Fast codeword search algorithm for real-time codebook generation inadaptive VQ

Adaptive vector quantisation is used in image sequence coding where the code-book is updated continuously to keep track with the changing source statistics. Hence, for real-time video coding applications, both the processes of quantising the input vectors and updating the codebook are required to be fast. Since the nearest codeword search is involved in both these processes, a fast codeword search algorithm can make the coding process time efficient. The authors describe a proposed codeword search algorithm with reduced search space. The algorithm uses the mean value and the sum of the absolute differences as the two criteria to reject unlikely codewords, thereby saving a great deal of computational time, while introducing no more distortion than the conventional full search algorithm. Simulation results obtained confirm the effectiveness of the proposed algorithm in terms of computational complexity     

A comparison of ring and tree embedding for real-time group multicast

In general topology networks, routing from one node to another over a tree embedded in the network is intuitively a good strategy, since it typically results in a route length of O(logn) links, n being the number of nodes in the network. Routing from one node to another over a ring embedded in the network results in route length of O(n) links. However, in group (many-to-many) multicast, the overall number of links traversed by each packet, i.e., the networks elements on which resources must possibly be reserved, is typically O(N) for both tree and ring embedding, where N is the size of the group. The paper focuses on tree versus ring embedding for real-time group multicast in which all packets should reach all the nodes in the group with a bounded end-to-end delay. Real-time properties are guaranteed by the deployment of time-driven priority in network nodes. In order to have a better understanding of the nontrivial problem of ring versus tree embedding, we consider static, dynamic and adaptive group multicast scenarios. Tree and ring embedding are compared using different metrics. The results are interesting and counterintuitive, showing that embedding a tree is not always the best strategy. In particular, dynamic and adaptive multicast on a tree require a protocol for updating state information during operation of the group. Such a protocol is not required on the ring where the circular topology and implicit token passing mechanisms are sufficient. Moreover, the bandwidth allocation on the ring for the three multicast scenarios is O(N), while on a general tree it is O(N) for the static multicast scenario and O(N/sup 2/) for the dynamic and adaptive multicast scenarios.     

实时红外成像场景生成技术的发展及应用

建模和仿真在包括导弹系统在内的宇航系统中的作用逐步提高,并将在今后二十年起到更加重要的作用.由于计算处理能力将提高几个数量级,计算和数据存储成本将进一步降低,且具有余量.仿真越来越复杂的物理过程的能力将变得更加受仿真所涉及子模型的拟真度的限制,而非受仿真所能得到的计算能力的充足性的限制.文中概述了建模和仿真技术在红外成...     

人民币冠字号码高速识别实时模板生成算法

在回顾了目前人民币冠字号码识别研究文献的基础上,提出了一种在高速走钞环境下用于识别冠字号码的实时模板生成算法.首先在装有CIS的验钞机上采集到足够完备的人民币图像,然后抠出冠字号码区域,对其进行倾斜校正、二值化处理、形态学处理、字符分割及高度归一化后,对每种字符位图生成对应的模板集合,再根据差异最大化的原理从模板集合中挑出5个形成最终的模板精简集合.最后,给出了应用此模板进行实时识别的效果数据及分析.     

PROFINET实时工业以太网通信技术分析

PROFINET是基于工业以太网的用于工业自动化的创新的、开放的现场总线协议,支持分散式现场设备和对时间苛求的系统,以及基于组件的分布式自动化系统的集成,对PROFINET实时工业以太网的实时通信机制、RT和IRT的协议及实时性进行了分析,阐述了PROFINET的技术特点,并对实时性进行了实验测试,充分说明了PROFINET的实时性.     

A real-time self-calibrated current mirror for wide range current reference generation,signal reproduction and delaying

Current Mirrors are widely used in current mode circuits like A/D Converters, current conveyors, filters etc. The most important features of a current mirror are its precision, its input and output, resistance and minimum voltage and its frequency response. Although several mirrors with extremely small current transfer error have been presented, this error is usually measured in the typical case. This error may significantly differ in real-time conditions depending on mismatches, process and temperature variations. Stimulated by the current reference generation required in an A/D Converter with novel binary tree architecture that has been recently presented, an appropriate current mirror architecture supported by real time calibration logic is described in this paper. This mirror can generate a high enough output current (up to 1 mA), with relatively low transfer error (<4%), in a descent frequency range of up to 1 GHz. It requires a 1–1.2 V voltage supply and dissipates a power that can be as low as 0.3 mW. The error is measured using mismatch and process variation Monte Carlo post-layout simulations in TSMC 90 nm process.     

Quantitative analysis of a new method for real-time generation of SNR estimates for digital phase modulation signals

A new method of estimating the signal-to-noise ratio for M-PSK receivers was presented previously, which derives that estimate from the locked-state value of a new family of carrier lock detectors. A quantitative analysis is undertaken in which it is shown that this method requires significantly less hardware and/or software resources than estimation from the received signal's error rate, is irrespective of the data sequence, and necessitates far fewer symbols in order to arrive at an equally accurate estimate.     

Characterization and comparison of noise generation forquasi-resonant and pulsewidth-modulated converters

A buck converter with a given output filter is operated with pulse-width modulated and quasi-resonant switching schemes at the same nominal load and switching frequency. Electromagnetic interference generated by the natural switching action of the converter is examined by spectral analysis. Interference caused by excitation of parasitic elements is examined experimentally. Quasi-resonant converters are found to have a lower switching frequency harmonic bandwidth than the equivalent pulse-width modulated converter, even with switching frequency control. The most significant parasitic responses are the turn-on current and turn-off voltage of the catch diode and the gate current of the MOSFET. A significant decrease in radiated and conducted noise occurs when the gate drive voltage rise and fall times are increased, which is possible without loss of efficiency using quasi-resonant switching     

Linux实时性能优化算法分析与研究

Linux以其内核精悍、功能强大、源代码公开、支持多种硬件平台以及支持丰富的开发工具等特点广泛应用在嵌入式系统领域.作为嵌入式产品的操作系统平台,实时性是一个很重要的目标.基于这个目标提出了一种提高Linux2.6实时性的O（1）算法,该算法设置了新的数据结构及进程调度过程,通过分析Linux 2.6的O（1）算法的时间复杂度,可以得知运用该算法可以极大提高系统的实时性能.     

Modeling of multileg sine-wave inverters: a geometric approach

Three fundamental sine-wave inverter topologies are analyzed: two-leg (one-phase, two-wire); three-leg (three-phase, three-wire); and four-leg (three-phase, four-wire). The topologies are “full-bridge” voltage-source inverters with LC filters suitable for producing sinusoidal output voltages. The switching states and corresponding output voltage vectors produced by each inverter are identified and presented along with an analysis of the geometric arrangement of these voltage vectors. A pattern of characteristics is established whereby the “qd” modeling forms commonly used with three-leg inverters are extended to address the expanded capabilities of the four-leg inverter. A unique 4×4 decoupling transformation matrix is presented for the four-leg inverter that enables direct transformation between the four-degree-of-freedom (DOF) leg-modulation space of the inverter and its corresponding 3-DOF output-voltage space. This is shown to be directly analogous to the well-known “abc-qd” transformation developed for the three-leg inverter. Fully decoupled models for each inverter are presented     

基于正交信号产生的方法比较

文中针对不同应用领域需要不同特性正交信号的问题,采用罗列比较的方法,通过具体电路的设计、制作、测试、分析、对比,得出了4种典型的正交信号产生方法及各自的优缺点。正交信号产生有4种典型的设计方案：单片机数字合成法,FPGA直接数字式频率合成器法,DDS集成芯片AD9851合成法,RC—CR相移网络法。文中介绍了这4种正交信号产生方法的具体原理并对各方法在幅值调节,频率调节范围,正交性等方面做了详细的对比,以便在不同设计要求下选择相应的设计方案。     

Target software generation: an approach for automatic mapping of SystemC specifications onto real-time operating systems

In this paper we present a new approach for automated target code generation for given real-time operating systems out of SystemC to support platform independent software development. Since SystemC becomes the most important language in electronic system level design, the support of a seamless design flow becomes an important task. During the system design process, SystemC is used to develop a “Golden Reference Model” that provides a well-suited platform for specification, simulation, and verification of embedded systems. Based on the “Golden Reference Model,” an important task of the design process is to map applications, that have been described either in C++ or directly in SystemC, to the specific real-time operating system which is running at the target processor. Since a manual mapping approach is time-consuming and error-prone, the mapping process should be performed automatically. This paper presents a new method for automated generation of code for a specified operating system just by using an abstract XML representation of the RTOS API.     

Analysis and design of injection-locked LC dividers for quadrature generation

Injection-locked LC dividers for low-power quadrature generation are discussed in this paper. Modeling the circuits as regenerative frequency dividers leads to very simple analytical expressions for the locking band, phase deviation from quadrature and phase noise. Maximizing the ratio between the injected and the biasing current is beneficial to all the above parameters whereas reducing the tank quality factor improves locking band and quadrature accuracy, though at the expense of current consumption, for given output amplitude. To validate the theory, experiments have been carried on a 0.18-/spl mu/m CMOS direct conversion IC, embedding an injection-locked quadrature generator, realized for the Universal Mobile Telecommunication System. Frequency locking range as large as 24% and phase deviation from quadrature around 0.8/spl deg/ are measured while each divider consumes 2 mA. The phase noise of the quadrature generator is determined by the driving oscillator phase noise because the dividers contribution is easily made negligible up to hundreds of megahertz offset.     

一种相位实时跟踪调整的光伏并网发电模拟系统

本文设计了一种光伏并网发电模拟系统,研究符合国家电网标准的输出电流,减少并网发电系统中的高次谐波分量。本系统以STM32F103ZET6为主控器,采用降压变压器及电压比较器提取电网中高压交流电的零相位时刻作为参考相位,对发电模拟系统的输出与参考相位之间存在的相位差进行比例调节,提高系统跟踪相位的速度和系统的稳定性。测试结果表明,本文设计的光伏并网发电模拟系统可输出50Hz且频率偏差小于0.1Hz的正弦波,符合国家电网要求,验证了方案的可行性与有效性。     

信息安全芯片测试中测试图形实时生成的方法

本文概述了TPM(可信平台模块)安全芯片在信息安全建设中的重要作用,以及TPM安全芯片的特点及测试难点,在测试TPM安全芯片过程中,自动下载密码时,可以根据密码算法的具体情况,采用不同的方法实时生成密码测试图形.本文重点介绍2种在测试TPM安全芯片中测试图形实时生成的方法,这2种方法从生成特定的安全算法密码到对芯片进行密码写入都是自动的、连续的、实时的.经在泰瑞达J750测试平台上实现一款信息安全芯片量产测试,证明了这2种方法是可行性的,高效的.     

重大活动实时无线电管理系统构架探析

从重大活动无线电管理的需求和特点出发,结合我国重大活动中无线电管理的实际情况,提出了适合重大活动的实时无线电管理系统构架,并阐述了系统的构成和工作过程。     

虚拟演播室系统设备的分析与比较

目前,许多厂家致力于虚拟演播室技术的开发与研究,在把产品推向市场的同时并不断地改进与完善。面对市场上种类繁多的产品,本文力求站在专业用户的角度,对面临的选择做一个理性的思考。以下通过对VI犤Z犦SET公司的IBIS虚拟演播室系统和国内一些厂家的产品,在虚拟演播室系统的三个关键性环节（主机部分、跟踪部分和色键部分）的比较,对虚拟演播室系统的设备进行分析。１系统主机在虚拟演播室系统中,系统的硬件平台应该为软件运行提供强有力的保证,其衡量的标准关键在于它的实时计算能力、绘图能力和视频处理能力。IBIS虚拟演播…     

基于STM32系列单片机的数控正弦波逆变电源设计与实现

提出一种高性能全数字式正弦波逆变电源的设计方案。该方案分为前后两级,前级采用推挽升压电路将榆入的直流电升压到350V左右的母线电压．后级采用全桥逆变电路,逆变桥输出经滤波器滤波后,用隔离变压器进行电压采样,电流互感器进行电流采样,以形成反馈环节,增加电源输出的稳定性。升压级PWM驱动及逆变级SPWM驱动均由STM32单片机产生。减小了硬件开支。基于上述方案试制的400W样机,具有输出短路保护、过流保护及输入过压保护、欠压保护功能。50Hz输出时频率偏差小于0．05Hz,满载（400W）效率高于87％,电压精度为220V±1％,THD小于1．5％。     

Analysis and implementation of a real-time predictive currentcontroller for permanent-magnet synchronous servo drives

A real-time current controller for PWM inverter-fed permanent-magnet synchronous motor drives is presented and analyzed. The proposed current control scheme is based on predictive control with a parallel integral loop added to compensate for the inaccuracy of the motor model and for the variations of motor parameters and DC voltage source. The proposed current control scheme is analyzed and its performance is evaluated by computer simulation. An EPROM-based implementation is presented in which calculations and pulsewidth modulation are executed by lookup tables resulting in high-speed operation. The controller performance is evaluated using a prototype l kW PM synchronous servo drive. Experimental results are given and discussed     

Analysis of sliding frame R-ALOHA protocol for real-time distributed wireless networks

In this article, performance of sliding frame (SF) R-ALOHA protocols for real-time distributed wireless networks is investigated analytically and by simulation. First, a discrete Markov chain and Monte Carlo modeling are constructed to evaluate dynamic behavior of the protocol in transient state including distribution of the system stabilization time (SST) and the average number of successful terminals. Furthermore, a hierarchical decomposition is conducted to simplify steady state analysis, thus generating two one-dimensional Markov chains for closed-form performance of SF R-ALOHA under local wireless environment. Terminals with Poisson message arrivals and Poisson message length are analyzed. Consequently, performance indices, such as throughput, the average message delay, and packet dropping probability, are derived from the proposed analytic models. Capture effects on the SF R-ALOHA system in the presence of multipath and shadowing are also obtained by the Markov chain analysis. The numerical results from the analytic models are compared with that from simulation and equilibrium point analysis, proving correctness, accuracy, and scalability of the decomposition. The results also reveal performance characteristics of the SF R-ALOHA system.