D/A和A/D转换器型谱的品种优化分析

本文从D/A与A/D转换器的基本概念和制造技术着手概述,特别对D/A和A/D转换器的应用之主要选择因素,进行了着重说明。随后,提出了D/A和A/D转换器优化品种的原则意见。     

A 175 Ms/s, 6 b, 160 mW, 3.3 V CMOS A/D converter

A 175 Ms/s A/D converter with a latency of one clock cycle is designed in a 0.7 μm digital CMOS technology. The resolution of the converter is 6 b while the power dissipation is only 160 mW. The A/D converter architecture is based on a continuous time analog preprocessing topology. A continuous time current interpolation circuit is implemented. The performance of the A/D converter is ruled by a tradeoff between speed, power, and accuracy     

cdma2000 1xEV-DO技术及发展

本首先比较了cdma2000lxEV-DO与cdma2000lx的主要区别，对cdma2000lxEV-DO中两种不同的系统架构(Phase I和Phase Ⅱ)进行了介绍，并针对Phase I描述了其A8／A9、A10／A11、A12、A13接口，然后给出了在cdma2000lx的基础上建立lxEV-DO网络的变迁，对目前lxEV-DO的试验和商用情况、设备和终端的提供情况进行了介绍，最后对终端发展进行了展望。     

Analogue to digital convertor architecture with a signal leveldetector

A new signal level detector for a flash-type A/D convertor is introduced. It operates like a comparator with the 1-of-n encoder of flash-type A/D convertors. Because the clock signal can be omitted in the application of the comparator, clock feedthrough noise is not a problem. A resolution of up to 8 bits in A/D conversion is feasible     

一种12位400 MHz电流开关型D/A转换器的设计

基于TSMC 0.25μm工艺、采用电流开关结构,设计了一个3.3 V 12位400 M采样率的D/A转换器。在电路中,设计了一种新的电压限幅结构,从而使其具有较好的动态性能。该D/A转换器在1 MHz输入信号下,无杂散动态范围(SFDR)达到83.75 dB;在12.5 MHz输入信号下,可获得70 dB的SFDR;在不同温度和工艺corner下,仿真得到的电路性能也都能达到上述指标。     

A cavity-backed rectangular aperture antenna with application to a tilted fan beam array antenna

A rectangular aperture of A/sub x//spl times/A/sub y/, cut in the top conducting plate of a triplate transmission line and backed by a cavity, radiates a tilted beam off the direction normal to the aperture. The mechanism of the radiation is explained using the Poynting vector distribution above the aperture and the phase distribution of the electric field over the aperture. The tilt angle is calculated as a function of side length A/sub x/ for a representative value of A/sub y/=18 mm=0.747/spl lambda//sub 12.45/, where /spl lambda//sub 12.45/ is the wavelength at a test frequency of 12.45 GHz. A tilted beam of approximately 27/spl deg/ is realized at A/sub x//A/sub y/=8/9 with a gain of approximately 8 dB. Using this value of A/sub x//A/sub y/, an array antenna composed of rectangular cavity-backed aperture elements is investigated. The array forms a tilted fan beam without phase shifters. The frequency responses of the gain and input impedance are discussed.     

EMD分解区域的数据研究

本文介绍了一种新的非线性、非平稳信号的处理方法—HHT方法,并运用此方法对地震波进行了理论分析,详细研究了其中的EMD方法及其实现过程;通过大量的数据分析,总结了这一方法的优越性,指出其具有良好筛分及不可良好筛分的适用数值范围,并总结了其中蕴涵的规律。当组合简谐波的频率固定,A2/A1很小,超过某一限值时;或者A2/A1很大,超过某一限值时,数据值不能用EMD方法进行筛分。当组合简谐波的幅值比A2/A1固定不变,而频率变化时,当f2/f1很小时,如超过某一限值;或者f2很接近f1,f2/f1超过某一限值时,数据y值不能用EMD方法进行筛分。      

一种由基本割集矩阵求网络图的方法

对于一个给定的网络图,可以确定对应的网络矩阵。同样,如果给定网络矩阵,也能够画出对应的网络图。本文讨论由基本割集矩阵求网络图的方法,该方法利用基本割集矩阵Q和降价关联矩阵A的关系,由Q得到A,进而画出对应的网络图。本文的讨论可供从事电路教学的教师参考。     

Reference refreshing cyclic analog-to-digital and digital-to-analog converters

A method of cyclic analog-to-digital (A/D) and digital-to-analog (D/A) conversion using switched-capacitor techniques is described. By periodically modifying the reference voltage to compensate for the nonideal signal-transfer-loop gain, it is possible in principle to build A/D and D/A converters whose linearity is independent of component ratios and that occupy only a small die area. These converters require two moderate-gain MOS operational amplifiers, one comparator, and a few capacitors. A test chip for A/D conversion was built and evaluated. The test data show that the A/D performs as a monotonic 13-bit converter with maximum 1-LSB differential and 2-LSB integral nonlinearity.     

A/D转换器非线性特性简易测试方法

A／D转换器非线性测试是A／D转换器静态特性测试的一项重要内容。相对于以往成本较高的测试方法，文章提出了一种简易可行的测试方法：利用高精度D／A转换器和低精度A／D转换器的精度差，借助8051仿真系统进行测试。实验表明，该方法成本低廉，操作简单，适用于A／D转换器非线性特性的初期评测。     

Stable and broad bandwidth multiwavelength fiber ring laser incorporating a highly nonlinear photonic crystal fiber

A stable and broad bandwidth multiwavelength fiber ring laser suitable for use in dense wavelength-division-multiplexing systems is demonstrated. A highly nonlinear photonic crystal fiber is inserted in the ring cavity to stabilize the power fluctuation and broaden the output spectrum. A thin-film Fabry-Pe/spl acute/rot etalon filter is used to get stable wavelength lasing. A Sagnac filter is employed to achieve uniform power distribution at each wavelength at the laser output. A laser with a power fluctuation about 0.1 dB in each wavelength within 20 min and with wavelength shift of less than 0.016 nm within 10 min is achieved. A stable 24-wavelength lasing operation with wavelength spacing of 0.8 nm within the 3-dB spectral range of 1573-1594 nm and signal-to-noise ratio better than 48 dB is observed experimentally.     

HJ-1A/B星CCD相机在轨辐射性能检测分析

为检测分析HJ-1A/B星CCD相机在轨辐射探测性能及其辐射定标的有效性,提出了基于多种光学特性地面目标的在轨检测方法。首先,介绍了HJ-1A/B星CCD相机在轨辐射性能检测方法,并基于2013年HJ-1A/B卫星地面同步观测试验数据,获取了HJ-1A/B星过境时刻的卫星入瞳处等效辐亮度。然后以该等效辐亮度为基准,对HJ-1A/B星CCD相机历次在轨辐射定标结果进行检验,分析HJ-1A/B星CCD相机的在轨运行期间辐射探测性能变化趋势。结果表明：HJ-1A/B星在轨运行过程中,辐射性能在不断发生变化;在轨运行5年多时间里,HJ-1A/B星的CCD相机各波段的辐射性能平均衰变量最低为3.7%,最大为39.6%;为保证遥感数据的定量化精度,定期的在轨绝对辐射定标十分必要。     

Inversion of complex matrices

The letter is concerned with the problem of inverting complex matrices of the form (A+iB) which frequently occur in systems theory. In particular, sufficient conditions for the nonsingularity of (A+iB) are presented for the cases when A is singular, B is singular, and both A and B are singular.     

PWM/PFM双模调制的高效率DC/DC开关电源

利用根据负载电流的大小改变调制模式的方法实现了一种降压型高转换效率的DC/DC开关电源,并采用二次集成的方式在芯片内部集成了功率p-M O SFET。当控制电压占空比小于20%时,采用PFM(Pu lse-F requency M odu lation)模式调制;占空比大于20%时,采用PWM(Pu lse-W idth M odu lation)模式调制,平均转换效率约为93%,输出电流范围可以从0.01 A到3.0 A。当输出驱动电流为3.0 A时,整个调制控制电路的功耗仅为6.0 mW。输入电压为5 V时,负载调整率小于1.5%;负载电流为0.01 A时,线性调整率小于0.5%。     

M带余弦调制滤波器组的设计

本文提出了一种近似重构的M带余弦调制滤波器组的设计方法.该方法将原型滤波器表示成A(z^L)B(z)的形式,通过优化低阶FIR滤波器A(z)的通带边缘频率,间接设计原型滤波器.在优化过程中,采用常用的Parks-McClellan算法设计滤波器A(z).文中给出的设计例子表明,该方法可获得很高阻带衰减的滤波器组.     

共振激活介质的反射特性

基于二能级原子系统的极化率理论,对共振激活介质界面的反常反射特性作了理论分析。以Nd:YAG激光介质为例,计算了界面的反射率R与入射激光波长(相对于原子线,中心的失谐量6)与场强AA的关·系曲线。在较低强度(AA～10~(-4))时,R与AA依然有关。     

CMOS pipelined A/D convertor using current divider

A novel dynamic current divider based CMOS pipelined A/D convertor principle is presented. A basic successive approximation scheme is applied, thus the signal is not modified (i.e. successively multiplied by two) along the A/D conversion. Consequently the most important speed limitation is lower than the time for signals to settle within 1/2 LSB in multiplying schemes.<>     

A low power 8-bit successive approximation register A/D for a wireless body sensor node

A power efficient 8-bit successive approximation register(SAR)A/D for the vital sign monitoring of a wireless body sensor network(WBSN)is presented.A charge redistribution architecture is employed.The prototype A/D is fabricated in 0.18 μm CMOS.The A/D achieves 7.SENOB with sampling rate varying from 64 kHz to 1.5 MHz.The power consumption varies from 10.8 to 225.7 μW.     

阿尔卡特呼叫中心解决方案

阿尔卡特呼叫中心解决方案基于局域网,采用ＣＳＴＡ作为主导通信协议,其Ａ４４００ＣＣｘ产品系列包括呼叫中心分配器Ａ４４００ ＣＣＤ、监管系统Ａ４４００ ＣＣＳ１管理器Ａ４４００ＣＣＭ、座席应用组件Ａ４４００ ＣＣＡ、万维网服务器Ａ４４００ ＣＣＷ以及语音应答、语音记录和其它配套设备。其中阿尔卡特４４００综合业务交换平台的基本结构采用阿尔卡特晶体结构技术;而公司的专利技术－－矩阵化分配方式则运用于呼叫     

低压断路器脱扣性能的有限元仿真

为了得到准确的设计参数,笔者采用有限元软件ANSYS电磁–热–结构耦合场分析方法,对热双金属片的热弹性变形进行仿真,通过建立有限元模型,模拟脱扣器驱动部件在各种要求工况下的热–结构特性,分别得到电流为:100 A,120 A,150 A,720 A时,热双金属片温度、位移随通电时间的瞬态关系,避免了数值计算时热双金属片温度偏差引入的误差。