基于并行PO/EEC的ISAR回波生成与成像仿真

为了满足基于模板的逆合成孔径雷达（ISAR）目标识别对海量高分辨模板图像的工程需求,提出了一种基于并行电磁散射特性计算技术的ISAR图像信号级仿真方法。首先,以OpenMP技术为基础采用并行物理光学和等效边缘电磁流对目标的电磁散射特性进行快速计算;其次,以步进频率波形为雷达发射波形结合目标的电磁散射特性生成了宽带雷达回波数据;最后,对使用距离多普勒算法对仿真回波数据进行处理生成ISAR像,并与点阵模型成像结果进行了对比分析。实现了对ISAR图像的信号级快速仿真,对ISAR系统设计与验证、ISAR图像解译和目标识别以及ISAR成像处理等具有重要意义。     

频率稳定度的测量

简单介绍了3种常用的测量短期频率稳定度的方法:差拍法,双混频法和频差倍增法,以及对于数据处理所采用的方法,并且在其中的差拍法和频差倍增法基础上提出一种改进的方法,从而可以提高整个系统的测量精度.     

一种新的双偶氮化合物的三阶非线性光学性能

合成了一种新的双偶氮化合物2,6-双[(2,4-二羟基苯基)偶氮]蒽醌,用IR,1 H NMR和元素分析表征了其结构.采用飞秒激光,运用简并四波混频法,研究了化合物在非共振状态下的三阶非线性光学性能.它的三阶非线性光学极化率χ(3)为3.37×10-13 esu,非线性折射率n2为6.21×10-12 esu,分子二阶超极化率γ为4.02×10-31 esu,响应时间τ为101 fs.分析了化合物的分子结构对三阶非线性光学性能的影响.增长共轭链,形成供吸供构型,增大取代基的吸或供电子能力等因素有利于获得较大的三阶非线性光学性能.     

波分复用系统的四波混频特性研究

本文对波分复用（WDM）光纤通信系统中的四波混频（FWM）特性进行了研究，得到了WDM可用于由多段不同长度，不同色散值的光纤组成的多级放大WDM系统FWM效应的计算方法，进而分析了单级、多级放大和色散补偿这3种特例的FWM特性，研究结果表明，标准单模光纤与高负色散值色散移位光纤的组合可以有效地抑制FWM混频效应。     

The 802.11n MIMO-OFDM Standard for Wireless LAN and Beyond

An overview is given of the new IEEE 802.11n standard. This is the first wireless LAN standard based on MIMO-OFDM, a technique pioneered by Airgo Networks to give a significant performance increase in both range and rate relative to conventional wireless LAN. Performance results show that net user throughputs over 100 Mbps are achievable, which is about four times larger than the maximum achievable throughput using IEEE 802.11a/g. For the same throughput, MIMO-OFDM achieves a range that is about 3 times larger than non-MIMO systems. This significant improvement in range-rate performance makes MIMO-OFDM the ideal solution not only for wireless LAN, but also for home entertainment networks and 4G networks. Richard van Nee received the M.Sc. degree in Electrical Engineering from Twente University in Enschede, the Netherlands, in 1990. In May 1995, he received the PhD degree from Delft University of Technology. From 1995 to 2000, he worked for Lucent Technologies Bell Labs on wireless LAN transmission techniques. He was one of the original proposers of the CCK and OFDM modulation techniques which were adopted by the IEEE 802.11b and IEEE802.11a wireless LAN standards. In 2001, he cofounded Airgo Networks that developed the first MIMO-OFDM modem for wireless LAN and which techniques form the basis of the IEEE 802.11n standard. Together with Ramjee Prasad, he wrote a book on OFDM, entitled ‘OFDM for Mobile Multimedia Communications.’ In 2002 he received the Dutch Veder award for his contributions to standardization of wireless communications.     

噪声系数分析仪浅析

论述了噪声系数分析仪的工作原理和噪声系数最基本的测量方法——Y因子法。介绍了噪声系数分析仪常见故障的维修方法及其关键技术。尤其是HP8970B噪声分析仪,送生产厂家维修,费用比较昂贵。摸索出了一套简便高效的维修方法,用自行设计的放大器有关电路替代原件,成功地进行了修复,对此进行了重点介绍。     

Structural and optical properties of AIN sputtering deposited on sapphire substrates with various orientations

AIN thin films were deposited on c-,a-and r-plane sapphire substrates by the magnetron sputtering technique.The in-fluence of high-temperature thermal annealing (HTTA) on the structural,optical properties as well as surface stoichiometry were comprehensively investigated.The significant narrowing of the (0002) diffraction peak to as low as 68 arcsec of AIN after HTTA implies a reduction of tilt component inside the AIN thin films,and consequently much-reduced dislocation densities.This is also supported by the appearance of E2(high) Raman peak and better Al-N stoichiometry after HTTA.Furthermore,the in-creased absorption edge after HTTA suggests a reduction of point defects acting as the absorption centers.It is concluded that HTTA is a universal post-treatment technique in improving the crystalline quality of sputtered AIN regardless of sapphire orienta-tion.     

基于光纤中四波混频效应的多信道波长转换性能的数值分析

高效多信道波长转换技术对于将来灵活的全光网络应用具有重要的意义。在本文中我们从数值上分析了幅度调制信号,相位调制信号,以及混合幅度调制信号和相位调制信号的多信道波长转换技术。本文同时也讨论了受激布里渊散射效应及其对于基于四波混频效应的高效波长转换技术的影响。分析结果表明差分相位调制信号（DPSK）更加适合基于四波混频效应的多信道波长转换技术,因为多信道OOK波长转换的信号将会受到无法避免的码型相关损耗效应的影响。在将来的应用中,当调制格式由传统的OOK格式部分升级为DPSK格式的时候,在多信道波长转换情况下的OOK信号对于升级的DPSK信号的影响必须要仔细考虑,并且这种影响随着OOK信道数目的增加变得更加严重。因此我们可以得出如下结论,DPSK信号更加适合于传输和多信道波长转换的需要,尤其是在长距离传输和高比特速率的系统中。     

超细CL-20/HMX共晶的制备、表征及其与推进剂组分的相容性

通过加入微量溶剂,采用超高效混合技术,在70 g的加速度条件下反应30 min制备得到摩尔比为2∶1的超细六硝基六氮杂异伍兹烷与奥克托今(CL-20/HMX)共晶,通过X射线粉末衍射、差示扫描量热法鉴定了CL-20/HMX共晶的形成,并对其形貌、粒度、感度等进行了表征测试。结果表明:制备的超细CL-20/HMX共晶纯度为92.6%,共晶炸药呈规则块状、表面光滑、粒径小于1μm、粒度分布均匀,其X射线衍射图在11.558°,13.264°,18.601°,24.474°,33.785°,36.269°处出现新的较强的衍射峰。超细CL-20/HMX共晶放热分解过程中只有一个放热分解峰,其放热峰温为248.3℃,其分解放热量(2192.1 J·g^-1),显著高于相同摩尔比的物理混合物(1327.3 J·g^-1)。按照GJB772A-1997《炸药试验方法》测得的摩擦感度比原料CL-20降低了16%,特性落高比原料CL-20提高28.6 cm,比原料HMX提高11.5 cm,形成共晶后安全性能更高。采用DSC法研究了超细CL-20/HMX共晶与推进剂常用组分均聚叠氮缩水甘油醚(HGAP)、硝化甘油/1,2,4-丁三醇三硝酸酯混合物(NG/BTTN)、缩二脲三异氰酸酯(N-100)、高氯酸铵(AP)、铝粉(Al)的相容性,发现超细CL-20/HMX共晶与NG/BTTN、AP、Al的相容性较好,与HGAP、N-100不相容。