接入网发展趋势和存在的问题

ＩＴＵ先后制定了ＡＮ接口建议Ｇ．９６４、Ｇ．９６５以及宽带接口建议Ｇ．９６７、１．４３２、Ｇ．９６６等。引人注目的接入技术有：铜线接入方面的ｘＤＳＬ、ＨＦＣ和非对称电缆调制解调器;光纤接入方面的Ｖ５接口技术、内置ＳＤＨ接入网、ＡＰＯＮ、ＳＤＶ等;无线本地环路以及宽带无线接入技术如ＬＭＤＳ、ＤＢＳ等。接入网的目标是建立全业务宽带接入网（ＦＳＮ）,最后文中指出了接入网建设中存在的问题。     

VLSI design investigation for low-cost, low-power FFT/IFFT processing in advanced VDSL transceivers

The problem of an efficient very large scale integration (VLSI) realization of the direct/inverse fast Fourier transform (FFT/IFFT) for digital subscriber line (DSL) applications is addressed in this paper. The design of scalable and very high-rate (VDSL) modem claims for large and high-throughput complex FFT computations while for massive and fast deployment of the xDSL family low-cost and low-power constraints are key issues. Throughout the paper we explore the design space at different levels (algorithm, arithmetic accuracy, architecture, technology) to achieve the best trade-off between processing performance, hardware complexity and power consumption. A programmable VLSI processor based on a FFT/IFFT cascade architecture plus pre/post-processing stages is discussed and characterized from the high-level choices down to the gate-level synthesis. Furthermore low-power design techniques, based on clock gating and data driven switching activity reduction, are used to decrease the power consumption exploiting the correlation of the FFT/IFFT coefficients and the statistics of the input signals. To this aim both frequency-division and time-division duplex schemes have been considered. The effects of supply voltage scaling and its consequence on circuit performance are examined in detail, as well as the use of different target technologies. Synthesis results for a 0.18 μm CMOS standard-cells technology show that the processor is suitable for real-time modulation and demodulation in scalable full-rate VDSL modem (64-4096 complex FFT, 20 Msample/s) with a power consumption of few tens of mW. These performances are very interesting when compared to state-of-the-art software implementations and custom VLSI ones.     

数字化脉冲激光引信探测系统设计与信号处理

针对以往模拟脉冲激光引信探测系统存在的测距误差较大的缺点,为进一步提高脉冲激光引信的测距精度,设计了一种数字化脉冲激光引信探测系统.该探测系统包括发射、接收和信号处理3部分,其中信号处理部分主要实现脉冲回波信号的高速实时采样与缓存、信噪比增强与时延估计.采用双通道ADC并行采样,实现了以200 MHz的等效采样频率对脉冲回波信号进行高速采样.当脉冲回波信号很微弱时,采用多脉冲相干平均算法提高了其信噪比,增强了对微弱回波信号的检测能力.通过最小二乘时延估计算法得到了回波时延,进而计算得到目标距离.测距实验结果表明:该探测系统测距精度较高,最大测距误差为0.25 m.     

DATA BYPASSING ARCHITECTURE AND CIRCUIT DESIGN FOR 32-BIT DIGITAL SIGNAL PROCESSOR

This paper presents a design method of ByPassing Unit（BPU） in 32-bit Digital Signal Processor（DSP）-MD32. MD32 is realized in 0.18 μm technology, 1.8V and 200 MHz working clock. It focuses on the Reduced Instruction Set Computer（RISC） architecture and DSP computation capability thoroughly, extends DSP with various addressing modes in a customized DSP pipeline stage architecture. The paper also discusses the architecture and circuit design of bypassing logic to fit MD32 architecture. The parallel execution of BPU with instruction decode in architecture level is applied to reduce time delay. The optimization of circuit that serial select with priority is analyzed in detail, and the result shows that about half of time delay is reduced after this optimization. Examples show that BPU is useful for improving the DSP＇s performance. The forwarding logic in MD32 realizes 8 data channels feedback and meets the working clock limit.     

A codec for HDTV signal transmission through terrestrial and satellite digital links

A codec for digital transmission of HDTV is described. The bit-rate compression algorithm is based on advanced techniques such as spatial discrete cosine transform (DCT), temporal differential PCM (DPCM), variable length coding. The codec is designed to operate with both the interlaced studio systems 1125/60 and 1250/50, and, thanks to the inherent flexibility of the packet structure, a wide range of line bit-rates can be used as a compromise between video quality and bit-rate constraints of the digital transmission link. The flexibility of the HDTV codec is highlightened through examples of applications over satellite digital links in practical situations.     

The Effect of Metric Modification on the Performance of TCM and Concatenated Systems Over Rayleigh Fading Channels

The performance improvement of conventional TCM schemes over frequency nonselective slow Rayleigh fading channels, caused by a slight modification on the metric calculation of the Viterbi decoder, is investigated in this paper. A statistical analysis of the Euclidean distances at the input of the Viterbi decoder is carried out to explain this improvement. Furthermore, the performance improvement of two concatenated coding systems incorporating the above modification, under the same conditions, is studied. The performance of the TCM and the concatenated systems is evaluated by Monte Carlo simulation. The results show that the examined systems, using the proposed modification on the metric calculation, achieve BER performances comparable to other codes and systems, especially designed for fading channels.     

A practical design of digital watermarking for video streaming services

A practical design of digital watermarking for video streaming services is proposed in this research. The information of a legitimate recipient is represented as a watermark, which is embedded in the video stream to serve as a cue to trace the recipient in case a clone of the video is illegally distributed. The watermark signals are designed to embed in some areas of video frames to benefit the video stream server, as the result of only partial actions required, including decoding, processing and re-encoding. The invariance of feature points and the self-similarity of hidden signals are further exploited to enable watermark detection without involving the original video. The watermark can decently survive transcoding processes and geometrical modifications of frames. The experimental results demonstrate the advantages of the proposed scheme in terms of watermark visibility, capacity and detection methodology.     

基带信号数字调制的设计与验证

数字信号的载波调制是数字通信中的关键技术,常用的载波调制技术有2ASK、2FSK、2PSK、QPSK、8PSK、4FSK等.这些电路的设计与验证用常规的方法来实现既费时又费力,借助于MultiSim10这一电子设计自动化工具,可以用VHDL建模的方法,实现基带信号数字调制的设计.使用在MultiSim10中创建的VHDL元件模型,设计出了基带信号常用的几种载波调制电路.通过观察分析电路输入输出波形,验证了载波调制和解调的实验结果.     

A co-designed coding,modulation and equalization scheme for the transmission of 155-52 Mbit/s data over a 72 MHz intelsat transponder. Part 2: Equalization

This paper reports on the application of co-designed coding, modulation and equalization techiques to an INTELSAT requirement for transmitting 155-52 Mbit/s data over a 72 MHz satellite channel. A specific solution as regards coding, modulation and equalization is proposed and analysed that differs from ‘standard’ concatenation in that the inner decoder integrates equalization, modulation and coding. In Part 2, a novel technique for integrating decision feedback equalization into the inner decoder is described. The gains in integrating the coding and equalization are shown to be significant for channels that need equalizing.     

数字倾角水平测试仪的研究与设计

角度测量在几何量测量中有着重要的地位,而倾角仪是测量平面角度的一种重要仪器.因此,倾角仪在道路桥梁、机器人技术、车电子控制、测绘仪器、建筑机械、设备安装、天线定位、海上平台监控等方面都有着广泛的应用,是人类生产活动中经常用到的一种工具.本文介绍了倾角仪的工作原理、传感器的选型,并以低功耗、精度高、全方位快速测量为目标,探究了倾角仪的测量原理及数据显示控制系统.     

程控交换机全数字音信号及多频信号设计方法

本文以新型数字交换机系统为背景,提出了全数字音信号和多频互控信号的设计方法。讨论了电路原理、编码方式,电平设计和脉冲信号的时序关系。最后给出了电原理图和试验数据结果。     

Performance evaluation of COFDM for digital audio broadcasting. I.Parametric study

This paper describes the performance of COFDM (coded orthogonal frequency division multiplexing) for digital audio broadcasting (DAB) over various multipath mobile radio channels. COFDM is a channel coding and modulation scheme which mitigates the adverse effects of fading by using wideband multicarrier modulation combined with time interleaving and a convolutional error correcting code. A guard interval is inserted at the transition between successive symbols to absorb the intersymbol interference created by the time domain spread of the mobile radio channel. The decoding process is performed using differential demodulation in conjunction with a soft decision Viterbi decoder. The COFDM evaluation is done by means of computer simulations. A parametric study of the proposed COFDM system is done in this first of a series of papers to determine the optimal system parameter values for operation at a radio frequency of 1.5 GHz. The results show that the parameter values proposed in the standard are indeed well suited for operation at 1.5 GHz. Using the set of optimal parameter values found, the COFDM performance is then evaluated in mobile radio channels typical of different geographical environments. Simulation results confirm the benefit that the system gains from frequency diversity found in the urban and hilly terrain areas     

宽带数字阵列雷达通道均衡方法的设计与实现

对于宽带数字阵列雷达,可以利用通道均衡技术减小通道内部的幅相起伏和通道之间幅相不一致所带来的性能恶化,然而常规的方法对噪声的影响较为敏感。本文首先提出了一种宽带通道频率响应特性测试的有效方法;其次讨论了标准通道选择方法和均衡滤波器特性提取方法,进而提出了一种改进的基于傅立叶变换法的均衡滤波器系数设计方法;最后提出了噪声条件下通道均衡效果评估方法。通过对均衡结果的分析,验证了本文方法的有效性。      

基于MSP430F169的水声遥控发射系统设计

随着水声通信技术的快速发展,水声遥控系统也已投入使用,它在水下通信、遥测及水下航行器的控制等方面有着广阔的应用前景.该设计基于微功耗单片机MSP430F169作为处理器设计路以便实现不同频率信号的产生、选择及显示,并选用D类功放对所产生的信号进行功率放大.系统软件根据所设计的电路进行移频编程,根据MFSK调制的基本原理,通过采用添加保护时间抵抗码间干扰的编码方案,完成不同遥控信号的产生、控制及显示.     

Le77D11/Le78D11用户线电话接口器件及其应用

Le77D11/Le78D11是Legerity公司生产的VoSLIC/VoSLAC芯片组.通过MPI编程接口配置寄存器,可实现不同要求的用户线接口的BORSCHT功能,用以满足不同国家的标准,具有广泛的应用性.介绍了Le77D11/Le78D11的性能及其应用.     

北高峰发射台信号传输和监控系统的设计应用

介绍了浙江广电集团北高峰发射台的概况和信号路由详细情况,论述了发射台电视信号的数字信号的传输分配以及电视信号的监测报警,并介绍电视发射机网管系统的应用.     

双环双通道接收数字式新算法的分析与设计

在把有方向性的双交叉环天线变为全向天线时,为了克服以往无法同时接收多个频率信号的问题,提出了一种水下导航中双环双通道接收甚低频信号的数字式新算法. 即两个通道的数字信号不在射频级进行组合,而在正交同步检波之后进行组合,实现了信号幅度的全向接收;至于信号相位的全向接收可由信号较强的单路同步检波结果计算实现. 分析和仿真结果表明：新算法设计合理有效,满足需求.     

Parallel vector processing of multidimensional orthogonal transforms for digital signal processing applications

This paper presents vector and parallel algorithms and implementations of one- and two-dimensional orthogonal transforms. The speed performances are evaluated on Cray X-MP/48 vector computer. The sinusoidal orthogonal transforms are computed using fast real Fourier transform (FFT) kernel. The non-sinusoidal orthogonal transform algorithms are derived by using direct factorizations of transform matrices. Concurrent processing is achieved by using the multitasking capability of Cray X-MP/48 to transform long data vectors and two-dimensional data vectors. The discrete orthogonal transforms discussed in this paper include: Fourier transform (DFT), cosine transform (DCT), sine transform (DST), Hartley transform (DHT), Walsh transform (DWHT) and Hadamard transform (DHDT). The factors affecting the speedup of vector and parallel processing of these transforms are considered. The vectorization techniques are illustrated by an FFT example.This work is supported in part by the National Science Foundation, Pittsburgh Supercomputing Center (grant number ECS-880012P) and by the PEW Science Education Program.     

在室内通信环境下UWB信号设计及性能分析

采用的脉冲波形在满足联邦通信委员会(FCC)发射要求的基础上,提出了在室内通信环境下,经过脉冲位置调制(PPM)的UWB信号延迟参数的优化设计方法,相对于传统的方法,性能有明显的提升。同时结合信号的数学模型,对信号的误码性能进行了分析与比较,这对于UWB系统在实际系统中的使用有很好的指导意义。