Maritime cognitive radio spectrum sensing based on multi-antenna cyclostationary feature detection

ABSTRACT

With the development of the maritime transportation industry, the number of ships is increasing and the ships are becoming more intelligent. Due to the rapid development of maritime communication, the demand for communication spectrum is increasing. Therefore, the maritime cognitive radio (CR) system is an effective solution. Because of the multipath fading caused by sea surface and atmosphere has a more serious influence on communication signals, which increases the instability of the signal reception, the spectrum sensing technology in maritime cognitive radio is more challenging than the spectrum sensing on land. In order to solve this problem, a cyclostationary detection algorithm for multiple antennas in fading model is proposed. A maximum ratio combining algorithm based on optimal weight correlation value (OWCV-MRC) is proposed for the diversity gain and system performance degradation caused by diversity technology on multipath fading channels. The algorithm uses the correlation values of the attenuation gains on the two different branches as the weighting coefficients of each branch, thus improving the coefficient matrix in the maximum ratio combining (MRC) algorithm. The simulation results show that the proposed algorithm can effectively detect the target signal in the fading channel with ultra-low signal to noise ratio (SNR).     

新型硅激光器系统的优化设计

通过在硅波导上添加反向偏压的PIN结构,建立了完整的全硅激光器系统.该系统包括半导体泵浦光源和硅波导放大器.建立的硅激光器增益模型,与已知的实验结果达到了很好的一致,并给出了泵浦光源输出波形和硅激光器的输出波形.该系统可以集成在很小的CMOS器件上,实现光电子器件的集成化,有着广泛的应用前景.     

数字对讲机互联网传输的中心站软件设计

对讲机的通信距离有限,提出一种通过Internet传输数字对讲机话音和数据。扩大对讲机通信范围的方案。数字对讲机通过串口与计算机相连,计算机作为中心站,完成数据的转发功能,并通过Internet传输数据。首先设计了数字对讲机和计算机之间通信的串口通信协议,在此基础上详细讲述了中心站的软件设计。中心站软件的设计主要包括三个部分,对讲机模块和计算机之间串口通信协议的设计和实现,通过Internet使用UDP协议的数据传输;使用Access数据库对对讲机用户号码及中心站IP地址的管理等。通过对中心站软件的测试表明,设计的串口通信协议可行,使用中心站软件能通过该方案有效地扩大对讲机的通信距离。     

单轴晶体材料的Casimir效应调控研究

Casimir效应最初表现为理想导体平板之间存在的真空作用力,近年来在微机械和纳米机械领域中具有重要影响和作用。考虑单轴晶体平行材料板的光轴几种不同取向,通过电磁场应力张量方法计算了单轴晶体平板间的Casimir作用力,其中平板间为真空区域。仿真结果表明,Casimir作用力在短距下受到较强抑制,而随着板间距的增大抑制逐渐放缓,直至可以恢复到约为理想导体板间力的1/10,同时Casimir力也随各晶体参数发生变化,进而可由此调控Casimir效应。     

Tunable thermo-optic switch based on fluid-filled photonic crystal fibers

A tunable thermo-optic intensity-modulated switch is investigated theoretically and numerically.It is based on the infiltra-tion of temperature-sensitive mixture liquids into index-guiding photonic crystal fibers(PCFs).The switching function attributes to the thermo-optic effect of the effective refractive index of the cladding.The simulation illustrates that the switch presents a tunable transition point according to the concentration of the mixture liquids,and the on-off switching functionality can be realized within a narrow temperature range of 2 oC.The switches have wide application for innovative all-in-fiber optical communication and logic devices.     

Near-Infrared Light Triggered Self-Powered Mechano-Optical Communication System using Wearable Photodetector Textile

The merging of humans and machines depends on the contact sensor medium used. However, this contact interaction inevitably leads to mechanical loss. Photodetectors are cutting-edge tools in optical communication that use controlled lighting to achieve efficient signal conversion to drive mechano–optical communication systems and provide an innovative interface for the Internet of Things services. Here, a self-powered, non-contact mechano–optical communication system based on a wearable Te@TeSe photodetector textile is presented, which encodes near-infrared light to modulate robotic manipulator actions. The wearable Te@TeSe photodetector textile enhanced the photocurrent and responsivity by 400 times compared to a pristine Te nanowire (NW) array. The type II heterojunction of Te@TeSe NWs is proved by first-principles calculations and simulated, providing insights on photogenic carrier transmission in Te@TeSe NWs. This system shows the possibility of duplicate real-time execution of mechanical gestures in virtual environments and paves the way for advanced optical devices applied to information transmission and mechano–optical communication.     

卫星导航系统技术和产业发展战略研究

简要描述了国内外卫星导航定位系统的现状及发展趋势。站在陆海空天综合电子信息一体化的角度,提出卫星导航综合应用与服务体系结构,说明了系统支撑技术及研究对策。最后指出了相关卫星导航技术和产业的发展思路。     

基于Talbot干涉的X射线光栅成像技术研究进展

从技术特点和研究热点的角度,综述了X射线光栅干涉成像技术与系统的国内外最新进展。介绍了具有代表性的基于Talbot-Lau干涉法的X射线光栅成像原理与系统结构,以及物质对X射线的衰减、折射与小角散射的多信息获取技术。综述了国内外对X射线光栅成像技术与系统的优化改进研究,主要包括光栅步进对高位置分辨率的松弛与大视场高分辨率光栅成像技术的实现。介绍了二维光栅与基于光栅的具有时间分辨率的四维成像技术的国内外最新发展动态。展望了X射线光栅成像技术的发展趋势。     

适用ROF无线通信系统的调度算法

提出了一种基于多业务的提供QOS保证的调度算法,主要应用在使用ROF技术的多媒体无线通信系统中。该算法是在研究Q-PFS算法的基础上,分析了ROF技术和多媒体无线通信的特点后提出的。算法解决了多业务情况下的无线资源的调度问题,实现吞吐量的最大化和各业务之间的公平性,同时保证了QOS。     

Microstructure and Electrical Properties of Low Temperature Processed Ohmic Contacts to p‐Type GaN

With Ni/Au and Pd/Au metal schemes and low temperature processing, we formed low resistance stable Ohmic contacts to p‐type GaN. Our investigation was preceded by conventional cleaning, followed by treatment in boiling HNO₃:HCl (1:3). Metallization was by thermally evaporating 30 nm Ni/15 nm Au or 25 nm Pd/15 nm Au. After heat treatment in O₂ + N₂ at various temperatures, the contacts were subsequently cooled in liquid nitrogen. Cryogenic cooling following heat treatment at 600 ·C decreased the specific contact resistance from 9.84·10^?4 Ωcm² to 2.65·10^?4 Ωcm² for the Ni/Au contacts, while this increased it from 1.80·10^?4 Ωcm² to 3.34·10^?4 Ωcm² for the Pd/Au contacts. The Ni/Au contacts showed slightly higher specific contact resistance than the Pd/Au contacts, although they were more stable than the Pd contacts. X‐ray photoelectron spectroscopy depth profiling showed the Ni contacts to be NiO followed by Au at the interface for the Ni/Au contacts, whereas the Pd/Au contacts exhibited a Pd:Au solid solution. The contacts quenched in liquid nitrogen following sintering were much more uniform under atomic force microscopy examination and gave a 3 times lower contact resistance with the Ni/Au design. Current‐voltage‐temperature analysis revealed that conduction was predominantly by thermionic field emission.