95 GHz三次谐波回旋管设计

采用线性理论和非线性理论研究了回旋管谐振腔结构、寄生模式抑制及注波互作用等问题。设计了一支工作在95 GHz的三次谐波回旋管,注波互作用结构采用标准开放式谐振单腔,工作模式为TE64, 采用电压45 kV、电流5 A、横纵速度比为1.5的小回旋电子注。在不考虑电子注速度离散及厚度的情况下,非线性理论分析表明,该回旋管可以获得14 kW功率输出,横向互作用效率约为18%,整管效率约11%。     

消除热库中量子位的消相干性

以二能级原子作为量子位,利用求解相互作用系统约化密度矩阵非对角元的方法,分别研究热库中量子位模型和依赖强度耦合Jaynes-Cummings模型的消相干特性.当外加驱动场消除消相干时,得到两种模型下驱动场必须满足的约束方程.?     

Effects of gordon-haus jitter on soliton transmission

The bit error rate (BER) performance of an optical soliton communication system is analyzed. Based on the jitter variance equation and the chi-square distribution for the amplified spontaneous emission noise, an analytic expression for the BER calculation is obtained. We have investigated the effects of Gordon-Haus jitter, which is due to the random phase shift of the soliton individual central wavelength induced by the amplified spontaneous emission noise of the amplifiers. Very good agreement has been obtained between our theory and the reported experimental results.     

太赫兹波段Smith-Purcell辐射的介质加载光栅高频特性

提出了一种用于Smith-Purcell效应器件的介质加载光栅慢波结构,通过研究该结构的注-波互作用过程,推导出带电子注的色散方程,并数值求解出波的线性增长率.利用色散方程,结合电磁场传播的边界条件,推导出Smith-Purcell效应振荡器工作所需的起振电流.详细研究了高频结构长度、电子注主要参数和介质相对介电常数对起振电流的影响,并与普通金属光栅结构进行了比较.结果表明:保持其他参数不变时,高频结构长度越短,起振电流越大;保持高频结构参数不变时,起振电流随电子注厚度和注-栅距离的增大而增大,随电子注电压的增大而减小;与金属光栅相比,介质的引入提高了注-波互作用的增长率,有效减小了振荡器的起振电流.理论计算结果与软件CHIPIC的模拟结果比较符合.     

一种易于硬件实现的图像有损压缩算法

原始图像数据经过小波变换后,根据子带系数之间在空间上和方向上所呈现出的带间相似性,将像素集合重新定义为集合树。通过对直流系数量化编码和交流系数比特深度编码中的参数K和熵编码中长度分别为3bit码字（choicel）和4bit码字（choice2）的编码方式的选择实现数据的渐进性编码,使产生的码流具有内嵌特性,可以对任意码流进行截取和译码,实现对码率的有效控制。提出了一种具有复杂度低、易于硬件实现的图像有损压缩算法。经过系统仿真证明此算法有利于提高重建图像的质量。     

基于混沌激光产生1 Gbit/s的随机数

利用光反馈半导体激光器产生的混沌激光作为随机数发生器的物理熵源,通过8位 ADC将熵源信息转化为二进制码,并经后续差分运算处理改善其随机性,最终获得了1 Gbit/s的随机数.所产生的随机数通过了NIST Special Publication 800-22的全部测试项. 关键词： 混沌激光 随机数发生器 半导体激光器 模数转换     

微型光学偶极阱中单原子相干操控Rabi振荡的实现及其应用

文章综述了Rabi振荡的基本原理以及微型光学偶极阱中单原子相干操控Rabi振荡的研究进展,同时介绍了其在单光子源、量子寄存器、量子计算等方面的应用,并简要介绍了作者所在小组在微型光学偶极阱中单原子操控方面的实验进展.     

用遗传算法构造光正交码

提出了一种利用遗传算法构造任意码长、码重、自相关限、互相关限光正交码(GA-OOC)的方法,设计了新的码字矩阵;分析了基于GA-OOC的光CDMA系统的误码率性能。仿真结果表明:该算法具有构造算法简单、易于编程实现的特点;与基于PC,EPC,QC和BIBD-OOC的光码分多址系统相比,GA-OOC的光码分多址系统具有更好的误码率性能。GA-OOC有望用于构造二维光地址码。     

High-speed transmission limitations due to Polarization Mode Dispersion

In this paper, the impacts of Polarization Mode Dispersion (PMD) on the performance of high-speed optical communication system have been reported at different bit rates. The two systems are modeled using older fibers with same PMD coefficient at different bit rates and third is with the new fiber with less PMD coefficient than that of the previous two. The attenuation, chromatic dispersion and non-linear effects have been disabled, so that all the variation of the results is due to PMD. The bit rate is varied from 2.5 to 40 Gbps and the length is varied from 1000 to 20,000 km. It is shown that the impact of PMD increases with the bit rate of system. It is also reported that the impact of PMD becomes intolerable at the bit rates of more than 40 Gbps. And also the PMD produces very minute impact on the system performance for same bit rate with the variation in the fiber length.     

Parameter allocation of parallel array bistable stochastic resonance and its application in communication systems

In this paper, we propose a parameter allocation scheme in a parallel array bistable stochastic resonance-based communication system(P-BSR-CS) to improve the performance of weak binary pulse amplitude modulated(BPAM) signal transmissions. The optimal parameter allocation policy of the P-BSR-CS is provided to minimize the bit error rate(BER)and maximize the channel capacity(CC) under the adiabatic approximation condition. On this basis, we further derive the best parameter selection theorem in realistic communication scenarios via variable transformation. Specifically, the P-BSR structure design not only brings the robustness of parameter selection optimization, where the optimal parameter pair is not fixed but variable in quite a wide range, but also produces outstanding system performance. Theoretical analysis and simulation results indicate that in the P-BSR-CS the proposed parameter allocation scheme yields considerable performance improvement, particularly in very low signal-to-noise ratio(SNR) environments.