DS-CDMA中扩频信号的循环平稳特性分析

介绍了循环平稳信号的基本概念，对DS—CDMA系统中直接序列扩频信号的循环平稳特性进行了详细的理论分析，通过计算机仿真实验验证了分析结果；仿真同时说明了利用信号的循环平稳特性可以进行有效地信号提取和干扰抑制，具有极大的应用前景。     

一般构形双基SAR多普勒特性分析

基于一般构形双基合成孔径雷达(SAR)的空间几何关系,分析了一般构形双基SAR的特点,给出了一般构形双基SAR回波的多普勒参数表达式。由于一般空间构形双基SAR发、收平台的运动矢量是不相等的,造成双基系统对场景中每一个点目标的成像几何结构是不同的,因此成像处理中除了需要校正距离空变量外,还需要补偿方位空变量。星机构形的实例分析验证了这种方位空变性。文中对一般构形双基SAR空变多普勒参数分析的结果为系统参数选择和二维空变补偿成像处理提供了相关的基础。     

长周期光纤光栅对结构参数的敏感特性

基于模式耦合理论,对影响长周期光纤光栅（LPFG）光谱特性的各种物理结构参数进行了研究,得到LPFG光谱特性响应的一系列定量或定性的规律。利用紫外线,通过振幅掩模法曝光H载掺Ge光纤制作了两根LPFG,写入的光栅长度分别为3.0 cm和4.5 cm,测得温度灵敏度分别为0.044 6 nm/℃和0.059 4 nm/℃...     

Development of the high-pressure electro-dynamic gradient crystal-growth technology for semi-insulating CdZnTe growth for radiation detector applications

The high-pressure electro-dynamic gradient (HP-EDG) crystal-growth technology has been recently developed and introduced at eV PRODUCTS to grow large-volume, semi-insulating (SI) CdZnTe single crystals for room-temperature x-ray and gamma-ray detector applications. The new HP growth technology significantly improves the downstream CdZnTe device-fabrication yield compared to earlier versions of the HP crystal-growth technology because of the improved structural and charge-transport properties of the CdZnTe ingots. The new state-of-the-art, HP-EDG crystal-growth systems offer exceptional flexibility and thermal and mechanical stability and allow the growth of high-purity CdZnTe ingots. The flexibility of the multi-zone heater system allows the dynamic control of heat flow to optimize the growth-interface shape during crystallization. This flexibility combined with an advanced control system, improved system diagnostics, and realistic heat-transport modeling provides an excellent platform for continuing process development. Initial results on large-diameter (140 mm), SI Cd_1−xZn_xTe (x=0.1) ingots grown in low temperature gradients with the HP-EDG technique show reduced defect density and complete elimination of ingot cracking. The increased single-crystal yield combined with the improved charge transport allows the fabrication of large-volume, high-sensitivity, high energy-resolution detector devices at increased yield. The CdZnTe ingots grown to date produced large-volume crystals (≥1cm³) with electron mobility-lifetime product (μτ_e) in the (3–7) × 10⁻³ cm²/V range. The lower-than-desired charge-transport uniformity of the HP-EDG CdZnTe ingots is associated with the high density of Te inclusions formed in the ingots during crystallization. The latest process-development efforts show a reduction in the Te-inclusion density, an increase of the charge-transport uniformity, and improved energy resolution of the large-volume detectors fabricated from these crystals.     

A Built-in-Self-Test Scheme for Segmented and Binary Weighted DACs

This paper describes a new Built-In-Self-Test(BIST) scheme for estimation of static non-linearity errors in segmented and binary weighted digital to analog converters (DACs). The BIST scheme comprises of a hierarchy of tests including tests for non-monotonicity, checks to detect if the DNL/INL errors exceed ±0.5 LSB and actual estimation of the DNL/INL. The BIST scheme has been experimentally verified on 10-bit segmented current steering DAC. The DAC, along with the additional circuits required for testing, was designed and fabricated using a 0.35 m process. Both simulation and experimental results are included in this paper. Errors estimated using the BIST scheme match well with measurements done on the fabricated device.     

怎样用SDA5000型数字电视分析仪测试双向放大器的反向插入损耗

介绍了SDA5000数字电视分析仪和漳州广电双向网络的改造方案,并简单地阐述了双向放大器的概念。介绍了SDA5000数字电视分析仪3个接口的作用,结合实际案例说明怎样用SDA5000数字电视分析仪测试双向放大器的插入损耗。     

基于51单片机的低频信号发生器的设计与仿真

基于改善传统正弦信号源价格昂贵,低频输出时性能不好且不便于自动调节的目的。采用AT89C51单片机,结合编程和软件查表的方法读取经离散化处理的波形信号。通过D/A把信号转化并还原所需的波形信号。进行了proteus计算机软件仿真,得到了与理论相应的锯齿波、方波、正弦波信号并实现了各种波形的自由切换以及频率、相位的改变和多相波的产生。     

数字电位器在加速度存储测试调理电路中的应用

针对跌落试验中双通道加速度存储测试仪,需要程控通道量程的需求,设计了基于贴片式非易失性数字电位器MAX5497,并结合C8051F340微处理器控制的增益可调节前置放大电路。文中较为详细地介绍了MAX5497芯片的主要特点、管脚功能和工作时序,给出了增益放大电路图,并利用微处理器对其反馈电阻进行程序设置。编写的相关电阻设置程序,对类似的增益放大电路设计有一定参考价值。     

一种用于检测薄膜均匀性的光谱方法

介绍了一种新的简单有效的薄膜均匀性信息获取方法,该方法基于我们先前提出的纳米薄膜厚度精确测量方法,它通过检测镀制在含有过渡层的衬底上不同位置的薄膜的光谱,并由其干涉峰间的差异获取薄膜的均匀性信息.与传统方法相比,该方法无需直接测量薄膜的厚度,减少了测量膜厚带来的误差和影响,因而可以快速得出薄膜均匀性结论.该方法操作方便...     

卫星认知无线通信中频谱感知算法比较

以实现卫星认知无线通信中频谱空穴探测为目的,列举并比较了目前用于频谱感知的六种算法。根据各个算法的自身特点指出其应用场合,分别分析了它们的优缺点,通过计算机仿真给出了能量检测、匹配滤波和压缩感知的检测性能,并指出压缩感知对硬件复杂度的要求最小,适合卫星认知无线通信。