凌特推出可编程硅振荡器LTC6906

凌特公司(Linear Technology)推出在100kHz时具有18uA超低工作电流的LTC69(16可编程硅振荡器。LTC6906是便携式设备的理想时钟芯片，其占板面积仅为LTC6906 THINSOT封装和一个电阻所占面积。这些振荡器无需旁路电容，可以编程至介于10kHz～1MHz之间的任何频率。     

用于以太网物理层时钟同步PLL的VCO设计

研究了一种基于以太网物理层时钟同步的高带宽低噪声压控振荡器（VCO）,该VCO采用交叉耦合的电流饥饿型环形振荡器,通过级联11级环路电路和改善其控制电压变换电路,优化了VCO的输出频率范围以及降低了输出时钟的相位噪声,完全满足以太网物理层芯片时钟电路的性能指标。基于TSMC3．3V0．25μmCMOS工艺的仿真结果表明,中心频率为250MHz时,压控增益为300MHz／V,其线性区覆盖范围是60～480MHz,在偏离中心频率600kHz处的相位噪声为-108dBc。     

纤巧型低频时钟芯片支持从1ms至9．5小时的长持续时间定时

凌力尔特公司（Linear Technology Corporation）推出简单和准确的低频时钟芯片UI、C6991,该芯片专门为长持续时间定时应用而设计。LTC6991是TimerBloxTM通用型硅定时器件系列的最新成员,它整合了准确的可编程振荡器与精准的电路和逻辑器件。一个极宽的可编程频率范围允许时钟以一个1ms至9．5小时的周期运作。     

时钟发生器芯片

时钟发生器AD955l可在多标准网络和通信基础设施系统中简化时钟设计，并减少对振荡器需求。AD9551时钟发生器采用一个新型的简化架构，它可以生成并转换多倍精度的网络时钟频率，使之能够替换多达5个振荡器。振荡器支持前向纠错（FEC）、延时、切换及精确频率生成功能等网络交换机、路由器及线卡中重要的功能特性，并提供一个串行外围接口（SPI）端口，其可选管脚的预设除法器数值用来提供一个频率比的分配，     

一种基于电容充放电的低功耗时钟发生器

基于SMIC 0.18μm CMOS工艺,设计了一种基于电容充放电的新型低功耗时钟发生器。为了减小温度变化引起的频率波动,设计了负温度系数偏置电路。采用了传统的占空比调节电路,可调节振荡波形的占空比。仿真结果显示,在3.3 V电源电压下,该振荡器可以稳定输出7.16 MHz频率的信号,相位噪声为-104.4 dBc/Hz,系统功耗为1.411 mW,其中环形振荡器功耗为0.811 mW。在-40℃～110℃温度变化范围内,振荡器的频率变化为7.116～7.191 MHz,容差在1.05%以内。同其他时钟发生器相比,该电路具有结构简单、功耗低,以及在宽温度范围内具有较高的频率稳定性等显著特点,能够满足芯片的工作要求,为芯片提供稳定时钟。     

低抖动时钟调整器

该系列共有L M K03000、LMK03000C、LMK03001、LMK03001C及LMK02000等五款产品。它们的时钟范围为1～200MHz，可将时钟信号的抖动减低至0．2ps，内置高性能的整数N锁相环路核心、压控振荡器以及3个LVDS和5个LVPECL时钟输出。LMK03000C及LMK03001C都可将信号抖动减少至0．4ps RMS，     

一种实用的电压控制环形振荡器

本文介绍了两种在集成电路中得到广泛应用的、作为内部时钟源的环形振荡器；RC环形振荡器和电压控制环形振荡器，并对引起振荡频率变化的关键因素进行了分析。     

Fox Electronics扩展HCMOS振荡器产品增添F32K系列振荡器

Fox Electronics Asia Ltd．现已扩充其HCMOS振荡器产品．推出最新的紧凑型3．3V F32K 32．768kHz振荡器系列。F32K振荡器的电流消耗仅为1．5μA,待机电流为250nA,是包括实时时钟（RTC）、微控制器子时钟、睡眠模式时钟和看门狗定时器时钟等广泛应用的理想选择。     

多输出时钟发生器

AD9520与AD9522多输出时钟发生器内置一个512Byte的嵌入式EEPROM存储器模块、分频器、扇出缓冲器，以及振荡范围为1．4～2．95GHz的VCO（压控振荡器）。其还可以使用振荡频率高达2．4GHZ的外部3．3V／5VVCO／VCXO（压控晶体振荡器）。     

一种基于频率-电压变换器的高精度时钟振荡器

采用一种新的不需要参考时钟输入的频率锁定环路结构,设计了一种基于频率-电压变换器的频率可调高精度时钟振荡器.通过电路补偿,减少工艺和温度对频率的影响.系统输出时钟的频率范围为22.5360 MHz,最坏情况下的变化小于±4.5%.电路采用GSMC 0.13 μmCMoS 1P8M工艺的3.3 V器件实现,核心版图面积约为0.05 mm2.版图后仿真表明,在3.3 V电源电压和200 MHz输出频率下,时钟的抖动峰-峰值为25 ps,锁定时间为2 μs,功耗为5 mw.     

On a wing and a prayer

Aircraft giants Boeing and Airbus are pinning their hopes on very different visions of how air travel will evolve in the coming decade.     

Building a in a flash supercomputer

A flash mob is a group of strangers, organized over the Internet, that comes together briefly, acts out a predetermined scenario-often something as simple as clapping for 30 seconds-and then disperses. A supercomputer is a very fast and powerful computer that outperforms most mainframes, at a cost, typically, of millions of dollars. Can a flash mob build a supercomputer? It can sure try, and so it did on 3 April at the University of San Francisco's Koret athletic center. The goal was to run the Linpack benchmark, a standard method of assessing the speed of supercomputers, to achieve a speed of at least 403 gigaflops (billion floating point operations per second). This would be fast enough to earn the system a place on the list of the world's fastest 500 supercomputers. The goal was not reached. The group reached just 180 gigaflops before it was time to pack up the computers and go home. However, even though the San Francisco effort fell short of speed goal, it did ignite imaginations.     

一年之间，物换星移

去年的这个时候,供货商们还在为生存而挣扎。如今,2009年的年报已经公布,许多供应商的年报业绩之好,就连最乐观的分析师也始料未及。这种变化的原因很简单：供应商们大幅削减成本,接下来是强劲的需求,这又导致了随后高企的设备利用率。     

Cooperative control of a human and a robot manipulator for positioning a cart on a frictionless plane

Robots may be expected to execute some tasks in cooperation with humans. Control systems for such robots should be appropriate to adapt to human characteristics in order to successfully accomplish the task. Pushing a cart on a frictionless plane in cooperation with a human is a basic example to such a task. To control the motion of an object from one point to another on a frictionless plane is impossible by only pushing in one direction without supporting it in the opposite direction, since as soon as the force is applied, the object will move without stopping its motion. In this paper, compliant cooperative positioning of a cart on a frictionless plane by a human and a manipulator is proposed using impedance control method with the parameters obtained from human–human cooperation.     

Analysis of a coaxial-to-waveguide adaptor including a discendedprobe and a tuning post

A field matching analysis of a coaxial-to-waveguide adaptor incorporating a disc-ended probe and a tuning post is presented. In this analysis, the tuning post is considered as a short-circuited second probe. A computer algorithm for calculating the input impedance of this structure is developed. This algorithm is used to investigate and improve the operation of a commercially available coaxial-to-waveguide adaptor     

Transmission-Line Properties of a Strip on a Dielectric Sheet on a Plane

The subject is a strip Iine formed of a strip and a parallel ground plane separated by a dielectric sheet (commonly termed "microstrip"). Building on the author's earlier papers all the significant properties are formulated in explicit form for practical applications. This may mean synthesis and/or analysis. Each formula is a close approximation for all shape ratios, obtained by a gradual transition between theoretical forms for the extremes of narrow and wide strips. The effect of thickness is formulated to a second-order approximation. Then the result is subjected to numerical differentiation for simple evaluation of the magnetic-loss power factor from the skin depth. The transition formulas are tested against derived formulas for overlapping narrow and wide ranges of shape. Some of these formulas are restated from the earlier derivations and others are derived herein. The latter include the second-order approximation for a narrow thin strip, and a close approximation for a narrow or wide square cross section in comparison with a circular cross section. Graphs are given for practical purposes, showing the wave resistance and magnetic loss for a wide range of shape and dielectric. For numerical reading, the formulas are suited for programming on a digital pocket calculator.     

基于智能手机压电基片上微液滴位置分析章

为了降低微流分析成本,该文提出了基于智能手机检测压电基片上目标微液滴方法,并开发出相应的应用软件,通过分析微液滴颜色信息和几何信息定位目标微液滴位置,结合分析时间获取微液滴输运速度。为验证提出方法的正确性,以5 μL黑色墨水溶液微液滴为研究对象,进行压电基片上微液滴识别和位置分析实验。结果表明,该文所提方法和开发的应用软件可识别和定位压电基片上微液滴,在功率为27.5 dBm时,第2~10 s段内微液滴输运速度为0.416 mm/s。     

The measurement of a large antenna using a spacecraft as a receiver

Two computational methods for obtaining the gain pattern of a large antenna using power levels recorded by a spacecraft are developed from the transmission equation. Nominally, the large antenna is linearly polarized while the spacecraft's receiving antennas are circularly polarized. Since the spacecraft has no attitude control system, the orientation of the receiving antennas is not known a priori nor its orientation the same from orbit to orbit. The first method relies on an independent spacecraft attitude determination system to furnish the orientation of the receiving antennas. It combines this information with receiving-antenna gain measurements to give the power level of the incident radiation. Losses due to polarization mismatch are taken into account, but polarization loss factors are not actually computed. The second method relates simultaneous measurements made by separate channels with separate receiving antennas. By solving a system of equations numerically, one can determine the direction of the incident radiation as well as its power level. This alleviates the need for an attitude determination system. These methods originated in the operations of the spacecraft NUSAT1 (northern Utah Satellite)