A pre-distortion based design method for digital audio graphic equalizer

The traditional design method for digital audio graphic equalizer using infinite impulse response filters usually has some deficiencies, including center frequency shift, narrower bandwidth at high frequency and inaccurate gain. In this paper, an improved method based on the modified bilinear transformation is proposed to design a digital audio graphic equalizer. The new bilinear mapping can compensate the center frequency shift, and pre-distorting the quality factors and optimizing the gains can correct the bandwidth and gain of each sub-band respectively. Experimental results reveal that both center frequency and bandwidth of the proposed digital graphic equalizer are strictly equal to the desired ones, and the average gain error decreases at least 2 dB.     

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.     

Comb filters — simulation and design

In this paper a technique in given for the simulation and implementation of comb filters. An apropriate discrete model of the comb filter is choosen and through simulation technique are calculated and optimized its parameters. As it is known comb filters are used for different applications (radars, control systems, e.t.c.) and give really good results. Before the realization the filter is simulated in time and frequency domain and tested through an appropriate computer program such as to obtain the desired frequency response. The used method is the “direct synthesis” of a digital filter.     

基于期望系统的PID频域逼近设计

为了能在时域和频域同时具有期望的系统性能,提出了一种基于期望系统的频域逼近设计方法：在开环幅相频率特性的低频段,待设计系统频率特性模型的实部与虚部分别逼近期望开环频率特性模型的实部与虚部,从而得到PID控制器的比例增益Kp和积分增益Ki;在开环幅相频率特性的中频段,以高于期望稳定裕度的幅值条件,获得微分增益Kd的置信区间,从而确保PID控制系统的稳定性。纯滞后系统和非最小相位系统的仿真研究表明,该方法能够获得与期望系统更近的时域跟踪性能以及不低于期望系统的频域稳定裕度;同时,与其它三种PID设计方法进行了频域性能对比和时域阶跃响应测试,结果表明所提出的PID设计方法能够获得更好的性能指标。液位控制实验显示：采用所提出的方法可以实现超调量为0,系统响应速度为被控对象开环响应的的4~5倍。     

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.     

A frequency response matching method for the design of digital controllers with constraints on the pole-zero locations

The purpose of the frequency response matching technique is to design a digital controller such that the frequency response of the resulting closed-loop system matches a specified frequency response model. The simplex method is employed to determine the controller's parameter values which minimize a function of the error between the two responses. This method permits constraints on the controller's gain and the pole-zero locations to be applied, for example, in order to reduce the highly oscillatory response of the output of the controller, a phenomenon which can be observed when applying other frequency response matching techniques. An example illustrating the use of the method, particularly at low sampling frequencies, is given.     

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.     

High order stable infinite impulse response filter design using cuckoo search algorithm

In this paper, an efficient technique for optimal design of digital infinite impulse response (IIR) filter with minimum passband error (e _p ), minimum stopband error (e _s ), high stopband attenuation (A _s ), and also free from limit cycle effect is proposed using cuckoo search (CS) algorithm. In the proposed method, error function, which is multi-model and non-differentiable in the heuristic surface, is constructed as the mean squared difference between the designed and desired response in frequency domain, and is optimized using CS algorithm. Computational efficiency of the proposed technique for exploration in search space is examined, and during exploration, stability of filter is maintained by considering lattice representation of the denominator polynomials, which requires less computational complexity as well as it improves the exploration ability in search space for designing higher filter taps. A comparative study of the proposed method with other algorithms is made, and the obtained results show that 90% reduction in errors is achieved using the proposed method. However, computational complexity in term of CPU time is increased as compared to other existing algorithms.     

A digital simulation method for flutter analysis

This paper presents a digital simulation method which yields the flutter speed, the flutter frequency, and the subcritical response of a system. The flutter system can be considered as a control system comprising a number of linear hysteresis elements, and the model of the digital simulation is obtained. The subcritical responses of all elements of the system are determined by the Runge-Kutta method, and all eigenvalues and eigenvectors are obtained by the QR method. Some numerical results are given. The flutter speed and frequency calculated by the present method and those by the V-g method agree quite well. Moreover, it yields the responses of all elements of the system unobtainable with other methods. These numerical results show that the digital simulation method for studying a flutter system is feasible, accurate, and convenient.     

Two-dimensional fractional-order digital differentiator design by using differential evolution algorithm

Designing a fractional-order digital differentiator often requires considerably complex mathematical operations and numerical approximations. Thus this paper will propose a simple method to achieve the fractional-order digital differentiator design, particularly for two-dimensional fractional-order differentiators. A two-dimensional finite impulse response (FIR) digital filter structure is utilized and designed so that its corresponding magnitude response can satisfy that of a desired fractional-order differentiator of two variables. The algorithm used to design such two-dimensional digital differentiator is the differential evolution (DE), which is one of evolutionary computations and has excellent searching capacity. The efficiency of the proposed scheme can be confirmed by some illustrative examples.     

Design of multipurpose digital FIR double-band filter using hybrid firefly differential evolution algorithm

Signal filtering can be treated as one of the basic requisite of communication networks. Design of an appropriate digital filter demands such filter coefficients that will create the desired frequency response with tolerable amount of ripples in the stop band(s) and pass band(s) along with high attenuation in the stop band(s). Now-a-days, artificial evolutionary methods are employed in the modern digital filter design due to lots of advantages over typical methods. In this paper, multipurpose digital linear phase double band filter (LPDBF) is designed proposing a hybrid meta-heuristic technique called hybrid firefly differential evolution (HFDE) algorithm. Generally these filters are required in different specific modern digital system networks for the simultaneous processing of signals present in two or three different channels. The proposed HFDE is an efficient evolutionary hybrid technique and is modelled considering both the optimization advantages of improved differential evolution (IDE) and firefly techniques. The global searching capability of IDE technique is strengthened by improved firefly movement. The performance of the proposed HFDE method of LPDBF design is contrasted with few popular optimal methods of design.     

基于非均匀离散傅立叶变换的数字音频水印算法

为了提高数字音频水印算法的安全性和鲁棒性,提出一种基于非均匀离散傅立叶变换(Nonurifarm Disxrete Fourier Transfarm,,NDFT)的幅度比较的音频水印算法.NDFT表示单位圆上的非均匀采样,嵌入水印时可以任意选取合适的频率点,由此提高了系统的安全性能.实验结果表明:提出的算法能有效抵抗...     

现代运动控制系统的数字式频响测试方法

频率响应是控制系统最为重要的特性之一,现代运动控制系统多采用数字式传感器作为反馈元件且可直接进行数字控制;为了更好地测试系统的频率响应,文中提出了一种新型的数字式频率响应测试方法,对测试的步骤、算法实现（包括FFT法,相关运算法,最小二乘法）、BODE图的绘制和数学模型的建立做了研究和总结归纳;实践证明,相比传统的频响测试方法,该方法适应了系统数字化的特点,减少了测试环节中的硬件,提高了计算过程的透明度和置信度,具有重要的工程应用价值。     

具有可调参数的模型降阶新方法

本文提出了一种具有可调参数的模型简化新方法.此法从系统动态特性上揭示了简化模 型与原系统之间"类等效"的对应关系.由对系统主要频率响应数据的拟合(或最优化方法)确 定参数.降阶模型不仅保持高阶系统的稳态特性(低频特性)和稳定性,还能按设计者需要有 选择地保持原系统的其它主要性能(例如带宽、相对稳定性等)、保持其它任意频段的特性.最 后,文章给出实例.     

Taylor series expansion based repetitive controllers for power converters,subject to fractional delays

Digital repetitive controllers are widely employed to track/reject the periodic signals with zero steady-state error. Their implementation involves the use of single or multiple digital delay elements. Practically, the delay element is implemented by the use of memory locations, where samples are held and released after a specific number of sampling periods, equivalent to the desired time delay. A problem arises when the desired time delay becomes a non-integer multiple of the sampling time. Such time delays can be accurately realized by employing a fractional delay filterThis paper presents a Taylor Series expansion based digital repetitive controller designed to implement any (integer, non-integer) delay in the control of power converters, occurring due to uncontrollable variations in the reference frequency. The T3644aylor Series expansion transforms the fractional delay filter design problem to a differentiator/sub-filter design. Finite impulse response (FIR) and infinite impulse response (IIR) fractional delay (FD) filter concepts can be applied to realize the required fractional delay. This structure provides efficient on-line tuning capabilities i.e. FD can easily generate any required fractional delay without redesigning the filter when the delay parameter varies. An example is demonstrated to show the effectiveness of this approach, for a single-phase power inverter feeding a passive load.     

一种非90°移相器的等波纹逼近设计方法

提出了一种非90°移相希尔伯特变换器的等波纹逼近设计方法。非90°移相器本质上是一种指定相位特性的全通滤波器。对于平稳的数字全通滤波器,其分母多项式一定具有最小相位。通过构造一个纯虚奇对称相位函数的方法推导出了分母多项式的相位函数与其复倒谱序列之间的关系;利用加权最小二乘法求得分母相位的等波纹逼近函数,进而利用上述关系求出其倒谱序列;依据复倒谱的基本理论,通过求解一个非线性递归差分方程得到分母多项式系数。设计实例表明,这种方法能够使设计的非90°移相器的相位函数在指定频带上实现等波纹逼近的要求,从而提高了非90°移相器的频率选择性。     

基于RLS的脉压雷达数字旁瓣抑制滤波器设计方法

采用自适应滤波器设计中的递归最小二乘(RLS)方法,通过合理安排输入信号与期望信号的结构来设计脉冲压缩雷达数字旁瓣抑制滤波器,具有算法简单实用,适用广泛的特点,可用于线性调频、二相码和多相码等各种信号.在滤波器抽头有限的情况下,峰值旁瓣电平低于-40dB;积累旁瓣电平较同类其他方法低2dB以上;主瓣宽度仅为单位采样符号间隔.     

Sensitivity shaping with degree constraint by nonlinear least-squares optimization

This paper presents a new approach to shaping of the frequency response of the sensitivity function. In this approach, a desired frequency response is assumed to be specified at a finite number of frequency points. A sensitivity shaping problem is formulated as an approximation problem to the desired frequency response with a function in a class of sensitivity functions with a degree bound. The sensitivity shaping problem is reduced to a finite-dimensional constrained nonlinear least-squares optimization problem. To solve the optimization problem numerically, standard algorithms for an unconstrained version of nonlinear least-squares problems are modified to incorporate the constraint. Numerical examples illustrate how these design parameters are tuned in an intuitive manner, as well as how the design proceeds in actual control problems.     

Structural modification with frequency response constraints for undamped mdof systems

A structural modification method which aims to change the structural design to match the desired frequency response behaviors is introduced. The calculations of frequency response sensitivities and reanalysis of frequency responses of a modified structure are efficiently carried out in a reduced modal space. Either a least square solution or an optimal solution with minimum structural weight subjected to various types of frequency response constraints can be obtained through an iteration loop which repeatedly uses the frequency response sensitivity data and reanalysis technique to achieve the design goal. A tremendous cost saving is expected when this is implemented in practical engineering design.