| 1. |
- Wang, Zhechao, et al.
(författare)
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Experimental realization of a low-loss nano-scale Si hybrid plasmonic waveguide
- 2011
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Ingår i: Optics InfoBase Conference Papers. - Washington : Optical Society of America. - 9781557529060
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Konferensbidrag (refereegranskat)abstract
- A novel hybrid plasmonic waveguide with nano-scale confinement, consisting of a metal layer separated from a SOI nano-rib by a thin silica layer has been realized. The loss of 0.01dB/μm allows for ultra-high density photonic integration.
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| 2. |
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| 3. |
- Gustafsson, Mats, et al.
(författare)
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An optimization approach to multi-dimensional time domain acoustic inverse problems
- 1997
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- An optimization approach to a multi-dimensional acoustic inverse problem in the time domain is considered. The density and/or the velocity are reconstructed by minimizing an objective functional. By introducing dual functions and using the Gauss divergence theorem, the gradient of the objective functional is found as an explicit expression. The parameters are then reconstructed by an iterative algorithm (the conjugate gradient method). The reconstruction algorithm is tested with noisy data, and these tests indicate that the algorithm is stable and robust. The computation time for the reconstruction is greatly improved when the analytic gradient is used.
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| 4. |
- Li, Hui, et al.
(författare)
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Calculating signal correlation in lossy dipole arrays using scattering parameters and efficiencies
- 2013
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Ingår i: 2013 7th European Conference on Antennas and Propagation, EuCAP 2013. - : EurAAP. - 2164-3342. - 9788890701832 - 9781467321877 ; , s. 519-523
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Konferensbidrag (refereegranskat)abstract
- Correlation coefficient, as a critical performance metric of multiple antenna systems, can be calculated from the 3D radiation patterns of the antennas for multipath environments with uniform 3D angular power spectrum. A simpler, faster and lower cost approach uses the antennas' scattering parameters to determine correlation coefficient. However, the method assumes lossless antennas, and hence only achieves good accuracy for antennas with high radiation efficiencies. In this work, a method for calculating correlation coefficients in lossy dipole arrays is proposed, using only the scattering parameters and radiation efficiencies. The method is based on the equivalent circuit of antennas, and it gives a significantly better estimate of the correlation coefficient than the existing methods. The proposed method is also applied to two folded monopole antennas in a compact terminal to demonstrate its effectiveness.
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| 5. |
- Liu, Qingkun, et al.
(författare)
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Switchable polarization-sensitive surface plasmon resonance of highly stable gold nanorods-liquid crystals composites
- 2011
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Ingår i: Optoelectronic Materials and Devices VI. - Washington, D.C. : SPIE. - 9780819489616
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Konferensbidrag (refereegranskat)abstract
- In this work, we demonstrate the bulk self-alignment of gold nanorods (GNRs) dispersed in lyotropic nematic liquid crystals (LCs) with high optical absorption coefficient at the surface plasmon resonant wavelength. The polymer-coated GNRs which show spontaneous long-range orientational ordering along the director of LC host exhibit long-term stability as well as high concentration. External magnetic field and shearing allow for alignment and realignment of the orientation of gold nanorods by changing the director of the liquid crystal matrix. This results in a switchable polarization-sensitive surface plasmon resonance exhibiting stark differences from that of the same nanorods in isotropic fluids. The devise-scale bulk nanoparticle alignment may enable optical metamaterial mass production and control of surface plasmon resonance of nanoparticles.
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| 6. |
- Zhang, Shuai, et al.
(författare)
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Compact UWB MIMO antenna for USB dongles with angle and polarization diversity
- 2012
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Ingår i: IEEE Antennas and Propagation Society, AP-S International Symposium (Digest). - 9784885522703 - 9781467310017 ; , s. 778-781
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Konferensbidrag (refereegranskat)abstract
- A compact dual-element antenna suitable for ultrawideband (UWB) MIMO operation is proposed in this work. The size of the antenna is 25 mm by 40 mm and it covers the lower UWB band of 3.15-5.15 GHz. Apart from the inherent wideband isolation obtained through the different angle and polarization characteristics in the radiation patterns of the individual elements, the gap between the two antenna elements is also utilized to enhance both the isolation and impedance bandwidths. Simulation and experimental results reveal that, within the band of interest, the achieved isolation is over 20 dB and the envelope correlation of the radiation patterns is below 0.1.
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| 7. |
- Fei, Chao, et al.
(författare)
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Underwater wireless optical communication utilizing low-complexity sparse pruned-term-based nonlinear decision-feedback equalization
- 2022
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Ingår i: Applied Optics. - : Optica Publishing Group. - 1559-128X .- 2155-3165. ; 61:22, s. 6534-6543
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Tidskriftsartikel (refereegranskat)abstract
- The nonlinearity of the light-emitting diode (LED) in underwater wireless optical communication (UWOC) systems is considered the one major limiting factor that degrades the system's performance. Volterra series-based nonlinear equalization is widely employed to mitigate such nonlinearity in communication systems. However, the conventional Volterra series-based model is of high complexity, especially for the nonlinearity of higher-order terms or longer memory lengths. In this paper, by pruning away some negligible beating terms and adaptively picking out some of the dominant terms while discarding the trivial ones, we propose and experimentally demonstrate a sparse pruned-term-based nonlinear decision-feedback equalization (SPT-NDFE) scheme for the LED-based UWOC system with an inappreciable performance degradation as compared to systems without the pruning strategy. Meanwhile, by replacing the self/cross beating terms with the terms formed by the absolute operation of a sum of two input samples instead of the product operation terms, a sparse pruned-term-based absolute operation nonlinear decision-feedback equalization (SPT-ANDFE) scheme is also introduced to further reduce complexity. The experimental results show that the SPT-NDFE scheme exhibits comparable performance as compared to the conventional NDFE (nonlinear decision-feedback equalization) scheme with lower complexity (the nonlinear coefficients are reduced by 63.63% as compared to the conventional NDFE scheme). While the SPT-ANDFE scheme yields suboptimal performance with further reduced complexity at the expense of a slight performance degradation, the robustness of the proposed schemes in different turbidity waters is experimentally verified. The proposed channel equalization schemes with low complexity and high performance are promising for power/energy-sensitive UWOC systems.
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| 8. |
- Liu, Hui, et al.
(författare)
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Compact broadband circularly polarized UHF RFID tag antenna for metallic mounting
- 2020
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Ingår i: Journal Electromagnetic Waves and Applications. - : Informa UK Limited. - 0920-5071 .- 1569-3937. ; 34:8, s. 989-1001
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Tidskriftsartikel (refereegranskat)abstract
- We report a broadband ultra-high frequency (UHF) radio frequency identification (RFID) tag antenna of compact size mounted on a metallic object in a near field communication (NFC) RFID system. One half of the square radiation patch has a semi-annular strip feedline embedded inside a semicircle-shaped slot to improve the antenna bandwidth and gain, and the other half of the radiation patch has an L-shaped slot and a shorting pin to increase the circular polarization (CP) bandwidth and reduce the antenna size. The resonant input impedance of the tag antenna can be tuned easily by varying the length of the semi-annular feedline, and the gap between the feedline and the etched semicircular slot. The proposed tag antenna has a wide measured impedance bandwidth (-10-dB |Gamma|) covering the whole operating frequency range of 181 MHz (from 790 to 971 MHz) for a UHF RFID system. The measured 3-dB axis ratio (AR) bandwidth is 43 MHz (from 895 to 938 MHz), which is much larger than those of the CP tag antennas reported in the literature for metallic objects. Further experiment has shown that the proposed tag antenna can provide a stable reading range when mounted on metal plates of various sizes.
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| 9. |
- Liu, Yuxi, et al.
(författare)
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A Dual-board Substrate Integrated Waveguide for Large Phase Delay Application
- 2021
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Ingår i: 2021 PHOTONICS & ELECTROMAGNETICS RESEARCH SYMPOSIUM (PIERS 2021). - : IEEE. ; , s. 180-183
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Konferensbidrag (refereegranskat)abstract
- A novel large phase-delay transmission line based on dual printed circuit boards (PCBs) for substrate integrated waveguide (SIW) is proposed. Rectangular slots and metallic vias are used to enhance the phase delay feature. The simulated results show the phase difference of the proposed phase-delayed SIW with dual PCBs is -577 degrees at the concerned frequency of 12 GHz. The phase-delay characteristic of proposed design has been analyzed through simulations compared with both micro-strip line and single-layer SIW which using the same definite physical length. The simulated results show that phase-delay performance of our design is far superior to that of the traditional microstrip or the single-layer SIW.
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| 10. |
- Dai, Daoxin, et al.
(författare)
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Silicon Multimode Photonic Integrated Devices For On-Chip Mode-Division-Multiplexed Optical Interconnects
- 2013
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Ingår i: Progress In Electromagnetics Research. - 1070-4698 .- 1559-8985. ; 143, s. 773-819
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Tidskriftsartikel (refereegranskat)abstract
- Multimode spatial-division multiplexing (SDM) technology has attracted much attention for its potential to enhance the capacity of an optical-interconnect link with a single wavelength carrier. For a mode-multiplexed optical-interconnect link, the functional elements are quite different from the conventional ones as multiple modes are involved. In this paper we give a review and discussion on multimode photonic integrated devices for mode-multiplexed optical-interconnects. Light propagation and mode conversion in tapered waveguides as well as bent waveguides are discussed first. Recent progress on mode converter-(de)multiplexers is then reviewed. The demands of some functional devices used for mode-multiplexed optical-interconnects are also discussed. In particular, the fabrication tolerance is analyzed in detail for our hybrid demultiplexer, which enables mode-/polarization-division-(de)multiplexing simultaneously.
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