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1.
带隙基准电压源广泛应用在模拟集成电路中,为集成电路芯片系统提供稳定的直流参考电压,是电路设计中不可或缺的一个单元模块。设计了1.25V CMOS 带隙基准电压源电路,采用斩波调制技术改进了电路结构,以提高输出基准电压的精度。基于CSMC 0.5μm CMOS 工艺,使用Cadence工具对未采用斩波调制的电路和采用斩波调制的电路的输出电压分别在typical工艺角下进行仿真。仿真结果显示,采用斩波调制后,输出基准电压由1.05V变化到1.21V,误差由16%减小到了3.28%。 相似文献
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本文提出了一种应用于D类音频系统的低噪声斩波运放电路.该电路主运放采用全差分电路结构,具有很高的PSRR和电压摆幅,同时采用T/H解调技术,有效地降低了低频噪声和残余电压失调.仿真结果表明在5V电源电压下,斩波频率150KHz时,输入等效噪声为31.12nV/√Hz,满足D类功放的要求.该电路已在SMIC 0.3Sum N阱工艺上MPW流片成功,功能测试正常. 相似文献
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为了消除由于晶体管不匹配产生的随机失调对带隙基准源精度的影响,设计了一种采用斩波调制技术的带隙基准电压源。该方法采用对称性OTA的结构来减小带隙基准电压源的系统失调,并利用带隙基准核心电路中的与绝对温度成正比(PTAT)的电流源为OTA提供自适应偏置,从而较小了整个电路的功耗。通过基于0.35μm CMOS工艺并使用Cadence Spectre工具对电路进行仿真,结果表明:斩波频率为100 Hz时,基准电压在室温(27℃)的输出为1.232 V,该带隙基准的供电电压的范围为1.4~3 V;在电压为3 V时,在-40~125℃温度范围内的温度系数为24.6 ppm/℃。 相似文献
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压电换能器通常输出微弱,使用辅助电源的自供电控制电路功耗大,其电源管理电路启动阈值高,启动速度慢,转换效率低.对同步电荷提取(SECE)电路进行建模和理论推导,提出了一种间歇性自供电控制电路原理.根据SECE电路输出的最大功率点,间歇性地给控制电路非常短时间供电,并解决了间歇供电易造成逻辑混乱的问题,大幅度减小自供电电路的功耗,提高电路的效率,电路在极低输入功率下也能快速启动.实验结果表明,在压电换能器输出21 Hz、3.6 V电压时,控制电路功耗低至0.19 μW,是常规控制电路总功耗的1/134;管理电路的启动功率阈值仅为0.39 μW,低于通常电路的1/14.该控制电路的工作原理也适用于其他容性内阻换能器的微弱能量采集和高效管理电路. 相似文献
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设计了一种应用增益增强技术和斩波稳定技术的全差分折叠式共源共栅运算放大器。整体放大器采用了折叠式共源共栅结构,主运算放大器采用增益增强技术和开关电容共模反馈,两个辅助运算放大器采用连续时间共模反馈以实现高增益。此外,还采用了斩波稳定技术,在放大器的前后加入斩波开关,达到了滤除低频噪声的效果。在基于SMIC 55nm工艺库,电源电压3.3V下,在Cadence平台利用Spectre进行模拟仿真,仿真结果表明:等效输出噪声低频处的噪声被滤除,运算放大器的增益为116.9dB,相位裕度为72°,单位增益带宽为355MHz,能够使放大器应用于低频域,能够满足Sigma-Delta调制器对于音频频域的设计需要。 相似文献
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本系统是一种高功率因数AC-DC开关稳压电源,以功率因数校正控制芯片UCC28019输出的PWM波形来控制核心电路Boost升压斩波电路,使电感交替的储存和释放能量,电容交替的充放电,使输入的24V交流电压能稳定输出36V的直流电压。同时该电路输入的交流电压和输出的直流电流在较宽的范围内变换时,也能输出稳定的直流电压,当输出的直流电流或输入的交流电压在一定范围内变换时有较好的负载调整率或电压调整率,输入侧的功率因数达到0.99,具有输出过流保护、输入欠压保护功能。 相似文献
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在分析微机械陀螺接口电路工作原理的基础上,采用中电集团第24研究所的3μm10 V P-well标准模拟CMOS工艺设计并制作了微机械陀螺ASIC接口电路.电路HSPICE仿真灵敏度为0.252 mV/aF.芯片面积为5.5 mm×4.4 mm,在此工艺流片并进行了芯片测试.结果表明,在10 V电源电压下,其功耗为49.3 mW,输出摆幅为4.85±3.1 V,输出节点的零点偏离为0.15 V.此芯片具有微陀螺驱动及信号检测功能,可实现与微陀螺敏感结构的双片集成. 相似文献
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European Community policy and the market 总被引:1,自引:0,他引:1
C. Lloyd 《Journal of Computer Assisted Learning》1993,9(2):86-91
Abstract This paper starts with some reflections on the policy considerations and priorities which are shaping European Commission (EC) research programmes. Then it attempts to position the current projects which seek to capitalise on information and communications technologies for learning in relation to these priorities and the apparent realities of the marketplace. It concludes that while there are grounds to be optimistic about the contribution EC programmes can make to the efficiency and standard of education and training, they are still too technology driven. 相似文献
12.
融合集成方法已经广泛应用在模式识别领域,然而一些基分类器实时性能稳定性较差,导致多分类器融合性能差,针对上述问题本文提出了一种新的基于多分类器的子融合集成分类器系统。该方法考虑在度量层融合层次之上通过对各类基多分类器进行动态选择,票数最多的类别作为融合系统中对特征向量识别的类别,构成一种新的自适应子融合集成分类器方法。实验表明,该方法比传统的分类器以及分类融合方法识别准确率明显更高,具有更好的鲁棒性。 相似文献
13.
David Poole 《Computational Intelligence》1989,5(2):97-110
Although there are many arguments that logic is an appropriate tool for artificial intelligence, there has been a perceived problem with the monotonicity of classical logic. This paper elaborates on the idea that reasoning should be viewed as theory formation where logic tells us the consequences of our assumptions. The two activities of predicting what is expected to be true and explaining observations are considered in a simple theory formation framework. Properties of each activity are discussed, along with a number of proposals as to what should be predicted or accepted as reasonable explanations. An architecture is proposed to combine explanation and prediction into one coherent framework. Algorithms used to implement the system as well as examples from a running implementation are given. 相似文献
14.
Watts S. Humphrey 《Annals of Software Engineering》2002,14(1-4):39-72
This paper provides the author's personal views and perspectives on software process improvement. Starting with his first work on technology assessment in IBM over 20 years ago, Watts Humphrey describes the process improvement work he has been directly involved in. This includes the development of the early process assessment methods, the original design of the CMM, and the introduction of the Personal Software Process (PSP)SM and Team Software Process (TSP){SM}. In addition to describing the original motivation for this work, the author also reviews many of the problems he and his associates encountered and why they solved them the way they did. He also comments on the outstanding issues and likely directions for future work. Finally, this work has built on the experiences and contributions of many people. Mr. Humphrey only describes work that he was personally involved in and he names many of the key contributors. However, so many people have been involved in this work that a full list of the important participants would be impractical. 相似文献
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基于复小波噪声方差显著修正的SAR图像去噪 总被引:4,自引:1,他引:3
提出了一种基于复小波域统计建模与噪声方差估计显著性修正相结合的合成孔径雷达(Synthetic Aperture Radar,SAR)图像斑点噪声滤波方法。该方法首先通过对数变换将乘性噪声模型转化为加性噪声模型,然后对变换后的图像进行双树复小波变换(Dualtree Complex Wavelet Transform,DCWT),并对复数小波系数的统计分布进行建模。在此先验分布的基础上,通过运用贝叶斯估计方法从含噪系数中恢复原始系数,达到滤除噪声的目的。实验结果表明该方法在去除噪声的同时保留了图像的细节信息,取得了很好的降噪效果。 相似文献
16.
R. NOSS 《Journal of Computer Assisted Learning》1987,3(1):2-12
Abstract This paper considers some results of a study designed to investigate the kinds of mathematical activity undertaken by children (aged between 8 and 11) as they learned to program in LOGO. A model of learning modes is proposed, which attempts to describe the ways in which children used and acquired understanding of the programming/mathematical concepts involved. The remainder of the paper is concerned with discussing the validity and limitations of the model, and its implications for further research and curriculum development. 相似文献
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C. Xiang 《控制理论与应用(英文版)》2014,12(3):217-217
正The demands of a rapidly advancing technology for faster and more accurate controllers have always had a strong influence on the progress of automatic control theory.In recent years control problems have been arising with increasing frequency in widely different areas,which cannot be addressed using conventional control techniques.The principal reason for this is the fact that a highly competitive economy is forcing systems to operate in regimes where 相似文献
18.
《浙江大学学报:C卷英文版》2014,(7)
正Aim The Journals of Zhejiang University-SCIENCE(A/B/C)areedited by the international board of distinguished Chinese andforeign scientists,and are aimed to present the latest devel-opments and achievements in scientific research in China andoverseas to the world’s scientific circles,especially to stimulateand promote academic exchange between Chinese and for-eign scientists everywhere. 相似文献
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Alan V. Di Vittorio 《Remote sensing of environment》2009,113(9):1948-2750
The relative concentrations of different pigments within a leaf have significant physiological and spectral consequences. Photosynthesis, light use efficiency, mass and energy exchange, and stress response are dependent on relationships among an ensemble of pigments. This ensemble also determines the visible characteristics of a leaf, which can be measured remotely and used to quantify leaf biochemistry and structure. But current remote sensing approaches are limited in their ability to resolve individual pigments. This paper focuses on the incorporation of three pigments—chlorophyll a, chlorophyll b, and total carotenoids—into the LIBERTY leaf radiative transfer model to better understand relationships between leaf biochemical, biophysical, and spectral properties.Pinus ponderosa and Pinus jeffreyi needles were collected from three sites in the California Sierra Nevada. Hemispheric single-leaf visible reflectance and transmittance and concentrations of chlorophylls a and b and total carotenoids of fresh needles were measured. These data were input to the enhanced LIBERTY model to estimate optical and biochemical properties of pine needles. The enhanced model successfully estimated reflectance (RMSE = 0.0255, BIAS = 0.00477, RMS%E = 16.7%), had variable success estimating transmittance (RMSE = 0.0442, BIAS = 0.0294, RMS%E = 181%), and generated very good estimates of carotenoid concentrations (RMSE = 2.48 µg/cm2, BIAS = 0.143 µg/cm2, RMS%E = 20.4%), good estimates of chlorophyll a concentrations (RMSE = 10.7 µg/cm2, BIAS = − 0.992 µg/cm2, RMS%E = 21.1%), and fair estimates of chlorophyll b concentrations (RMSE = 7.49 µg/cm2, BIAS = − 2.12 µg/cm2, RMS%E = 43.7%). Overall root mean squared errors of reflectance, transmittance, and pigment concentration estimates were lower for the three-pigment model than for the single-pigment model. The algorithm to estimate three in vivo specific absorption coefficients is robust, although estimated values are distorted by inconsistencies in model biophysics. The capacity to invert the model from single-leaf reflectance and transmittance was added to the model so it could be coupled with vegetation canopy models to estimate canopy biochemistry from remotely sensed data. 相似文献
20.
Philip Marks 《Cryptologia》2018,42(1):1-80
This article discusses the history and design of the special versions of the bombe key-finding machines used by Britain’s Government Code & Cypher School (GC&CS) during World War II to attack the Enigma traffic of the Abwehr (the German military intelligence service). These special bombes were based on the design of their more numerous counterparts used against the traffic of the German armed services, but differed from them in important ways that highlight the adaptability of the British bombe design, and the power and flexibility of the diagonal board. Also discussed are the changes in the Abwehr indicating system that drove the development of these machines, the ingenious ways in which they were used, and some related developments involving the bombes used by the U.S. Navy’s cryptanalytic unit (OP-20-G). 相似文献