一种新的噪声系数测量方法

测量含有自动增益控制(AGC)电路的射频模块噪声系数时,使用Y因子法将改变模块的功率增益,进而无法测定.本文提出了一种新的噪声系数测量方法.该方法在信噪比较小的条件下用误码率推算前端的载噪比,避免了用仪器标定载噪比受信道滤波器通带平坦性影响较大的问题;测量过程中,AGC输入端信号和噪声的总功率几乎不变,能够保证AGC功率增益不变,从而可准确测量含有AGC电路的射频模块噪声系数.通过理论推导和数值模拟分析了随机误差、系统误差、实验温度以及测量次数对噪声系数估计的影响,验证了方法的有效性.本文成果已用于我国"北斗一号"卫星导航定位用户机的射频模块测量.     

免疫型光纤倏逝波生物传感器的研究与发展

介绍了基于倏逝波激发的荧光免疫型光纤生物传感器的基本原理,针对其中应用的各种方法进行了分析。基于倏逝波激发的荧光免疫型光纤生物传感器的免疫检测方法、探头发展和系统结构发展．对国内外的最新产品和技术及其应用情况进行了介绍和概述,并结合新技术的出现和系统整体结构的演变趋势对免疫型倏逝波光纤生物传感器的发展进行了展望。     

激光涂层零件的多冲碰撞形变效应与分析

报道了多冲碰撞载荷下激光涂层零件塑性变形现象。利用坐标网格法、显微分析法等分析了激光涂层零件的多碰累积变形现象和规律。这种塑性变形在常温即可发生,且具有低应力和累积特性。变形发生在涂层表面及以下一段区域内,并由大到小呈梯度变化。碰撞能量驱动、冲击温升效应、晶界滑动与迁移、亚结构的形成与孪晶等,是引起多碰累积变形的可能原因。     

cdma2000 1xEV-DO空中接口安全层协议研究

EVDO技术为3G提供了更高的空中接口分组数据速率,同时在安全方面也提出了新的需求。详细介绍了EVDO空中接口安全层协议的内容,包括密钥交换协议、安全协议、认证协议和加密协议,并对安全层协议的安全性作了简要的分析。     

卫星与地面移动通信系统综合环境下的一种位置管理策略

提出了一种在卫星与地面移动系统综合环境下的位置管理方案，即把两系统相重叠的小区设置为边界位置区(BLA)，漫游用户在BLA中进行位置更新，呼叫到达时，BLA中的位置寄存器配合系统进行寻呼。通过计算和数值分析证明该方案不仅可以使原有两系统结构不发生变化，并且能有效减小位置更新与寻呼造成的系统开销。     

Synchronized chaotic optical communications at high bit rates

Basic issues regarding synchronized chaotic optical communications at high bit rates using semiconductor lasers are considered. Recent experimental results on broadband, high-frequency, phase-locked chaos synchronization, and message encoding-decoding at 2.5 Gb/s are presented. System performance at a bit rate of 10 Gb/s is numerically studied for the application of three encryption schemes, namely chaos shift keying, chaos masking, and additive chaos modulation, to three chaotic semiconductor laser systems, namely the optical injection system, the optical feedback system, and the optoelectronic feedback system. By causing synchronization error in the forms of synchronization deviation and desynchronization bursts, the channel noise and the laser noise both have significant effects on the system performance at high bit rates. Among the three laser systems, the optoelectronic feedback system has the best performance while the optical feedback system has the worst. Among the three encryption schemes, only the performance of additive chaos modulation with low-noise lasers is acceptable at high bit rates.     

Impact of temperature cycle profile on fatigue life of solder joints

In this paper the influence of the temperature cycle time history profile on the fatigue life of ball grid array (BGA) solder joints is studied. Temperature time history in a Pentium processor laptop computer was measured for a three-month period by means of thermocouples placed inside the computer. In addition, Pentium BGA packages were subjected to industry standard temperature cycles and also to in-situ measured temperature cycle profiles. Inelastic strain accumulation in each solder joint during thermal cycling was measured by high sensitivity Moire interferometry technique. Results indicate that fatigue life of the solder joint is not independent of the temperature cycle profile used. Industry standard temperature cycle profile leads to conservative fatigue life observations by underestimating the actual number of cycles to failure.     

An FDTD/ray-tracing analysis method for wave penetration through inhomogeneous walls

A novel method of studying wave penetration through inhomogeneous walls using the hybrid technique based on combining finite-difference time-domain (FDTD) and ray tracing methods is presented . The FDTD method is used to analyze the transmission characteristics of inhomogeneous walls. Using the knowledge of the tangential electric and magnetic field distributions along the borders of the FDTD computation domain, rays are sent out to cover the rest of the environment so that prediction of signal coverage can be made more efficiently without compromising the accuracy. Numerical results of the method have been compared and shown to agree very well with those of measurement and those of full wave analysis. Examples have shown the inadequacy of the traditional ray tracing method in the presence of walls made of concrete blocks. However, the proposed method can accurately predict signal coverage by taking into account the scattered fields by the inhomogeneity inside the walls. The method does not add much to computational complexity. Reduction in computation time is even more significant when the incident waves can be approximated to be plane waves and the wall structure is periodic.     

二阶非线性晶体法-珀谐振腔内的级联非线性现象

研究了 10 6 4nm红外激光通过具有LBO二阶非线性晶体的法 珀谐振腔的级联二阶非线性。研究结果表明 ,由于法 珀谐振腔的光反馈作用提高了谐振波长在LBO晶体内的功率密度 ,当 30 0mW的 10 6 4nm连续光入射时 ,仍可观察到级联二阶非线性现象。     

MPEG4及其基于3G的汽车电子应用

随着3G的发展和汽车电子行业的兴起，移动通讯和多媒体结合更加紧密，其中MPEG4起着不可缺少的桥梁作用。MPEG4的低码率和高压缩能力以及在传输过程中强容错能力和强纠错能力，保障了网络多媒体传输的实时性、稳定性和可靠性。MPEG4有着其他视频标准不具备的优势，在将来的3G时代，MPEG4应用领域更加广泛，特别当汽车集交通工具、移动通信和网络多媒体于一体时。本文介绍和分析了MPEG4的容错和抗错特性以及在汽车电子领域的应用。