改进的状态反馈算法

基于李亚普诺夫方程的状态反馈增益算法是极点配置算法中比较常见的一种.为保证方程有解,该算法要求系统的开环和闭环极点不能重合.改进了状态反馈增益算法,可以任意配置线性定常能控系统的极点.     

An improved interconnection technique

This paper deals with an improved interconnection technique for use with thin film hybrid ICs, SAW devices and semiconductor devices based on shallow diffusions eg. MOS-FETS $\text{h}\text{f}$ transistors etc., In this technique, the thin film strips of specific width and length (or shape) formed photolithographically on specific substrates are floated off and used for bonding the contact pads to the package leads by thermocompression/ultrasonic bonding methods. The technique has been successfully used for bonding SAW devices and discrete MOS-FETS.     

一种改进的图像匹配技术

图像匹配技术具有广泛应用,寻求高效率、高精度、健壮性好以及复杂度低的图像匹配算法是当下计算机视觉中的研究重点之一.本文对各种特征点提取和匹配算法进行了对比分析,在此之上提出了一种改进的特征提取以及图像匹配算法,提高了匹配算法的鲁棒性.     

An efficient algorithm for the control of a microprocessor-basedsingle-phase to three-phase cycloconverter

An efficient algorithm is designed to calculate the intersection points of a cosine wave and a reference wave in a cycloconverter. The proposed algorithm requires a smaller number of comparisons to calculate the required intersections than the conventional linear search method; hence, processor time is reduced. The algorithm can be implemented on a microprocessor-based cycloconverter multiple feedback system. The reduced number of comparisons as compared with the linear search method make the algorithm useful for many applications in microprocessor-based control circuits     

An improved common-mode feedback loop for the differential-difference amplifier

Unconditional stability of the high-gain amplifiers is a mandatory requirement for a reliable steady-state condition of time-discrete systems, especially for all blocks designed to sample-and-hold (S/H) circuits. Compared to differential path, the common-mode feedback loop is often affected by poles and zeros shifting that degrades the large signal response of the amplifiers. This drawback is made worse in some well-known topologies as the difference-differential amplifier (DDA) that shows non-constant transconductance and poor linearity. This work proposes a body-driven positive-feedback frequency compensation technique (BD-PFFC) to improve the linearity for precision DDA-based S/H applications. Theoretical calculations and circuit simulations carried out in a 0.13 μm process are also given to demonstrate its validity.     

一种改进的激光反馈干涉测振系统

通过引入匹配透镜而改进了激光反馈干涉测振系统,使系统能够测量具有粗糙表面的样品以及线度小至微米级的样品。还大大放宽了样品的对准容差约一个量级。     

一种改进的MC-CDMA系统ORC技术

基于对频率非选择性Rayleigh衰落信道中采用ORC(orthogonality restoring combining)技术的MC-CDMA系统误码率下边界的分析,提出了忽略最弱子载波(信道衰减系数最小的子载波)的改进ORC检测方案。仿真结果表明,该方案比传统ORC在性能上有很大提高,比较接近MMSEC技术;如果忽略过多的弱子载波反而会影响用户间扩频码的正交性,引起系统性能恶化。改进方案具有随子载波数线性增长的运算复杂度,是一种比较实用的MC-CDMA系统检测技术。     

An improved PWM technique for AC choppers

A novel pulse-width-modulated (PWM) control technique for AC choppers is proposed that has the advantages of enabling linear control of the fundamental component of the output voltage and complete elimination of its harmonics up to a specified order. Theoretical comparisons are made with other basic PWM techniques, and the computed performance indicates the superiority of the present method. The carrier wave required for the new technique is easily determined as a modification of a basic triangular wave that enables these beneficial features to be obtained over the full range of chopper operation and can be implemented by the storage of relatively simple control equations. An experiment has verified the feasibility of the method as applied to the control of a single-phase automatic voltage regulator. In the experiment, the modified triangular carrier wave is used to generate the required PWM switching function. Good agreement is obtained between the calculated and experimental results     

An adaptive technique for transmit antenna diversity with feedback

Transmit antenna diversity (TAD) has been employed for third-generation wireless systems. We propose an adaptive technique for TAD with feedback. It is shown that the proposed adaptive technique can efficiently increase the number of transmit antennas without significantly increasing the feedback bit rate under ideal conditions. As a result, we can increase the number of transmit antennas and expect a performance improvement. Unfortunately, the proposed adaptive technique suffers from channel variation and error propagation due to feedback error. From this, the use of the adaptive technique shall be limited: it can be effective for indoor communications and for pedestrians with a reliable feedback channel     

一种改进的数字同频直放站自适应反馈干扰抑制算法

基于数字地面电视广播(Digital Terrestrial Television Broadcasting,DTTB)同频直放站的回波干扰抑制,提出了一种变步长块LMS(Variable Step- size Block Normalized Least Mean Square,VSSBNLMS)自适应算法.此算法的目的是为了提高传统回波干扰抑制的自适应算法的收敛速度和降低计算复杂度.其将输入信号分为长度相等的块,在每一个数据块内,权值向量只更新一次,有效地降低了计算复杂度.另外,该算法通过输出误差控制更新步长的变化,与传统的归一化LMS(NLMS)和块LMS(BLMS)算法相比,提高了收敛速度.仿真结果表明,该算法具有良好的收敛速度和回波干扰抑制性能.     

基于锁相环的载波跟踪改进技术

载波跟踪作为现代通信技术的一个重要组成部分,主要用于通信接收端的载波恢复,由于信号传输过程中各种因素的影响,接收端必须采用载波跟踪技术来消除频偏的影响,文中针对常见的锁相环技术,提出了一种基于限幅的鉴相方法,将其应用于QPSK判决反馈环路中,仿真结果表明,该方法减轻了环路输出频率和相位的抖动,有效提高了载波的跟踪精度。     

An improved calibration technique for free-space measurement ofcomplex permittivity

A calibration technique for free-space measurement of the permittivity and conductivity has been developed, taking account of antenna-medium coupling. Thus, the accuracy is improved compared to previously used calibration. Two examples are given to illustrate this improvement     

An improved frequency compensation technique for CMOS operational amplifiers

The commonly used two-stage CMOS operational amplifier suffers from two basic performance limitations due to the RC compensation network around the second gain stage. First, it provides stable operation for only a limited range of capacitive loads, and second, the power supply rejection shows severe degradation above the open-loop pole frequency. The technique described provides stable operation for a much larger range of capacitive loads, as well as much improved V/SUB BB/ power supply rejection over very wide bandwidths for the same basic operational amplifier circuit. The author presents a mathematical analysis of this new technique in terms of its frequency and noise characteristics followed by its implementation in all n-well CMOS process. Experimental results show 70-dB negative power supply rejection at 100 kHz and an input noise density of 58 nV/(Hz)/SUP 1/2/ at 1 kHz.     

一种改进的离散代数重建算法(DART)

医学CT中的图像往往由几种已知的灰度值组成,利用这些先验知识可降低重建条件提高图像重建质量。因此提出一种基于联立迭代算法(SIRT)的离散代数重建算法(DART),并且通过实验实现了在少数投影数目和小角度范围下的图像重建,并与其他几种传统的重建算法进行了比较,结果显示DART能从更少的投影数据下更精确地重建出图像同时有效地抑制了噪声。     

An adaptive approach to suppress powerful impulsive interference

In this paper the problem of impulsive noise suppression by using adaptive prediction technique is considered. The Time Domain Notch Filter structure and a procedure to estimate the filter coefficients are proposed. The considered algorithm is linear and does not require any auxiliary reference input. Performance evaluation indicates that the use of this algorithm does not change the signal-to-noise ratio (SNR) whose value remains almost independent of impulsive interference power. On the other hand, the signal-to-impulsive interference ratio (SIR) in the output increases with a decrease in the input SIR. This property of the proposed algorithm is the most essential difference between it and the commonly employed algorithms. The results of computer simulation of a noncoherent detection system applied to the on-off-keying modulation are given. The obtained results confirm that the proposed algorithm enables a transmission in the background of high power impulsive interference.     

An initialization technique for improved MTI performance in phased array radars

A technique is described for employing recursive digital moving-target-indicator (MTI) filters in phased array radars without the undesirable transient effects normally encountered in these filters.     

An approach to suppress speckle noise and enhance edge

Anisotropic diffusion has good effect on reducing noise and preserving edge, but it may lose some details due to the blocky effect and can not suppress speckle effectively. The Laplacian factor is used to process the observed image which is considered as a piecewise planar image, so the Fourth Order Anisotropic Diffusion （FOAD） can avoid the blocky effect. The edge is preserved and enhanced by the Line Edge Detector （LED） based on stick technique and hypothesis test optimizing method. An approach called the Fourth Order Anisotropic Diffusion and Edge Enhancing （FOADEE）, where the LED is combined with the FOAD, is presented. For quantitative evaluation and comparison with the LED, the FOAD and the FOADEE, two parameters as measure of the noise suppression and edge preservation are introduced. It is proved that the novel method can not only suppress speckle prominently but also preserve even enhance edge and useful details effectively by applying it to the phantoms and tissue images.     

An experimental adaptive array to suppress weak interfering signals

An experimental adaptive antenna system to suppress weak interfering signals is described. It is a sidelobe canceller with two auxiliary elements. Modified feedback loops are used to control the array weights. The received signals are simulated in hardware for parameter control. Digital processing is used for algorithm implementation and performance evaluation. The experimental results are presented. They show that interfering signals as much as 10 dB below the thermal noise level in the main channel are suppressed by 20-30 dB. Such a system has potential application in suppressing the interference encountered in direct broadcast satellite communication systems     

An improved iterative technique for the quasi-TEM analysis ofgeneralized planar lines

The generalized bioconjugate gradient method (GBGM) and fast Fourier transform (FFT) algorithm are used for the quasi-transverse electromagnetic (TEM) analysis of generalized multistrip lines embedded in multilayered lossless/lossy, iso/anisotropic dielectric and/or magnetic media. Important computational improvement is achieved by including asymptotic extraction techniques in the determination of the spatial Green's function matrix. Comparisons with other iterative procedures are presented. Several practical structures are analyzed and numerical results are compared with previously published data