多通道并列数据采集系统非均匀采样校正

在超高速多通道并列数据采集系统中,由于各路间的时延不等而造成采样实际上是非均匀采样,由此引起的误差成了此时系统的主要误差。目前文献中对该时处误差进行校正只有一种方法,即在模拟域上对采样时钏的延迟进行校正。文中提出一种新方法,将采样数据流通过一个给定群延迟的全通数字滤波器来校正数据,而并非时钟的时序。与传统方法相比,该方法具有数字化的优越性。     

基于动态采样的锁相放大微弱信号检测

摘要：基于相关检测原理设计了一种数字锁相放大器,重点研究了采样频率与相关运算结果的关系。发现参考信号为方波而采样频率与信号频率成一定关系时,系统相关运算存在固有误差。为减少该误差,首次将动态采样法引入数字锁相放大器设计中,运算发现动态采样的采样频率数越多,奇点产生的误差越少。基于LabVIEW软件对所设计的检测系统进行了仿真测试,测试结果表明该数字锁定放大器在信号幅度为5V、噪声标准差小于等于50时（SNR=-34.04dB）,能有效地检测出频率为500KHz以下的信号,系统检测结果与理论计算值的相对误差基本不超过2%。     

基于MATLAB在线数字滤波器设计与误差分析

为了获取高精度有效信号在信号检测系统中,常常需要进行滤波,将设置频率以外的信号彻底清除,数字滤波器广泛应用于各种测量系统。基于MATLAB的在线数字滤波器设计过程简单易行,不仅具有较高的精度和稳定性,还有运算速度快,延迟小的特点,可以满足测量要求。但在实际应用时如果采样数据长度选择不当,输出波形会出现失真。通过实验分析了采样数据长度与波形失真的关系,在使用时要兼顾误差与延迟,保证数字滤波测量精度。     

带观测时滞和丢失的网络化系统的故障检测

研究一类带有一步通信时滞和观测数据丢失的离散时间网络化系统的故障检测问题。通过在接收端引入寄存器将数据丢失转化为通信时滞,用一个二进制的随机序列描述由于网络的引入所带来的观测信号的随机时滞。对原系统的状态与故障诊断滤波器的状态进行增广,可以将原故障检测问题转化为一个H∞滤波问题。以线性矩阵不等式的形式得到了滤波器存在的一个充分条件,进而得到滤波器的参数。仿真说明了该方法的有效性。     

基于FPGA的LMS自适应滤波器设计

提出一种基于LMS(Least Mean Square)自适应算法的滤波方法,介绍该方法在低频信号滤波上的应用及在FPGA平台上实现。传统数字滤波器FIR、IIR滤波器针对不同的系统和干扰信号,其滤波参数不固定。因此,在窄带信号的滤波处理中,传统滤波器对信号滤波降噪的效果往往受到衰减增益限制。提出的方法先以CORDIC(Coordinate Rotation Digital Computer)算法产生的正弦信号来调制采样信号,根据采样信号与基准信号误差使其权向量沿负梯度方向终止于维纳解。该方法在类直流输入及带宽窄的情况下仍能有效过滤高频噪声,读取低检测信号幅值。理论分析和实验结果表明,与传统滤波方法对比,该滤波方法在处理窄带信号的滤波上更具有优势。     

基于并行滤波器的回波抵消技术方案

为了提高数字直放站回波抵消的收敛速度,首先研究了基于自适应滤波器的回波抵消技术,然后对其中的自适应滤波器的递推算法进行改进,形成了两个自适应滤波器并行计算、联合递推更新权值的技术方案。由于调节两个自适应滤波器权值的误差信号产生方式不同,方案可分为两种：方案一将回波抵消后的信号同时作为调节两个滤波器权值的误差信号(同时);方案二将天线接收信号与第一个滤波器输出信号的差值作为调节第一个滤波器权值的误差信号,而将该误差信号与第二个滤波器输出信号的差值作为调节第二个滤波器权值的误差信号(分别)。仿真结果表明,改进技术方案使回波抵消收敛速度提高11.11%~17.78%,从而有效改善了数字直放站回波抵消收敛速度慢的状况。     

开关式电容低通滤波器噪音研究

在大多数仪器系统中，一个开关式电容滤波器不会将大量误差引入信号。但在某些特殊情况下，滤波器会对信号产生影响，并表现为噪音和误差信号，本文着重介绍了如何小 种非希望信号分量的影响。     

嵌入式系统中数字滤波器的分析和设计

分析了嵌入式系统中信号采样,对信号进行滤波处理.讨论了滤波器在实际应用里的作用,如何削减干扰信号,增强有用信号.并详细介绍了数字滤波器的特点、分类和数字滤波器的设计方法.在线性时不变系统中,用Z变换来对系统进行滤波、补偿或控制,能很好地复制时域的问题.     

随机网络控制系统的量化L2-L∞滤波

考虑到带宽有限网络环境下信号需经过量化处理才能进行发送,研究了一类带宽受限随机网络控制系统的L_2-L_∞滤波问题。采用对数量化器,将量化后的测量信号作为滤波器输入信号。首先将滤波误差系统建模成范数有界不确定随机时滞系统,进一步基于线性矩阵不等式方法推出了该随机网络控制系统的稳定性和滤波器设计的充分条件,并将滤波器的设计转化为一个凸优化的求解问题。所设计的滤波器能够保证相对于所有能量有界的外界扰动信号,随机网络控制系统的L_2-L_∞性能指标小于一定值γ。仿真实例证实了该设计方法的有效性。     

基于信号重构的并行ADC定时误差校准

多通道时间交叠式AD会引入定时误差,而这种定时误差会导致镜频杂散。本文基于非均匀采样信号的重构理论,提出了一种利用内插滤波器组对定时误差进行消除的方法。其设计思想是将时间交叠式AD问题转化为周期性重复的非均匀采样,并结合两通道并行ADC,给出了详细的内插滤波器设计方法。仿真实验结果表明,本文提出的算法对校准定时误差非常有效,并行AD输出的镜频信号得到很好的抑制。     

线性相位FIR数字滤波器设计的随机抽样递推最小二乘算法

本文考虑了基于加权平方误差准则线性相位FIR数字滤波器的设计问题，提出一种随机抽样递推最小二乘（RS－RLS）设计方法．将设计问题看成一个线性系统的辨识问题，辨识参数所需的数据由一随机抽样法产生，辨识算法采用递推最小二乘法上RS-RLS设计法简单易用，设计范例说明这一方法具有很高的设计精度．     

LMI designmethod for networked-based PID control

In this paper, we propose a methodology for the design of networked PID controllers for second-order delayed processes using linear matrix inequalities. The proposed procedure takes into account time-varying delay on the plant, time-varying delays induced by the network and packed dropouts. The design is carried on entirely using a continuous-time model of the closed-loop system where time-varying delays are used to represent sampling and holding occurring in a discrete-time digital PID controller.     

A novel algorithm for the design of selective FIR filters with arbitrary amplitude and phase characteristics

In this paper, a novel analytic technique is presented for the design of finite impulse response digital filters with simultaneous amplitude and phase requirements. The design process relies on the interpolation concept and is based on the generation of arbitrary amplitude and phase polynomials. The new class of FIR filters lays in between the exact linear phase filters at all frequencies and the minimum phase FIR filters based on the amplitude approximation only. It interpolates arbitrary (e.g., linear) phase response in the passband and arbitrary amplitude characteristics in pass- and stopbands. The introduced class of filters can be used on the amplitude and phase equalization of both FIR and IIR digital filters. Illustrative examples are included in order to investigate the main properties of these filters and to demonstrate that the proposed design method leads to a significant saving in the arithmetic computations.     

Coupled design of test signals, sampling intervals, and filters for system identification

This paper discusses the problem of optimal design of experimental conditions for linear system identification. It is demonstrated that, in general, to achieve maximal return from an experiment, coupled design of all the experimental conditions, namely the test signal, sampling intervals and filters, should be carried out simultaneously. For the case of uniform sampling it is shown that joint design of the presampling filter, sampling rate and input can be carded out in the frequency domain. For the case of nonuniform sampling a sequential design procedure is developed which optimizes the information increment between samples.     

均匀线列阵时域宽带波束形成方法研究

时域宽带恒定束宽波束形成技术一般采用特殊频率响应的FIR滤波器组实现对不同频率的加权.对水下常用的均匀线列阵,利用切比雪夫方法设计了形成宽带恒定束宽波束的权值.通过对切比雪夫方法设计权值特性的分析,推导出实现加权的FIR滤波器组的相位响应关系式.根据推导结果得出设计的FlR滤波器组应为一组斜率不同的线性相位响应FIR滤波器.推导了滤波器组相位响应的计算公式.给出三种特殊频率响应FIR滤波器设计算法.通过仿真结果比较了三种方法设计的用于实现均匀线列阵恒定束宽加权的FIR滤波器组的性能.     

Optimal design of FIR linear phase digital filters via convex quadratic programming method

Many methods exist for designing FIR linear phase digital filters by using various optimization techniques. An optimization design method via the convex quadratic programming method is investigated in this paper. The aim of this method is to design digital filters with certain desired frequency responses that keep the passband ripple to a minimum while maintaining a balance between opposite characteristics of frequency responses, i.e. the narrow transition band and the great stopband attenuation. In order to verify the effectiveness of this method, low-pass filters are designed and comparison studies with other typical optimization methods are given.     

Optimal PID automatic voltage regulator for synchronous machines

The design and testing of an optimal PID automatic voltage regulator for synchronous machines is treated. The proposed digital PID regulator combines automatic voltage regulation with the function of a power system stabilizer. The PID and stabilizing signal parameters are optimized based on a linear quadratic performance index using the Simplex method. The design of the regulator is achieved directly without using a linearised mathematical model, and only impulse responses of the system are required during the optimization procedure. The microcomputer-based regulator with digital filters has been tested on a laboratory model turbogenerator system. Simulation and experimental results are presented, showing that the regulator provides very good performance, which is superior to that obtained with a conventional automatic voltage regulator with power system stabilizer.     

Stability theory for linear time-invariant plants with periodicdigital controllers

The control of a linear time-invariant plant by a digital controller composed of a sampler, a periodic discrete-time component, and a zero-order hold is considered. The stability of such a configuration is analyzed. It is shown how closed-loop zeros can be placed using such a scheme. As a consequence, it is proved that the gain margin can be arbitrarily assigned by suitable choice of sampling time and digital controller. The design procedure is constructive, using state-space methods