基于复多相滤波器组的信道化接收机

本文讨论了多相滤波器实现信道化接收机的原理,并结合复解析滤波器具有负频率分量为零、冲激响应函数实部和虚部有90°相移的特点,给出一种基于复解析滤波器组的信道化接收机的实现方案。最后通过Matlab对调幅(AM)信号的解调仿真验证了该接收机设计的正确性和可行性。     

采用射频直采技术的超宽带软件无线电平台

针对现代无线电系统对超宽带、可重构、多功能等需求日益增长的问题,基于射频直接采样技术,构建了一套符合PXI(PCI extensions for Instrumentation)标准的通用化超宽带软件无线电平台,硬件上以数模转换芯片AD9173和模数转换芯片ADC083000为核心,直接采样率高达3 Gsample/s;采用20 nm工艺制程的UltraScale Kintex FPGA,以IP(Intellectual Property)化开发理念设计FPGA固件,实现用户可编程。该平台能够满足0.1~1.4 GHz超宽带软件无线电应用需求,瞬时带宽高达1.3 GHz。     

A Soft Lithiophilic Graphene Aerogel for Stable Lithium Metal Anode

The lithium metal anode is one of the most promising anodes for next‐generation high‐energy‐density batteries. However, the severe growth of Li dendrites and large volume expansion leads to rapid capacity decay and shortened lifetime, especially in high current density and high capacity. Herein, a soft 3D Au nanoparticles@graphene hybrid aerogel (Au? GA) as a lithiophilic host for lithium metal anode is proposed. The large surface area and interconnected conductive pathways of the Au? GA significantly decrease the local current density of the electrode, enabling uniform Li deposition. Furthermore, the 3D porous structure effectively accommodates the large volume expansion during Li plating/stripping, and the Li_xAu alloy serves as a solid solution buffer layer to completely eliminate the Li nucleation over‐potential. Symmetric cells can stably cycle at 8 mA cm^?2 for 8 mAh cm^?2 and exhibit ultra‐long cycling: 1800 h at 2 mA cm^?2 for 2 mAh cm^?2, and 1200 h at 4 mA cm^?2 for 4 mAh cm^?2, with low over‐potential. Full cells assemble with a Cu@Au? GA? Li anode and LiFePO₄ cathode, can sustain a high rate of 8 C, and retain a high capacity of 59.6 mAh g^?1 after 1100 cycles at 2 C.     

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).     

基于激光信息和射频识别的运动轨迹跟踪研究

为提高运动轨迹跟踪精度,设计了基于激光信息和射频识别的运动轨迹跟踪方法,首先将射频识别阅读器与激光传感器采集数据进行速度估算处理,并利用加权因子对激光传感器估算速度进行平滑处理,然后通过相似度对比方法匹配激光传感器与射频识别阅读器获取的运动目标速度,采用粒子滤波算法融合激光传感器与射频传感器获取的运动目标速度,通过粒子滤波的预测、更新与重采样三个阶段实现准确的运动目标轨迹跟踪,最后实验结果表明,该方法对目标的运动轨迹跟踪精确度高达99%。     

基于激光冲击的航空发动机风扇性能优化设计

航空发动机风扇性能是整个发动系统的核心,为了优化航空发动机的性能,提出一种基于激光冲击的航空发动机风扇性能优化系统设计方案。系统采用嵌入式设计技术,采用激光冲击技术进行航空发动机风扇性能相关参数检测,进行航空发动机风扇智能控制算法设计。结合传感器分布式检测技术进行航空发动机风扇转动状态测试,对航空发动机风扇性能优化系统的模块设计包括AD模块、智能信息处理模块、集成控制模块、激光冲击时钟控制模块、中断模块以及复位模块组成,采用激光冲击进行发动机风扇性能的智能监测和状态模式识别,结合ADSP-BF537进行发动机风扇性能检测的数据分析和智能控制,实现系统硬件设计。测试结果表明,设计的航空发动机风扇性能优化系统能实时监测风扇状态特征,提高对发动机风扇的远程智能控制能力。     

一种新型小型化宽带无人机机载智能天线研究

随着无人机系统的发展,无人机无线链路需要具有智能波束跟踪能力的小型化宽带高增益定向波束实现无线连接与组网。以电抗加载理论为基础,研究一款机载电控无源阵列天线(ESPAR),为了实现宽带效果,中心部位馈电的主振子以单锥天线作为激励,以寄生单元高度、单元间间距和加载电抗参量为优化参量,经过参数扫描、筛选和优化,给出了仿真结果,并进行了样机制作,给出了测试结果,实现了机载智能天线的小型化与宽带化。     

工业烟气黑度监测系统工程技术研究

利用远程监控技术,采集企业违规排放烟气图像,并通过计算机图像识别技术实现对排放黑烟进行自动监测,自动分析其黑度等级,为环保执法提供依据。文章是根据环境保护对烟尘排放的具体技术要求,设计了一套城市烟气黑度自动监测系统解决方案并付诸工程实施。重点叙述了烟气黑度识别技术、无线宽带网建设、图像传输技术等项目建设的关键与技术难点。系统建成后,有效解决了工业黑烟排放污染源的监控。该系统可靠,操作简便,监控直观,达到了系统预期的工程目标,此工程技术值得在智慧城市建设中推广应用。     

Enhanced spectrum sensing using a combination of energy detector,matched filter and cyclic prefix

In this paper, we propose a sensing scheme based on energy detection, matched filter and cyclic prefix. Both Equal Gain Combining (EGC) and optimal combination of the aforementioned detectors are investigated in cooperative and non-cooperative spectrum sensing scenarios. In packet transmission systems such as OFDM (Orthogonal Frequency Division Multiple access) systems, the proposed scheme takes advantage of utilizing more samples than individual detectors, i.e., cyclic prefix, training or pilot samples, and data payload samples. The proposed combine-sensing scheme offers higher detection probability and lower false alarm probability, as compared with the performance of individual detectors over the same frame duration. Simulation results are congruent with the theoretical curves and confirm the validity of our derivations.     

电容式RF MEMS谐振器

介绍了应用于通信领域的电容式RF MEMS谐振器及其在通信系统小型化中的优势。对电容式微机械谐振器进行了综合分析,包括基本工作过程分析、基本参数的理论分析及等效电路的分析。介绍了目前几种常用结构的谐振器,包括梳状谐振器、梁式谐振器及盘式谐振器的工作过程和谐振频率的发展空间。重点分析了谐振器的电容间隙及锚这两个重要的结构参数对谐振器性能的影响。最后,对电容式微机械谐振器存在的问题作了总结,对其发展趋势做出展望。