1 大连理工大学 电气工程学院, 辽宁 大连 116024
2 大连理工大学 电子信息与电气工程学部, 辽宁 大连 116024
针对可穿戴设备电源的供电及续航问题, 采用了筒壳结构的压电能量收集器。探究了可穿戴筒壳结构压电能量收集器俘能的本质, 并提出结构优化设计方案。首先指出筒壳结构的承载能力和初始能量与厚度成正比, 且随着跨度的增大而减小; 其次通过有限元仿真研究了基底和聚偏二氟乙烯(PVDF)压电薄膜尺寸与应力、应变的关系, 指出PVDF的尺寸应尽可能与应力、应变较大的区域相符合, 没必要完全覆盖基底, 并给出优化模型; 最后通过实验验证了厚度、跨度和曲率半径优化尺寸的合理性, 综合考虑了人体穿戴的舒适度。优化设计方案中, 筒壳结构的厚为125~150 μm, 跨度为19~22.2 mm, 曲率半径为10~15 mm, 输出电压可达13~18 V。
可穿戴 筒壳结构 压电能量收集 聚偏二氟乙烯(PVDF) 优化 wearable cylindrical shell piezoelectric energy harvesting polyvinylidene fluoride(PVDF) optimization
复旦大学通信科学与工程系电磁波信息科学教育部重点实验室,上海 200433
为了提高传统点对点单输入单输出(SISO)可见光系统的传输速率,提出了多输入多输出 (MIMO)的可见光系统。考虑到接收端系统复杂度的问题,多输入单输出 (MISO)可见光通信系统则更受关注。本文研究了基于脉冲幅度调制 (PAM)的 MISO可见光通信系统,并通过实验证明该系统在特定场景中的运用优势。此外,针对可见光通信系统中 LED光源、功率放大器等关键器件存在非线性效应,本文基于两发一收的 2×1 MISO可见光通信系统,设计了两路低阶 PAM信号在光域叠加产生高阶 PAM信号的新型的等概率编码映射方案,并通过 RGB-LED的红灯完成净比特速率 700 Mb/s的传输实验系统验证,证明了此方案在实际中的可行性及优越性。
光通信 可见光通信 多输入单输出 等概率编码 脉冲幅度调制 optical communications visible light communication multiple input single output (MISO) equal
Author Affiliations
Abstract
State Key Lab of ASIC, Department of Communication Science and Engineering, Fudan University, Shanghai 200433, China
In this Letter, we propose a novel constellation-shaping carrier-less amplitude and phase (CAP) modulation scheme to alleviate the systematic nonlinearity in visible light communication (VLC) systems. A simple geometric transformation shaping method is employed to convert the normal square lattice constellation into multiple circular constellations. The feasibility and performance are investigated and experimentally demonstrated by a 1.25 Gb/s CAP-modulated VLC system. The results indicate that the circular constellation has better resistance to systematic nonlinearity compared with a rectangular constellation. The dynamic range of input signal peak-to-peak values promotes 20% at a low bias voltage nonlinear area and 50% at a high bias voltage nonlinear area. To the best of our knowledge, this is the first time constellation-shaping CAP has ever been reported in indoor high data rate VLC systems.
060.4080 Modulation 060.2605 Free-space optical communication Chinese Optics Letters
2017, 15(3): 030602
Author Affiliations
Abstract
Department of Communication Science and Engineering, and Key Laboratory for Information Science of Electromagnetic Waves (MoE), Fudan University, Shanghai 200433, China
High-speed multi-user access with high spectral efficiency is one of the key challenges for band-limited visible light communication (VLC) systems. In this paper, we propose a novel scheme for effective multiple-access VLC systems based on multi-band, Nyquist-filtered pulse amplitude modulation (PAM)-8 modulation. Within this scenario, the spectral efficiency can be improved from 1.5 to 2.73 b/s/Hz by implementing an appropriate Nyquist filter to suppress spectral bandwidth. We experimentally demonstrate a multi-band VLC system at 1.2 Gb/s after 1 m indoor free space transmission. The system performances have also been thoroughly investigated for different sub-band numbers, utilizing a rectangular filter in the frequency domain and a Nyquist filter based on square root raised cosine. The results show that the Nyquist-filtered PAM-8 signal can outperform a rectangular filtered signal. The maximum improvement of system capacity is up to 1.67 times for the Nyquist-filtered multi-band system. The results clearly show the advantage and feasibility of multi-band Nyquist PAM for high-speed multiple-access VLC systems.
(060.0060) Fiber optics and optical communications (060.2605) Free-space optical communication (230.3670) Light-emitting diodes. Photonics Research
2017, 5(6): 06000588
Author Affiliations
Abstract
Key Laboratory for Information Science of Electromagnetic Waves (MoE), Department of Communication Science and Engineering, Fudan University, Shanghai 200433, China
Light-emitting diode (LED)-based visible light communication (VLC) has become a potential candidate for nextgeneration ultra-high-speed indoor wireless communication. In this paper, four special-shaped 8-quadrature amplitude modulation (QAM) constellations are investigated in a single-carrier VLC system. It is numerically verified and experimentally demonstrated that circular (7,1) shows obvious superiority in the performance of the dynamic range of signal voltage peak-to-peak (vpp) value and bit error rate (BER). Next best is rectangular, followed by triangular; circular (4,4) has the worst performance. A data rate of 1.515 Gbit/s is successfully achieved by circular (7,1) employing a red chip LED over 0.5 m indoor free space transmission below a BER threshold of 3.8 × 10?3. Compared with circular (4,4), the traditional 8-QAM constellation, circular (7,1) provides a wider dynamic range of signal vpp, a higher data rate, and a longer transmission distance. To the best of our knowledge, this is the first investigation into the performance differences of special-shaped 8-QAM constellations in a highspeed, single-carrier VLC system, and the results comprehensively demonstrate that circular (7,1) is the optimal option.
Free-space optical communication Free-space optical communication Optical communications Optical communications Light-emitting diodes Light-emitting diodes Photonics Research
2016, 4(6): 06000249
1 中国工程物理研究院 上海激光等离子体研究所,上海 201800
2 郑州交通职业学院 机电工程系,郑州 450062
结合快点火靶丸预压缩涉及的基本物理问题,分析了驱动激光脉冲波形对材料压缩过程的影响,并利用辐射流体力学程序MULTI模拟了不同激光波形下的材料压缩情况。结果表明:通过调节激光脉冲波形,优化激光初始强度、激光强度开始上升时间和上升速度,控制压缩过程中的熵增,可以获得更高的材料压缩度。
惯性约束聚变 快点火 材料压缩 激光脉冲波形 数值模拟 inertial confinement fusion fast ignition fuel compression laser pulse shape numerical simulation