KNbO3：Fe的红外光折变效应

利用1.15μm He-Ne激光对光折变晶体KNbO_3:Fe的二波耦合实验测量,得到二波耦合增益系数为1.4cm~(-1),频率响应时间为5ms.在红外波段的初步实验结果与可见波段的规律相符.     

载流子浓度对光折变LiNbO3晶体二波耦合增益的影响

根据光折变微观机制和Ｋｕｋｈｔａｒｅｖ带导模型，分析了ＬｉＮｂＯ３晶体二波耦合系数与载流子深度的关系。结果表明二波耦合系数随流子浓度的升高而增大，并逐渐趋于一稳定值。测量了不同Ｃｅ掺杂浓度Ｃｅ：ＬｉＮｂＯ３晶体二波耦合指数增益与载流子浓度的关系，实验结果与理论分析一致。     

GaAs中瞬态二波耦合及其光的偏振——一种实现红外ps光开关的新途径

测量了瞬态二波耦合增益随泵浦光与探测光相对延迟改变而变化的曲线,并分析了瞬态二波耦合中各种过程的特性。预计并观察到了耦合光偏振的改变,证明了ps脉冲二波耦合是一种实现ps光开关的新途径。     

聚合物辅助水热法合成钽铌酸钾纳米晶

以Nb2O5和Ta2O5为前驱反应物,KOH为矿化剂,采用水热法和聚合物辅助水热法两种合成工艺制备了KTa0.25Nb0.75(KTN)纳米晶。通过X线衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(FEM)等技术,对合成产物进行了系统的研究。实验结果表明,表面活性剂聚乙烯醇(PVA)的量和矿化剂KOH的摩尔浓度是影响KTN纳米晶微观结构和形貌的关键因素。采用单纯水热工艺制备的KTN粉体,当c(KOH)达6mol/L、反应温度为200℃及反应时间24h,可生成纯钙钛矿相KTN。在较高碱度条件(c(KOH)=8mol/L)下,表面活性剂PVA的量不改变水热反应最终产物,但晶粒尺寸随表面活性剂量的加大逐渐减小。在较低碱度条件(c(KOH)=4mol/L)下,加入适量的表面活性剂PVA有利于在较温和条件下生成纯钙钛矿结构KTN纳米晶。     

螺旋慢波系统高频特性的计算机仿真

介绍了用德国CST(Computer Simulation Technology)公司提供的微波工作室MWS(Microwave Studio)4．2软件模拟计算螺旋线慢波系统的色散特性和耦合阻抗的理论方法。通过对矩形夹持杆支撑螺旋慢波结构的模拟计算,与测试结果相比色散特性的平均模拟误差为1．5%左右,耦合阻抗的平均误差为0．3％左右;相比于MAFIA仿真,计算精度更高,计算时间更短。     

BaTiO_3晶体光折变效应振荡器和机理研究

在薄征Ce:BaTiO3晶体和体块Rh:BaTiO3晶体实现了光折变效应振荡器,利用前向二波耦合和相向二波耦合建立了光折变效应准线笥F－P腔模型,并从实验结果上进行了验证和分析,同时分析了光振荡现象对BaTiO3晶体的受激光折变散射自泵浦相位共轭的影响。     

顺电相KTN晶体中相位栅的衍射效率分析

为了在应用中提高读出光的衍射效率,必须合理选择参量。采用将KOGELNIK的耦合波理论与Kukhtarev方程相结合,可以得出顺电相KTN晶体中透射型相位栅衍射效率的解析式。对影响光栅衍射效率的各因素进行计算分析,发现衍射效率对入射角、晶体厚度以及外加电场的变化敏感,而45°入射角附近出现较宽的高衍射区。另外,晶体的吸收对衍射效率的影响可以忽略。结果表明,该计算分析有助于在实践中调整参量以获得较高的读出光衍射效率。     

BaTiO_3晶体光折变效应振荡器和机理研究

在薄片 Ce:Ba Ti O3晶体和体块 Rh:Ba Ti O3晶体实现了光折变效应振荡器。利用前向二波耦合和相向二波耦合理论建立了光折变效应准线性 F- P腔模型 ,并从实验结果上进行了验证和分析 ,同时分析了光振荡现象对 Ba Ti O3晶体的受激光折变散射自泵浦相位共轭的影响     

双掺杂Zn,Fe：LiNbO3晶体的二波耦合效应的研究

在固液同成分ＬｉＮｂＯ３中，同时掺入６％ＺｎＯ（摩尔比）和０．０５％Ｆｅ２Ｏ３（摩尔比），用提拉法生长了双掺杂Ｚｎ，Ｆｅ，ＬｉＮｂＯ３晶体，这是一种性能优良的光折变晶体材料。文章用二波耦合技术研究了晶体的耦合增益和衍射效率，Ｚｎ，Ｆｅ：ＬｉＮｂＯ３的光致折射率变化值达１０＾－５，且响应速率达到秒量级，这是双掺Ｚｎ，Ｆｅ两种杂质共同作用的结果。     

波在暖电离层中的传播和耦合

本文研究了波在暖电离层中的传播。文中导出了用拆射率n表示的波的色散关系,并由此推导出分层暖电离层中q的方程。所有这些方程都被用于用射线方法研究波在暖电离层中的传播,模式联接和波的线性耦合。 本文还讨论了波方程的奇点、等离子体波与电磁波的耦合。在波耦合区中,波的场可以通过求解波方程在奇点附近的解而求得。文中比较了用射线方法和全波方程研究波耦合时电波传播的结果。 本文所得结果对研究用无线电波加热电离层实验中的吸收区域是有用的。     

用于场致发光灯稳定驱动的Boost电路

稳定性是开关电源设计的技术指标之一。电压拓扑中影响稳定性的因素主要由误差放大器引入,电流拓扑相对于电压拓扑虽有不少改进,但也给电路稳定性带来了新的影响因素,特别是次谐波振荡问题。为使输出电压稳定,满足EL灯的使用要求,文中提出了一种稳定的用于EL灯驱动的Boost电路,该设计用带使能控制的电流比较器代替误差放大器,提高了电路的稳定性。文中详细分析了电路的工作过程,给出了电路的仿真结果。该电路响应时间为60μs,基准电流源为4.3μA,负载调整率为6%,电路稳定输出范围70～100V,适用于19.4cm2～38.7cm2(3in2～6in2)的EL灯。该电路结构简单、稳定性好、响应快、功耗低、易于集成。     

Optimization Techniques for FPGA-Based Wave-Pipelined DSP Blocks

In this paper, techniques for efficient implementation of field-programmable gate-array (FPGA)-based wave-pipelined (WP) multipliers, accumulators, and filters are presented. A comparison of the performance of WP and pipelined systems has been made. Major contributions of this paper are development of an on-chip clock generation scheme which permits finer tuning of the frequency, a synthesis technique that reduces the area and latency by 25%, a placement utility that results in 10%–40% increase in speed and proposal of an interleaving scheme for filters that reduces the number of multipliers required by 50%. WP multipliers of size 2$times$6 and the filters using them are found to be 11% faster and require lower power than those using pipelined multipliers. Filters with higher order WP multipliers also operate with lower power at the cost of speed. The delay-register products of such filters are found to be about 60% lower than those using the pipelined multipliers. The paper also outlines applications of these techniques for the Spartan II FPGAs and a self-tuning scheme for optimizing the speed.     

LD端面泵浦Nd：YVO_4激光器及其高阶横模的工作特性

报道了ＬＤ端面泵浦Ｎｄ：ＹＶＯ_４激光器的实验结果，获得了２３．６％的光－光转换效率，相应的斜效率为２８．８％。特别对在泵浦光与腔模匹配欠佳时高阶横模的起振特性作了比较详细的实验研究和定性讨论。     

Laser isolation of shunted regions in industrial solar cells

This paper provides proof of concept for a technique that uses laser‐ablated grooves to locally isolate shunted regions in industrial silicon solar cells. The shunted regions are located using photoluminescence imaging and then isolated from the active cell area with a Nd:YAG laser. By applying this shunt isolation technique, we demonstrate that a strongly shunted 9·6% efficient industrial screen‐printed solar cell could be recovered to 13·3%. With further development this technique could be applied in an industrial environment to mitigate yield losses and improve average cell efficiencies. Copyright © 2007 John Wiley & Sons, Ltd.     

TD-LTE与TD-SCDMA系统共存子帧配比兼容分析研究

对于当前TD-LTE与TD-SCDMA系统邻频共存的情况,由于两者皆为TDD系统,所以TD-LTE必须与TD-SCDMA系统的子帧配比兼容以避免系统间干扰;给出了两者共存时兼容的子帧配比,研究了此子帧配比下TD-LTE的两种特殊时隙配比方案SSP5与SSP6,并从下行资源利用情况、单小区下行峰值吞吐量、基站可规避干扰距离等方面将两方案做了对比分析,指出SSP6能够更好地利用系统的下行资源,有利于提升系统容量。     

声光锁模器件的最佳电学匹配

第一,介绍了LC匹配网路的设计及调试方法,可使换能器所吸收的振荡器输出的功率达到95%以上.用0.5瓦的射频功率驱动铌酸锂-重火石玻璃声光锁模器,零级光(6328(?))的调制度达92%.第二,介绍一种在54.3～54.7兆赫范围内连续可调,稳定度为(1～2)×10~(-6)的振荡器电路及其调试方法.     

Optimization of Mobile IPv6-Based Handovers to Support VoIP Services in Wireless Heterogeneous Networks

The support of voice over Internet Protocol (VoIP) services in next-generation wireless systems requires the coupling of mobility with quality of service. The mobile node can experience disruptions or even intermittent disconnections of an ongoing real-time session due to handovers. The duration of such interruptions is called disruption time or handover delay and can heavily affect user satisfaction. Therefore, this delay needs to be minimized to provide good-quality VoIP services. In this paper, the focus is on the network layer mobility, specifically on mobile Internet Protocols (MIPs), since they are natural candidates for providing mobility at layer 3. Using analytical models, the authors evaluate MIPv4, MIPv6, fast MIPv6 (FMIPv6), and hierarchical MIPv6 (HMIPv6) and compare their performances in terms of handover delay for VoIP services. To optimize the handover delay, the authors propose to use the adaptive retransmission timer described in this paper. The results obtained using the adaptive timer technique show that for a 3% frame error rate and a 128-kb/s channel, the handoff delay is about 0.075 s (predictive) and 0.051 s (reactive) for FMIPv6. It is around 0.047 s [intra-mobile anchor point (MAP)] and 1.47 s (inter-MAP) for HMIPv6, around 1 s for MIPv6, and 0.26 s for MIPv4     

Low-Loss 4–6-GHz Tunable Filter With 3-Bit High-$Q$ Orthogonal Bias RF-MEMS Capacitance Network

This paper presents a low-loss 4-6-GHz 3-bit tunable filter on a quartz substrate using a high-Q 3-bit orthogonal bias RF microelectromechanical systems capacitance network. Detailed design equations for the capacitively loaded coupled lambda/2 resonators and with capacitive external coupling and source-load impedance loading are discussed. Measurements show an unloaded Q of 85-170, an insertion loss of 1.5-2.8 dB, and a 1-dB bandwidth of 4.35plusmn0.35% at 4-6 GHz. The measured third-order intermodulation intercept point and 1-dB power compression point at 5.91 GHz are > 40 and 27.5 dBm, respectively. The unloaded Q can be improved to 125-210 with the use of a thicker bottom electrode. To our knowledge, this is the highest Q tunable planar filter to date at this frequency range.     

移动IPv6实施的关键问题及在CDMA网络中的应用

IPv4的NAT缺陷、缺乏固定地址限制了CDMA网络中移动IP业务的发展,CDMA移动网络向IPv6承载过渡是必然趋势。本文探讨了移动IPv6在CDMA网络中的应用,着重分析了CDMA网络中应用移动IPv6所面临的服务质量、安全、认证、DNS自动发现、演进等问题,并对现有CDMA网络实体的改动加以阐述。     

具有梯形有源振子的印刷引向天线研究

设计了一种采用平衡微带线馈电的具有梯形有源振子的印刷引向天线。对梯形印刷有源振子的阻抗特性进行了仿真,在此基础上进行了改进,首先是有源振子加载反射器,然后是有源振子加载引向器和反射器。仿真了天线的阻抗特性和辐射特性,并分别制作了天线实物进行测试。仿真与实验结果表明,有源振子加载引向器和反射器后的工作频带为2.0~2.45GHz,相对带宽达20.2%,带内增益为6dB 左右,且具有较小的尺寸（60 mm×65 mm）,可用于移动通信领域。