Comment and discussion on digital processing of PD pulses

Some of the more salient aspects of the digital processing technology of PD signals are examined. Most of the efforts in this field are concentrated on the application of digital analyzers for pulse height analysis, pattern recognition and identification of the physical phenomena. It is demonstrated that errors in the signal processing unit can lead to dominant mistakes in the interpretation of the test results     

基于压缩感知算法的数字预失真简化模型

为了能够在保证功放建模精度的基础上减少模型系数个数,本文创新性的提出一种基于压缩感知算法的功放简化模型,该模型使用去重复稀疏度自适应匹配追踪（RDSAMP）算法对模型系数进行简化。相较于广义记忆多项式（GMP）、分段简化动态偏差减少（PSDDR）全系数模型,数字预失真测试结果表明本文提出的简化模型建模精度分别提高1dB、-0.6dB,达到-46.01dB,邻信道功率比（ACPR）分别提高3.2dB、-1dB,达到-50dBc,与此同时,模型系数个数分别大幅度减少了72%、65%。因此,本文提出的模型能够在保持建模精度的基础上大幅度减少模型系数,对目前存在的功放模型简化问题有很高的参考价值。     

局部放电超高频脉冲分段采集及相角计算方法

采用连续采样方法检测局部放电信号成本较高,为此提出一种分段采集模式。采用高、低速系统分别采集局部放电超高频脉冲及工频信号,利用局部放电脉冲同步触发工频信号。采用模糊聚类方法计算所采集工频信号的实时基波频率,进而基于傅里叶级数算法,计算所采集工频信号的初始相位角,并以此作为局部放电脉冲的相角。通过局部放电脉冲相角、局部放电脉冲时间间隔及工频信号频率计算整个局部放电脉冲链相角。仿真试验和现场检测验证了所提方法的有效性和实用性。     

A note on Pareto statistics of partial microdischarge spots

Pareto statistics of microdischarges have been examined within two different representations. The first one is the commonly used height (amplitude) representation while the second is the newly proposed representation based on areas of plane spots created by microdischarges on dielectric surfaces.     

超声测距数字信号采集系统

介绍了一个完整的超声测距数字信号采集系统,该系统包括通用超声波发射电路,超声波接收电路和ＰＣ机数据采集系统。     

基于FPGA的GHz宽带中频数字采集系统的设计

针对大带宽复杂电磁信号的测试分析,介绍了一种基于FPGA的GHz带宽中频数字采集系统的设计,论述了系统的硬件总体设计和信号处理算法设计方案。采集系统ADC以1.6GHz采样率对中频信号进行采样,然后通过FPGA进行数字信号处理,通过对传统多相滤波算法的改进,设计了FPGA的高速大带宽信号的数字滤波方案,并采用多路并行处理的方法设计了高速数字正交混频算法,实现了最大为640 MHz的分析带宽和带内多路信号分析的功能。     

波导大功率负载长度对微放电的影响

波导大功率负载作为微波系统重要的终端器件,在航天系统上有非常广泛的应用.基于航天工程应用,对波导负载内部不同位置的微放电阈值进行分析,通过仿真软件截取负载不同位置的电场强度,从而进一步分析计算各个位置上的微放电阈值.结果表明,对于不同的波导负载吸收长度,内部电场强度并非线性变化,因此设计波导负载时应留有足够的吸收长度,...     

基于PCI总线的CCD数字相机采集系统设计

针对高速图像信号采集系统中数据传输量大的特点,提出了一种基于PCI总线的CCD数字相机采集系统的设计方法,给出了系统整体设计方案。采集系统以Camera Link和PCI总线为接口,结合FIFO、PCI9054和FPGA来实现计算机对CCD相机的设置和图像数据的采集。Camera link接口实现低压差分信号至TTL信号的转化和相机与图像采集卡之间的串行通信,PCI9054实现本地端与PCI端的桥接使用户接口设计简单,FIFO实现对高速采集后的海量数据进行缓存,FPGA实现整个系统的时序控制。这很好的解决了计算机与数字相机进行高速、大数据量传输的难题。     

基于FPGA及数字倍频技术实现数据同步采集的研究

应用GPS授时技术提出一种电力系统交流电气信号同步采集的设计方案.设计采用自顶向下的设计方法,选用了可编程逻辑控制器件FPGA芯片作为硬件开发平台完成GPS系统对时、数字倍频、A/D转换同步采样控制和数据存储的集成.实现了电力系统内部不同变电站之间以及变电站内部不同单元之间数据同步采集及存储等功能.此外给出了使用综合开发平台Quartus II设计软件进行的仿真与分析.数据同步采集在电力系统集成保护中具有实际应用价值.     

激光测距的高速采集与处理电路的设计

针对激光测距接收电路提出了将激光回波数字化处理的方法。基于激光测距中激光信号脉冲窄、上升沿陡、实时性要求高的特点,提出了采用ADC FPGA DSP的高速数据采集与实时处理的设计方案,详细介绍了电路的具体设计方法。分别对2MHz正弦波和重复频率5kHz脉宽为80ns的窄脉冲进行了采集实验,结果表明电路满足设计要求。     

用于电能质量检测的数据采集卡研制

结合电能质量五项指标,开发了用于电能质量检测的数据采集卡.该卡采用了DSP数字信号处理器和PCI总线技术,能实时采集数据.并采用了两片六通道高速A/D转换器和运用了锁相同步技术,对三相电压和电流信号能进行定时采样和等间隔采样,这样得到的数据对于下一步电能质量指标进行分析更为合理.本文最后还简要介绍了DSP的C语言开发和PCI插卡的驱动程序编写技术.     

基于FPGA及数字倍频技术实现数据同步采集的研究

应用GPS授时技术提出一种电力系统交流电气信号同步采集的设计方案。设计采用自顶向下的设计方法,选用了可编程逻辑控制器件FPGA芯片作为硬件开发平台完成GPS系统对时、数字倍频、A/D转换同步采样控制和数据存储的集成。实现了电力系统内部不同变电站之间以及变电站内部不同单元之间数据同步采集及存储等功能。此外给出了使用综合开发平台Quartus II设计软件进行的仿真与分析。数据同步采集在电力系统集成保护中具有实际应用价值。     

用于电能质量检测的数据采集卡研制

结合电能质量五项指标,开发了用于电能质量检测的数据采集卡。该卡采用了DSP数字信号处理器和PCI总线技术,能实时采集数据。并采用了两片六通道高速A/D转换器和运用了锁相同步技术,对三相电压和电流信号能进行定时采样和等间隔采样,这样得到的数据对于下一步电能质量指标进行分析更为合理。本文最后还简要介绍了DSP的C语言开发和PCI插卡的驱动程序编写技术。     

基于LabVIEW和数据采集卡的数字序列输出研究

首先介绍了数字序列输出的设计思想和用到的主要函数,在基本理论支撑的基础上,结合虚拟仪器技术,提出了一种以美国NI公司推出的虚拟仪器开发软件LabVIEW为开发环境,利用数据采集卡的数字硬件资源来进行数字序列输出的实现方法,有效地解决了多数字序列输出时的同步问题.所述方法在实际应用中取得了良好的效果.     

Electron avalanches. II. Fractal morphology of partial microdischarge spots on dielectric barriers

For pt.I see ibid., vol.10, no.4, p. 689-699 (2003). Microdischarge spots appearing on surfaces of dielectric barriers in sandwiched electrode systems have been studied. The study has been focused on streamer microdischarges which are a subject of continual interest not only in plasma physics (dielectric barrier discharges) but also in HV technology (partial discharges). The microdischarge spots have been visualized using photographic films that have played the role of dielectric barriers in experiments. The digitized pictures of microdischarge spots have been subjected to multifractal analysis. An inner structure of spots has been revealed and ascribed to streamer heads. The monofractal nature of the overall sets of microdischarge spots as well as the monofractality of the borders of the dark spot centers has been indicated. The inner structure of the dark centers has been classified as a non-fractal planar object. The study represents a first attempt to analyze microdischarge spots on dielectric barriers using general multifractal formalism.     

Compensation for unknown acquisition delay caused by digital receiver without external synchronization in NMR and MRI

The unknown acquisition delay problem caused by a digital receiver without external synchronization in NMR and MRI applications is discussed in detail. An effective procedure is suggested for overcoming the problem. The main features of the proposed method include minimal hardware modifications and highly efficient algorithms. It is important to note that this method does not rely on any special architecture for the digital receiver. To test the method, a digital receiver was implemented using a commercially available single-chip IC. Finally, the method was verified on a 0.3-T home-built MRI system. The experimental results show that the proposed method may be a useful tool for correcting the unknown acquisition delay arising from commercially available digital receivers without external synchronization in NMR and MRI.     

GLED的简易制程

要制作高级的GLED必须实施相关的专利技术,并与现有的制程诀窍相结合,这对于想试产GLED的普通厂家来说无疑是件困难的事.介绍如何应用现有的管形荧光灯设备和材料实施GLED的简易生产.     

Simplified analysis of feedback amplifiers

A very simple and general method for the analysis of feedback amplifiers with large-loop gain is presented in this paper. The general properties of feedback amplifiers, such as gain and input and output resistances, are obtained using an open-loop circuit where the loading effect of the feedback network is easily taken into account. Emphasis is placed on quick, intuitive, and reliable calculations, useful for both the analysis and design of feedback amplifiers.     

Measurement of 10-fs laser pulses

We report full characterization of the intensity and phase of ~10-fs optical pulses using second-harmonic-generation frequency-resolved-optical-gating (SHG FROG). We summarize the subtleties in such measurements, compare these measurements with predicted pulse shapes, and describe the implications of these measurements for the creation of even shorter pulses. We also discuss the problem of validating these measurements. Previous measurements of such short pulses using techniques such as autocorrelation have been difficult to validate because at best incomplete information is obtained and internal self-consistency checks are lacking. FROG measurements of these pulses, in contrast, can be validated, for several reasons. First, the complete pulse-shape information provided by FROG allows significantly better comparison of experimental data with theoretical models than do measurements of the autocorrelation trace of a pulse. Second, there exist internal self-consistency checks in FROG that are not present in other pulse-measurement techniques. Indeed, we show how to correct a FROG trace with systematic error using one of these checks     

Generation of attosecond X-ray laser pulses

We propose to generate as-X-ray laser pulses by beating of two or more X-ray laser lines with a frequency separation in the range of 10/sup 15/ Hz. We focus on nickel-like X-ray lasers, some of which have a few almost equidistant laser gain lines with an appropriate difference frequency. It is shown that in the case of three or more lines, these can be phase-locked by means of a Langmuir wave generated in the gain medium at a suitable electron density.