Toward a group delay reduction in digital filtering

Finite impulse response (FIR) filters are often used in digital signal processing applications because their linear phase properties do not introduce group delay distortion. While this property is desirable, we may also desire that the filter exhibit zero group delay to suppress the causal time offset between the input and output of the filter. We can minimize the causal delay by the use of recursive minimum phase filters but these introduce an objectionable group delay distortion. We desire both zero group delay and a nonrecursive impulse response (IR). This filter can be applied to input signals indirectly through a modified overlap and save FFT based circular convolution. The desired result is obtained in our proposed new filtering technique: the modified overlap and save method (MOSM). We accomplish this by redefining the time origin of the prototype filter's impulse response by circularly shifting the response in the FFT filter time vector till the symmetry point coincides with the vector's zero index.     

A New Design Approach for Nearly Linear Phase Stable IIR Filter using Fractional Derivative

In this paper,a new design method for digital infinite impulse response(IIR)filters with nearly linear-phase response is presented using fractional derivative constraints(FDCs).In the proposed method,design problem of an IIR frlter is constructed as the minimization of phase error between the desired and designed phase response of an allpass filter(APF)such that the designed lowpass filter(LPF)or highpass frlter(HPF)yields less passband(ep),and stopband errors(es)with optimal stopband attenuation(As).In order to have accurate passband(pb)response,FDCs are imposed on appropriate reference frequency,where the optimality of these FDCs are ensured by using a new greedy based sorting mechanism.The simulated results reflect the efficiency of the proposed method in term of improved passband response along with better transition width.However,small reduction in^is observed within the allowable limit,when compared to noin-fractional design approach,but the designed filter remains immune to wordlength(WL)effect.     

无限冲激响应数字滤波器的设计与MATLAB仿真

滤波器是一种能使有用频率信号通过而同时抑制(或大为表减)无用频率信号的电子装置.与模拟滤波器相比,数字滤波器在性能等方面都显示出明显的优点,而且还可以借助计算机软件编程方式实现.为了能够根据要求设计出符合指标的数字滤波器并进行软件仿真,选用了MATLAB软件实现滤波器设计.采用了冲激响应不变法使数字滤波器能模仿模拟滤波...     

等间隔分数时延滤波器及其线性插值设计

针对宽带数字信号精确可变时延需求,研究等间隔分数时延滤波器及其线性插值方法。现有分数时延滤波器设计方法不能应用于可变时延,基于多采样率信号处理理论,提出等间隔分数时延滤波器设计方法。将所需时延近似为等间隔分数时延,选取对应时延滤波器组对信号进行时延,满足工程中变分数时延滤波需求。为提高时延滤波精度,提出对相邻滤波器系数线性插值的分数时延滤波器设计方法。对线性调频信号仿真结果表明,所提方法与常规分数时延滤波方法运算量相当,且适用于宽带信号的精确可变时延应用。     

基于FPGA动态可重构的高速、高质量的图像放大

为了能高速、高质量地进行图像放大，提出了一种以硬件方法完成高阶图像插值运算来实现图像放大的新方法。该方法为了保证图像放大后的质量，采用了3次B-样条来对图像放大后的像素点灰度值进行插值运算，并提出一种基于IIR和FIR数字滤波器的3次B-样条插值法的高速实现方案。另外，为了能在系统中实现不同倍数图像放大，系统中还引入了基于FPGA的动态可重构技术，即通过实时地改变FPGA的配置，以实现不同的算法。同时还针对256灰度级图像设计出一种基于FPGA的高速、高质量的硬件图像放大及显示系统。     

Discrete‐time repetitive controller for time‐delay systems with disturbance observer

A novel discrete‐time repetitive controller design for time‐delay systems subject to a periodic reference and exogenous periodic disturbances is presented. The main idea behind the proposed approach is to take advantage of the plant delay in the controller design, and not to compensate for the effect of this delay. To facilitate this concept, we introduce an appropriate time‐delay and a compensator in a positive feedback connection with the plant, such that a generator for periodic signals is constructed. Then a proportional controller is used to stabilize the closed‐loop system. The tracking control capability is thus guaranteed according to the internal model principle (IMP). In addition, to attenuate external periodic disturbances, a disturbance observer (DO) is developed to simultaneously achieve reference tracking and disturbance rejection. The possible fractional delay due to the digital discretization is handled by using a fractional delay filter approximation. The proposed controller has a simple structure, in which only a proportional parameter and a low‐pass filter are required to be chosen. The closed‐loop stability conditions and a robustness analysis under model uncertainties are studied. Numerical simulations and practical experiments on a servo motor system are conducted to verify the feasibility and simplicity of the proposed controller. Copyright © 2011 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society     

Maximum sensitivity based fractional IMC–PID controller design for non-integer order system with time delay

A simple approach with a small number of tuning parameters is a key goal in fractional order controller design. Recently there have been a number of limited attempts to bring about improvements in these areas. In this paper, a new design method for a fractional order PID controller based on internal model control (IMC) is proposed to handle non-integer order systems with time delay. In order to reduce the number of tuning parameters and mitigate the impact of time delay, the fractional order internal model control scheme is used. Considering the robustness of the control system with respect to process variations and model uncertainty, maximum sensitivity is applied to the tuning of the parameters. The resulting controller has the structure of a fractional order PID which is cascaded with a filter. This is named a fractional IMC–PID controller. Numerical results are given to show the efficiency of the proposed controller.     

基于FPGA的高速高质量图像旋转

为了进行高质量、高速的图像旋转变换 ,通过对传统图像旋转矩阵的分解 ,将图像在二维空间中的旋转运算分解成为三次一维空间内的平移运算 ,从而将用于图像旋转运算的二维插值运算简化为在一维空间中进行的一维插值运算。为了保证图像旋转后的质量 ,采用 3阶 B-样条对每次平移后像素点的灰度值进行插值运算 ,并提出了一种基于 IIR和 FIR数字滤波器的 3阶 B-样条插值法的高速实现方案 ;最后针对 2 5 6灰度级 ,2 5 6× 2 5 6像素的图像设计出一种基于 FPGA的高速、高质量的硬件图像旋转及显示系统     

一种求解雷达目标冲激响应的并行算法

雷达目标的冲激响应是目标识别中的一种重要手段，可以从冲激响应中提取目标的各种特征，如目标的谐振频率等。为了实时地获得目标的冲激响应，本文提出了一种基于共轭梯度法的并行算法，同时改进了共轭梯度法的终止选代条件。经计算机仿真及对实测数据的计算，证明了这种方法的有效性。     

Fractional Fourier domain analysis of decimation and interpolation

The sampling rate conversion is always used in order to decrease computational amount and storage load in a system. The fractional Fourier transform (FRFT) is a powerful tool for the analysis of nonstationary signals, especially, chirp-like signal. Thus, it has become an active area in the signal processing community, with many applications of radar, communication, electronic warfare, and information security. Therefore, it is necessary for us to generalize the theorem for Fourier domain analysis of decimation and interpolation. Firstly, this paper defines the digital fre- quency in the fractional Fourier domain (FRFD) through the sampling theorems with FRFT. Secondly, FRFD analysis of decimation and interpolation is proposed in this paper with digital frequency in FRFD followed by the studies of interpolation filter and decimation filter in FRFD. Using these results, FRFD analysis of the sam- pling rate conversion by a rational factor is illustrated. The noble identities of decimation and interpolation in FRFD are then deduced using previous results and the fractional convolution theorem. The proposed theorems in this study are the bases for the generalizations of the multirate signal processing in FRFD, which can advance the filter banks theorems in FRFD. Finally, the theorems introduced in this paper are validated by simulations.     

A nearly optimum linear-phase digital FIR filters design

A new simple method to design linear-phase finite impulse response (FIR) digital filters, based on the steepest-descent optimization method, is presented in this paper. Starting from the specifications of the desired frequency response and a maximum approximation error a nearly optimum digital filter is obtained. Tests have shown that this method is alternative to other traditional ones such as Frequency Sampling and Parks–McClellan, mainly when other than brick wall frequency response is required as a desired frequency response.     

Analysis and design of a robust odd-harmonic repetitive controller for an active filter under variable network frequency

Frequency variations in the electrical network may cause a dramatic performance decay in repetitive controlled active filters intended to remove odd-harmonic distortion in single-phase AC loads. This work presents an odd-harmonic repetitive controller for a shunt active power filter that addresses such a performance problem. This is achieved by means of an adaptive change of the sampling period of the digital controller. However, this action implies structural changes that may result in an overall destabilization of the closed-loop system. Hence, a small-gain theorem-based robust control design technique allows to obtain a controller which assures BIBO stability in the required sampling period interval. Experimental results validate the proposal.     

变频电网三相有源电力滤波器重复控制策略

为了在变频环境下,提高三相并联型有源电力滤波器的电流跟踪性能和补偿效果,提出了一种基于并联通用内模,具有频率自适应性的复合重复控制策略.提出的并联通用内模能依据指令电流谐波成份的变化动态调节内模的补偿范围和延迟时间,并进一步将延迟时间缩短至同等补偿范围内模的一半,显著提高了重复控制器动态性能和适应能力.内模中由电网频率变化引起的分数阶延时环节,采用线性插值法近似,使基于并联通用内模的重复控制器具有频率自适应性.采用插入式结构设计了复合重复控制系统.详细分析了复合控制系统的稳定条件和收敛性.以飞机变频电网并联型有源电力滤波器系统为应用环境,将提出的复合重复控制策略与其他控制策略进行了对比.仿真和实验结果验证了提出的复合重复控制策略的有效性和优越性.     

互相关技术中基于零阶保持器的离散冲激响应模型

利用互相关技术能有效估计线性系统的冲激响应。然而,对于基于数值计算的互相关技术,D/A和A/D转换器的使用必然会带来原理性的误差。该文利用零阶保持器（ZOH）模型从理论上分析了离散时间系统的冲激响应,即它与连续系统冲激响应之间的关系,并给出了时域解析表达式。通过该公式可以直观地把握冲激响应估计的逼真度。     

Fault detection for nonlinear networked control systems with stochastic interval delay characterisation

In this article, we are concerned with the fault detection (FD) problem for nonlinear networked control systems (NCSs) with network-induced stochastic interval delay. By employing the information of probabilistic distribution of networked-induced time-varying delay, nonlinear constraint and the FD filter, nonlinear stochastic delay system model is established. Based on the obtained nonlinear model, utilising FD filter as residual generator, FD of nonlinear NCSs is formulated as nonlinear H _∞-filtering problem. Especially, the stochastic stability and prescribed H _∞ attenuation level are achieved using the Lyapunov functional approach, the desired FD filter is constructed in terms of certain linear matrix inequalities, which depends on not only nonlinear level but also on delay-interval and delay-interval-occurrence-rate. Numerical examples are provided to illustrate the effectiveness and applicability of proposed technique.     

电能质量监测装置数字滤波器设计应用研究

利用数字滤波器数据处理速度快、系统工作性能稳定、能获得理想的幅度特性等特点,设计一种应用于某系列高端电能质量监测装置的数字滤波器,通过仿真实验和实际采样信号处理证明,此种数字滤波器可提高监测装置测量信号的信噪比,可达到[2009]《电能质量监测终端技术规范》试行国标A级标准.     

数字下变频中的FPGA高效滤波器设计

介绍了一种在FPGA上实现高效窄带有限冲击响应滤波器(FIR)的设计方法.该方法利用数字下变频抗混叠滤波器的多速率和窄带的特点,采用插值FIR滤波器(IFIR)和多相滤波器相结合的设计思路,实现了该滤波器的高效设计.     

Fractionally Delayed Kalman Filter

The conventional Kalman filter is based on the assumption of non-delayed measurements. Several modifications appear to address this problem, but they are constrained by two crucial assumptions: 1) the delay is an integer multiple of the sampling interval, and 2) a stochastic model representing the relationship between delayed measurements and a sequence of possible non-delayed measurements is known. Practical problems often fail to satisfy these assumptions, leading to poor estimation accuracy and frequent track-failure. This paper introduces a new variant of the Kalman filter, which is free from the stochastic model requirement and addresses the problem of fractional delay.The proposed algorithm fixes the maximum delay(problem specific), which can be tuned by the practitioners for varying delay possibilities. A sequence of hypothetically defined intermediate instants characterizes fractional delays while maximum likelihood based delay identification could preclude the stochastic model requirement. Fractional delay realization could help in improving estimation accuracy. Moreover, precluding the need of a stochastic model could enhance the practical applicability. A comparative analysis with ordinary Kalman filter shows the high estimation accuracy of the proposed method in the presence of delay.     

Power and delay efficient fir filter design using ESSA and VL-CSKA based booth multiplier

FIR filter plays a major role in digital image processing applications. The power and delay performance of any FIR filter depends on the switching activities between the filter coefficients (FCs) and its basic arithmetic operations (i.e., multiplication and addition) performed in the convolution equations. In this paper, a new FIR filter is designed using Enhanced Squirrel Search Algorithm (ESSA) and Variable latency Carry skip adder (VL-CSKA) based booth multiplier. The proposed ESSA algorithm selects an optimal FC by minimizing the switching activities of FC based on the ripple contents, power and Transition width parameter to meet the required specifications of FIR filter in the frequency domain. Also, the VL-CSKA based booth multiplier is proposed to reduce the delay of FIR filter with parallel addition of partial products (PPs). In this design, the VL-CSKA adders utilize variable size and compound gate-based skip logic to deduce the delay with low power. The proposed FIR filter is simulated in Xilinx working platform by developing Verilog coding. The simulation result shows that the proposed FIR filter outperforms the state-of-the-art FIR filters by consuming only 0.142 mW power with delay of 28.175 ns.     

Input–output method to fault detection for discrete-time fuzzy networked systems with time-varying delay and multiple packet losses

The fault detection (FD) problem for discrete-time fuzzy networked systems with time-varying delay and multiple packet losses is investigated in this paper. The communication links between the plant and the FD filter (FDF) are assumed to be imperfect, and the missing probability is governed by an individual random variable satisfying a certain probabilistic distribution over the interval [0 1]. The discrete-time delayed fuzzy networked system is first transformed into the form of interconnect ion of two subsystems by applying an input–output method and a two-term approximation approach, which are employed to approximate the time-varying delay. Our attention is focused on the design of fuzzy FDF (FFDF) such that, for all data missing conditions, the overall FD dynamics are input–output stable in mean square and preserves a guaranteed performance. Sufficient conditions are first established via H_∞ performance analysis for the existence of the desired FFDF; meanwhile, the corresponding solvability conditions for the desired FFDF gains are characterised in terms of the feasibility of a convex optimisation problem. Moreover, we show that the obtained criteria based on the input–output approach can also be established by applying the direct Lyapunov method to the original time-delay systems. Finally, simulation examples are provided to demonstrate the effectiveness of the proposed approaches.