浅析控制贴片质量的关键因素

贴片质量一直困扰贴片机使用者，本文从元器件选择、贴片机结构与性能两个角度阐述了其如何影响贴片质量。以元器件尺寸、端头电极与引线电极、平整度、料带等方面细述如何选择元器件以提高贴片质量，并细述了如何选择与设置贴片机吸嘴和贴片压力来提高贴片质量。     

Switching Schemes for Reducing Capacitor Mismatch Sensitivity of Quasi-Passive Cyclic DAC

An alternately complementary switching is proposed to reduce the quasi-passive cyclic DAC error caused by capacitor mismatch, and a hybrid switching is adopted to further enhance its accuracy. With 1.1% moderate capacitor mismatch, the achievable effective number of bits is as high as 15. It is shown that a three-fold improvement in accuracy can be fulfilled by the proposed hybrid switching. Since the DAC owns better immunity to process variations, smaller capacitors can be utilized to diminish both chip cost and power consumption.      

Ergodic Properties for Multirate Linear Systems

Stochastic analysis of a multirate linear system typically requires the signals in the system to possess certain ergodic properties. Among them, ergodicity in the mean and ergodicity in the correlation are the most commonly used ones. We show that multirate operations and time-variant linear filtering can destroy these ergodic properties. Motivated by this fact, we introduce the notions of strong ergodicity in the mean and strong ergodicity in the correlation. We show that these properties are preserved under a number of operations, namely, downsampling, upsampling, addition, and uniformly stable linear (time-variant) filtering. We also show that white random processes with uniformly bounded second moments are strongly ergodic in the mean and that mutually independent random processes with uniformly bounded fourth moments are jointly strongly ergodic in the correlation. The main implication of these results is that if a multirate linear system is driven by white (independent) random processes with uniformly bounded second (fourth) moments, then every signal in the system is strongly ergodic in the mean (correlation) and therefore ergodic in the mean (correlation). An application of these results is also discussed     

Wavebeam Multiplication Phenomena to RF Power Distribution Systems of High-Energy Linear Accelerators

A new quasi-optical concept of electrically proof Delay Line Distribution System (DLDS) for high-energy electron/positron accelerators is proposed. In order to increase microwave power, used for particle acceleration, the concept assumes summing up of a few wavebeams in multimode rectangular waveguide. Operating by mutual phases of the wavebeams, to be produced by coherent sources, the system allows also a distribution of long multiplied RF pulses on a set of acceleration sections. Calculations of key components are fulfilled at 34 GHz frequency.     

线性码的周期分布与广义周期分布

本文提供了计算任意［ｎ，ｋ］线性码的周期分布｛｜＂Ｐｉ｜：１≤ｉ≤ｎ｝与广义周期分布｛｜Ｐｉ｜：１≤ｉ≤ｎ｝的方法，对任意线性码中以ｒ为周期的码字个数｜Ｄｒ｜和以ｒ为广义周期的码字个数｜Ｄｒ｜给出了一个普遍适用的上界和下界。     

大规模晶圆级焊球置放关键的成功因素

芯片规模封装是对焊球置放至晶圆、条和基板上有更快增长需求的技术之一。明确合适工艺所需的关键成功因素可以使我们确立一整套最佳的工作方法,并保证能达到生产能力、产量和置放焊球成本方面的目标。     

Robust Filtering for Linear Time-Invariant Continuous Systems

The problem of robust filtering for linear time-invariant (LTI) continuous systems subject to parametric uncertainties is treated in this paper through transfer function and polynomial representations, and then in the state-space domain. The basic idea consists of introducing the gradient of the estimation error with respect to the uncertain parameters in the optimization scheme via a epsiv-contaminated model. The general solution to the problem is given in the transfer function representation while, in the polynomial framework, the causal estimator is obtained by means of a spectral factorization and a Diophantine equation. The state-space realization of the causal estimator is discussed. Examples show the ability of the proposed technique to provide a reliable estimation in presence of model uncertainty.     

Criteria for Stability of Linear Control Systems

As it is well known,it is significant to know whether a matrix is an H-matrix or not in stability analysis of linear control systems. However,to distinguish H-matrices is difficult in real applications. In this paper,a practical extension of the sufficient conditions for H-matrices is investigated under some conditions. A larger scale of H-matrices which can be judged by the proposed method is shown by the numerical examples.     

Blind Linear MMSE Receivers for MC-CDMA Systems

This paper studies blind constrained minimum output energy (CMOE)-based and subspace-based linear minimum mean-squared-error (LMMSE) detectors for multi-carrier code division multiple access (MC-CDMA) systems. By imposing quadratic weight constraint, the CMOE detector is made more robust against signature waveform mismatch, and a better performance over the standard CMOE detector is obtained. Because of separation of signal and noise subspaces, the more complicated subspace-based LMMSE detector has better performance than the CMOE detector. The recursive subspace tracking algorithms are also investigated for the subspace-based MMSE receiver. Numerical results show that the steady-state performance of the robust CMOE detector is close to the subspace-based MMSE method. The blind mode decision-directed LMMSE detection is studied where the blind detectors are used for initial adaptation. Numerical simulations illustrate that the blind mode decision-directed MMSE detection substantially improves the system performance when the frequency-selective channel is slowly-varying     

Closed-Loop MIMO系统线性预编码技术

本文讨论了Closed-Loop MIMO系统在有限反馈资源下如何进行反馈的方法,即两种发射端线性预编码的思路,特别是其中的反馈码本设计问题。由于需要接收端向发射端反馈信道信息,而上行反馈资源又非常有限,所以发射端线性预编码技术成为解决把MIMO技术应用于新一代蜂窝系统或无线局域网的关键问题之一,具有无限广阔的发展前景。     

Algebraic Methods for Optimizing Constant Multiplications in Linear Systems

Constant multiplications can be efficiently implemented in hardware by converting them into a sequence of nested additions and shift operations. They can be optimized further by finding common subexpressions among these operations. In this work, we present algebraic methods for eliminating common subexpressions. Algebraic techniques are established in multi-level logic synthesis for the minimization of the number of literals and hence gates to implement Boolean logic. In this work we use the concepts of two of these methods, namely rectangle covering and fast extract (FX) and adapt them to the problem of optimizing linear arithmetic expressions. The main advantage of using such methods is that we can optimize systems consisting of multiple variables, which is not possible using the conventional optimization techniques. Our optimizations are aimed at reducing the area and power consumption of the hardware, and experimental results show up to 30.3% improvement in the number of operations over conventional techniques. Synthesis and simulation results show up to 30% area reduction and up to 27% power reduction. We also modified our algorithm to perform delay aware optimization, where we perform common subexpression elimination such that the delay is not exceeded beyond a particular value.

Reconfiguration of Distribution Systems using the Newton Method in Quadratic Formulations

The distribution system reconfiguration problem is concerned with finding the state of all switches in a set of primary distribution feeders so that a given objective function is optimised, typically the minimisation of the total electrical loss. Constraints such as Kirchhoff’s Current Law (KCL) and branch capacity are usually enforced. An additional and important constraint is also imposed so that the obtained solutions are all radial. This optimisation problem is a Mixed-Integer Non-Linear Optimisation Problem, in which the integer variables represent the state of the switches and the continuous variables represent the current flowing through the branches. The paper develops new quadratic formulations for the continuous part of the problem. It is shown that all the formulations lead to convex problems, which guarantees that the global minimum is unique and hence allows an efficient application of the standard Newton Method. The paper also presents a new integer search based on the well-known Branch-and-Bound Method. Results from the application of the proposed approaches to three different distribution systems are presented and discussed.     

Checksum-Based Probabilistic Transient-Error Compensation for Linear Digital Systems

In this paper, a probabilistic compensation technique for minimizing the effect of transient errors effect is proposed. The focus is to develop a compensation technique for DSP applications in which exact error compensation is not necessary and end-to-end system level performance is degraded minimally as long as the impact of the ldquonoiserdquo injected into the system by the transient errors is minimized. The proposed technique, called checksum-based probabilistic compensation, uses real-number checksum codes for error detection and partial compensation. Traditional coding techniques need a code of distance three and relatively complex calculations for perfect error correction. Here, it is shown that a distance-two code can be used to perform probabilistic error compensation in linear systems with the objective of improving the signal-to-noise ratio in the presence of random transient errors. The goal is to have a technique with small power and area overhead and to perform compensation in real time with negligible latency. The proposed technique is comprehensive and can handle errors in the combinational circuitry and storage elements. Comparison against a system with no error correction shows that up to 13-dB SNR improvement is possible. The area, power, and timing overheads of the proposed technique are analyzed.     

FIR Filtering for Discrete-Time Markov Jump Linear Systems

This paper is concerned with finite impulse response (FIR) filtering problem for discrete-time linear system which possesses stochastically jumping parameters described by a finite-state Markov process. An FIR filter processes the measured inputs and outputs on a finite receding horizon linearly and the filter gain is obtained by minimizing variance of the error between real state and estimated one. According to inverse computation, system matrix is always assumed to be non-singular. In terms of engineering application, we must have complete access to the current time jump mode. The FIR filter is presented in batch form and recursive form, respectively, and Kalman filter is also addressed for comparison. Finally, a numerical example is given to illustrate the design procedure and their effectiveness.     

The AOR Iterative Method for Preconditioned Linear Systems

In Ref.[1], two preconditioned methods for linear system Ax = b (1) are introduced, where nnAC×∈ ,nb∈ C are given and nx ∈ C is unknown. It is given as the following preconditioned methods. The preconditioned linear system A~ x= b~ (2) where A~ = (I S~)A, and b~ = (I S~)b with S~=????????????? 000000001LMMMMLLna and the preconditioned linear system A =(3) 0where I is the identity matrix, L and U are strictly lower and upper triangular matrices obtained from A, respectively. The c…     

线性时滞系统的时滞相关稳定性

本文讨论了线性时滞系统x(t)=Ax( ) Bx(t-τ)渐近稳定的时滞界限，利用Lyapunov—Krasovskii泛函及H∞范数理论，获得了线性时滞系统时滞相关稳定的充分条件，同时得到了一个新的时滞界限的代数估计式。将本文结果应用于实际系统，计算简单，并且扩大了时滞的稳定区域，降低了对时滞的保守性。分析结果还表明，线性时滞系统的稳定性可以转化为一定常无时滞的线性系统的H∞控制问题。     

Gain-Constrained Kalman Filtering for Linear and Nonlinear Systems

This paper considers the state-estimation problem with a constraint on the data-injection gain. Special cases of this problem include the enforcing of a linear equality constraint in the state vector, the enforcing of unbiased estimation for systems with unknown inputs, and simplification of the estimator structure for large-scale systems. Both the one-step gain-constrained Kalman predictor and the two-step gain-constrained Kalman filter are presented. The latter is extended to the nonlinear case, yielding the gain-constrained unscented Kalman filter. Two illustrative examples are presented.