Design of some 2-D filters through the transformation technique

The transformation technique is a powerful tool for designing 2-D FIR filters. However, it is not useful for the design of specially shaped filters with passband/stopband regions not centred around the origin. The authors extend this technique to design two types of filters. A notch filter has a stopband centred about a small region in the 2-D frequency plane. The authors propose an extension to the transformation technique with the windowing concept to achieve the design of notch filters. A directional filter has a passband extending fully along a straight line passing through the origin. The transformation technique is further extended to yield such directional filters. Design and application examples for both these filters are also presented     

Design of filter banks using transformation of variables: newresults

The design problem of multirate filter banks can be divided into two parts. The first part involves the issue of reconstruction errors. The second part involves the issue of designing good quality subband filters. There is a class of techniques that we refer to as transformation of variables which satisfactorily addresses the two parts of the design problem. This class of filter banks is specified by its prototype filters and transformation (kernel). It is the flexibility and relative ease in designing the kernel that enables the technique to satisfactorily address the second part of the design problem. We present two new methods of designing the kernel that will enhance the design techniques' flexibility and effectiveness. The first is the combination of the McClellan transformation and rotation operators. The second introduces and uses the concept of directional singular value decomposition (SVD)     

On two-channel filter banks with directional vanishing moments.

The contourlet transform was proposed to address the limited directional resolution of the separable wavelet transform. One way to guarantee good approximation behavior is to let the directional filters in the contourlet filter bank have sharp frequency response. This requires filters with large support size. We seek to isolate the key filter property that ensures good approximation. In this direction, we propose filters with directional vanishing moments (DVM). These filters, we show, annihilate information along a given direction. We study two-channel filter banks with DVM filters. We provide conditions under which the design of DVM filter banks is possible. A complete characterization of the product filter is, thus, obtained. We propose a design framework that avoids 2-D factorization using the mapping technique. The filters designed, when used in the contourlet transform, exhibit nonlinear approximation comparable to the conventional filters while being shorter and, therefore, providing better visual quality with less ringing artifacts. Furthermore, experiments show that the proposed filters outperform the conventional ones in image approximation and denoising.     

Joint use of time-domain and windowed method for design of modulated DFT filter banks

A novel and efficient technique to design modulated discrete Fourier transform （DFT） filter banks is introduced in this paper. The proposed method first relaxes the limits that the synthesis filters are the time-reversed version of the analysis filters and then adopts the time domain formula of the perfect reconstruction property as the solution to design the synthesis filters. The prototype filter in analysis filter banks is designed based on Fourier-Kaiser window approach. Simulation results show that the designed filter banks approximately satisfy the perfect reconstruction with controllable reconstruction errors.     

基于设计空间的有源滤波器设计

提出了一种运用符号和数值计算与离散非线性优化相结合的滤波器设计方法——设计空间法,把滤波器的技术指标,即滤波器设计中要用到的一组参数映射到设计空间,并根据给定的准则寻找该设计空间的最佳解决方案。最后通过实例阐述了用设计空间法设计的低Q值RC滤波器,并且得到了较好的设计结果。     

Design of zero-phase recursive 2-D variable filters with quadrantal symmetries

The digital filters with adjustable frequency-domain characteristics are called variable filters. Variable filters are useful in the applications where the filter characteristics are needed to be changeable during the course of signal processing. In such cases, if the existing traditional constant filter design techniques are applied to the design of new filters to satisfy the new desired characteristics when necessary, it will take a huge amount of design time. So it is desirable to have an efficient method which can fast obtain the new desired frequency-domain characteristics. Generally speaking, the frequency-domain characteristics of variable filters are determined by a set of spectral parameters such as cutoff frequency, transition bandwidth and passband width. Therefore, the characteristics of variable filters are the multi-dimensional (M-D) functions of such spectral parameters. This paper proposes an efficient technique which simplifies the difficult problem of designing a 2-D variable filter with quadrantally symmetric magnitude characteristics as the simple one that only needs the normal one-dimensional (1-D) constant digital filter designs and 1-D polynomial approximations. In applying such 2-D variable filters, only varying the part of 1-D polynomials can easily obtain new desired frequency-domain characteristics.     

低功耗、低灵敏度有源带通滤波器设计的新方法

提出运用低通到带通的频率变换法与阻容细化法相结合的思想,直接利用2阶的低通(LP)滤波器原型电路实现4阶低功耗、低灵敏度的带通(BP)滤波电路的设计新方法。具体而言,通过对低通原型滤波电路进行阻抗变换以及时其对应的RC电路实现所谓“有损的LP-BP变换”,就可以实现带通(BP)滤波电路的设计。选用2阶切比雪夫(Chebyshev)低通滤波器电路为原型,给出4阶带通滤波器的具体设计过程,并通过PSpice软件来验证此种方法的可行性和实用性。     

Design of transimpedance low-pass filters

The input of a transimpedance filter is a current signal, while its output is a voltage signal. In this article, a design method for a transimpedance filter is introduced. Also, the topologies and calculation methods of the parameters of three biquadratic transimpedance low-pass (LP) filter circuits are presented in detail, according to the value of Q which is low or medium or high. As for the high-order filter, it can be designed by transimpedance LP biquad section as first stage cascaded with voltage-mode LP filters. Finally, to verify the effectiveness of the design, a design example of a high-order transimpedance LP filter is given.     

Design of nonseparable 3-D filter banks/wavelet bases usingtransformations of variables

The authors present a technique to design two-channel filter banks in three dimensions where the sampling is on the FCO (face centred orthorhombic) lattice, The ideal 3-D sub-band is of the truncated octahedron shape. The design technique is based transformation of variable method equivalent to the generalised McClellan transformation. The filters are FIR, have linear phase and achieve perfect reconstruction. Although the sub-band shape is quite complicated, the ideal frequency characteristics are well approximated. This is illustrated with an example. The technique provides the flexibility of controlling the frequency characteristics of the filters with ease. The filters can be implemented quite efficiently due to the highly symmetrical nature of the coefficients of the transformation. The authors also modify and extend the basic design technique to impose the zero property (the number of zeros of the filter transfer function at the aliasing frequency) on the sub-band filters. This property is important when the filter bank is used iteratively in a tree-structured manner as a discrete wavelet transform system and the issue of regularity arises. Several design examples are presented to illustrate the design technique     

基于免疫算法的FIR数字滤波器优化设计

针对频率采样技术设计FIR滤波器的特点,推导出阻带衰减关于滤波器阶数和过渡带采样值的优化函数,并具体设计了免疫算法对其优化求解.仿真验证表明,较之以往方法,其效果较好,对基于频率采样技术的FIR滤波器优化设计具有重要意义.     

高频低损耗声表面波滤波器研制

回顾了低损耗声表面波滤波器的主要设计方法，介绍了镜像阻抗连接换能器结构中调整滤波器带宽的设计技术，给出了在９６０ＭＨｚ高频下的两种试验结果，相对带宽分别为１％和２％，插入损耗小于５ｄＢ，阻带抑制优于５０ｄＢ。     

巴特沃斯数字陷波滤波器的设计

随着数字技术的发展,数字滤波器在许多领域得到广泛的应用。研究一种在Matlab语言环境下设计IIR数字陷波滤波器的方法,在数字陷波滤波器设计过程中,先进行模拟低通滤波器的设计,然后进行模拟低通/模拟带阻滤波器转换,最后采用双线性变化法将模拟陷波滤波器转化成数字陷波滤波器。提出一种用所有零点和极点来表达数字陷波器传递函数的方法,同时给出以巴特沃斯模拟低通为原型设计数字陷波滤波器的程序。     

模拟跨阻低通滤波器的设计

跨阻滤波器的输入为电流信号,输出为电压信号.本文给出了跨阻滤波器的设计方法,并按照品质因数Q的低、中、高详细介绍了三种双二阶节跨阻低通滤波器的电路拓扑结构及其参数计算方法.二阶跨阻低通滤波器与传统滤波器相级联即可实现高阶跨阻低通滤波器.最后,通过高阶跨阻低通滤波器的设计实例,验证文中所给出的设计方法的有效性.     

FPGA在数字滤波器设计中的应用

介绍了FIR数字滤波器的硬件实现技术,结合Altera公司的FLEX10K系列芯片提出了实现FIR数字滤波器的硬件电路的方案,设计出一种8阶FIR数字滤波器,并且推广到16阶及32阶,以及实现滤波器的AHDL语言。基于FPGA的电路系统设计及其仿真结果表明此系统合理、可靠且满足设计要求。     

多级方向加权最小二乘滤波器及其在多传感器图像融合中的应用

针对多尺度分解在图像融合领域中的广泛应用,本文提出了一种多级方向加权最小二乘滤波器图像多尺度几何分析方法。该方法利用加权最小二乘滤波器对图像进行多级边缘保持分解,得到一个近似图像和多个不同尺度上的细节图像,然后采用小尺寸方向剪切滤波器对细节图像进行方向分析,在不同尺度上生成多个方向细节图像。根据近似图像和方向细节图像所具有的不同物理意义,分别采用不同的融合策略对分解后的图像系数进行合并处理,最后应用多级方向加权最小二乘滤波器的逆变换得到融合图像。多组图像融合实验结果表明,在图像融合领域,本文提出的基于多级方向加权最小二乘滤波器的图像分解方法优于已有文献中的一些典型多尺度分解方法。     

广播电视发射系统中滤波器的温度补偿

频率稳定性是微波滤波器的重要技术指标之一。保证频率稳定,对滤波器谐振腔进行温度补偿是较为有效的方法。主要探讨温度补偿新技术,对目前比较常用的几种微波滤波器的温度补偿技术进行阐述,并给出改进法来提高微波滤波器频率稳定性。随着广播电视及其通信技术的飞速发展,温度补偿技术必将随着市场需求的增加而获得更快发展。     

Flexible design of multidimensional perfect reconstruction FIR2-band filters using transformations of variables

An approach to designing multidimensional linear-phase FIR diamond subband filters having the perfect reconstruction property is presented. It is based on a transformation of variables technique and is equivalent to the generalized McClellan transformation. Methods for designing a whole class of transformation are given. The approach consists of two parts; design of the transformation and design of the 1-D filters. The use of Lagrange halfband filters to design the 1-D filters is discussed. The modification of a particular Lagrange halfband filter which gives a pair of simple 1-D filters that are almost similar to each other in their frequency characteristics but still form a perfect reconstruction pair is presented. The design technique is extended to other types of two-channel sampling lattice and subband shapes, in particular, the parallelogram and the diagonally quadrant subband cases. Several numerical design examples are presented to illustrate the flexibility of the design method.     

基于FPGA的高阶高速FIR滤波器设计与实现

提出了一种基于FPGA的高阶高速FIR滤波器的设计与实现方法。通过一个169阶的均方根升余弦滚降滤波器的设计,介绍了如何应用流水线技术来设计高阶高速FIR滤波器,并且对所设计的FIR滤波器性能、资源占用进行了分析。     

一种可变带宽FRM滤波新结构

设计窄过渡带FIR滤波器的一种非常有效的方法是采用频率响应屏蔽技术(FRM).但是如果过渡带要求过窄,经典FRM滤波器各子滤波器的阶数会变得很高.据此,本文提出一种可变带宽镜像半带滤波FRM滤波新结构,通过增加两个镜像半带滤波器,将原型滤波器及其互补滤波器的镜像分别分成奇偶两部分,使得原型滤波器和屏蔽滤波器的设计更加灵活,并降低了滤波器的计算复杂度,达到了设计高效窄过渡带滤波器的目的.理论分析和实例均验证了该结构的有效性.     

一种适合于窄过渡带FIR滤波器设计的方法

介绍了一种适合于窄过渡带FIR(有限冲击响应)滤波器设计的方法———频罩法,首先设计一个原型滤波器,将该滤波器每个延迟部分延迟M点可产生尖锐过渡带,对其施加不同中心频率的低阶频罩滤波器,即可得到所需的尖锐带通滤波器,该方法实现窄带FIR滤波器所需的阶数仅为直接设计的50%左右;然后讨论了其VHDL(超高速集成电路硬件描述语言)实现算法,最后介绍了利用FPGA(现场可编程门阵列)实现此系统的设计方案,并分析了实际硬件设计过程中涉及的问题。