一种新的阻抗计型晶体测试仪

本文介绍了一种国内新型的阻抗计型晶体电参数测试仪，该仪器可在１￣６０ＭＨｚ频率范围内测量晶体的１０项电参数，其抗水平和性能指标达到国外同类产品的先进水平。     

DDS技术在高频石英晶体测试系统中的应用

在此介绍了一种以DDS芯片AD9912作为信号源的高频石英晶体测试系统。AD9912是一款直接数字频率合成芯片。一方面,AD9912内部时钟速度可高达1GSPS,并集成了14位数／模转换器,可以直接输出400MHz信号;另一方面,AD9912的频率控制字为48位,可以小于4μHz的分辨率输出信号。由于采用了DDS芯片AD9912作为信号源,所设计的石英晶体测试系统能够在20kHz～400MHz范围内测试石英晶体的串联谐振频率。与国内目前普遍使用的基于振荡器和阻抗计测试方法的测试仪相比,该测试系统具有测试频率范围宽、重复精度高等优点。     

一种晶体滤波器测试系统

一种晶体滤波器测试的虚拟仪器系统,采用了逐点法．相比扫频法具有较高的准确度。该方案的主要特点在于,硬件方面采用直接数字频率合成技术（DDS）构成信号源,结合下变频电路,最终由个人计算机完成信号的处理,由此构成了一个虚拟仪器系统。这种硬件结构具有明显的成本优势和组成上的灵活性;软件方面,使用了基于个人计算机的快速傅里叶变换（FFT）算法、音频积累,尤其是调试数据库的应用,大大简化了调试过程。该系统具备快捷、高效的特点,方便了晶体滤波器的测试。     

LST-9.0MHz晶体滤波器的研制

设计制作了一种以AT切基频压电石英晶体振子为滤波元件的LST-9.0 MHz型分立式带通晶体滤波器.滤波电路采用两节差接桥型电路即格型网络,输入信号在输入端为双路平衡输入,网络输入/输出端阻抗不对称,直流不共地,具有在-55～ 85℃工作环境温度范围内、工作频率9.0 MHz时,中心频率偏差≤200 Hz、矩形系数≤2.5的特性.     

测量夹具电容对石英晶体频率测量的影响

为了提高测量精度,仿真分析了在π网络测量法中,石英晶体测试夹具间电容对串联谐振频率测量的影响,根据石英晶体的电模型及π网络法石英晶体测量系统中π网络的理论模型和实际模型的差异,分析了影响石英晶体谐振频率测量精度的因素,并在此基础上提出了补偿方法。实验结果表明,经过补偿后石英晶体串联谐振频率的测量精度可达到±2×10-6。     

金刚石结构光子晶体的计算与制备

通过平面波法计算金刚石结构光子晶体的禁带特征,得出:当RA=0.16时,禁带宽度最大;当晶格常数a=8.5mm时,对应的最大禁带宽度为3.5GHz,对应的禁带范围为15.3～18.7GHz.利用CAD软件设计了在x,y,z三个方向上的周期数分别为2,4,6的金刚石结构的光子晶体模型,并采用立体印刷技术制备出了17.4mm×36.54mm× 54.32mm的三维微波金刚石光子晶体.最终通过HP网络测试仪对样品的禁带特征进行测试,结果表明;在晶体的＜100》方向上存在频率为14.7～18.5GHz的光子禁带,这与理论值相一致.当电磁波频率为17GHz时,对应的衰减率为-30dB.     

Statek公司新推微型晶体CX11系列

Statek公司新近推微型晶体CX11系列，其尺寸仅为3．2mm×1．50mm×0，90mm，如此小的尺寸适合用于人体内医疗遥测领域。该晶体的频率范围为20～250MHz，在工作温度范围内具有严格频率稳定性。     

LST-15MHz晶体滤波器的研制

利用AT-切厚度振动模式的压电石英晶体振子，和当今晶体滤波器设计中最为常用的格型网络——差接桥型电路，成功设计研制了“LST-15MHz型”讯号双路平衡输入、输入/输出阻抗不对称两节差接桥型电路分立式带通滤波器新品种。它具有在一55～＋85℃工作环境温度范围内、工作频率15MHz时，中心频率偏差≤200Hz、矩形系数≤2．5的特性。     

金刚石结构光子晶体的计算与制备

通过平面波法计算金刚石结构光子晶体的禁带特征,得出当RA=0.16时,禁带宽度最大;当晶格常数a=8.5mm时,对应的最大禁带宽度为3.5GHz,对应的禁带范围为15.3～18.7GHz.利用CAD软件设计了在x,y,z三个方向上的周期数分别为2,4,6的金刚石结构的光子晶体模型,并采用立体印刷技术制备出了17.4mm×36.54mm× 54.32mm的三维微波金刚石光子晶体.最终通过HP网络测试仪对样品的禁带特征进行测试,结果表明;在晶体的＜100》方向上存在频率为14.7～18.5GHz的光子禁带,这与理论值相一致.当电磁波频率为17GHz时,对应的衰减率为-30dB.     

电子测量仪器

第五类局域网电缆测试仪在第一代的第五类型电缆测试仪之中，仪器信号的不平衡及内在的近程串扰（ＮＥＸＴ）是产生测试误差的主要原因。ＬＡＮｃａｔＶ是第一部经严格设计可以免除这种误差的手提电缆测试仪，并对第五类型线的测试提供高度的可信度。该产品是由美国Ｄａｔａｃｏｍ公司生产，北京龙讯达公司总代理的。所有精确测试第五类型电缆的功能均已包含在本机种内。自动测试功能使ＬＡＮｃａｔＶ进行接线图、近程串扰（ＮＥＸＴ）、衰减量、长度、电阻、特性阻抗及衰减量对串扰比等电缆验证测试。每种测试项目在检修时可以单独进行。尤…     

LED器件热阻测试仪的研制

本文介绍了LED热阻测试仪的工作原理、实现方法、技术指标以及使用效果.主要研究测试系统中的程控时序控制和多路数据采集、高精度器件壳温测量与控制等技术,设计开发了LED热阻测试仪和配套恒温夹具.LED热阻测试仪的研制解决了国内LED生产和使用中迫切需要解决的热阻测试问题.对于提高我国功率LED产品的可靠性,填补国内LED热阻测试的空白,具有重要意义.     

Measurement of Crystal Impedances at Low Levels

It is very important to know the impedances of crystal dilodes when constructing circuits such as mixers and detectors in which the crystals are used. It is always difficult to measure these impedances due to the nonlinear characteristics of the crystals but it is most difficult to make the measurements at minimum levels at which the crystals operate, since with such methods as the slotted line, the detector must operate at a still lower level to obtain the required probe decoupling. Thus, since the load whose impedance is being measured is itself a crystal operating at its minimum level, it is practically impossible to obtain a detector with sutlicient sensitivity to make the measurement. Crystal impedances at these minimum levels are of utmost importance as it is here that optimum matching is essential for maximum sensitivity. This paper describes practical tectilques which use only standard equipment to measure crystal impedances at low levels. The detector used is a crystal of the same type as that being measured. The method is capable of precise results and good measurements can be obtained at low levels with little more effort than is normally required in making careful impedance measurements.     

Advanced thermal tester for accurate measurement of internalthermal resistance of high power electronic modules

A thermal tester has been developed for the accurate measurement of the internal thermal resistance of high-power electronic modules. The tester is designed for the simultaneous measurement of 20 electronic modules each dissipating in excess of 200 W. The heat dissipated is transmitted to the ambient by water-cooled cold plates dedicated to each test site. The tester system layout, mounting assembly, hydraulic design, cold-plate spreader design and data acquisition instrumentation are described. Sample measurements and the associated uncertainty are also discussed. The sample results are validated by comparison with thermal modeling     

Investigation into socketed CDM (SDM) tester parasitics

The ESD Association standards working group 5.3.2 is analyzing the procedure and stress that is applied to a device under test (DUT) using a socketed discharge model (SDM) test system, formerly referred to as socketed CDM. Our final goal is to define an SDM tester specification that will guarantee test result reproducibility across different test equipment. This paper investigates the effect of tester background parasitics on the discharge current waveforms of an SDM tester. Characteristic waveforms were studied and SDM testing was performed on actual devices. It is shown that SDM tester parasitics determine the stress applied to the DUT. This directly impacts the SDM failure threshold voltage levels and may lead to miscorrelation and non-reproducibility of test results across different SDM test systems. This paper empirically determines the relative contributions of the various tester parasitics to the total stress applied to the DUT. Our investigations indicate that the tester provides a 10–20 pF parasitic capacitance discharge into each pin of the device. Tester background parasitic elements play such an important role in the SDM discharge event that correlation between test systems built by different manufacturers is unlikely without completely duplicating a particular tester.     

TN型液晶双折射率的简易测量方法

为了实现一种简易的测量TN型液晶双折射率的方法,根据等厚干涉原理设计了一种楔形液晶盒。通过调节入射光的偏振方向而无需调整液晶分子取向实现寻常光（o光）和非寻常光（e光）,成功测量了液晶长轴方向和短轴方向的折射率。结果表明,本方法简单方便,能达到测量的基本要求。     

新型液晶灌注机的自动控制系统

液晶灌注是个复杂的工艺过程，各种工艺参数的条件非常重要，必须严格按工艺流程进行，否则直接影响液晶屏的电子性能，介绍了新型液晶灌注机的生产工艺过程。及自动控制系统的功能及技术指标，并详细介绍了软件，硬件的设计。     

液晶显示投影机原理与维护

介绍了液晶显示投影机的基本原理、使用维护及其发展趋势.液晶投影机使用中要特别注意通风与散热和防尘与清洁.性能先进、使用方便的液晶投影机及其他类型投影机正在进入家庭消费市场.     

Microwave Switching by Crystal Diodes

This paper gives the results of an investigation of the use of a microwave crystal as an RF switching element. Variation of a dc bias applied to the crystal will change its impedance, thereby providing an electronic control of microwave power. Empirical data are correlated with the physical structure of the crystal and its equivalent circuit to establish the frequency and power limitations of the switch. A comparison is also made of the switching properties of germanium and silicon crystals. Curves are given for predicting the switching capacity of any diode once its impedance has been normalized with respect to the characteristic impedance of the waveguide. Some methods are suggested for improving the bandwidth and power capacity of the crystal switch.     

一种基于FPGA伪彩液晶显示系统的设计

根据场序法彩色液晶显示原理和功能要求,基于XILINX公司Spartan3系列FP-GA,采用硬件描述语言Verilog设计了一种伪彩液晶显示控制电路,并利用单色液晶屏和三基色的LED背光源完成了场序法伪彩液晶显示控制系统的设计与实现。仿真和测试结果表明,该系统的设计控制灵活可靠,能够实现场序法伪彩液晶显示时序和控制功能。     

网络分析仪在滤波器测试中的应用

为解决某型非标准阻抗滤波器由于测试系统老化带来的测试问题,利用网络分析仪实现了滤波器的测试.介绍了旧测试系统与网络分析仪的测试原理和它们之间的区别,阐述了网络分析仪Agilent E5071C替代频率特性测试仪BT-3、信号源XFC-6、超高频毫伏表QF2270、频率计8000C四台仪表测试滤波器的实现方法.实验证明,用网络分析仪测试数值一致性好、操作简单、精度高、减少了工作量、提高了生产效率.