优化高分辨率DAC的DC测量

在讨论一种具有22bit线性度和存在1．4V最低有效位噪声的24bn数模转换器（DAC）的时候，一位同事问到，“测试时应该如何测量微伏（V）级的电压？”测量高分辨率直流（DC）电压是很复杂的。在测试过程中，时间就是金钱．所以这为快速、精确地完成测量提出了一项持久的挑战。     

High resolution measurement of microwave refraction on short tropospheric paths

A method of measuring angle of arrival, or angle of fire, of a microwave signal transmitted over a short line-of-sight path is described. The method used is similar to that employed in conical scan, or simultaneous lobing, radars. Accuracy in angular measurement is achieved by utilizing the portion of the antenna pattern in which the gain function varies rapidly with angle. Using 4-ft aperture antennas operating at 35 GHz on a6frac{1}{2}-mi path, angle of fire is detected linearly with an accuracy ofpm 0.010deg, and the resolution may be as good aspm 0.002deg. The effects of random atmospheric turbulence on the results is investigated. Many examples of layered structure have been observed, but the most dramatic records come when the atmosphere is unstable and large changes in refraction occur, e.g., at the onset of land and sea breezes.     

监测接收机高分辨率快速扫描设计与实现

本方案针对无线频谱监测接收机在常规监测中由于扫描速度慢,分辨率低,从而造成信号截获概率低的问题,在总结和分析不同频谱扫描方式特点的基础上,基于软件多线程协调工作的思想,在相互衔接的调谐步进点上设计了一种基于多DSP并行处理的FFT步进扫描方案,发挥其在高分辨率频谱处理上的优势,便于让用户在常规监测时尽可能地发现突发的瞬...     

Quantitative measurement with high time resolution of internal waveforms on MOS RAMs using a modified scanning electron microscope

The growing packing density of integrated circuits calls, to an increasing extent, for the testing of the functioning of the individual circuits of ICs. If a mechanical prober is used for this purpose, the resulting capacitive loading of the circuit is liable to alter its performance. It is shown in the present work that the electron beam represents an ideal nonloading and nondestructive probe which can be finely focused and positioned on measuring points within the circuit under test. A modified scanning electron microscope allows the recording of waveforms within a circuit with a voltage resolution of the order of 10-100 mV and a time resolution of less than 1 ns. The efficiency of the technique was demonstrated by measuring the internally derived clock pulses and the voltage distributions of a digit-line of a 4096-bit MOS RAM and comparing the results with computer simulations.     

Thermo-acoustic effects on images for high resolution scanning acoustic microscopy

A novel scanning acoustic microscopy (SAM) technique employing thermal effects to improve the contrast of acoustic images has been demonstrated. Experiments were performed on a buried channel in a thick perspex block; it was found that short periods of sample heating can lead to a stronger image contrast.<>     

激光无接触高电压测试

本文介绍用氦-氖激光器作为光源,电光晶体 LiNbO_3作普克尔盒,运用横向调制在150千伏的50赫电压下的实验,最大相对误差 n_(max)=7.7%,平均相对误差≤2.0%。     

非接触式扫描反射镜定位精度检测方法

扫描反射镜的定位精度直接影响超光谱成像仪的工作性能,为了对扫描反射镜定位精度进行检测而不影响其运动性能,提出了一种基于双经纬仪的非接触式检测方法。利用光学向量反射和坐标变换原理对该方法进行了理论分析,给出了精确的扫描反射镜定位误差计算公式。为了减少实际检测时调整工作量,基于理论计算和工程简化的方法给出了允许的调平误差。对待检扫描反射镜进行了定位精度检测实验,表明该检测方法具有测角范围大、调整过程简单、检测精度高等优点。     

激光测高仪中飞行时间的高精度测量方法的研究

激光测高仪是测量激光脉冲的飞行时间来获得测高仪与探测目标之间的距离,因此激光飞行时间测量的准确性是衡量其系统能力的根本指标.文中阐述了时间间隔高精度测量技术及其最新进展.介绍了传统的测量时间间隔的方法的不足,引入了插入法.并采用粗测和精测相结合的方法来满足大范围、高精度的测量需求.文中详细介绍了模拟插入法、Vernier法、延时线法以及时间数字转换法在FPGA新技术中的应用.     

平板介质的微波分裂腔法介电常数测试技术

为实现微波频段平板类介质材料的介电常数的无损测试,研究了分裂式圆柱形谐振腔测试方法。介绍了分裂式圆柱形谐振腔的电磁场分析理论,采用模式匹配技术实现了介质加载条件下腔内电磁场分布的精确求解,得到了腔体谐振频率与材料介电常数之间的准确关系。在理论分析的基础上,制作了空腔谐振频率为10 GHz的分裂式谐振腔,并与前期研制的闭式谐振腔进行对比测试,介电常数实部测量结果相对误差小于1%。与国外同类产品进行对比测试,介电常数实部结果基本一致,损耗角正切测量结果更接近于文献参考值。因此,微波分裂腔法能够实现平板介质板材的无损测量,具有准确度高,使用方便等突出优势,可在微波频段内实现介电常数为1～20,损耗角正切为1×10^-3～1×10^-5,板材厚度为0.1～2.0 mm的各类平板介质材料介电常数的准确测试。     

利用游标效应提高微波光子学扫描式频率测量效率

受激布里渊散射效应被广泛用于微波光子学频率测量中,然而该效应的测频系统存在扫描时间长、响应速度慢的问题,为了提高该系统的扫描效率,提出了基于频率梳泵浦和游标效应的改进方案。阐述了此方案的测频原理和改进机制,并进行了理论分析和仿真验证。改进后的系统在频率测量精度100 MHz、系统带宽50 GHz时,扫描次数降低为原来的7%,在相同精度和扫描次数下,带宽更大,表明新方案的系统性能得到了大幅提升。     

Voltage measurement at high and microwave frequencies in coaxial systems

The progress and up-to-date state-of-the-art in measuring voltages at frequencies to 10 GHz and higher is briefly described. The trend towards higher frequencies in voltmeter design is indicated. Advantages of voltage measurements and standards over computation of voltages from power and impedance measurements are briefly discussed. Some pending development problems are indicated and major steps are proposed to improve the application of voltmeters at frequencies above 30 MHz.     

Novel method for high resolution measurement of laser output spectrum

The spectral spread of the best stabilised semiconductor lasers has been reduced to several megahertz. Conventional spectroscopy techniques cannot offer a spectral resolution fine enough for measuring such a sharp spectrum. The letter proposes a novel method by which 50 kHz resolution can be obtained. The principle, experimental set-up and results are described.     

高光谱分辨率激光雷达测量低层大气温度

基于碘分子滤波器对大气气溶胶散射的强吸收特性,滤除低层大气中气溶胶散射的影响,从而利用分子瑞利后向散射信号强度反演低层大气温度.激光雷达低层大气温度测量结果与探空数据进行了对比,显示出较好的一致性,温度偏差在9 km内不大于3 K.讨论了激光雷达测得的大气温度与探空数据对比结果之间存在的系统偏差和由于参考高度温度初始值引起的激光雷达温度反演结果的变化.     

高分辨率遥感图像融合技术的研究

图像融合已成为图像理解和计算机视觉领域中的一项重要而有用的新技术,多源遥感图像数据融合也成为遥感领域的研究热点,其目的是将来自多信息源的图像数据加以智能化合成,产生比单一传感器数据更精确、更可靠的描述和判决,使融合图像更符合人和机器的视觉特性,更有利于诸如目标检测与识别等进一步的图像理解与分析。     

三维激光扫描测体积技术及其应用进展

三维激光扫描技术因具有准确性强、检测效率高、无损等优势而被应用于各行各业的物体体积测量。本文概括了利用三维激光扫描技术获取物体轮廓表面信息的几种光学原理;综述了三维激光扫描测体积系统中点云数据获取、点云数据预处理、三维重建与体积计算的研究进展;对三维激光扫描测体积技术在各类行业中的应用现状进行总结分析;最终展望了三维激光扫描技术在不规则体体积测量上面临的挑战和未来的发展趋势。     

高功率微波脉冲的相位测量方法初探

本文概述了常用的高频信号相位测量的方法,分析了鉴相器和数字示波器直接测量两种方法的不确定度来源, 并设计实验系统对示波器直接测量的结果进行了不确定度分析,最后利用数字示波器对S 波段相对论速调管放大器的相 位进行了实验验证的测量,证实了该方法的可行性。     

用于高功率微波测量的圆极化微带阵列天线

在进行高功率微波(HPM)辐射场测量时,测量天线的极化匹配对测量精度影响较大。为提高测量精度,介绍一种微带圆极化阵列天线,采用功分器作为馈电网络,获得了小于1 d B的轴比,与非阵列圆极化微带天线相比,使轴比降低约1 d B。因此,当采用该圆极化阵列天线测量线极化微波的远场辐射时,使极化失配对测量结果的影响由±13%降至±3.6%左右。     

光纤F-P腔干涉纳米级位移高分辨率测量

激光抗干扰性好、复用能力强,光纤F P腔干涉仪结构简单、灵敏度高,适于纳米级位移测量。为了进一步提高分辨率,扩展测量范围,本文对光纤F P腔干涉信号的相位和功率进行分析。首先给出了二倍次方功率和分辨率的关系,找出了提高分辨率的途径。然后给出了二倍次方功率和干涉条纹变化的关系,确定了测量条件。最后根据光纤波在F P腔内干涉形成的滞后相位,通过多次希尔伯特变换,实现了待测物体位移重构。数值模拟和实验证明了该方法能够实现高分辨率纳米级位移测量,误差小。     

High resolution spherical microwave holography

A practical technique is developed to determine the electric and/or magnetic field on objects and sources inside a spherical measurement surface. The technique, known as spherical microwave holography (SMH), provides a nondestructive, nonintrusive method of point-by-point evaluation of antennas and radomes over their spatial extent. The resolution capability of SMH is developed and demonstrated by measurements. Resolution in SMH is only limited by the measurement system's capabilities. Dielectric and metallic obstacles on the surface of a radome are located and identified. Resolution as small as 0.33λ₀ is demonstrated