线性相位NPR DFT滤波器组设计

提出了一种具有不同分析和综合原型滤波器的线性相位过采样NPR DFT调制滤波器组的设计方法。根据滤波器组在子带混叠、系统输出混叠、系统失真三方面的要求,推导并给出了相应的设计算法。不同的分析、综合原型滤波器的使用增加了设计自由度,可以有效改善滤波器组的整体性能。另外,由于考虑了线性相位约束,滤波器组的通带平坦性约束变得更为简单,简化了设计算法。     

近似完全重构DFT调制滤波器组的设计

提出了一种新的近似完全重构（NPR）离散傅立叶变换（DFT）调制滤波器组的原型滤波器设计方法。其优化的目标函数由滤波器组的输出混叠、输出失真及原型滤波器的阻带能量所导出。在此设计方法中,利用DFT调制滤波器组的特殊结构合理简化了滤波器组的输出混叠,输出失真。原型滤波器的设计最终被转化为一个简单的非线性优化问题。与目前的DFT调制滤波器组的设计方法相比,该方法提供了相当大的灵活性同时具有简单的优化描述。仿真结果证实了所提出的设计方法的有效性。     

基于正交镜像滤波器组的子带脉冲压缩方法

针对超宽带雷达频带分割滤波器不理想、导致子带脉冲压缩和直接脉冲压缩结果相差较大的问题,本文提出了基于正交镜像滤波器组的子带脉冲压缩方法。首先设计了近似完全重建的正交镜像滤波器组,定义目标函数为通带误差、阻带能量和失真转移函数平方误差的加权和,通过无约束的变尺度方法将其最小化,然后用设计的正交镜像滤波器作为频带分割滤波器,实现子带脉冲压缩。仿真结果表明,本文设计的正交镜像滤波器组,相比现有的设计,具有更小的峰值重建误差、通带和阻带误差。提出的子带脉冲压缩方法,与传统方法相比,主副瓣比和主瓣宽度等脉压性能也明显提高。     

FMT系统的滤波器组优化设计

传统滤波多音调制(FMT)系统的原型滤波器阻带衰减不够大,过渡带宽度衰减速度慢,导致系统性能较低。为此,提出一种基于FMT系统载波间干扰抑制的滤波器组优化设计方法。通过优化滤波器组中原型滤波器的通带截止频率、过渡带宽度和旁瓣峰值来提高FMT系统的子信道频谱约束性。仿真结果表明,采用该优化方法设计的原型滤波器具有较小的过渡带宽度和旁瓣峰值,对应的FMT系统具有更好的子信道频谱约束性和误码率性能。     

基于Simulink的数字下变频系统的设计与仿真

针对数字下变频中低通抽取滤波器通带失真大、资源消耗严重等问题,采用锐化技术和二阶多项式插值补偿滤波器设计了基于Simulink的数字下变频系统,并利用Simulink构建系统模型。仿真结果表明,该系统不仅可以达到降低信号频率和速率的目的,同时可以有效改善抽取滤波器的通带与阻带特性,并减少了系统工作量。     

基于分离指标的宽阻带低通滤波器设计

常见的开路短截线和阶跃阻抗结构在微带低通器设计中较为成熟,但是这些结构的低通滤波器受到寄生通带的影响,阻带不够宽;提出了一种基于分离指标的宽阻带低通滤波器设计方法,利用计算机仿真软件ADS,对常见的阶跃阻抗低通滤波器进行结构改进;该方法将低通滤波器设计指标重点分为滚降率和宽阻带抑制两部分,分别利用椭圆滤波器和巴特沃斯滤波器的本身特性实现设计目的,最后进行级联优化;此结构综合设计方法简单严谨,易于实现,改进的低通滤波器性能优越,实现了宽阻带的设计需求,通带0~3 GHz,插入损耗<0.5 dB,阻带4~12 GHz,抑制>45 dB。     

基于QPSO的两通道正交镜像滤波器组的优化设计*

通过分析两通道正交镜像滤波器组的重构条件,提出了一种新的两通道正交镜像滤波器(QMF)组的设计方法,将完全重构的两通道QMF组的设计问题转换为由原型低通滤波器在通带、阻带和过渡带幅频响应的均方误差加权和组成的一种无约束的非线性优化问题,用量子粒子群优化算法(QPSO)来有效求解该类优化问题,获得该问题的全局最优解.最后...     

有源滤波器的一种“模式”设计法

本文扼要介绍了一种模式设计法进行有源滤波器的设计。分析了提出模式设计法的依据,提出了具体设计方法,提供了大量的数据和图表。它根据对滤波器的具体技术要求(通带频率、阻带频率、通带波纹、阻带衰耗等),查表得出滤波器的阶次(即决定滤波器的传递函数)、电路形式以及电路参数,然后进行频率定标和阻抗定标,就可以完成滤波器的设计。文中给出了两个带通滤波器设计实例,并与实验结果进行了比较。     

任意长度余弦调制滤波器组的设计

一般我们对线性相位原型滤波器进行调制得到长度为N=2mM的完全重构FIR滤波器组,其中M为通道数.在本文中提出了原型滤波器长度为任意的.完全重构余弦调制滤波器组.原型滤波器的设计大多涉及到多参数非线性优化问题,设计复杂度高.本文使用了拉格朗日乘数法.通过迭代实现了原型滤波器的设计.这种方法设计简单,计算量大大减少,对初值不敏感.并且可以实现令人满意的通带效果.     

基于DDS的低通滤波器设计与仿真

分析了几种经典滤波器特性,重点研究了DDS系统中低通滤波器的设计方法。根据DDS的结构特点和输出杂散频谱特性,结合滤波器技术指标使用了归一化法完成了一个九阶椭圆函数低通滤波器的设计,使其通带截至频率为120MHz、通带内最大衰减为0.2dB、在135MHz处阻带内最小衰减为66dB。通过Multisim10对其进行仿真后可以得出,使用此种方法设计的低通滤波器过渡带陡峭、幅频特性仿真良好,并且能够很好地满足预期的技术指标。     

A hybrid method for designing linear-phase quadrature mirror filter bank

In this work, a hybrid method in frequency domain for design of a linear-phase quadrature mirror filter bank is proposed. The nonlinear least square hybrid method based on Levenberg–Marquardt (LM) and Quasi-Newton (QN) is developed for the design of a low-pass prototype filter whose responses in the passband and stopband are ideal, and the filter bank response at quadrature frequency is 0.707. The proposed method is employed to optimize the quadratic measure of ideal characteristics of the prototype filter and filter bank at quadrature frequency. Performance and effectiveness of the proposed method in terms of peak reconstruction error (PRE), mean squares error in passband and stopband regions, and error in transition band at quadrature frequency are shown through numerical examples and comparison of the results with other existing method. It was found that the proposed method is very simple and easy to implement for QMF bank design problem.     

Structure-specified IIR filter and control design using real structured genetic algorithm

This paper develops an innovative optimization method, real structured genetic algorithm (RSGA), which combines the advantages of traditional real genetic algorithm (RGA) with structured genetic algorithm (SGA), and applies it for digital filter and control design optimization problems. For infinite impulse response (IIR) filter designs, the proposed approach fulfills all types of filters by minimizing the order of the filter and the absolute error of both passband and stopband. Both system structure and parametric variables are simultaneously optimized via the proposed chromosome scheme. The approach has also been extended to deal with robust control design problems. The approach offers an effective method for designing an optimal controller with robust stability. Simulation and experimental results conveys the excellence of the proposed algorithm over traditional approaches in convergence speed, performance, cost effectiveness, and attains simpler structure.     

Design of coplanar waveguide elliptic low pass filters

This article proposes three design topologies of coplanar waveguide elliptic low pass filters. The design procedure is simple and explained in detail for the first topology. Numerical results are provided using the commercially available simulation softwares IE3D and HFSS to show the validity of the design with very good agreement. The proposed filters yield less than 0.1 dB attenuation in the passband (0–2 GHz), with a controllable slope of the transition between passband and stopband. The width of the rejection band is increased by simple filter cascading resulting in a passband to stopband ratio of up to 1:6. © 2009 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2009.     

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 novel two-stage nonrecursive architecture for the design of generalized comb filters

This paper presents a novel two-stage class of decimation filters with superior spurious signal rejection performance around the so-called folding bands, i.e., frequency intervals whose signals get folded down to baseband due to decimation. The key idea to enhance signal rejection in the frequency domain lies on an effective way to place the zeros of a classical comb filter in the aforementioned folding bands. On the other hand, the paper provides a mathematical framework for designing two-stage multiplierless and nonrecursive structures of the proposed filters.Examples are provided to highlight the key steps in the design of the proposed filters. Moreover, the frequency behavior of the proposed filters in both baseband and stopband is compared with classical and generalized comb filters, and a droop compensator is proposed to counteract the passband distortion of the proposed filters.     

Alternating Analysis and Synthesis Filters: A New Pseudo-QMF Bank

Cruz-Roldán, F., Amo-López, P., Martín-Martín, P., and López-Ferreras, F., Alternating Analysis and Synthesis Filters: A New Pseudo-QMF Bank, Digital Signal Processing11 (2001) 329–345The process of designing a prototype filter for a pseudo quadrature mirror filter (QMF) cosine-modulated bank can require the optimization of a highly nonlinear cost function to obtain its coefficients or the calculation of a spectral factor of a valid 2Mth band filter. This article presents a new method for designing pseudo-QMF banks in which none of the aforementioned procedures are required. To obtain the coefficients of the prototype filter we can use any technique which enables us to design linear-phase Type I or Type II FIR filters. The result is a system in which amplitude distortion is very low, there is no phase distortion at all, and aliasing is slightly higher than the stopband attenuation of the prototype filter obtained. Several examples are included.