双月形圆周阵列超表面生成涡旋光束的研究

涡旋光束作为一种近年来新兴的结构化光束,因 自身携带轨道角动量的特性,使其在光学微操控、 生物医学、光信息传输等领域有着极大的应用前景。在以往生成涡旋光束的报道中,通常存 在器件尺寸较 大、激发光为圆偏光以及波长单一等问题,本文提出了一种基于双月形金属银单元与二氧化 硅基底结合的 亚波长尺寸超构表面来实现涡旋光束的生成。此种结构尺寸微小,且可以在偏振方向任意的 线偏光入射下, 通过调节超表面的双月形金属单元的横向尺寸来实现多种波长的涡旋光束输出。     

Golden angle‐inspired design of massive MIMO tapered slot array with less correlation for 5G lower band applications

In this article, for the first time, we come up with a nature‐inspired MIMO antenna configuration that could provide less correlated wireless channels for 5G lower band (3000‐4200 MHz). Essentially, the cross‐correlation among the antenna elements is reduced by incorporating the concept of golden angle into a cylindrical configuration of tapered slot antenna array. The golden angle helps in arranging the end‐fire radiating tapered slot antennas (TSAs) in such a way that there will not be any spatial overlap among the radiation fields of the individual antenna elements. The idea is validated with 24 TSA elements placed in a cylindrical fashion. The envelope correlation coefficient (ECC) is calculated from the simulations in ANSYS HFSS and verified with measurements. The ECC value is found to be less than 0.01 in the range of 3 GHz to 4.25 GHz. The impedance matching and mutual coupling between the elements are found to be very good in the above‐mentioned frequency range from the simulations and measurements. It is believed that the application of golden angle concept to MIMO antennas would open up the windows for implementation of dense massive MIMO.     

多用户干扰信道下建模于流形上的联合干扰对齐预编码

首先从子空间对齐的角度将干扰信号功率和有用信号功率联合优化的问题建模于Grassmannian流形上,有约束的最优化问题被转化为降维的无约束的最优化问题。然后利用Grassmannian流形的几何特性,提出了一种基于Grassmannian 流形上共轭梯度算法的联合干扰对齐预编码方案。计算机仿真表明,该算法兼顾干扰信号功率的最小化和有用信号功率的最大化,可以有效提高系统的和速率性能,而且该算法可以有效解决Grassmannian流形上最陡下降算法每次寻优的 90°转折问题,具有更高的收敛速度。     

穿戴式生理信号检测与分析系统的实现

系统实现了一种穿戴式生理信号检测与分析装置,可实现人体的基本生理参数实时检测。以STM32L152单片机为主控制器,AM2520与APDS-9008组成的光电传感器和MLX90615红外传感器作为核心采集模块,分别采集人体的PPG信号和皮温信号,并通过蓝牙模块HJ-580将数据传至安卓智能手机,用手机作为客户端实时显示心率、呼吸、皮温和心率变异性的结果。目前各模块已经PCB制板并调试完成,结果表明,该系统具有功能多样性、易穿戴等特点。     

Performance analysis of impulse‐radio ultra‐wideband energy detector system using cooperative dual‐hop amplify and forward strategy

A novel analytical representation of bit error rate (BER) performance of an impulse‐radio ultra‐wideband energy detector on–off keying system using cooperative dual‐hop amplify and forward relay technology, with various diversity combining schemes over IEEE 802.15.4a environment is presented in this paper. In particular, the approximate expressions based on energy detection principle are derived for various diversity combining cases, namely linear optimal combining, linear combining, and selective combining. Simulation results depict an improvement in BER performance, with increase in number of relay paths (L ) and decrease in number of frames per symbol (N _f ). Furthermore, the BER performance of the impulse‐radio ultra‐wideband energy detector on–off keying system improves substantially using dual‐hop cooperative amplify and forward scheme, compared with that of non‐cooperative or single link scenario. Among the diversity combining schemes, linear optimal diversity combining performs better when compared with linear diversity combining and selective combining. The analytical BER expressions are validated with the simulation results, which confirm the accuracy and precision in approximation used in the investigation of BER. Copyright © 2015 John Wiley & Sons, Ltd.     

The performance of MIMO system using MRT scheme in vehicular systems

In this paper an inter‐vehicle multiple‐input multiple‐output system using maximal ratio transmission (MRT) scheme is proposed, and its performance is investigated where the proposed system uses multiple antennas for transmission and reception. It has the advantage of increasing effectively the diversity order without changing the receiver. As far as we know, MRT has not been employed in vehicular systems to improve system performance. Specifically, error performance of the MRT with different number of antennas at the transmitting and receiving stations has been examined, ie, MRT (2, 1) and MRT (2, 2) in a vehicular system in which cascaded Nakagami‐m fading distribution used. First, we derive expressions of probability distribution function and then moment generating function of end‐to‐end signal‐to‐noise ratio. Based on these expressions, we obtain the symbol error rate expression on account of examining the performance of the considered system. Then, the upper bounds for the symbol error rate expressions for high enough signal‐to‐noise ratio values have been calculated. Finally, we validate the confirmation of obtained theoretical results through simulation results and furthermore show that the multiple‐input multiple‐output system using MRT scheme can provide the full diversity.      

Time diversity evaluation for attenuation mitigation method using attenuation data in Thailand and Japan

In order to support future satellite broadcasting and communication in the Ka band and above, the time diversity method provides a novel attenuation mitigation technique for maintaining satellite service availability at levels between 99.9 and 99.99%. In this paper, the time diversity method is analyzed using various time delays from between 1 min and 1 h in an effort to mitigate convective rain attenuation by using various beacon signal transmission delays. For comparison purposes, receiver beacon data from Japan and Thailand are presented to highlight tropical and non‐tropical zone regional differences, and the International Telecommunications Union (ITU) R P.618‐12 standard is used for scaling up the Thaicom beacon frequencies from 12.57 and 12.59 GHz in the Ku band to 19.45 GHz, which is the Ka band frequency used by Japan's communication satellite (CS) beacon. We found that the time diversity method is very useful for mitigating the effects of rain attenuation. Copyright © 2016 John Wiley & Sons, Ltd.     

基于偏好信息的双阈值多目标粒子群算法

以获取偏好解为研究重点,提出了一种双阈值多目标粒子群( multi-objective particle swarm optimization with double thresholds,DT-MOPSO)算法。该算法利用g-支配增加选择压力,借助光束距离阈值σ控制非劣解的数量。另外,引入多样性指标的阈值实现对解集的分布性的控制。当解集的多样性指标低于阈值时,采用自适应网格技术增加解的多样性。通过对典型问题的测试,验证了改进算法的正确性和有效性。     

不同地震波作用方向的大型渡槽动力响应分析

以南水北调中线工程中某大型渡槽结构为研究对象,采用ADINA软件中的势流体单元研究考虑流固耦合作用下渡槽结构的动力响应规律。本文对渡槽结构在顺槽向、双向和三向地震波作用下的动力响应分别进行了仿真研究。并分析了附加质量法和ADINA完全流固耦合法在计算流固耦合问题上的异同,及多维地震波对结构动力响应的影响。结果表明:水深及地震作用方向对渡槽结构的动力响应影响较大,且应在双向地震波作用下来研究结构的动力响应问题。     

一种适用于多场景的窄带LMS信道模型

针对现存陆地移动卫星(land mobile satellite,LMS)信道模型使用场景有限及状态持续时间概率密度函数(state duration probability density function,SDPDF)不精确问题,提出能准确有效地描述更多操作场景的窄带LMS信道模型.利用对数正态分布近似SDPDF的Semi-Markov链实现状态序列.在每一状态内结合传播参数生成服从Loo分布的载噪比时间序列.通过在慢衰落成分中引入多普勒频移以增加参数数据库及扩展适用场景.研究不同场景下状态概率、载噪比时间序列的一阶统计特性和90%信号有效性所需的余量,并与实测值比较.研究结果表明:该模型能在多场景下有效地代表阴影条件,且在不同信道环境中的各仰角和方位角下具有较好适用性,可用于系统性能分析.