基于遗传算法的FIR滤波器设计

提出一种FIR数字滤波器的优化设计方法,即将遗传算法应用于频率采样法的FIR数字滤波器设计中。结合给定的FIR数字带通滤波器的技术指标,用遗传算法得到频率采样法中过渡带的最佳采样值,并分别用遗传算法与查表法对过渡带中采样点的频率采样法进行仿真实现。实验结果表明,采用遗传算法设计FIR数字滤波器可获得最大的阻带最小衰减,从而解决了传统查表法不能保证最优的问题。     

基于MATLAB的Sigma-Delta ADC中数字滤波器设计

为了将Sigma-Delta ADC中的SDM (Sigma-Delta Modulator)的输出码流降采样以达到Nyquist采样频率,基于实际的AUDIO CODEC项目,本文对两种数字滤波器(FIR(Finite Impulse Response)和IIR(Infinite Impulse Response))的MATLAB设计进行了描述和比较.其所需处理的SDM输出码流的过采样频率为11.2896MHz,数字滤波器完成256倍的降采样最终达到采样频率为44.1MHz,在音频范围内其最终仿真结果均达到SNDR在14bits以上.     

带宽给定条件下的全数字接收机频率规划

本文分析了带宽给定条件下,全数字接收机中频频率与采样频率的约束关系;导出了采样频率给定条件下,使得数字滤波器过渡带宽最大的中频频率表达式.最后,本文以GPS P(Y) 码接收机频率规划为例给出了设计实例.     

数字卫星广播系统采样时钟同步方法

针对数字卫星广播系统中采样时钟偏差会严重影响接收性能的问题,提出了一种采样频率和相位同步方法。该方法利用迟早门进行采样误差估计,利用Farrow滤波器进行插值处理。通过采样频偏调整环路控制Farrow滤波器,实现采样频率和相位同步。实验结果表明,该方法能够在高强度噪声干扰和较大载波频偏环境下,快速准确的实现采样时钟同步。该方法还可以广泛应用于数字地面广播、数字移动广播等多个领域。     

基于两种对称频率采样的全相位FIR滤波器设计

该文提出基于两种对称频率采样的全相位FIR滤波器设计方法,证明了在无窗和单窗情况下, 依据传统对称和偶对称的频率向量设计出的全相位传递曲线分别通过/N的偶数倍和奇数倍的数字角频率点, 因而全相位滤波器可较精确地控制边界频率。仿真实验证明, 这两种类型的全相位滤波器性能优于神经网络方法设计出的滤波器。     

基于单自由度振动模型的IIR数字滤波器设计

无限冲击响应(IIR)数字滤波器设计通常需要先设计S域滤波器,再变换到Z域。为简化IIR数字滤波器的设计过程,本文提出利用单自由度系统(SDOF)模型直接设计IIR数字滤波器的方法,包括低通、带通、高通、带阻等。仿真结果表明设计过程直接、简单,滤波器参数不需要随采样频率而变,具有良好特性,是一种设计IIR数字滤波器的简便易用的新方法。     

微型SAR的数字下变频设计

在微型SAR实时成像样机的设计中,对雷达回波在中频进行采样,然后采用数字下变频技术实现正交解调,可以减少系统的复杂性,提高雷达的数字化程度和性能。该文针对微型SAR方案中数字下变频设计中的难点,即采样频率高达2 Gsps,带宽900 MHz,实时处理的难度很大,根据具体设计参数优化了数字下变频的实现结构,重点比较了并行FIR滤波器和快行FIR滤波器的差别,然后在FPGA中编程实现了数字下变频模块,给出资源占用情况、运行速度和量化噪声影响,最后给出在微型SAR技术项目中的实际应用结果,理想的成像结果表明了该设计的正确性。     

有限冲击响应数字滤波器的DSP实现

数字滤波是信号处理过程的主要方式,FIR数字滤波器以其系统稳定和易实现线性相位应用更为广泛。设计了采用窗函数法的FIR数字带通滤波器,在DSP中采用单采样模式,在每一个采样周期内只产生一个信号输出值,实时处理采样后的信号。通过MATLAB进行滤波器的仿真,修改滤波器的参数使其达到设计指标。利用窗函数法设立的FIR数字滤波器,是获得较好的主瓣最大能量和旁瓣衰减意义下的最佳设计方法。     

无线传感节点的滤波处理探究

本文介绍了无线传感节点中模拟滤波器和数字滤波器的设计,结合两种滤波器共同消除传感节点在信号采集过程中存在的射频干扰和频率混叠。针对节点在高采样率采集而要求过渡带窄的情况,在不降低滤波效果的前提下,进行下采样并分级滤波,降低了数字滤波的计算量。     

雷达接收机数字化分析

通过实践证明,雷达数字接收机与模拟接收机相比,无论从电路结构还是从性能上,都充分体现了其优越性。在介绍某种雷达中频数字接收机的基础上,重点阐述了直接数字频率合成技术、直接中频采样和数字下变频技术,并给出了这2种数字技术的实现方法。介绍了直接数字频率合成芯片AD9854,并根据易于宽带滤波器设计的原则,推导了给定参数下使低通滤波器过渡带最宽的最佳采样频率。     

基于FIR与相位补偿IIR滤波器的雷达回波信号处理

FIR与IIR频率选择滤波器的设计,被广泛应用于数字信号处理领域之中。文章以雷达回波信号的数字处理为例,首先分别设计FIR,IIR滤波器完成了对信号特定频率分量的滤除。进而,针对IIR滤波器的非线性相位,基于最优化设计全通系统实现了相位补偿,并对FIR,IIR滤波器进行了综合比较。     

Design of two-channel linear-phase QMF banks based on real IIR all-pass filters

The design of two-channel linear-phase quadrature mirror filter (QMF) banks constructed by real infinite impulse response (IIR) digital all-pass filters is considered. The design problem is appropriately formulated to result in a simple optimisation problem. Using a variant of Karmarkar's algorithm, the optimisation problem can be efficiently solved through a frequency sampling and iterative approximation method to find the real coefficients for the IIR digital all-pass filters. The resulting two-channel QMF banks possess an approximately linear phase response without magnitude distortion. The effectiveness of the proposed technique is achieved by forming an appropriate Chebyshev approximation of the desired phase response and then finding its solution from a linear subspace in a few iterations. Finally, several simulation examples are presented for illustration and comparison     

Generalized digital Butterworth filter design

This correspondence introduces a new class of infinite impulse response (IIR) digital filters that unifies the classical digital Butterworth filter and the well-known maximally flat FIR filter. New closed-form expressions are provided, and a straightforward design technique is described. The new IIR digital filters have more zeros than poles (away from the origin), and their (monotonic) square magnitude frequency responses are maximally flat at ω=0 and at ω=π. Another result of the correspondence is that for a specified cutoff frequency and a specified number of zeros, there is only one valid way in which to split the zeros between z=-1 and the passband. This technique also permits continuous variation of the cutoff frequency. IIR filters having more zeros than poles are of interest because often, to obtain a good tradeoff between performance and implementation complexity, just a few poles are best     

Digital integrator design using Simpson rule and fractional delay filter

The IIR digital integrator is designed by using the Simpson integration rule and fractional delay filter. To improve the design accuracy of a conventional Simpson IIR integrator at high frequency, the sampling interval is reduced from T to 0.5T. As a result, a fractional delay filter needed to be designed in the proposed Simpson integrator. However, this problem can be solved easily by applying well-documented design techniques of the FIR and all-pass fractional delay filters. Several design examples are illustrated to demonstrate the effectiveness of the proposed method.     

Maxflat Fractional Delay IIR Filter Design

Fractional delay (FD) filters are an important class of digital filters and are useful in various signal processing applications. This paper discusses a design problem of FD infinite-impulse-response (IIR) filters with the maxflat frequency response in frequency domain. First, a flatness condition of FD filters at an arbitrarily specified frequency point is described, and then a system of linear equations is derived from the flatness condition. Therefore, a set of filter coefficients can be easily obtained by solving this system of linear equations. For a special case in which the frequency response is required to be maxflat at omega = 0 or pi , a closed-form expression for its filter coefficients is derived by solving a linear system of Vandermonde equations. It is also shown that the existing maxflat FD finite-impulse-response (FIR) and IIR filters are special cases of the FD IIR filters proposed in this paper. Finally, some examples are presented to demonstrate the effectiveness of the proposed filters.     

Frequency domain design of FIR and IIR Laplacian of Gaussian filters for edge detection

This work addresses the design of LoG filters in the frequency domain within a structure formed by the cascade of quasi-Gaussian and discrete Laplacian filters. The main feature of such a structure is that it requires half the number of convolutions of the classical structure in which the LoG transfer function is expressed as the sum of two separable transfer functions of 1-D Gaussian and LoG type. Such a perspective allows one to rephrase the design of IIR and FIR filters for edge detection as a frequency domain approximation problem solvable by standard digital filter design tools. The zero-phase IIR solutions have a good performance at low orders and approximation errors practically independent of the aperture parameter. The characteristics of the nearly linear-phase IIR filters solving the problem suggest the consideration of linear-phase FIR filters with zeros constrained on the unit circle. The use of such filters leads to remarkable computational savings with respect to the filters designed by impulse response sampling. The agreement between the edge values obtained by the filters designed according to the scheme proposed in this work and those obtained by standard techniques is very good.Work carried out with the financial support of the C.N.R.-Progetto Finalizzato Robotica, contract no. 91.01942.PF67.     

Design of stable IIR digital filter based on least P-power error criterion

In this paper, the least p-power error criterion is presented to design digital infinite impulse response (IIR) filters to have an arbitrarily prescribed frequency response. First, an iterative quadratic programming (QP) method is used to design a stable unconstrained one-dimensional IIR filter whose optimal filter coefficients are obtained by solving the QP problem in each iteration. Then, the proposed method is extended to design constrained IIR filters and two-dimensional IIR filters with a separable denominator polynomial. Finally, design examples of the low-pass filter are demonstrated to illustrate the effectiveness of the proposed iterative QP method.     

PCLS IIR digital filters with simultaneous frequency responsemagnitude and group delay specifications

This paper presents the peak-constrained least-squares (PCLS) approach to designing IIR digital filters. PCLS IIR digital filters that meet simultaneous specifications on the frequency response magnitude and the group delay are introduced. As a point of reference, we consider the IIR digital filter design problem that appears in Deczky's (1972) classic paper and in the popular textbook by Oppenheim and Schafer (1989). In addition, the same design problem appears in the IIR filter design chapter by Higgins and Munson (1993) in the Handbook for Digital Signal Processing. By using our new algorithm with simultaneous optimization of the frequency response magnitude and the group delay, we obtain a dramatic improvement in the solution of this classic IIR digital filter design problem. Starting from the same filter structure and the same specifications for the frequency response magnitude as in the works of Deczky, Oppenheim and Schafer, and Higgins and Munson, we are able to reduce the group delay ripple by a factor of 35. In another design problem that originated in Deczky's work, we use PCLS optimization to reduce the group delay ripple by a factor of 40 at the same time we reduce the stopband energy by 6 dB, without sacrificing any other performance measure. The group delay ripple in this IIR digital filter example is reduced to only ±0.002 samples     

Least-squares design of IIR filters with prescribed magnitude andphase responses and a pole radius constraint

This paper presents a method for the frequency domain design of infinite impulse response (IIR) digital filters. The proposed method designs filters approximating prescribed magnitude and phase responses. IIR filters of this kind can have approximately linear-phase responses in their passbands, or they can equalize magnitude and phase responses of given systems. In many cases, these filters can be implemented with less memory and with fewer computations per output sample than equivalent finite impulse response (FIR) digital filters. An important feature of the proposed method is the possibility to specify a maximum radius for the poles of the designed rational transfer function. Consequently, stability can be guaranteed, and undesired effects of implementations using fixed-point arithmetic can be alleviated by restricting the poles to keep a prescribed distance from the unit circle. This is achieved by applying Rouche's theorem in the proposed design algorithm. We motivate the use of IIR filters with an unequal number of poles and zeros outside the origin of the complex plane. In order to satisfy simultaneous specifications on magnitude and phase responses, it is advantageous to use IIR filters with only a few poles outside the origin of the z-plane and an arbitrary number of zeros. Filters of this type are a compromise between IIR filters with optimum magnitude responses and phase-approximating FIR filters. We use design examples to compare filters designed by the proposed method to those obtained by other methods. In addition, we compare the proposed general IIR filters with other popular more specialized structures such as FIR filters and cascaded systems consisting of frequency-selective IIR filters and phase-equalizing allpass filters     

基于免疫算法的IIR数字滤波器优化与实现

由于IIR数字滤波器设计实质上是一个非线性高维复杂函数优化问题,文中提出基于具有全局搜索能力强,收敛速度快特点的免疫算法实现IIR数字滤波器优化设计的新方法,给出了IIR滤波器优化设计的数学模型,描述了应用免疫算法优化设计IIR数字滤波器的具体实现步骤。通过低通和高通IIR数字滤波器设计的仿真结果表明方法的有效性和高效性。