具有近似线性相位特性的多相波数字滤波器的设计

不考虑相位失真,而要求满足比较苛刻的振幅特性的时候,和FIR滤波器比较起来,采用 IIR 滤波器,计算量要小很多.但对某些IIR滤波器,采取适当的方法,也可以使其相位失真变得很小.本文提出一种新的设计方法,用来设计振幅响应完全满足设计要求,而相位特性用Chebyshev 近似来实现的多相波数字滤波器.这种方法的关键在于确定通带中的若干衰减零点.文中对需要的最小衰减零点数作了估计.实例表明,用这种方法设计的滤波器,时延小,相位特性非常接近线性.     

FIR滤波器线性相位特性的研究

本文通过对滤波器的线性相位研究,介绍FIR滤波器的线性相位的4种特性,详细分析了FIR滤波器的线性相位的幅度特性,并在MATLAB下对FIR滤波器的4种特性进行模拟仿真实验,得到FIR数字滤波器的相位特性只取决于冲击响应的对称性.     

基于雷米兹交换算法设计线性相位对数FIR滤波器

根据线性相位对数FIR滤波器幅度响应与线性相位FIR滤波器幅度响应的关系 ,将线性相位对数滤波器设计转换为线性相位FIR滤波器设计。该方法直接采用雷米兹交换算法即可获得线性相位对数滤波器通带和阻带的等纹波特性。另外 ,该方法既可基于频域均匀采样也可基于频域非均匀采样 ,具有一定的通用性和灵活性     

新型密集波分解复用器的实验研究

为了易于实现解复用波长数目和间隔上的升级,设计了一种新型16波长/100GHz间隔密集波分解复用器.该器件由100GHz光梳状滤波器和200GHz介质膜滤波器构成:利用光梳状滤波器的并行输出来扩展解复用信道之间的间隔,通过介质膜滤波器的串联来实现不同波长的解复用.实验研究表明,该器件具有良好的性能,能够满足系统升级的需要.     

一种瞬态巴特沃兹一切比雪夫滤波器的简单设计方法

瞬态巴特沃兹一切比雪夫滤波器(TBC)的一些特性得到了研究,并且获得了这种滤波器的简单设计方法。这种滤波器与对应的切比雪夫滤波器相比,在满足幅值要求的情况下,所需的阶数一样多,或最多高一阶。此外,它的相位响应线性得到了改善。     

采用数字滤波器的音频系统的频域均衡(二)--均衡实例

提出了设计用于对模拟系统(它们是模拟和数字混合音频信号处理的组成部分)的频域特性(如幅度和相位响应)进行均衡的数字滤波器.数值实例向人们展示了采用数字滤波器进行均衡带来的优越性.介绍了几种音频方面的应用(如反折叠滤波器、扬声器均衡和ΣΔ型数据变换器的均衡).研究了一些密切相关的课题,如高效多速率滤波器构造、参数建模以及递归数字滤波器与非递归数字滤波器的比较.     

Chebyshev过渡型滤波器设计和分析

传统的Chebyshev滤波器具有较差的相位特性,其阶跃响应具有较大的过冲和较长的调节时间。本文从传递函数的极点角度,对Chebyshev滤波器进行了改进,改进后的滤波器表现出典型的过渡特性,在对幅度特性影响较小的情况下,改善了传统Chebyshev滤波器的相位特性和阶跃响应。通过对滤波器极点的调整,消除了传统Chebyshev滤波器过冲和传统偶数阶Chebyshev滤波器的稳态误差。     

同相线性相位分频网络研究

分频网络频率响应与声音重放效果密切相关,科研人员从不同的角度对分频网络的设计进行了大量研究,较多集中于幅频响应.从分频网络的相频响应出发,使用贝塞尔全通滤波器近似线性相位滤波器,并构造了同相分频网络.在此提出的方法同时满足了线性相位和同相两个要求,在保证分频网络的总幅频响应恒定的情况下,改善了相频响应.实验表明,该方法切实可行.     

全相位数字滤波

本文提出全相位DFT数字滤波器,全相位FIR滤波器及全相位FFT频谱分析.全相位数字滤波器它有良好的滤波器频率特性,适用於频谱分析,多路复用和扩频通信中窄带干扰抑制等频域自适应滤波器.     

用级联二阶节设计高阶带通滤波器的一种简单方法（续）

用级联二阶节设计高阶带通滤波器的一种简单方法（续）解放军广州通信学院陈俊一，单严，王光祥（上接９５年第２期）４．单个二阶带通滤波器增益特性与相位特性ＬＴＣ１０５９，６０，６１，６４中的每个二阶节的输出和教科书中的带通滤波器的增益与相位响应十分近似。其...     

针对级联型ⅡR滤波器群延时的均衡优化技术

为了减小由非恒定群延时所引起的滤波器的输出信号失真,本文提出一种适用于级联型无限长脉冲响应数字滤波器的群延时均衡优化方法.通过在级联型ⅡR数字滤波器每一级的输出插入全通均衡器,减小群延时在通带范围内的变化,进而减小滤波器的输出信号失真.对于本文提出的群延时优化方法,当采用1阶和2阶均衡器进行电路优化时,在0~100Hz的通带范围内,分别将群延时的变化量减小了28.19%和49.93%.基于0.18μm CMOS标准单元库进行逻辑综合与版图设计,最终得到整个滤波电路IP核版图的面积为0.1747mm².相比于已有文献方法,本文方法在群延时优化上效果显著,电路实现上功耗和面积较小,非常适合片上系统应用.     

Design of Bessel low-pass filter using DGS for RF/microwave applications

A synthesis method to design a defected ground structures (DGS)-based Bessel low-pass filter (LPF) using a triangular and an open-square (OS)-type DGS is reported. For the five-pole Bessel LPF at f_c = 2.5 GHz, we get 10.6 dB/GHz selectivity using the triangular DGS; while the OS-type DGS provides 39 dB/GHz selectivity. For these two filters, the 10 dB impedance matching BW is 76% and 84%, respectively. It is a much wider BW that is obtained for a lumped element Bessel LPF. The maximum group delay (GD) variation within the pass band is 25pS and 28pS, respectively. The 20 dB rejection BW can be increased from 5.8 GHz to 18.8 GHz with increase in the order of filter from 5 to 11. We have also presented the design of a compact five-pole DGS-based elliptic filter with selectivity 38.2 dB/GHz and 17.8 dB return loss. Results on the DGS-based elliptic filter, Butterworth and Chebyshev filters are also presented. The experimental results are compared against the recently reported LPFs. Our reported filters perform better with respect to selectivity and group delay variation. The flatter GD and high selectivity, along with a wide 10 dB impedance matching BW, make the DGS Bessel filter a candidate for high-speed data communication, front end of a wideband communication system and efficiency improvement of a power amplifier.     

Folded Architecture for Digital Gammatone Filter Used in Speech Processor of Cochlear Implant

Emerging trends in the area of digital very large scale integration (VLSI) signal processing can lead to a reduction in the cost of the cochlear implant. Digital signal processing algorithms are repetitively used in speech processors for filtering and encoding operations. The critical paths in these algorithms limit the performance of the speech processors. These algorithms must be transformed to accommodate processors designed to be high speed and have less area and low power. This can be realized by basing the design of the auditory filter banks for the processors on digital VLSI signal processing concepts. By applying a folding algorithm to the second‐order digital gammatone filter (GTF), the number of multipliers is reduced from five to one and the number of adders is reduced from three to one, without changing the characteristics of the filter. Folded second‐order filter sections are cascaded with three similar structures to realize the eighth‐order digital GTF whose response is a close match to the human cochlea response. The silicon area is reduced from twenty to four multipliers and from twelve to four adders by using the folding architecture.     

基于全相位遍历机制的FBG谱线识别系统

提出一种基于全相位遍历机制FIR滤波技术实现光纤Bragg光栅（FBG）波长信息精确提取方案。系统在数字时钟控制下产生锯齿波电压对可调谐Fabry-Perot（FP）滤波器进行扫描,结合虚拟仪器（Ⅵ）技术,数据采集卡在同步时钟控制下实时读取FBG波长数据,并利用Matlab对采集的数据进行离线全相位滤波处理。实验结果表...     

基于DDS的低通滤波器的设计与实现

基于DOS技术的基本原理，以设计低通滤波器为目的，采用EDA软件Multisim2001进行仿真，研究了低通滤波器的设计方法，确定了低通滤波器的结构、阶数，并设计相关参数，得出了截至频率为120MHz的7阶的低通滤波器，其幅频特性好，具有快速的衰减性。     

二阶锥规划方法对于低群延时复系数有限冲激响应数字滤波器优化设计

针对低群延时复系数有限冲激响应数字滤波器优化设计问题,提出了一种幅度和相位独立约束的等纹波设计新方法.该方法在相位误差一定的条件下对幅度的上界和下界分别采取复数圆约束和线性不等式约束,不仅提高了幅度约束的精度,而且将非凸的滤波器设计问题转化为二阶锥规划问题;同时,为抑制通带边缘附近较大的群延时震荡效应,引入了相位误差一...     

A novel compact K band PBG microstrip structure band-pass filter

A novel K band band-pass filter based on photonic band-gap (PBG) is presented. The proposed structures exhibit low insertion loss, compact size, simple fabrication and slow-wave characteristics. Due to slow-wave characteristic, PBG structure minimizes the pass-band filter to one-tenth of conventional filters with spurious-free response and deep attenuation levels. The miniature band-pass filter was simulated, realized and measured. There is a good agreement between the experiment and simulation results had been achieved. Its center pass-band frequency of this filter is 25.2?GHz, and insertion loss is less than ?4.5?dB.     

线性失真对OFDM传输信号质量的影响分析

分析了线性失真对OFDM传输信号质量的影响。结合数字调幅广播(DRM)系统，分别对相位和幅度的线性失真作了具体分析和仿真，提出了DRM系统滤波器设计的指标要求。     

Design of recursive variable digital filters with theoretically guaranteed stability

Stability is one of the most concerned issues in designing a recursive variable digital filter (VDF). This is because the coefficients of a recursive VDF constantly vary in the tuning process, and updating the coefficients may incur instability. Thus, an appropriate measure needs to be taken for ensuring its stability. This paper presents a new coefficient transformation (CT) method for transforming the coefficients of a recursive transfer-function denominator into a set of new coefficients. From the viewpoint of conventional constant-coefficient filter (constant filter) design, the new coefficients can take arbitrary values without incurring instability. For designing a stable VDF, we apply this CT to the variable case and approximate each transformed coefficient as a distinct polynomial in the tuning parameter. Thus, we can change the filter coefficients by changing the value of the tuning parameter, and thus tune the magnitude response. Thanks to the proposed CT, updating the filter coefficients will never incur instability. This is the core part of the CT-based design approach. In this paper, we utilise a weighting function to ignore the transition-band errors and thus enhance the design accuracy of important frequency bands (passband and stopband). Moreover, the polynomials use different degrees so as to reduce the VDF complexity. Two design examples (lowpass VDF and bandpass VDF) are provided for verifying the design accuracy and checking the stability.