双线性变换法中预畸变概念的补充

现有数字信号处理教材在讲述双线性变换法中预畸变概念时略有不足,在一定程度上影响了读者对“畸变”、“预畸变”以及“为什么叫预畸变”等概念的理解和掌握。通过一个滤波器设计实例,较自然地引出了双线性变换法预畸变的概念,并指出了预畸变概念适用的前提,即不能脱离相比较的模拟环境。教学实践证明,通过该实例讲述预畸变的概念,能有效加深学生对预畸变概念的认识和理解。     

IIR数字滤波器的研究与设计

文中探讨了利用模拟滤波器设计IIR数字滤波器过程中的转换方法,脉冲响应不变法和双线性变换法,在MATLAB中以两种方法设计了数字巴特沃思低通滤波器。探讨了MATLAB中非低通数字滤波器的完全工具函数设计法和分步函数设计法,以上述方法分别设计了切比雪夫I型数字低通、高通、带通、带阻滤波器。     

用双线性变换法设计IIR滤波器

给出了用双线性变换法设计IIR数字滤波器的方法,并通过用MATLAB语言来实现。双线性法可以使系统经变换后仍保持原有特性,而且这种方法是S域和Z域的单值一一对应,克服了频率交叠产生的混叠效应;最后使用MATLAB语言实现了满足要求的低通IIR滤波器,从而证明了椭圆滤波器具有最优特性。     

IIR数字滤波器设计中两种主要离散化方法的比较

对IIR数字滤波器设计中的脉冲响应不变法和双线性变换法等两种主要离散化方法的原理、步骤进行了论述;就它们在对滤波器性能的影响方面进行了比较。最后,给出了设计中两种离散化方法的选用准则。     

用于计算机仿真的实用数字滤波器

本文提出了一种用于光电对抗计算机仿真的实用数字滤波器 ,该数字滤波器的设计是利用模拟域频带变换法和数字化方法 ,根据双线性变换法中离散系统函数与模拟系统函数的系数关系式实现的。仿真结果表明 ,较好地满足了仿真系统的要求。     

用于计算机仿真的实用数字滤波器

本文提出了一种用于光电对抗计算机仿真的实用数字滤波器,该数字滤波器的设计是利用模拟域频带变换法和数字化方法,根据双线性变换法中离散系统函数与模拟系统函数的系数关系式实现的。仿真结果表明,较好地满足了仿真系统的要求。     

双线性变换法原理的解释

现有信号与系统教材或数字信号处理教材对数字滤波器设计中的双线性变换公式未给出完全的物理概念解释,这在一定程度上影响了初学者对双线性变换法原理的理解和掌握。考虑到讲授对象为初学者及课堂讲授时间的限制,根据笔者的教学体会,本文从连续时间系统的基本环节、积分的数值计算、一阶系统和高阶系统的离散实现等几个步骤,对双线性变换法的原理作简单而系统的阐述,以供参考。     

基于DSP的IIR数字滤波器的设计

根据IIR滤波器的特点,在DSP环境下用双线性变换法设计IIR数字滤波器,并对输入信号进行滤波分析。     

数字滤波器仿真软件评估的谱分析方法研究

本文讨论了仿真模型验证常用的技术方法,针对数字滤波器仿真软件的特点,提出了采用谱分析的方法进行可信性评估.以双线性变换法设计的IIR数字滤波器仿真软件的可信性评估为例,应用Matlab软件分别采用程序设计法、基于SPTool的频谱分析方法和基于Simulink的频谱分析方法实现了对数字滤波器仿真软件滤波结果的频谱分析.     

基于Matlab的IIR数字滤波器设计

数字滤波是数字信号处理的重要内容,可分为FIR和IIR两大类。文章介绍了基于MATLAB的IIR数字滤波器设计方法。先确定性能参数,再按照映射规则(冲激响应不变法或双线性变换法)变换成模拟滤波器的性能参数,然后采用一定的逼近方法(巴特沃斯型或切比雪夫型)设计模拟滤波器,最后将模拟滤波器按照映射规则转变成数字滤波器。通过Matlab实验仿真,成功地设计出了满足预定指标的IIR数字滤波器。     

基于时频分布的MPSK信号识别解调

通信信号的自动识别解调技术受到日益广泛的重视。针对衰落信道中广泛存在的多普勒频移现象,本文提出了一种MPSK信号数字化识别解调的方法。该方法基于信号的时频分布,在时频二维平面上对MPSK信号进行分析,用双线性变换提取基带相位信息,并且实时估计和跟踪载波频率,从而实现MPSK信号识别解调。文中还给出了对一个QPSK信号进行数字化识别解调的仿真结果,并讨论了信噪比、窗函数对解调性能的影响。最后以QPSK信号为例,给出了解调器性能的仿真曲线。     

Switched-capacitor bandpass filter based on simulation of canonical reactance sections

A design method is described for switched-capacitor filters. It is based on the simulation of doubly terminated reactance filters in a canonical tandem section configuration and using the bilinear s-to-z transformation between the frequency planes of the continuous-time reference filter and the discrete-time switched-capacitor filter. The switched-capacitor circuits are completely insensitive to parasitic capacitances. The method permits the switched-capacitor realization of the whole class of lossless two-ports.     

Effect of dielectric support on the inner conductor of eccentriccoaxial line

This paper presents a method for the evaluation of the effect of the dielectric support between the inner and the outer conductors of eccentric coaxial line. Two different conformal mappings are used to obtain two different approximate formulas for the evaluation of the capacitance of this structure. First, a cotangent hyperbolic transformation is used, which transforms the conductor boundaries to parallel straight lines, and the circle surrounding the dielectric support to a curved contour. The same structure is also analyzed using a bilinear transformation expressed in terms of mutually inverse points followed by a logarithmic transformation. In each case, an expression for the capacitance is found by replacing the continuous curve representing the dielectric boundary by a number of infinitesimally small discrete steps. A comparison of numerical data obtained by the two methods is presented     

Simple state-space formulations of 2-D frequency transformation and double bilinear transformation

In this paper, an explicit relationship between the two-dimensional (2-D) frequency transformation and the theory of linear fractional transformation (LFT) representation is shown. Based on this relationship, a simple alternative state-space formulation of 2-D frequency transformation for 2-D digital filters is derived by utilizing the well-known Redheffer star product of LFT representations. The proposed formulation is then utilized to establish a simple relationship between the state-space representations of a 2-D continuous system and a 2-D discrete system which are related by the double bilinear transformation. Moreover, the inherent relations among the proposed formulations and the existing results are discussed. It turns out that all the existing results given in the literature can be unified as special or equivalent cases by the new state-space formulation of 2-D frequency transformation in a very concise and elegant form. Numerical examples are given to illustrate the effectiveness of the proposed formulations.     

Synthesis of a first-order passive complex filter with band-pass/band-elimination characteristics

In this paper, a new passive complex filter is proposed. In the same fashion as the traditional real band-pass filter, the proposed circuit is also designed through the frequency transformation. In order to obtain the prototype complex filter suitable for passive realization, the extended lowpass–highpass transformation or the bilinear lowpass–lowpass transformation different from the well-known frequency shifting method is adopted. These transformations give two filters; however, the final circuits become identical to each other. The proposed circuit has two output terminals. One is the complex band-pass output, and the other is for the complex band-elimination. The proposed circuit includes a capacitor, an autotransformer or an inductor and termination resistors only. Because the proposed circuit has terminating resistors at both of the input and the output sides, it is suitable for high frequency application. As an example, two first-order complex filters which operate in 100 kHz and 10 MHz are designed and their frequency responses are measured. It is shown that the measured frequency responses agree with the theoretical ones through experiment.     

The design of two channel IIR QMF bank directly from analogue prototype

This article presents a new method for designing two-band quadrature mirror filter (QMF) banks. Analytic solution of the filter coefficients is obtained in the s-domain. The characteristic function of the new filter has one multiple pole in the pass-band and one multiple zero in the stop-band. As a consequence, the transfer function has a single ripple, both in the pass-band and in the stop-band. Lowpass and highpass filter pair is double complementary in the s-plane. The gain responses of the lowpass and highpass filter pair at the crossover frequency are approximately 3?dB below their maximum values. Using the bilinear transformation, the analogue filter transfer function is mapped into the corresponding digital filter transfer function, so that the analogue crossover frequency is mapped into the digital frequency corresponding to ω?=?π/2. The filter characteristic exhibits Butterworth-like behaviour near the origin and Chebyshev-like behaviour (of the third order) near the pass-band edge.     

Digital Filter Design Techniques in the Frequency Domain

The frequency domain of wide-band linear sampleddata filters is considered. The sampled-data filter is termed ?wideband? when the frequency range of useful approximation to its continuous counterpart approaches half the sampling frequency. Sampled-data filter representations for continuous filters can be obtained using several different design procedures.[1] A particular design method utilizing the bilinear transformation is developed. The method is especially useful in designing wide-band sampleddata filters which exhibit relatively flat frequency-magnitude characteristics in successive pass- and stop-bands. Filters of this type are widely used in network simulation and data processing problems.[2] The design method possesses two chief advantages over the standard z transform.[3] The first is that the transformation used is purely algebraic in form. This means it can be applied easily to a continuous filter having a rational transfer characteristic expressed in either polynomial or factored form. The second advantage is the elimination of aliasing[4] errors inherent in the standard z transform. Thus, the sampled-data filter obtained by this design method exhibits the same frequency response characteristics as the continuous filter, except for a nonlinear warping of the frequency scale. Compenation for this warping can be made by a suitable frequency scale modification. Some of the more common filter networks to which the design method can be applied effectively are the Butterworth, Bessel, Chebyshev, and elliptic-filter structures. The design method consists first of obtaining a rational transfer characteristic for a continuous filter that satisfies the design specifications.     

基于双线性变换法的智能车数字控制器设计

为了使智能车更稳定地行驶在跑道上,引入了PID算法以增加速度和角度的控制精度,使小车更快更准地到达既定参数。在传统的PID算法中通常使用后向差分法来实现从连续化数字控制器到离散化的转换,这种方法精度低且不能保证相同的频率响应。文中引入双线性变换法来实现离散化过程,实验证明,该方法变换简单、精度更高,且可以使小车更加稳定快速地在不同轨道上行驶。     

基于小波的双线性插值误差补偿算法的图像放大

为了尽可能地保持低分辨率图像的基本信息,提高图像的视觉效果和空间分辨率,本文提出一种基于小波的双线性插值误差补偿算法。该算法增加双线性插值的误差补偿项,利用Sobel算子设定插值点的边缘方向,得到初始放大图像。利用小波提取高频成分,原始图像幅值增强充当低频部分,再经过小波逆变换得到高分辨率图像。实验结果表明,相对于传统的图像放大算法,该算法考虑到全局相关性,得到更加清晰的边缘信息。