A Novel Time-Domain Approach for Extracting Broadband Models of Power Delivery NetworksWith Resonance Effect

Resonance noise, or power/ground bounce noise, on the power and ground planes of high-speed circuit packages is one of the main concerns of signal integrity or power integrity issues. A novel time-domain approach is proposed to synthesize the broadband models of the power/ground planes with resonance effect. Using waveforms either from measurements by time-domain reflectrometry or simulations by the finite-difference time-domain method, the time-domain step response of the planes is characterized with a pole-residue representation obtained through the matrix pencil method. Lumped circuit equivalent circuit models are then synthesized through the pole-residue representations. The synthesized model can accurately predict the resonance behavior of power/ground planes over a wide frequency range. These models can be efficiently incorporated into the currently available circuit simulator such as HSPICE for the consideration of power/ground bouncing noise in high-speed circuits. Three cases are tested to demonstrate the validity and broadband accuracy of the proposed approach.      

A Broadband and Parametric Model of Differential Via Holes Using Space-Mapping Neural Network

This letter presents a novel broadband and completely parametric model of differential via holes by virtue of the space-mapping neural network technique. This model consists of a neural network and an equivalent circuit that is utilized to account for various EM effects of differential via holes. The neural network is trained to learn the multi-dimensional mapping between the geometrical variables and the values of independent circuit elements in the equivalent circuit. Once trained with the EM data, this model provides accurate and fast prediction of the EM behavior of differential via holes with geometry parameters as variables. Experiments in comparison with measurement data and EM simulations are included to demonstrate the merits of this new model in both the frequency and time domains.      

一种分析双绞线串扰的时域方法

针对双绞线的特殊结构,提出了一种分析单线与双绞线时域串扰特性的简易方法。将单线和双绞线一起看作一组均匀多导体传输线按特定方式的级联,应用广义多端口网络概念,建立组间的电压控制方程,每一组多导体传输线采用时域有限差分方法进行求解,进而确定单线与双绞线的串扰电压时域波形。仿真结果与实验结果吻合较好,验证了该时域方法的正确性。     

Exact solution of a π-pulse problem

The exact solution describing steady-state resonant pulse propagation in a two-level inverted medium is given. This steady-state pulse is often referred to as a 180° or π-pulse. No approximation of a slowly varying envelope is made, and hence the solution satisfies the second-order wave equation as well as the equations of motion of the density matrix of the system. As a result the theory is able to describe very short pulses, whose width can be of the order of the period of the optical carrier. The model for the system includes a nonresonant loss and a finite value of the transverse relaxation time T2, but neglects dispersion in the host medium. The steady-state pulse is found to be frequency modulated and asymmetric in shape.     

一种通用的仿射不变特征区域提取方法

本文利用尺度-空间理论和自相关矩阵的局部形状提出了一种通用的提取仿射不变特征区域的方法.首先,在尺度-空间中对图像的归一化高斯微分求三维局部极大值获得特征点和特征尺度位置,然后在特征点的特征尺度上用自相关矩阵刻画局部的灰度变化,提取的椭圆区域即为仿射不变特征区域.在此通用方法框架下构造了Harris3D、Laplace3D、Hessian3D和Localjet43D四种仿射不变特征区域算法.实验结果表明这四种算法都具有照度、旋转和尺度不变性.用本文设计的一种仿射不变性仿真实验方法验证了算法的仿射不变性.比较四种算法发现除了Harris3D性能稍差外其他三种算法性能接近.     

一种新的宽带信号正交分量的解调方法

在D通道均匀DFT分析滤波器组基础上给出了一种新的信号正交分量的解调结构 ,为解调宽带信号 (B fc)的正交分量 ,系统采用两组D通道均匀DFT分析滤波器组通带互补方法 ,以克服单组滤波器中滤波器的非理想性所造成的信号失真。在频域中当信号频谱处于两个或更多个滤波器通道时 ,通过频谱组合办法直接得到实信号的正半谱或负半谱。在载波频率已恢复的情况下给出了IQ正交分量的解调算法。仿真证明该系统结构和算法的正确性和高效性     

Variation of diffusion length with processing in dielectrically isolated π-silicon tubs

The variation of minority-electron diffusion length with processing in dielectrically isolated π-silicon tubs is investigated using electron-beam-induced current measurements. The analysis of these measurements is complicated by the six boundary conditions on the π-silicon. The diffusion lengths measured in virgin π-tub silicon are ≤ 250 µm while those in π-silicon undergoing a phosphorus getter are >> 250 µm. The determination of exact values for the diffusion lengths as a function of processing are not possible without a more complete understanding of the parasitic effects of the inversion region at the tub walls. Trends in the diffusion lengths are indicative of trends in the carrier lifetime, which are critical in the high-voltage applications for silicon tubs.     

The Pulsed-Field Multiport Antenna System Reciprocity Relation and Its Applications—A Time-Domain Approach

A novel time-domain approach to the derivation of the pulsed electromagnetic field multiport antenna system reciprocity theorem is presented. The theorem interrelates the field and system properties in two states: the transmitting state and the receiving state. General time-domain Thevenin (voltage-source, impedance-based) and Norton (electric-current source, admittance-based) type equivalent circuits are constructed for antenna systems whose local properties are described in terms of multiport Kirchhoff circuits. Applications to an indoor wireless communication performance analysis and the analysis of cosmic microwave background radiation measurement are briefly indicated. Numerical results are provided for the pulsed-field transfer between two wire loops, a configuration that is representative for the operation of wireless telecommunication systems and for the pulsed-field EM interference analysis in nano-electronic integrated circuit devices.     

宽带网络差异化服务模式分析

近年来，宽带接入用户数增幅显著，但运营商却并未从中获益，同时网络缺乏对高质量业务的支撑能力也限制了互联网业务的发展。通过分析IP网络承载业务的特点，得到差异化建设的目标，进而从当前的网络能力、业务需求两方面分析得出宽带网络差异化的模式。     

A Time-Domain Based Approach for Short-Term Fading Depth Evaluation in Wideband Mobile Communication Systems

In this paper a time-domain technique for wideband fading depth evaluation, is proposed, which is applicable to both Line-of-Sight and Non-Line-of-Sight cases, and the probability functions of the wideband received power are derived, contributing for filling in the gap of short-term fading characterisation in wideband systems. Application examples for different systems, namely GSM, UMTS and HIPERLAN/2, working in different standard reference environments, are shown. As expected, it is observed that Rayleigh and Rice distributions are appropriate for evaluating the fading margins for GSM in some environments; nevertheless, for UMTS and HIPERLAN/2, fading margins are usually well below the ones obtained from considering these narrowband distributions, the differences reaching up to around 10 and 13 dB, respectively. A simple relationship between the physical and the geometrical environment properties, and the rms delay spread of the propagation channel is also proposed, establishing a relationship between two models independently derived by different authors. Using the proposed relationship, fading depth results from the proposed time-domain technique are compared with the ones for an environment-geometry based one, and a good agreement is verified. The difference in fading depth between both approaches is roughly below 2 dB. Filipe D. Cardoso received the Licenciado, M.Sc. and Ph.D. degrees in Electrical and Computer Engineering from IST/Technical University of Lisbon in 1991, 1996 and 2004, respectively. Since 1994 he has been with the Department of Electrical Engineering of EST/Polytechnic Institute of Setúbal, Setúbal, Portugal, where he is an Adjunct Professor in the Telecommunications area. He is also a researcher at the Telecommunications Institute, Lisbon. He has been a member of COST 273 and IST/FLOWS European projects and is involved in the Network of Excellence in Wireless Communications (NEWCOM). He has authored papers in national and international conferences and journals, for which he has also served as a reviewer. His research interests include wireless/mobile channel characterisation and modelling and future Mobile Broadband Systems. Luis M. Correia received the Ph.D. in electrical and computer engineering from IST/Technical University of Lisbon in 1991, where he is currently a professor in telecommunications, with a focus on wireless/mobile communications in the areas of channel characterisation, traffic, services, and cellular planning. He as acted as a consultant for Portuguese GSM operators and for the telecommunications regulator. Besides being responsible for research projects at the national level, he was or is part of various ones within European frameworks (RACE, ACTS, and IST). He participated in and was co-editor of the Final Report for COST 231, Chairman and editor of the Final Report for COST 259, and is currently Chairman of COST 273. He was and is responsible for the supervision of students at both the M.Sc. and Ph.D. levels. He has authored papers and communications in international journals and conferences, for which he has also served as a reviewer, has been a co-editor of a special issue of a journal on wireless broadband systems, and is currently the editor for Wireless Systems in the European Transactions on Telecommunications. He as served as evaluator and auditor in ACTS, ESPRIT and IST frameworks. He was Chairman of the Technical Program Committee of PIMRC 2002.     

Test of Mechanical Failure for Via Holes and Solder Joints of Complex Interconnect Structure

It is known that certain faults associated with the process might be generated in any phases of the fabrication and assembly of the complex interconnection structure in a high-speed PCB composed of via holes, solder joints and traces, which will inevitably discount the electrical performance of the circuit. To address the issue, a fault-voltage detection method is proposed in this paper, firstly the equivalent fault circuit of the complex interconnection structure in high-speed PCB is scanned to extract the fault voltage, then the optimal function curve can be fitted out by the least squares method based on the faultless voltage. The empirical research on the via hole crack and solder joint void have validated that this method can effectively avoid the false tests derived under the low-frequency, major-fault and high-frequency, minor-fault conditions, and can also depict more accurately how the fault parameter varies with the changes in the frequency and fault degree, and it bears a relatively strong applicability in minor-fault of hiht-speed PCB tests.     

一种带孔外壳对天线辐射场抗干扰效应的计算模型和方法

由于不同型号外壳上都具有通风孔、散热孔、通光孔等小孔,研究外壳上小孔对天线辐射场的影响效应就十分必要,建立模型的主要意义在于:通过分析天线辐射场从小孔处渗透入壳内的衍射波分布状态,有助于了解小孔衍射对外壳电磁防护能力的影响,并找到该辐射场对壳内电子元件产生干扰最强的位置,从而为外壳抗干扰效应的分析和电磁敏感元件的安装定位提供参考。针对小孔的特点研究其衍射效应,文章建立一种带孔外壳对天线辐射场抗干扰效应的计算模型,给出计算通过小孔的电磁辐射场的计算方法,为电磁敏感器件的定位提供参考。     

A Design-for-Digital-Testability Circuit Structure for Σ- ∆ Modulators

A design-for-digital-testability (DfDT) switched-capacitor circuit structure for testing Sigma-Delta modulators with digital stimuli is presented to reduce the overall testing cost. In the test mode, the DfDT circuits are reconfigured as a one-bit digital-to-charge converter to accept a repetitively applied Sigma-Delta modulated bit-stream as its stimulus. The single-bit characteristic ensures that the generated stimulus is nonlinearity free. In addition, the proposed DfDT structure reuses most of the analog components in the test mode and keeps the same loads for the operational amplifiers as if they were in the normal mode. It thereby achieves many advantages including lower cost, higher fault coverage, higher measurement accuracy, and the capability of performing at-speed tests. A second-order Sigma-Delta modulator was designed and fabricated to demonstrate the effectiveness of the DfDT structure. Our experimental results show that the digital test is able to measure a harmonic distortion lower than -106 dBFS. Meanwhile, the dynamic range measured with the digital stimulus is as high as 84.4 dB at an over-sampling ratio of 128. The proposed DfDT scheme can be easily applied to other types of Sigma-Delta modulators, making them also digitally testable.     

A Parametric Approach to Suboptimal Signal Detection in α-Stable Noise

This paper deals with the detection of a known deterministic signal embedded in alpha-stable noise. The implementation of the optimal receiver requires the explicit expression of the probability density function (pdf) of the noise. Unfortunately, since there exists no closed-form for the pdf of alpha-stable distributed random variables, numerical integrations are required. To avoid such numerical approximations, we suggest a low-complexity parametric suboptimal detector well matched to essential properties of alpha-stable noises. This receiver does not require the explicit expression of the noise pdf. In addition, parameter optimization is fast for several optimization criteria and the selected receiver allows retrieval of the optimal Gaussian detector (matched filter) as well as the locally optimal detector in the Cauchy context. The performance of the detector is studied and a comparison with the optimal solution along with a variety of classical detectors is given. The robustness of the detector against the signal amplitude and the stability index alpha of the noise is discussed     

A Reduced-CP Approach to SC/FDE Block Transmission for Broadband Wireless Communications

For conventional cyclic prefix (CP)-assisted single-carrier/frequency-domain equalization (SC/FDE) implementations, as well as for orthogonal frequency-division multiplexing (OFDM) implementations, the CP length is known to be selected on the basis of the expected maximum delay spread. Next, the data block size can be chosen to be large enough to minimize the CP overhead, yet small enough to make the channel variation over the block negligible. This paper considers the possibility of reducing the overall CP assistance, when transmitting sequences of SC blocks, while avoiding an excessively long fast Fourier transform window for FDE purposes and keeping good FDE performances through low-complexity, noniterative receiver techniques. These techniques, which take advantage of specially designed frame structures, rely on a basic algorithm for decision-directed correction (DDC) of the FDE inputs when the CP is not long enough to cope with the time-dispersive channel effects. More specifically, we present and evaluate a novel class of reduced-CP SC/FDE schemes, which takes advantage of a special frame structure for replacing "useless" CP redundancy by fully useful channel coding redundancy, with the help of the DDC algorithm. When using the DDC-FDE technique with these especially designed frame structures, the impact of previous decisions, which are not error-free, is shown to be rather small, thereby allowing a power-efficiency advantage (in addition to the obvious bandwidth-efficiency advantage) over conventional block transmission implementations under full-length CP. Additionally, the DDC algorithm is also shown to be useful to improve the power efficiency of these conventional implementations     

一种在汉语文本中抽取重复字串的快速算法

词典未登录词的处理是自然语言处理不可或缺的研究方向.抽取文本中重复出现的字串是抽取未登录词最为直接简便的方法.以往算法运行速度较慢,无法满足海量文本快速处理的要求.遵循“左结合优先”和“最长匹配”原则,本文提出一种快速算法:位置记忆跳跃匹配.该方法最差情况下时间复杂度为o(t²),其中t为重复字串的重复次数.比较实验表明,本方法速度提高明显,数据结构简单,处理过程一次扫描完成.     

A Power Optimized Continuous-Time ∆Σ ADC for Audio Applications

We present design considerations for low-power continuous-time modulators. Circuit design details and measurement results for a 15 bit audio modulator are given. The converter, designed in a 0.18 mum CMOS technology, achieves a dynamic range of 93.5 dB in a 24 kHz bandwidth and dissipates 90 muW from a 1.8 V supply. It features a third-order active-RC loop filter, a very low-power 4-bit flash quantizer, and an efficient excess-delay compensation scheme to reduce power dissipation.     

A New Approach in the Computation of Ultrahigh Degree Equal-Ripple Polynomials for 90°-Coupler Synthesis

An improved efficient numerical method for the computation of ultrahigh degree equal-ripple polynomials, necessary for the synthesis of multielement 90° coupler, is presented. The highest degree computed was N=201 with an accuracy better than 10/sup -20/. For the calculation of the impedances of the equivalent stepped impedance filter an optimization procedure is also described. Finally, based on the N coupling factors k/sub i/ of the sections, the continuous coupling curve is achieved using spline interpolation. Experimental results of a continuously tapered 8.34-dB coupler constructed in three-layer polyolefin stripline are presented.     

A Broadband and Miniaturized Common-Mode Filter for Gigahertz Differential Signals Based on Negative-Permittivity Metamaterials

A novel wideband and miniaturized common-mode noise suppression filter is proposed based on the concept of an effective negative-permittivity metamaterial (MM) transmission line (TL). The propagation properties for the odd and even modes in the proposed structure are derived from the TL theory and Bloch theorem. Two- and four-port equivalent-circuit models are developed to explain the common-mode suppression characteristics. The dispersion relation has a good agreement with the full-wave simulation and measurement result. Based on the low-temperature co-fired ceramic fabrication technology, miniaturized common-mode filters with four and eight cells are realized using the concept of the effective negative-permittivity MM. For the four-cell structure, the filter size is $0.16~{mmb{lambda}}{hbox{g}} times 0.26~{mmb{lambda}}{hbox{g}}$ with the corresponding real size of ${hbox{3.2}}~{hbox{mm}}times {hbox{5.12}}~{hbox{mm}}$. It is found that the common-mode noise can be reduced over 10 dB from 3.8 to 7.1 GHz with the fractional bandwidth of 60% in the frequency domain, and is reduced over 50% for voltage amplitude in the time domain. More importantly, the differential signal integrity, in terms of insertion loss and group delay in the frequency domain and eye diagrams in the time domain, is not degraded within the wide stopband. To our best knowledge, it is the first broadband common-mode filter designed for gigahertz differential signals based on the concept of MM TL with most compact size.