基于大数据分析的频谱资源管控系统设计

针对电磁环境恶化,频谱资源匮乏、分配不均及其在空间、时间和频域上存在的高度相关性的问题,文中提出了一种基于大数据分析的频谱资源管控系统。该系统由频谱监测与存储、数据分析处理和管控中心3个功能模块组成。首先,采用分布式的数据采集架构采集频谱信息和GPS信息;然后,使用大数据分析技术预测下一次时刻频谱资源的使用情况,以合理的检测可用信道、提高频谱监测的效率,优化频谱监测的策略;最后,使用管控中心管理不同等级用户的频谱使用权限。仿真测试结果表明,该系统能有效地处理海量的频谱数据、提高频谱资源的利用率。     

区域气象与雷电活动对雷击风险评估的细化与改进

本文以武汉市安山液化天然气存储基地为案例,提出利用区域内气象与雷电活动环境数据,针对重点雷击风险评估对象进行参数的修正,细化了风险评估服务的项目,改进了传统风险评估的实效性与针对性,为重点区域的雷电风险评估服务提供了更为实际科学的依据,能够有效地减低因雷电导致的人员伤亡、财产损失等各项灾害。     

迫弹激光引信用脉冲半导体激光电源的设计与应用

设计了适应于迫弹激光近炸引信的小体积、低电压、窄脉宽、高功率的脉冲半导体激光电源.采用电容充放电的模式,选用高速大功率MOSFET管作为开关,设计了相应的高速开关控制电路.激光电源模块的重复频率高达50kHz,常规热电池供电电压条件下的输出脉冲激光峰值功率为9W,光脉冲上升沿为4.2 ns,光脉宽为10 ns,为有效提...     

A second-order double-sampled delta-sigma modulator usingindividual-level averaging

A second-order double-sampled delta-sigma modulator is described. It uses all individual-level-averaging switching scheme to convert capacitor mismatch into high-pass noise. With a sampling rate of 25 MHz and an oversampling ratio of 128, the maximum measured signal-to-noise-and-distortion ratio is 82.2 dB, and the total harmonic distortion is -91.0 dB when the input is 2.5 dB below full scale. The modulator is fully differential, occupies 3.75 mm² in a 1.2-μm CMOS process, and dissipates 25.9 mW (10.2 mW analog and 15.7 mW digital)     

Comparative study of micro-BGA reliability under bending stress

The micro-ball grid array (/spl mu/BGA), a form of chip scale package (CSP), was developed as one of the most advanced surface mount devices, which may be assembled by ordinary surface mount technology. In the latest /spl mu/BGA type, eutectic tin-lead solder ball bumps are used instead of plated nickel and gold (Ni/Au) bumps. Assembly and reliability of the /spl mu/BGA's PCB, which is soldered by conventional surface mount technology, has been studied in this paper. The bending cycle test (1000 /spl mu//spl epsi/ to -1000 /spl mu//spl epsi/), is used to investigate the fatigue failure of solder joints of /spl mu/BGA, PBGA, and CBGA packages reflowed with different heating factors (Q/sub /spl eta//), defined as the integral of the measured temperature over the dwell time above liquidus (183/spl deg/C). The fatigue lifetime of the /spl mu/BGA assemblies firstly increases and then decreases with increasing heating factor. The greatest lifetime happens while Q/sub /spl eta// is near 500 second-degree. The optimal Q/sub n/ range is between 300 and 750 s/spl deg/C. In this range, the lifetime of the /spl mu/BGA assembly is greater than 4500 cycles if the assemblies are reflowed in nitrogen ambient. SEM micrographs reveal that both /spl mu/ & P-BGA assemblies fail in the solder joint at all heating factors. All fractures are near and parallel to the PCB pad. In the /spl mu/BGA assemblies cracks always initiate at the point of the acute angle where the solder joint joins the PCB pad, and then propagate in the section between the Ni/sub 3/Sn/sub 4/ intermetallic compound (IMC) layer and the bulk solder. In the CBGA assembly reliability test, the failures are in the form of delamination, at the interface between the ceramic base and metallization pad.     

Study of the self-alignment of no-flow underfill for micro-BGA assembly

As a concept to achieve high throughput low cost flip-chip assembly, a process development activity is underway, implementing next generation flip-chip processing based on large area underfill printing/dispensing, IC placement, and simultaneous solder interconnect reflow and underfill cure. The self-alignment of micro-BGA (ball grid array, BGA) package using flux and two types of no-flow underfill is discussed in this paper. A “rapid ramp” temperature profile is optimized for reflow of micro-BGA using no-flow underfill for self-aligning and soldering. The effect of bonding force on the self-alignment is also described. A SOFTEX real time X-ray inspection system was used to inspect samples to ensure the correct misalignment before reflow, and determine the residual displacement of solder joints after reflow. Cross-sections of the micro-BGA samples are taken using scanning electronic microscope. Our experimental results show that the self-alignment of micro-BGA using flux is very good even though the initial misalignment was greater than 50% from the pad center. When using no-flow underfill, the self-alignment is inferior to that of using flux. However, for a misalignment of no larger than 25% from the pad center, the package is also able to self-align with S1 no-flow underfill. However, when the misalignment is 37.5–50% from the pad center, there are 10–14% residual displacement after reflow. The reason is the underfill resistant force inhibiting the self-alignment of the package due to rapid increment of underfill viscosity during reflow. The self-alignment of micro-BGA package using no-flow underfill allows only <25% misalignment prior to the soldering. During assembling, although the bonding force does not influence on the self-alignment of no-flow underfill, a threshold bonding force is necessary to make all solder balls contact with PCB pads, for good soldering. The no-flow underfill is necessary to modify the fluxing/curing chemistry for overcoming the effect of tin metal salt produced during soldering on underfill curing, and for maintaining the low viscosity during soldering to help self-alignment.     

基于下视图像的打击效果评估系统研究

研究了打击效果评估的基本概念及该技术在国外的发展与应用情况,提出了基于下视图像的毁伤特征提取方法与典型目标毁伤评估准则。从物理级、功能级和系统级三个层次对打击效果评估进行了描述,提出了基于变化检测的物理级毁伤效果评估方法、基于自动目标识别的物理级毁伤评估方法和基于专家知识库的功能级毁伤评估方法,开发实现了基于下视图像的典型目标打击效果评估系统。仿真结果表明,所提出打击效果评估方法是有效的。     

基于S3F9488与CP2512的电子产品应用设计

运用电容触摸检测芯片CP2512与单片机S3F9488进行电路设计.触摸检测芯片CP2512通过检测电容的变化量来感知外界数据的变化,通过I2C协议把CP2512采集的数据送到S3F9488,S3F9488根据采集到的数据进行相应的功率控制.本文给出了CP2512与S3F9488的硬件设计图.该方案的设计可以使家电产品更加耐用、美观;能有效地提高产品的抗干扰能力,提升产品的品质.该电路的设计为家电产品提够了一种低成本解决方案,最终在电磁炉中得到了实现.     

Stretchable Anti-Fogging Tapes for Diverse Transparent Materials

Surface wetting prevents surface fogging on transparent materials by facilitating filmwise condensation with specific chemistry, but suffers from material and geometry selectivity. Extreme environments associated with high humidity and mechanical loading further limit their anti-fogging persistence. Here, a stretchable anti-fogging tape (SAT) that can be applied to diverse transparent materials with varied curvatures for persistent fogging prevention is reported. The SAT consists of three synergistically combined transparent layers: i) a stretchable and tough layer with large elastic recovery, ii) an endurant anti-fogging layer insensitive to ambient humidity, and iii) a robustly and reversibly adhesive layer. The SAT maintains high total transmittance (>90%) and low diffuse transmittance (<5%) in high-humidity environments, under various modes of mechanical deformations, and over a prolonged lifetime (193 days tested so far). Two applications are demonstrated, including the SAT-adhered eyeglasses and goggles for clear fog-free vision, and the SAT-adhered condensation cover for efficient solar-powered freshwater production.     

基于IMU数据与双星定位系统组合的机载SAR运动补偿

该文主要介绍了机载SAR平台运动误差中惯性测量单元(IMU)系统误差的补偿方法。由于双星定位系统误差不随时间递增,该文利用双星定位系统(GEOSTAR)与IMU进行组合,消除随时间递增的IMU系统误差,提高IMU定位精度,从而减轻SAR成像处理器运动补偿的负担。