高效数字FIR滤波器及滤波器组的设计

发布时间：2018-01-31 01:08

本文关键词： 频率响应遮蔽技术 FIR数字滤波器非线性优化算法非线性变换可重构滤波器组助听器　出处：《山东大学》2015年硕士论文　论文类型：学位论文

【摘要】：数字滤波器被广泛应用在数字信号处理系统中,主要用来降噪和提取有用信息,滤波器的复杂度与滤波器的过渡带宽成反比,当过渡带极窄时,系统的复杂度会急剧增加,功耗也越大。频率响应遮蔽技术(FRM)使用了系数非常稀疏的子滤波器,可以大大降低窄过渡带滤波器的复杂度。滤波器组也是数字信号处理系统和通信系统重要的组成部分,主要用来提取各个子带信号,为后续处理做准备。目前比较常见的为余弦调制滤波器组、离散傅里叶变换调制滤波器组和多相滤波器组,用于软件无线电收发,数字通信,语音信号处理系统等,本文主要关注数字助听系统中滤波器组的设计。本文重点研究了低复杂度滤波器设计和适用于助听系统的低时延可重构滤波器组设计,主要工作如下：1、提出了新型二级FRM滤波器结构和设计方法。FRM技术是设计具有窄过渡带特性FIR滤波器的一种高效方法,当滤波器的过渡带比较窄的时候,可以用多级FRM进一步减少其复杂度。对于传统的二级FRM滤波器,存在以下两个约束条件：1)原型滤波器的内插因子必须是第二级遮蔽滤波器内插因子的整数倍；2)第二级两个遮蔽滤波器的内插因子相同。本文提出的新型结构打破了这两个约束条件,采用新的计算方法确定各个子滤波器的设计参数,并结合非线性优化算法联合优化各个子滤波器。在新型结构中,假如原型滤波器和第二级两个遮蔽滤波器的内插因子分别为M,P,Q,当满足P=Q, M=kP时,得到的最优解与传统的二级FRM滤波器相同。当有一个等式不满足,改进型结构比传统结构复杂度更低,因此新型结构在硬件实现中功耗更小。2、提出了适用于助听器的低时延可重构滤波器组。大部分学者在研究适用于助听系统的滤波器组时,主要集中于固定的滤波器组结构,这种结构只能为听力损失患者提供单一的听力补偿。由于不同的听损患者具有不同的听力损失特性,固定的滤波器组往往不能提供匹配的响度补偿。本文提出了一种具有低时延特性的可重构滤波器组。首先通过余弦调制低通FIR滤波器得到一个均匀滤波器组,然后采用非线性变换将均匀滤波器组映射为非均匀滤波器组,最后通过控制参数,实现可重构的滤波器组。该滤波器组可以提供四种不同的响度补偿方式,并且无需改变滤波器组的结构和任何子滤波器的系数。经实例验证,与其他设计方法相比,该滤波器组具有较好的匹配性和较低的群时延。
[Abstract]:Digital filter is widely used in digital signal processing system, mainly used to reduce noise and extract useful information. The complexity of the filter is inversely proportional to the bandwidth of the filter, when the transition band is extremely narrow. The complexity of the system increases dramatically and the power consumption increases. FRM (Frequency response masking technique) uses subfilters with very sparse coefficients. The filter bank is also an important part of digital signal processing system and communication system, which is mainly used to extract each sub-band signal. In order to prepare for the subsequent processing. At present, the common filters are cosine modulation filter bank, discrete Fourier transform modulation filter bank and polyphase filter bank, which are used for software radio transceiver and digital communication. This paper focuses on the design of filter banks in digital hearing aid systems. This paper focuses on the design of low-complexity filters and low-delay reconfigurable filter banks for hearing aid systems. The main work is as follows: 1. The structure and design method of a new two-stage FRM filter. FRM technology is an efficient method to design FIR filter with narrow transition band characteristics. When the transition band of the filter is narrow, the complexity of the filter can be further reduced by multistage FRM. The interpolation factor of the prototype filter must be an integer multiple of the interpolation factor of the second level masking filter. 2) the interpolation factor of the second stage of the two filters is the same. The new structure in this paper breaks the two constraints and uses a new calculation method to determine the design parameters of each sub-filter. In the new structure, if the interpolation factor of the prototype filter and the second stage shadowing filter are MnP Q, respectively, the PQ is satisfied. The optimal solution is the same as the traditional two-stage FRM filter. When an equation is not satisfied, the complexity of the improved structure is lower than that of the traditional one. Therefore, the new structure has lower power consumption in hardware implementation. A low delay reconfigurable filter bank for hearing aids is proposed. Most of the researchers are studying the filter banks suitable for hearing aid systems. It mainly focuses on the fixed filter bank structure which can only provide a single hearing compensation for hearing loss patients because different hearing loss patients have different hearing loss characteristics. Fixed filter banks are often unable to provide matching loudness compensation. In this paper, a reconfigurable filter bank with low delay is proposed. First, a uniform filter bank is obtained by CoSine modulated low pass FIR filter. . Then the uniform filter bank is mapped to a non-uniform filter bank by nonlinear transformation. Finally, the reconfigurable filter bank is realized by controlling the parameters. The filter bank can provide four different loudness compensation methods. There is no need to change the structure of the filter bank and the coefficients of any subfilters. Compared with other design methods, the filter bank has better matching performance and lower group delay.
【学位授予单位】：山东大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN713

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