变电站综合自动化系统的安全措施

分析变电站综合自动化系统中测控装置和监控装置分别在出现故障情况下所需要采取的必要的安全措施,以保证综合自动化系统的正常运行。     

A low‐profile antenna with circularly polarized reconfigurable and omnidirectional radiation patterns

A low profile circularly polarized (CP) antenna with reconfigurable polarization is designed and presented, which can radiate omnidirectional patterns that can be switched between left‐hand circularly polarized (LHCP) and right‐hand circularly polarized (RHCP). A pair of arc‐shaped complementary dipoles is acted as reconfigurable elements by bridging four pin diodes at the dipole arced arms. A meander phase shift line is employed to connected the arc dipole arms and plate cavity to adjust the phase relationship of two sources. The proposed antenna exhibits the omnidirectional radiation pattern by combining six identical elements placed in a circular array configuration. 24 p‐i‐n diodes are exploited to six elements, by manipulating the dc bias voltage across the diodes, the polarization state of the antenna can be switched. The patterns of the antenna are similar to that of a dipole, but its size is only about Φ0.87 × 0.029λ₀ at 5.8 GHz. The overlapped bandwidth of measured 3‐dB axial ratio (AR) and 10‐dB return loss is 5.724‐5.87 and 5.738‐5.91 GHz for two polarization states, which are right on the target of ISM band. It can be well adapted to medical diagnosis systems.     

Design of a broadband dielectric resonator antenna and its application in low sensitivity frequency beam‐scanning array with wide scanning angle and suppressed sidelobes

In this paper, a broadband dielectric resonator antenna (DRA) with a simple H‐slot feeding structure is proposed. The broad bandwidth (~45%) and uni‐directional radiation enable this DRA suitable to work as a radiation element in the construction of a beam‐scanning array with not only low frequency sensitivity which is important for accurate angle estimation of in‐coming targets, but also a wide scanning range. Moreover, stable coupling coefficients are established around all the above three resonances with respect to its corresponding feeding line, ensuring a low sidelobe level (SLL) across the whole operating frequency range. In order to realize such a DRA, a latticed rectangular structure is utilized to generate the lower two resonances, while the upper resonance is generated by its H‐shaped feeding slot. The shape of the latticed dielectric resonator is also modified according to a 3‐D printed fixing structure for an accurate installation. A 20‐element beam‐scanning prototype is demonstrated and manufactured. The range of scanning angle is from ?36° to +13° within the bandwidth of 10 to 16 GHz, corresponding to a frequency sensitivity of only 122.5 MHz/^o. The achieved SLL are smaller than 19 dB for all scanning beams. The above performance indicates that, this array is very suitable for near‐range radar systems requiring an accurate angle estimation.     

一种高压摆率低电压CMOS AB类放大器的设计

为了增加单位增益频率与压摆率,并能够工作在低电源电压下,同时降低偏置电流,提出了一种改进的基于0.18μm CMOS工艺的AB类放大器,其采用多级放大器结构,第一级为具有电流镜负载的NMOS差分对,第二反相级由共源放大器实现,第三极为AB类放大器,其能够在±500 m V电源下工作.电路仿真结果显示该放大器相位裕度为87°;总补偿电容为5 p F,与传统放大器相比减少了50%;单位增益频率为21.17 MHz,比传统放大器增大约10倍;压摆率为7.5和8.57 V/μs,与传统电路相比,分别增加了2.8倍和2.6倍.此外,与其他文献相比,该放大器具有较大的单位增益带宽和压摆率以及较小的功耗.     

基于GNU Radio和USRP的切换天线方向调制物理层安全系统

提出了一种切换天线方向调制物理层安全传输系统,利用天线的切换选择扰乱非期望方向的窃听者进行信息窃密,实现了视距空间的保密通信。基于GNU Radio和USRP软件无线电平台,结合高速射频开关、FPGA控制板、网络收发模块以及阵列天线搭建了实验验证系统。通过测试窃听者位于不同方位角的视频传输质量和信号星座样式验证了该方法的可行性,结果表明与传统阵列天线相比,切换天线方向调制技术能提供更安全的视距通信。     

应用LCA分析中国典型钢铁企业的环境负荷

为得到钢材的环境负荷,基于生命周期评价方法对中国典型钢铁企业中不同流程中的各工序,系统、定量地分析评价环境负荷.采用GaBi 4.3软件提供的CML2001环境影响分类方法,将各工序的环境影响进行分类,并根据特征化因子,分析生产1 t钢材产生的环境影响.分析结果表明:长流程生产过程主要的环境影响是焦化、烧结、高炉炼铁和废钢回收环节产生的水生生态毒性、人体毒性、化石能源耗竭和矿产资源耗竭等.其中,长流程的炼钢过程对气候变化、人体毒性、水生生态毒性和固体废弃物的影响较大,分别约占该类型总环境影响值的30%,95%,50%和90%;短流程生产过程主要的环境影响为铁水和电炉炼钢过程产生的气候变化、酸化和光化学臭氧形成等.该研究结果可为钢铁企业调整两种不同流程提供一定的理论依据,有助于准确发现生产过程中各环节节能降耗、降低环境负荷的潜力所在,从而有利于钢铁企业对生产流程进行改进或优化.     

高选择性陷波超宽带天线设计

The resonant properties of the interdigital capacitance loading loop resonator (IDCLLR) and its dual counterpart complimentary interdigital capacitance loading loop resonator (CIDCLLR) are studied. Due to the high capacitance/inductance of the IDCLLR/CIDCLLR, the resonators can generate lower resonant frequencies and narrower resonant bandwidths than many other structures. A compact ultra-wideband (UWB) antenna with quadruple sharp band-notching characteristics is presented by utilizing IDCLLRs and CIDCLLRs. Measured results show that the proposed antenna has a wide bandwidth from 3 to 11GHz(VSWR<2), with four sharp notched bands centered on 3.5, 5.2, 5.8 and 7.5GHz, respectively, avoiding the elimination of many useful frequencies. Moreover, the presence of IDCLLRs and CIDCLLRs scarcely affects the performance of the UWB antenna at its operating frequencies.     

偏馈式构架反射器展开冲击特性分析

As the off-fed truss reflector is connected to the platform by a single edge and deployed rapidly through being driven by the spring, the impact influence acts obviously on both the reflector and the platform. Due to limitations of the ground test, the in-orbit deployment impact characteristics of truss reflector are difficult to obtain. Then, by taking a certain reflector as the research object, a dynamic model is established with multibody dynamic software. Based on the modified model with ground deployable tests, in-orbit deployment impact characteristics are obtained by simulation analysis. Therefore, the method for multibody dynamic modeling is suitable for truss reflector dynamic research, and the result is useful for the deployable reliability optimization.     

相控阵天线接收组件自动测试系统设计

深入分析了相控阵天线接收组件自动测试系统的工程需求,提出一种适用于大数据量测试与处理的自动测试系统实现方法。本方法在采用以太网搭建硬件测试平台的基础上,为了实现自动化和高速化测试,提出了全套系统基于MATLAB开发的软件实现方法。实验结果表明,该自动测试系统与人工测试及人工处理数据相比,在多种应用场景下均大大提高了接收组件的批量测试效率和数据处理速度,并已成功用于某型相控阵天线接收组件的批量测试及数据处理中。     

基于UTD的机体散射体对机载天线耦合布局影响研究

通过研究不同形状机体散射体对机载天线间互耦特性的影响,可对飞机机载天线布局设计提供理论指导。利用一致性几何绕射理论(the uniform geometrical theory of diffraction,UTD)场的局部性原理计算典型结构问题快速、简便的优点,对半圆柱、三角柱、长方体等典型的机体散射体两侧天线耦合度进行了计算和分析验证,得到了不同形状机体散射体两侧天线的最大和最小耦合度值的粗略位置,同时也证明了该方法的正确性。最后,将上述得到的不同形状机体散射体两侧天线的布局结果应用于实际飞机的简化模型上,并通过Feko仿真了飞机机翼上两对点之间单极子天线的耦合度值,与UTD计算结果进行对比,误差较小,证实了该方法的正确性。该方法对于飞机天线布局预设计相对于普通方法具有计算简便、快速的特点,具有一定的实用价值。