Design of minimum sensitivity multiple loop feedback bandpass active filters

A method is described for determining multiple loop feedback topologies which yield minimum sensitivities for symmetrical, all-pole bandpass filters. The procedure begins with a follow-the-leader feedback (FLF) topology and additional feedback loops are constructed until minimum sensitivity is achieved. Filters comprised of identical second-order sections and non-identical sections, respectively, are considered.     

Frequency limitations of active-R filters using operational amplifiers

Active-R filters are designed using internally compensated operational amplifiers (OA) and resistors only. A one-pole or 6 dB roll off model for the PA's is assumed in these designs. This model is adequate for active-RC filters. However, for active-R filters such an assumption leads to serious accuracy as well as stability problems, thereby limiting the highest operating frequency of these filters to well below their potential maximum. It is shown in this article that a two-pole or 12 dB roll off model more accurately reflects the behaviour of the OA's for the above active-R realizations. A quantitative measure of the limitation imposed by this model on such realizations is also presented. Extensive computer simulation and experimental tests have been carried out that verify closely the theoretical predictions.     

Design of switched-capacitor filters using non-ideal op amps

A general synthesis procedure is given for the realization of switched-capacitor filters in the z-domain. The method uses biphased switches, capacitors and non-ideal op amps with finite gain-bandwidth product. The design includes at the outset the effects of the op amp gain-bandwidth product. Two examples are given which have been verified by a computer program.     

Error analysis in fixed-point digital filters using sign-magnitude truncation

The quantization error of a digital filter employing fixed-point arithmetic with sign-magnitude truncation is analyzed. The effect of coefficient quantization is also included. Exact analyses are presented first for Gaussian, sinusoidal and Gaussian plus sinusoidal inputs. Quasi-linearization is then employed to yield a simple computation method of the output noise variance. The resulting expression contains parameters that depend on the input signal statistics. An upper bound is given that is independent of these statistics. Explicit expressions are given for the second-order sections of the digital filter realized in the D1 and D2 forms together with a general expression for the cascade connection of the second-order sections.     

A continuous finite-time convergence fixed-lag FIR smoother using multiple IIR filters

In this paper, we propose a continuous finite-time convergence finite impulse response (FIR) fixed-lag smoother using multiple, or more than two, computationally efficient IIR filters. We describe the optimal design to improve and further optimize an existing scheme based on two IIR filters. Multiple IIR filters are utilized to minimize the estimation error variance of the proposed smoother under the condition that its estimate converges to a real state in a finite time. As the number of adopted IIR filters increases, the proposed smoother improves and its performance approaches that of the heavy computational fixed-lag minimum variance FIR smoother. By choosing the appropriate number of IIR filters, we can balance the trade-off between improved accuracy and increased implementation costs. To realize the optimal design of IIR filters with the limited number of IIR filters, their gains are determined using a particle swarm optimization scheme. Numerical examples are used to show that with an increasing number of IIR filters, the estimation error variance decreases monotonically while guaranteeing finite-time convergence.     

Parasitic tolerant designs of sampled data filters using switched capacitors and unity gain amplifiers

New and systematic procedures are presented for realizing sampled data filter (SDF) functions using switched capacitors (SCs) and unity gain amplifiers (UGAs). The procedures are attractive and simple to implement. Any SDF, recursive or non-recursive and of any order, can be realized using the methods presented. The designs of biquadratic SDFs is discussed in detail. The resulting realizations possess the property that the numerator and denominator coefficients of the SDF functions can be controlled by independent capacitance ratios. This makes the filters attractive for adaptive applications. The sensitivity properties of the resulting filters are analyzed and guidelines given for obtaining low sensitivity realizations. A method is also suggested to make the filters relatively insensitive to the parasitic capacitances in the circuit. Finally, a step by step procedure, easily implemented in a computer, is given. Starting from the given analog filter specifications, the method yields a design that has very low sensitivity, uses minimum total capacitance and is tolerant of the various parasitic capacitances in the circuit. Experimental results show very good agreement with the theoretical analysis.     

Dynamic surface asymptotic tracking of a class of uncertain nonlinear hysteretic systems using adaptive filters

This paper is concerned with the problem of dynamic surface asymptotic tracking for a class of uncertain nonlinear systems preceded by Bouc–Wen type of hysteresis nonlinearity. By introducing the nonlinear filters with a positive time-varying integral function, a novel robust adaptive control algorithm is presented without constructing the hysteresis inverse. Unlike some existing adaptive control schemes for systems with input hysteresis, the proposed controller not only solves the issue of “explosion of complexity” inherent in the recursive procedure, but also produces the asymptotic tracking in spite of input hysteresis and external disturbances. Finally, two simulation examples are presented to confirm the effectiveness of the developed control strategy.     

Transient responses of m-derived filters

The analytic expressions of the unit-impulse and the unit-step responses ofthe classical m-derived and the composite filters are derived. The equations have been computed by means of an IBM 360 Model 44 digital computer. Normalized curves of the unit-step response are presented. They are completely universal and can be applied to specific situations by rescaling the axes.     

S波段20W Doherty功放的设计

3GPP长期演进（LTE）项目是近两年来3GPP启动的最大的新技术研发项目,为了满足3GPP对LTE项目的相关要求,必须提出在更高的频段设计高效功率放大器的方案。文章通过ADS2008设计了一个工作在C波段的DPA,中心频率为2350MHz,仿真结果显示最终的输出功率为20W,带宽为100M,最大效率为51．18％。     

Block implementation of two-dimensional digital filters

A novel principle known as block transformation is developed for the block implementation of two-dimensional (2-D) digital filters. It employs the one-dimensional (1-D) block implementation concept forwarded by Burrus (7) as a basic tool. Using this block transformation principle three distinct forms of 2-D block equations are derived. The generalized nature of the approach presented here facilitates the straightforward extension of this technique to higher dimensional digital filters.     

Rational approximation of three-dimensional digital filters

Two techniques are developed for approximating a given three-dimensional (3-D) digital filter by a 3-D rational function. The one is by a general 3-D rational function and the other by a 3-D rational function which is separable in the denominator. Each technique relies on the use of mixed first and second information, in the form of a finite portion of the impulse response and its autocorrelation sequence. The approximation is performed by solving a set of linear equations. The separable-denominator approximation is more advantageous due to the guaranteed stability and reduced amount of calculations.     

基于主动式边界基元模型的多类目标识别方法

针对形状特征,提出了一种基于主动式边界基元模型的多类目标自动识别方法. 该方法以主动式边界基元为基础构建字典,可准确描述各类目标的形状结构, 不受尺度、旋转等变化的影响;然后,综合分析上下文信息进行概率学习,采用级联框架和Bootstrap动态采样训练最优边界分类器,实现目标的类别识别和位置定位,并可获取精确形状. 实验结果表明,该方法能有效提取多种类型和复杂结构的目标,具有较强的实用价值.     

试论西部地区增长极战略的实施构想

西部大开发是一项难度极大的系统工程 ,几十年来形成的宿疾显然难以在短期内得以治愈。本文旨在以发展经济学中的“增长极”理论为指导 ,从培育西部地区增长极和强化其扩散效应入手 ,以期在纷繁芜杂的西部开发战略思路中寻觅一个新的契入点 ,以推动不发达地区通过不平衡发展战略 ,最终实现经济的整体进步。一、增长极理论概述增长极理论最初由法国经济学家佩鲁 (ＦｒａｎｃｏｉｓＰｅｒｒｏｕｘ)提出 ,后来 ,法国经济学家布代维尔 (Ｊ Ｂ Ｂ ｏｕｄｅｖｉｌｌｅ) ,美国城市经济学家弗里德曼 (ＪｏｈｎＦｒｉｓｈ ｍａｎ) ,瑞典经济学家缪尔…     

影响环形预应力混凝土电杆力学性能的因素

分析了环形预应力混凝土电杆在生产过程中影响其力学性能的主要因素,包括有电杆的混凝土强度、钢筋骨架和钢筋张拉、离心速度和时间、蒸汽养护温度和时间、以及保护层厚度等。通过对环形预应力混凝土电杆生产工艺的分析得出,只有严格按照电杆制造技术条件组织生产,才能生产出力学性能优异的电杆产品,     

一种细棒件连续计数下料方案的研究

通过对细棒件小五金的属性研究设计了一种针对细棒五金件的连续计数下料方案。包含了细棒件存储单元、导流阵列单元、细棒件输送单元。通过控制步进电机的脉冲,从而控制下料的个数。同时利用Solidworks软件对设计装置进行装配建模,为机构优化设计提供了可靠的依据,验证了设计的可行性。     

西藏电杆生产企业质量状况分析

本文通过几年对西藏全区电杆生产企业的产品质量检测情况，结合自己的工作经验，从电杆的各个性能指标方面分析西藏电杆行业的现状，造成不合格产品的原因。并提出提高产品质量的建议。     

A class of fast and accurate deterministic trend decomposition in the spectral domain using simple and sharp diffusive filters

This study proposes a spectral domain algorithm to remove the deterministic non-periodic trend from a time series using a class of fast, sharp and diffusive filters. These filters are principally the iterative moving least squares methods weighted using Gaussian windows. The responses of the filters expressed in analytic forms are proven to be diffusive. If it is a polynomial of finite degree, the embedded trend can be decoupled by the filters with specific order and iteration steps. The filters’ order, transition zone, error tolerance, iteration number and smoothing factor are subject to two algebraic equations to form a specific class. The operation counts of all filters are slightly larger than twice that applying a Fast Fourier Transform (FFT). It is numerically shown for a given transition zone and tolerance, there is a filter generating the shortest error penetration distance among all the filters. If either the trend or a spectral band is the main concern, there is an optimal strategy to shrink the error penetration distance. The numerical results show the filter has better performance than several existing methods. In addition, four examples successfully show direct applications of the filter’s response.