利用CAZAC序列的OFDM频率同步方法

频率偏移估计是OFDM (Orthogonal Frequency Division Multiplexing)的关键技术。该文提出了在一个OFDM符号内利用两个重复的CAZAC (Constant Amplitude Zero Auto Correlation)序列进行频率偏移估计的新方法,估计范围可达整个OFDM带宽。用于同步的训练序列还可用于信道估计和均衡,这将提高系统的数据传输效率。此算法同步精度达到了Schmidl提出的Cramer-Rao bound,有效性在AWGN和Rayleigh多径信道下得到了验证。     

一种采用频率变换的自供电电源管理电路

 在低频率条件下,采用直接阻抗匹配的原理,设计的压电材料换能器电源管理电路,匹配电感值很大.本文采用频率变换,设计了一种自供电电源管理电路.分析了频率变换的原理.将低频信号变换至较高频率,匹配电感值很小,有利于电路的小型化.该管理电路还可以在宽频带内对于压电换能器实现匹配.实验结果表明,电路实现了频率变换,匹配电感值和电路体积都大大减小.电源管理电路的最大采集功率为181.6mW,能量采集效率可以达到44.8%.当0.47法拉的储能电容电压为1.13V时,该电路最大放电功率可达110mW,放电时间持续620ms,能够驱动无线传感器在一个周期内正常工作.     

高频高压电源中倍压器的设计

倍压器作为高压电源的重要组成部分对于提高电源的性能具有特殊作用。分析了倍压器相关参数对电源性能的影响规律,用理论分析的方法设计了一种半臂式倍压器,并对其进行了实际测试。仿真与测试结果表明,倍压器参数优化对于电源性能具有显著影响,且实现了倍压器设计的优化。     

高频高压软开关DC/AC电源的仿真研究

脱硫脱硝供电电源及电除尘器中，需要一个高频率、高电压的交流电源叠加在高压直流电源上。由于交流电源输出效率及开关频率较高，在硬开关状态下，开关损耗较大。解决这一问题的方法之一是用软开关实现该电路的功能。本文给出全桥DC/AC变换电路在硬开关状态以及在安桥移相控制软开关状态下的PSPICE仿真结果，说明全桥移相控制软开关方法在本电路中的可行性。     

Elastic DVS Management in Processors With Discrete Voltage/Frequency Modes

Applying classical dynamic voltage scaling (DVS) techniques to real-time systems running on processors with discrete voltage/frequency modes causes a waste of computational resources. In fact, whenever the ideal speed level computed by the DVS algorithm is not available in the system, to guarantee the feasibility of the task set, the processor speed must be set to the nearest level greater than the optimal one, thus underutilizing the system. Whenever the task set allows a certain degree of flexibility in specifying timing constraints, rate adaptation techniques can be adopted to balance performance (which is a function of task rates) versus energy consumption (which is a function of the processor speed). In this paper, we propose a new method that combines discrete DVS management with elastic scheduling to fully exploit the available computational resources. Depending on the application requirements, the algorithm can be set to improve performance or reduce energy consumption, so enhancing the flexibility of the system. A reclaiming mechanism is also used to take advantage of early completions. To make the proposed approach usable in real-world applications, the task model is enhanced to consider some of the real CPU characteristics, such as discrete voltage/frequency levels, switching overhead, task execution times nonlinear with the frequency, and tasks with different power consumption. Implementation issues and experimental results for the proposed algorithm are also discussed     

用于测量工频高电压的直波导电压传感器

介绍了一种用于测量工频电压的以Y切Z传钛扩散LiNbO_3基底直波导作为敏感元件的光学电压传感器,直波导电压传感器利用Pockels效应,将直波导的固有相位差调整至接近π/2,在不需要加1/4波片的条件下实现工频电压的线性传感。利用直波导可以直接耦合进光纤的特性,全部器件采用光纤连接,大大减少了光路空间,提高了光路的稳定性。分析了这种电压传感器的工作原理与输入输出特性,并对100~3000V的工频电压进行了测量。初步研究了其温度特性,在-40℃~60℃的温度范围内,变比误差达到5.29%。根据理论与测量分析,这种电压传感器可以用于工频高电压的测量。     

Improving the Performance of Hyperspectral Image and Signal Processing Algorithms Using Parallel,Distributed and Specialized Hardware-Based Systems

Advances in sensor technology are revolutionizing the way remotely sensed data is collected, managed and analyzed. The incorporation of latest-generation sensors to airborne and satellite platforms is currently producing a nearly continual stream of high-dimensional data, and this explosion in the amount of collected information has rapidly created new processing challenges. For instance, hyperspectral signal processing is a new technique in remote sensing that generates hundreds of spectral bands at different wavelength channels for the same area on the surface of the Earth. Many current and future applications of remote sensing in Earth science, space science, and soon in exploration science will require (near) real-time processing capabilities. In recent years, several efforts have been directed towards the incorporation of high-performance computing (HPC) systems and architectures in remote sensing missions. With the aim of providing an overview of current and new trends in parallel and distributed systems for remote sensing applications, this paper explores three HPC-based paradigms for efficient implementation of the Pixel Purity Index (PPI) algorithm, available from the popular Kodak’s Research Systems ENVI software package, as a representative case study for demonstration purposes. Several different parallel programming techniques are used to improve the performance of the PPI on a variety of parallel platforms, including a set of message passing interface (MPI)-based implementations on a massively parallel Beowulf cluster at NASA’s Goddard Space Flight Center in Maryland and on a variety of heterogeneous networks of workstations at University of Maryland; a Handel-C implementation of the algorithm on a Virtex-II field programmable gate array (FPGA); and a compute unified device architecture (CUDA)-based implementation on graphical processing units (GPUs) of NVidia. Combined, these parts deliver an excellent snapshot of the state-of-the-art in those areas, and offer a thoughtful perspective on the potential and emerging challenges of adapting HPC systems to remote sensing problems.     

电力系统提高电能质量的方法研究

电能质量对于电力系统的生产效率及电能的上网传输十分重要,文章在分析电能质量诸多影响因素的基础上,对提高电能质量的方法展开探讨,给出了具体提高电能质量的方法与措施,有助于进一步提高电力系统电能生产质量。     

一种带频率识别功能的抗辐照高压电源设计

设计了一种具有频率识别功能的抗辐射高压电源.该电路鉴频范围15～25 kHz,输出电压7 800 V,输出电压建立时间小于1 s.通过对电路结构的优化,减少了输出高压建立时间,减小了鉴频电路对输出电压的延时;通过采用数字鉴频,提高了鉴频电路的抗辐射能力,提升了整体电路的综合抗辐射能力.研制的具有鉴频功能的高压电源可同时满足抗中子注量、抗总计量、抗γ剂量率等要求.仿真结果和最终测试波形表明,电路设计满足要求.     

几种高功率微波频率诊断方法

本文介绍了诊断高功率微波频率的滤波法、外差法的原理及其装置的设计、性能和应用结果。分析比较表明，这三种方法及装置各有其特点和适用范围，应用中应根据实际需要选择其中一种或几种相互对比验证。     

一种低耐压器件实现的压电陶瓷驱动电源

介绍采用普通低耐压器件三端可调集成稳压块实现的３００Ｖ输出的压电陶瓷驱动电源的设计思想，电路原理，设计计算及安装调试等内容，该设计的特点是电路简单，可靠性好，经济实用。     

智能电话电源管理系统的重要设计技术

新的3.xG智能电话将传统的2G蜂窝式电话功能与PDA的功能特色结合起来,并包容了数码相机、音乐播放器(MP3)以及全球定位系统。种类如此之多的功能,离不开为数众多的元器件。它们中的大多数有着不同的电源电压要求,而且消耗的电流越来越多,要求更大的功耗。同时,消费者希望电话越来越小。本文将给出两种电源管理系统,它们将有助于系统设计者在最新一代蜂窝式电话的相互矛盾的目标间寻求恰当的平衡——功耗要求不断上升;外形应尽可能地小;效率要最优化以延长电池工作时间;电源轨噪声/纹波要保持在可接受的范围之内。图1示出从2G话音电话发…     

DSP系统电源管理技术

电源效率既取决于硬件设计与组件选择,又取决于基于软件的电源管理技术。文章讨论了嵌入式系统的电源管理技术,介绍了如何将其集成到DSP的RTOS 中,并以TI的DSP/BIOS操作系统为例,给出了电源管理软件技术的实施方法。     

Measurement of Power Frequency Fluctuations Using the FFT

A new method for detecting fluctuations in the fundamental frequency component of a power system, by relating it to a leakage coefficient in the FFT, is presented. The phenomenon of leakage in the FFT is used advantageously to increase spectral resolution. The leakage coefficient is a quantitative measure of the deviation from the fundamental frequency component with respect to the sampling frequency. Theoretical aspects are considered along with a method for on-line implementation.     

功率双基区晶体管（DUBAT）及其压（流）控调频效应

在重点考虑了提高击穿电压和增大电流容量的基础上，设计并研制出功率型ＤＵＢＡＴ。其主要参数达到：ＢＶ（ＣＥ０）≥１２０Ｖ，Ｉ（ＣＭ）≥２Ａ，ＲＮ≈５０～１１０Ω，Ｐ（ＣＭ）≥１０Ｗ。并在此器件上首次发现了电压（流）控制调节脉冲频率效应。     

1．5kW机载雷达发射机高频高压电源

介绍了机载雷达发射机1.5kW高频高压电源的设计,分析了其工作原理,并对一些关键技术进行了论述。通过采用零电压开关多谐振变换器和提高高压电源的工作频率,使高压电源的性能得到很大的提高,该高压电源具有功率密度高、效率高、可靠性高等优点。实验结果证明了该高压电源的实用性,可以满足机载雷达发射机的要求。     

高压电源管理中内部稳压器的设计

设计了一用于高压电源管理芯片中的内部稳压器电路,为系统中低压模块提供稳定的电源电压输入.电路分为基准和线性稳压器两个部分.整个电路结构为:峰值电流源为Brokaw基准供电,获得的基准电压输入后端放大器的正向端中,运用线性稳压器结构进行降压,为后级各模块提供三组不同的电压,又根据各个电源使用场合的不同,对数字电源加入关断机制,并且加强了功率电源的负载调整能力,有效地防止了后续模块的不正常工作.系统测试表明,电路能够产生三组需要的电压,并在容差范围内能够使系统正常工作.     

基于高压变频器的大功率电机软启动

高压变频器以其节能优势在电气传动领域广泛应用,对大功率风机、水泵的生产工艺改善,电网适应性具有良好的应用效果;本文通过分析大功率电机软启动的技术特点,基于TMEIC高压变频软启的案列,为高压变频应用提供借鉴。     

利用RPLS算法实现电力系统频率跟踪

针对在电力系统频率跟踪算法中推导过程复杂、计算量大等问题,提出了一种利用递推偏最小二乘法(RPLS)实现电力系统频率跟踪的新算法。该方法在递推过程中,采用滑动窗法更新数据,同时引入了适当的遗忘因子。仿真结果表明,该算法在电力系统频率跟踪中具有计算复杂度小,推导过程简单,频率跟踪收敛速度快,测量精度高的特点,其是电力系统频率跟踪中的一种新方法。