差分探测器偏振光学相干层析信号分析

分析了使用差分探测器的偏振光学相干层析(PS-OCT)统噪声,讨论影响系统信噪比(SNR)的因素,模拟SNR随这些因素的变化趋势,根据分析得出实现最佳SNR的参数条件,为提高PS-OCT系统SNR提供了理论依据.相关实验验证了模拟结果的正确性.     

电离层延迟对分布式SAR编队相对定位的影响

建立星载GPS单层电离层延迟模型,利用CHAMP卫星双频GPS观测资料确定的单层投影高度为580 km.仿真分析了电离层延迟对分布式SAR编队CDGPS(载波相位差分GPS)相对定位的影响,主要分析结果表明:在mm量级的星间相对定位中,电离层延迟影响不可被忽略;太阳活动对相对定位的影响显著,当星间距离取1 km,在太阳活动强年,由差分电离层延迟引起的相对定位误差达到8.5mm,是太阳活动弱年的2倍.     

Chip-to-chip optical interconnects: more bandwidth,more powerful

This paper aims to compare the electrical chip-to-chip interconnects and optical interconnect from the physical view and the computing performance view. Using transmission line theory, the constraints of transmission bandwidth is obtained. The calculation indicates that ideal maximum electrical capacity density is much lower than the experimental optical interconnected one. In this calculation, all the parameters come from International Technology Roadmap for Semiconductors (ITRS) and reports of world-class laboratories. Compared with bandwidth, application is a more important factor, which has great influence on the technology development direction and deployment in the real scenarios. Therefore, we take fast Fourier transform (FFT) computation as an example to study whether and how the optical interconnect technology has influences on the computing performance. One of most popular topology, mesh architecture is evaluated in this paper. The results illustrate the bandwidth increase will lift up the speedup and efficiency, especially for the clusters with many processors working cooperatively. From the above analysis, it is shown that the unique features of optical interconnects make it possible to provide more bandwidth, and then bring great advantage to computing performance.     

Performance analysis of amplify-and-forward relaying with hybrid-ARQ in Rayleigh fading channels

Hybrid automatic repeat request (HARQ) is a well-known technique for improving system throughput and link performance of wireless communication systems, including cooperative communication systems. The amplify-and-forward (AF) relaying method is one of the most attractive cooperative diversity schemes because of its low complexity. In this article, the end-to-end performance in terms of block error rate (BLER) and normalized throughput of AF relaying with HARQ transmission under the Rayleigh fading channel is analyzed. Numerical results validate the proposed analysis and demonstrate the gain of HARQ schemes in AF relaying systems. This analytical method can be extended to the systems with other HARQ protocols and other cooperative relaying schemes.     

帧同步系统的FPGA设计与实现

为能在数字通信系统的接收端将每帧数据区分开,实现正确译码,提出一种采用FPGA实现帧同步系统的设计方案。同步保护电路的设计提高系统的可靠性,在Quartus II开发软件上用硬件描述语言实现帧同步电路设计,并给出FPGA设计的实验仿真,实验结果表明该电路系统工作正确可靠,满足设计要求。     

针对小型无线电装置的运动分析算法

小型无线电测量装置能够方便地同时测量功率及多普勒频率信息。通过研究基于功率和多普勒频率的目标运动分析算法,运用迭代最小二乘方法给出数值解。仿真实验显示,仅依靠功率信息,在低信噪比的情况下无法正确估计运动参数。而通过结合功率及多普勒频率信息能得到更准确的运动参数估计,适合于实际应用。     

固态封装型的体声波谐振器的制备与性能分析

以Ti/Mo为布喇格反射层,在Mo底电极上沉积了高c轴择优取向的AlN薄膜,并采用微机电系统(MEMS)工艺制备了固态封装型体声波谐振器.用原子力显微镜(AFM)、场发射扫描电子显微镜(FESEM)测试了布喇格反射层的粗糙度和截面,用微波探针台和网络分析仪测试了以优化工艺参数条件制备的谐振器(FBAR)的频率特性,得到谐振器的谐振频率为2.51 GHz,有效机电耦合系数为3.89%,串并联品质因数为134.2和97.8.     

三阶1-1-1级联Σ-Δ调制器的设计及仿真

采用MASH结构,设计了一款三阶(1-1-1)级联Σ-Δ调制器;讨论了各个模块的增益系数,设计了数字校正电路,并运用Matlab/Simulink对调制器进行了行为级仿真.当输入信号带宽为20 kHz,过采样比为64时,仿真模型得到87.7 dB的信噪比,精度为14.28位.与其他结构的调制器相比,该调制器更加稳定,动态范围更大,可应用于处理音频信号的A/D转换器.     

船牌识别系统中的变形校正方法研究

因摄像机角度而造成的图像倾斜和畸变,会给船牌的字符分割和识别带来不利影响.针对此问题,提出了一种新的变形校正方法.首先对定位后的船牌采用轮廓跟踪算法提取轮廓信息;然后采用一种基于Hough变换和K均值聚类直线拟合算法取得牌照的边框参数;最后通过双线性空间变换和灰度插值完成图像的校正.实验表明,这里提出的方法符合船牌图像的特点,具有较高的鲁棒性和工程实用性.     

自动量程切换电压测量系统设计

电压测量是电子系统中不可或缺的一项技术,随着待测电压动态范围的急剧扩大,需要能实现量程自动切换的测量方法。提出一种自动量程切换电压测量系统的设计方法,该系统基于程控增益放大器器件,使用单片机控制其增益实现量程的自动切换。针对信道误差、温度漂移等问题,采用通道自校准技术,降低了信道对于测量的误差。通过对实际软硬件的测试表明,该系统能准确根据大小信号调整量程,并对系统及环境误差有一定的抗干扰能力。