ARM+FPGA的双模导航接收机硬件平台设计

卫星导航系统能够为广大用户提供全天时、全天候、高精度的导航、定位和授时服务.本文介绍一种基于ARM+FPGA架构的GPS/BDS双模导航接收机的设计方法.该设计分为3部分:射频部分电路设计、FPGA部分电路设计和ARM电路设计.其中,射频部分主要完成GPS/L1频点、BD2/B1以及B3频点卫星信号的下变频及采样.FPGA部分做信号处理,ARM负责信息处理.经过测试,此设计是可行的,能够达到导航接收机对于定位和授时精度的要求.     

一种紧耦合Ubuntu系统的卫星导航接收机设计

提出了一种采用ARM+FPGA架构的紧耦合Ubuntu系统的卫星导航接收机的设计,ARM上运行Ubuntu系统, ARM与FPGA之间通过 ARM自带的 GPMC接口进行通信,重点解决 Ubuntu 系统与 GPMC 通信相关的驱动软件设计问题。首先介绍了 ARM Cortex A8的GPMC接口原理,然后给出了Ubuntu系统的主要软件驱动模块的设计思路。本设计结合了ARM和FPGA各自的优点,借助Ubuntu系统自身强大的功能,加快了接收机的研发速度,增加了其稳定性。     

基于ARM+FPGA北斗接收机设计

作为新一代卫星导航系统,北斗卫星导航系统是我国自主研制的全球卫星定位与通信系统.随着北斗系统的逐步改进和完善以及我国经济、军事、民用等各方面需求的不断加强,北斗系统将具有更多和更广泛的应用领域.本文在了解卫星导航原理的基础上,介绍了一种基于ARM+FPGA架构的导航接收机系统,分别介绍了接收机的硬件系统架构和软件系统架构:接收机的射频前端采用SE4120芯片,基带处理部分采用ARM9内核的AT91 SAM9G20芯片和CycloneⅢ系列的EP3C120F484芯片.同时阐述来接收机的软件设计,包括捕获引擎、跟踪引擎、解凋电文,定位解算等.     

高速数字信号处理器系统电源设计

研究了DSP+FPGA高速数字信号处理器系统电源的供电需求,采用了开关电源和线性稳压电源的混合电源系统,解决了高速数字信号处理器系统电源的供电问题。经实际的测试验证表明设计的该系统电源满足各个高速处理模块的供电需求,也表明该系统电源的突出优点是供电电源的高稳定性。     

基于ARM+FPGA的GPS接收机设计

针对GPS接收机在民用和军事领域的重要应用,设计了一种基于ARM+ FPGA的GPS接收机.接收机的射频前端采用GP2015芯片,基带处理部分采用ARM9内核的A191 SAM9261芯片和CycloneⅡ系列的EP2C70F67218芯片.同时阐述来接收机的软件设计,包括捕获引擎、跟踪引擎、解调电文,定位解算等.该接...     

基 ＡＤ９３６１的北斗接收机终端性能评估方法研究

为满足北斗定位导航系统中接收机基带信号处理算法研究的需要,设计了一种运行于软件无线电平台、输出数据全面多样的北斗接收机平台,并对其进行了详细的指标评估和定位验证。该接收机运行于由ARM、FPGA和AD9361组成的软件无线电平台上,利用AD9361射频前端得到北斗B1信号的中频采样数据,通过FPGA和ARM实现北斗卫星的快速捕获、跟踪及位置解算等信号处理流程。利用已知参数的模拟导航信号对接收机进行了性能指标评估,并进行了实际场景的定位实验。实验测试表明,该接收机捕获、跟踪等过程性能表现良好,导航定位精度及动态定位精度较高,可输出标准原始观测量数据,满足一般的北斗接收机基带信号处理及定位算法研究的需要。     

基于FPGA+ARM的视觉导航轮式机器人

根据自动运输的需求,以FPGA+ARM为核心,设计一种基于视觉导航的自主式轮式机器人,使用FPGA控制图像的实时采集、存储和显示,用ARM实现路径识别、通信并控制执行机构和传感器。路径识别的基本思想是采样二值化并去噪,再检测出场景中的路径,由路径跟踪模块进行导航计算。实验结果表明,该机器人的控制准确可靠,能正确地跟踪预先设置的引导轨线。     

基于PCIe总线的卫星导航信号传输系统设计

为了满足高精度软件接收机对卫星导航中频信号传输系统的新要求,设计了一种基于PCIe总线的传输系统.该系统以Virtex-5 FPGA为核心控制器件,以DMA方式通过4通道PCIe接口传输导航卫星数据.详细介绍传输系统AD模块、DMA控制模块、中断模块等核心模块的FPGA实现方法.经过测试与验证,系统读写速率分别达到了800 MB/s和650 MB/s,可以满足不同层次导航软件接收机对原始导航数据的需求.     

基于SOPC的扩频接收机设计与实现

采用FPGA+DSP模式实现的扩频接收机存在开发周期长、实现难度大等缺点。针对该问题,基于可编程片上系统,利用FPGA内的嵌入式软核NiosII代替DSP处理器和通用控制器,在单片FPGA内实现整个BD/GLONASS组合导航定位接收机。阐述匹配滤波器、相关器、载波跟踪环和码跟踪环的算法理论与实现方法。在24 h内的静态定位结果表明,该接收机的定位精度满足要求。     

基于FPGA的激光测距控制系统设计

本文介绍一种基于FPGA和ARM9的激光测距系统的硬件原理设计和软件设计方案.该方案采用SICK公司的户外型激光传感器LMS221,和ALTERA公司cyclone系列的EP1C12Q24017 FPGA芯片.控制系统采用ARM+FPGA的结构,系统运行嵌入式Linux操作系统,从而保证系统可以灵活的实现高速数据采集和实时数据传输.     

European Community policy and the market

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.     

一种自适应子融合集成多分类器方法

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。     

Explanation and prediction: an architecture for default and abductive reasoning

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.     

Three Process Perspectives: Organizations, Teams, and People

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.     

基于复小波噪声方差显著修正的SAR图像去噪

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。     

How do children do mathematics with LOGO?

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.     

Editorial: Special issue on recent advances in hybrid control theory and applications

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     

Information for Authors

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.     

Enhancing a leaf radiative transfer model to estimate concentrations and in vivo specific absorption coefficients of total carotenoids and chlorophylls a and b from single-needle reflectance and transmittance

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.     

Mr. Twinn’s bombes

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).