存在同信道干扰和多用户分集的多蜂窝系统性能分析

考虑存在来自其他蜂窝的不同功率同信道干扰的多用户上行链路,分析了基站采用多用户调度和最大比合并接收时的系统性能.在期望信号和干扰信号分别为Nakgami-m和Rayleigh时,运用基于概率密度函数的性能分析法推导了系统中断概率和平均误符号率(ASER)的闭合表达式.仿真结论显示,系统中断概率和ASER的解析曲线与数值仿真结果一致,系统性能随着天线数和用户数的增大而提升,多天线和多用户分集增益明显,干扰功率有较大差异时系统中断概率性能有所下降.     

一种高性能LVDS收发器的设计

基于0.18μm SiGe BiCMOS工艺,设计了一种用于10位200 MHz高速流水线模数转换器的CMOS LVDS收发电路。该收发电路由发射器(TX)和接收器(RX)组成。发射器通过带共模反馈的闭环控制电路,将0~3.3 V的CMOS信号转换成(1.2±0.35)V的LVDS信号。接收器采用一个轨至轨预运算放大器保证LVDS信号的完整接收,并实现一定的增益,之后由迟滞比较器和输出缓冲器实现对共模噪声的抑制以及信号驱动能力的提高,最终正确恢复出CMOS信号。仿真结果表明,在400 MHz脉冲输入下,收发器可以稳定工作在3.3 V电源电压,总功耗仅为22.4 mW。     

山西广电传输网长距离传输数字微波信号的工程实践

山西广播电视无线传输网采用数字微波作为全省广播电视干线网的传输手段,主要以提高传输效率和传输质量的各种抗衰落技术手段为中心,阐述了空间分集、频率分集、增加直放站等技术对长距离传输微波信号的作用和效果,为干线网中数字微波信号的长距离传输与安全播出提供了很好的解决办法。     

Frequency acquisition synchronization for multiple antenna systems

In this paper, we consider the problem of frequency acquisition synchronization by using multiple antennas over wireless fading channels. We introduce frequency synchronization with different combining schemes including space diversity and time diversity. Their performance is estimated for a Rayleigh fading channel with an analysis both theoretically and by simulation. We investigate the relationship between the mean squared error (MSE) and the average signal‐to‐noise ratio (SNR) for combining of different blocks and antennas. Both the carrier frequency offset and the sampling frequency offset are estimated when multiple antennas are utilized for signal transmission. The estimation with maximum ratio combining (MRC) scheme is presented in detail, and the estimation with selection combining scheme and equal gain combining scheme are introduced briefly. The simulation results explicitly show that the performance of the frequency acquisition synchronization with MRC scheme is better than that of others and that the MSE at low SNR is not very close to the Cramér–Rao low bound in multiblock combining frequency synchronization. Furthermore, the results address that in order to improve the performance, the total number of receive antennas will be increased exponentially. Copyright © 2013 John Wiley & Sons, Ltd.     

Performance analysis of modulation diversity with OSTBC transmission over Nakagami-m fading channels

In this paper performance of modulation diversity with multiple-input multiple-output transmission is studied over flat Nakagami-m fading channels with arbitrary fading parameter m. In the system, orthogonal space-time block coding and maximal ratio combining like combiner are used for transmission and reception, respectively. Exact pairwise error probability expression is derived to observe performance of the system. Moreover, in order to obtain the diversity order of the system, asymptotic pairwise error probability expression is also derived. Optimum rotation angles are analytically obtained for binary and quadrature phase shift keying modulations. Theoretical results are validated by Monte Carlo simulations.     

Nakagami衰落信道下合作分集的无线家庭网络性能分析

提出在未来无线家庭网中采用合作分集的思想,通信时利用处于空闲状态的终端用户对所发送信息进行中继发送,保证整个网络误码率性能、中断概率以及发送功率达到最佳折衷.在Nakagami平衰落信道条件下研究了再生中继和非再生中继两种合作方式下的中断概率和误码率性能,给出误码率和中断概率的解析表达式,并用matlaab进行仿真,仿真结果表明,在低信噪比条件下再生中继大大优于非再生中继方式,但高信噪比条件下两者性能接近.     

中国普通野生稻线粒体DNA的限制性片段长度多态性

用BamHI／H454、BamHI／pQT2-7-1、EcoRI／B376和EcoRI／pQT12四种酶／探针组合对85份普通野生稻、亚洲栽培稻和橹稻进行了线粒体DNA的限制性片段长度多态性的分析．共检测到16条多态性带，15种表型，组合成14种线粒体DNA变异类型．其中抽稻和粳稻的线粒体DNA已分化，培稻偏粳型，大部分普通野生稻属（或偏）拉型，但江西的东乡普通野生稻类型比较独特．中国普遍野生稻的线粒体DNA与地理分布相关，湖南的江永、茶陵和江西的东乡等不同的群体以地理位置相聚，随地理梯度遗传分化由少到多．     

1.5μm InP/InGaAs MQW-LD驱动电路的设计

讨论了由4个InP/InGaAs HBT构成的OEIC光发射机驱动电路的设计。研究结果表明.由最佳性能的HBT构成的驱动电路,其性能不一定就是最佳的,驱动电路的性能与激光器的串联电阻有很大关系。本文对激光器的串联电阻为9Ω的情况,从几何参数优化设计一驱动电路,其调制带宽可达3.4GHz,脉码凋制时。开关时间约为100ps。用它驱动一多量子阱激光器,脉码调制时,光信号响应开头时间约为288ps。     

用于表面粗糙度检测的双波长光纤传感器研究

论述了用于表面粗糙度测量的双波长光纤传感器的工作原理和实验装置，实验结果表明该系统具有线性好、抗干扰性强、测量精度高、可测微小面积等特点。推导了该传感器系统的测量误差公式，数值计算了温度变化造成的测量误差并据此做出了温度一测量误差关系曲线，分析了双波长传感器方案对于温度误差的改善程度。     

Two Schemes of Blind MMSE Multiuser Receiver for Space-Time Coded CDMA Systems

1　IntroductionIthasbeenshownthatthecapacityofwirelesscommunicationsystemscanbeincreaseddramatical lybyemployingmultipletransmittingandreceivingantennas.Space timecodinghasbeenpaidmoreat tentionrecentlybecauseitisaneffectivewaytoex ploitspatialandtemporaldiversity[1～2 ] .Despitealossincodingadvantage,space timeblockcodingcanofferthemaximumdiversitygainbasedononlythelinearprocessingatthereceiver[3～ 4] andhasbeenproposedtobeusedin 3Gsystems.InterferencesuppressionismorechallenginginCDMAsyste…