在无铅环境中的热风整平

当电子工业走向无铅焊接的时候,热风焊料整平仍然是继续可焊性保护的优选方法。     

基于LotusNotes的文档ID应用剖析

介绍了文档数据库Lotus Domino／Notes的特点．对其文档处理的核心，即Notes文档的ID构成机制作了系统剖析．并在此基础上分析了如何在文档复制中运用ID的不同组件以及如何运用API程序访问文档ID等。     

本地传输网优化思路

首先介绍了本地传输网所承载的业务,然后介绍了本地传输网的现状,接着概括总结了本地传输网目前存在的问题,最后提出了调整和优化思路。     

DC/DC电源中的电磁干扰及其对策

概述了电磁干扰(EMI)和电磁兼容(EMC)的基本知识，对DC／DC电源中的电磁干扰进行了综合分析，并给出了各自的解决方案。     

串行及并行A/D转换器在高速数据采集中的采样差别性分析

串行和并行接口模式是A/D转换器诸多分类中的一种,但却是应用中器件选择的一个重要指标.在同样的转换分辨率及转换速度的前提下,不同的接口方式不但影响了电路结构,更重要的是将在高速数据采集的过程中对采样周期产生较大影响.本文通过12位串行ADC ADS7822和并行ADC ADS774与AT89C51的接口电路,给出二者采样时间的差异性.     

基于FPGA的ASI信号接收与发送的实现

提出了一种用FPGA芯片代替Cypress公司的CY78933和CY78923芯片来实现ASI信号接收与发送的方案，详细阐述了DVB—ASI接口的硬件组成与FPGA实现，该接口符合DVB—ASI的接口规范，可实现270Mbps的信号传输，已经得到实际运用。     

如何构建面向3G时代的业务支撑系统

业务支撑系统作为3G运营的重要组成，它的建设情况直接决定了电信运营商今后3G运营的成败，文章简单介绍了如何构建面向3G时代的业务支撑系统，对建设今后的业务支撑系统提供建议。     

基于FPGA的CAVLC编解码器设计与实现

H．264标准在基本档次和扩展档次中采用CAVLC熵编码，完成对变换系数残差块的编码。提出一种基于FPGA的H．264标准的CAVLC编解码器，程序代码用verilog硬件描述语言编写，并在QuartusⅡ中进行了仿真验证，可以实现对每个残差块数据的编解码并将其按照宏块光栅扫描的顺序输出到存储器，因此适合于嵌入在最终的码流中。仿真结果表明此CAVLC编解码器达到H．264标准中基本档次和扩展档次level3．0的性能要求。     

1/f noise in large-area Hg<Subscript>1−x</Subscript>Cd<Subscript>x</Subscript>Te photodiodes

The 1/f noise in photovoltaic (PV) molecular-beam epitaxy (MBE)-grown Hg_1−xCd_xTe double-layer planar heterostructure (DLPH) large-area detectors is a critical noise component with the potential to limit sensitivity of the cross-track infrared sounder (CrIS) instrument. Therefore, an understanding of the origins and mechanisms of noise currents in these PV detectors is of great importance. Excess low-frequency noise has been measured on a number of 1000-μm-diameter active-area detectors of varying “quality” (i.e., having a wide range of I-V characteristics at 78 K). The 1/f noise was measured as a function of cut-off wavelength under illuminated conditions. For short-wave infrared (SWIR) detectors at 98 K, minimal 1/f noise was measured when the total current was dominated by diffusion with white noise spectral density in the mid-10⁻¹⁵A/Hz^1/2 range. For SWIR detectors dominated by other than diffusion current, the ratio, α, of the noise current in unit bandwidth i_n(f = 1 Hz, V_d = −60 mV, and Δf = 1 Hz) to dark current I_d(V_d = −60 mV) was α_SW-d = i_n/I_d ∼ 1 × 10⁻³. The SWIR detectors measured at 0 mV under illuminated conditions had median α_SW-P = i_n/I_ph ∼ 7 × 10⁻⁶. For mid-wave infrared (MWIR) detectors, α_MW-d = i_n/I_d ∼ 2 × 10⁻⁴, due to tunneling current contributions to the 1/f noise. Measurements on forty-nine 1000-μm-diameter MWIR detectors under illuminated conditions at 98 K and −60 mV bias resulted in α_MW-P = i_n/I_ph = 4.16 ± 1.69 × 10⁻⁶. A significant point to note is that the photo-induced noise spectra are nearly identical at 0 mV and 100 mV reverse bias, with a noise-current-to-photocurrent ratio, α_MW-P, in the mid 10⁻⁶ range. For long-wave infrared (LWIR) detectors measured at 78 K, the ratio, α_LW-d = i_n/I_d ∼ 6 × 10⁻⁶, for the best performers. The majority of the LWIR detectors exhibited α_LW-d on the order of 2 × 10⁻⁵. The photo-induced 1/f noise had α_LW-P = i_n/I_ph ∼ 5 × 10⁻⁶. The value of the noise-current-to-dark-current ratio, α appears to increase with increasing bandgap. It is not clear if this is due to different current mechanisms impacting 1/f noise performance. Measurements on detectors of different bandgaps are needed at temperatures where diffusion current is the dominant current. Excess low-frequency noise measurements made as a function of detector reverse bias indicate 1/f noise may result primarily from the dominant current mechanism at each particular bias. The 1/f noise was not a direct function of the applied bias.     

从PZT体系看无铅压电陶瓷的可能应用

总结了主要以(Bi0.5Na0.5)TiO3和NaNbO3为基的无铅压电陶瓷的性能，以Pb(Ti，Zr)TiO3基二元系、三元系压电陶瓷的性能与应用为参考，分析了无铅压电陶瓷可能的器件应用。此外，还对拓宽无铅压电陶瓷应用需要改进的性能提出了建议。