array antenna, playing a role as the multi-beam feed for the reflector antenna. The prominent capability of large continuous Field-of-View (FoV) coverage and fast survey speed makes PAF the promising feed for radio telescopes. In this paper, the effect of feed array of PAF on the gain fluctuations over FoV is analyzed on a sim- plified model of the Five-hundred-meter Spherical Aperture radio Telescope (FAST), including illu- mination pattern edge taper, element spacing, element arrangement and element amount. And the differences between rectangular and hexagonal array arrangements are compared. The relationship between the FoV and array configuration are concluded at last.展开更多
Improving hot-spot intensity is a key issue in surface-enhanced Raman scattering （SERS）. The bowtie nanoantenna （BNA） is an effective device used to concentrate light energy into a nanoscale volume and produce str...Improving hot-spot intensity is a key issue in surface-enhanced Raman scattering （SERS）. The bowtie nanoantenna （BNA） is an effective device used to concentrate light energy into a nanoscale volume and produce strong hot spots. Nanosphere lithography （NSL） is a large-area and low-cost technique to produce BNA arrays; however, the SERS activity of NSL-fabricated BNAs is limited. In this paper, we present a simple method to improve the SERS activity of conventional NSL-fabricated BNAs by modifying their geometry. The new configuration is termed ＂silver-coated elevated bowtie nanoantenna＂ （SCEBNA）. SCEBNAs perform intensive near-field enhancement in the gap cavities owing to the integrated contribution of the ＂lightning rod＂ effect, resonance coupling, and the formation of the plasmonic Fabry-Perot cavity. Experimental measurements and finite-difference time-domain simulations revealed that the hot-spot intensity and the substrate enhancement factor can be optimized by adjusting the silver thickness. The optimal sample has the capability of trace-amount detection with fine reproducibility.展开更多
A multi-band multi-antenna system has become an important trend in the development of mobile communication systems.However,strong mutual coupling tends to occur between antenna elements with a small space,distorting a...A multi-band multi-antenna system has become an important trend in the development of mobile communication systems.However,strong mutual coupling tends to occur between antenna elements with a small space,distorting array antennas’performance.Therefore,in the multiple-input multiple-output(MIMO)antenna system,high isolation based on miniaturization of the antenna array has been pursued.We study in depth the methods of decoupling between antenna elements.Reasons for the existence of mutual coupling and advantages of mutual coupling reduction are analyzed.Then the decoupling methods proposed in recent works are compared and analyzed.Finally,we propose a metasurface consisting of double-layer short wires,which can be applied to improve the port isolation of antennas arranged along the H-plane and E-plane.Results show that the proposed metasurface has good decoupling effect on a closely placed antenna array.展开更多
基金Partly supported by the Ministry of Science and Technology of the People's Republic of China under the State Key Development Program for Basic Research (No. 2012CB821800)
文摘Phased Array Feed (PAF) is a small two-dimensional phased array antenna, playing a role as the multi-beam feed for the reflector antenna. The prominent capability of large continuous Field-of-View (FoV) coverage and fast survey speed makes PAF the promising feed for radio telescopes. In this paper, the effect of feed array of PAF on the gain fluctuations over FoV is analyzed on a sim- plified model of the Five-hundred-meter Spherical Aperture radio Telescope (FAST), including illu- mination pattern edge taper, element spacing, element arrangement and element amount. And the differences between rectangular and hexagonal array arrangements are compared. The relationship between the FoV and array configuration are concluded at last.
基金Acknowledgements This work was supported by the National Natural Science Foundation of China （No. 21273092） and the National Basic Research Program of China （No. 2009CB939701）.
文摘Improving hot-spot intensity is a key issue in surface-enhanced Raman scattering （SERS）. The bowtie nanoantenna （BNA） is an effective device used to concentrate light energy into a nanoscale volume and produce strong hot spots. Nanosphere lithography （NSL） is a large-area and low-cost technique to produce BNA arrays; however, the SERS activity of NSL-fabricated BNAs is limited. In this paper, we present a simple method to improve the SERS activity of conventional NSL-fabricated BNAs by modifying their geometry. The new configuration is termed ＂silver-coated elevated bowtie nanoantenna＂ （SCEBNA）. SCEBNAs perform intensive near-field enhancement in the gap cavities owing to the integrated contribution of the ＂lightning rod＂ effect, resonance coupling, and the formation of the plasmonic Fabry-Perot cavity. Experimental measurements and finite-difference time-domain simulations revealed that the hot-spot intensity and the substrate enhancement factor can be optimized by adjusting the silver thickness. The optimal sample has the capability of trace-amount detection with fine reproducibility.
基金Project supported by the National Natural Science Foundation of China(No.61701366).
文摘A multi-band multi-antenna system has become an important trend in the development of mobile communication systems.However,strong mutual coupling tends to occur between antenna elements with a small space,distorting array antennas’performance.Therefore,in the multiple-input multiple-output(MIMO)antenna system,high isolation based on miniaturization of the antenna array has been pursued.We study in depth the methods of decoupling between antenna elements.Reasons for the existence of mutual coupling and advantages of mutual coupling reduction are analyzed.Then the decoupling methods proposed in recent works are compared and analyzed.Finally,we propose a metasurface consisting of double-layer short wires,which can be applied to improve the port isolation of antennas arranged along the H-plane and E-plane.Results show that the proposed metasurface has good decoupling effect on a closely placed antenna array.
