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1、毕业（设计）论文英 文 翻 译系 别 电子信息工程系 专 业 电子信息工程 班 级 学生姓名 学 号 指导教师 英文原文 The simulation and the realization of the digital filterWith the information age and the advent of the digital world, digital signal processing has become one of todays most important disciplines and door technology. Digital signal process
2、ing in communications, voice, images, automatic control, radar, military, aerospace, medical and household appliances, and many other fields widely applied. In the digital signal processing applications, the digital filter is important and has been widely applied.1、 figures Uniton :Analog and digita
3、l filtersIn signal processing, the function of a filter is to remove unwanted parts of the signal, such as random noise, or to extract useful parts of the signal, such as the components lying within a certain frequency range. There are two main kinds of filter, analog and digital. They are quite dif
4、ferent in their physical makeup and in how they work. An analog filter uses analog electronic circuits made up from components such as resistors, capacitors and opamps to produce the required filtering effect. Such filter circuits are widely used in such applications as noise reduction, video signal
5、 enhancement, graphic equalisers in hi-fi systems, and many other areas. There are well-established standard techniques for designing an analog filter circuit for a given requirement. At all stages, the signal being filtered is an electrical voltage or current which is the direct analogue of the phy
6、sical quantity (e.g. a sound or video signal or transducer output) involved. A digital filter uses a digital processor to perform numerical calculations on sampled values of the signal. The processor may be a general-purpose computer such as a PC, or a specialised DSP (Digital Signal Processor) chip
7、. The analog input signal must first be sampled and digitised using an ADC (analog to digital converter). The resulting binary numbers, representing successive sampled values of the input signal, are transferred to the processor, which carries out numerical calculations on them. These calculations t
8、ypically involve multiplying the input values by constants and adding the products together. If necessary, the results of these calculations, which now represent sampled values of the filtered signal, are output through a DAC (digital to analog converter) to convert the signal back to analog form. N
9、ote that in a digital filter, the signal is represented by a sequence of numbers, rather than a voltage or current. Unit refers to the input signals used to filter hardware or software. If the filter input, output signals are separated, they are bound to respond to the impact of the Unit is separate
10、d, such as digital filters filter definition. Digital filter function, which was to import sequences X transformation into export operations through a series Y.According to figures filter function 24-hour live response characteristics, digital filters can be divided into two, namely, unlimited long
11、live long live the corresponding IIR filter and the limited response to FIR filters. IIR filters have the advantage of the digital filter design can use simulation results, and simulation filter design of a large number of tables may facilitate simple. It is the shortcomings of the nonlinear phase;
12、Linear phase if required, will use the entire network phase-correction. Image processing and transmission of data collection is required with linear phase filters identity. And FIR linear phase digital filter to achieve, but an arbitrary margin characteristics. Impact from the digital filter respons
13、e of the units can be divided into two broad categories : the impact of the limited response (FIR) filters, and unlimited number of shocks to (IIR) digital filters.FIR filters can be strictly linear phase, but because the system FIR filter function extremity fixed at the original point, it can only
14、use the higher number of bands to achieve their high selectivity for the same filter design indicators FIR filter called band than a few high-IIR 5-10 times, the cost is higher, Signal delay is also larger. But if the same linear phase, IIR filters must be network-wide calibration phase, the same se
15、ction also increase the number of filters and network complexity. FIR filters can be used to achieve non-Digui way, not in a limited precision of a shock, and into the homes and quantitative factors of uncertainty arising from the impact of errors than IIR filter small number, and FIR filter can be
16、used FFT algorithms, the computational speed. But unlike IIR filter can filter through the simulation results, there is no ready-made formula FIR filter must use computer-aided design software (such as MATLAB) to calculate. So, a broader application of FIR filters, and IIR filters are not very stric
17、t requirements on occasions.Unit from sub-functions can be divided into the following four categories :(1) Low-filter (LPF)(2) high-filter (HPF)(3) belt-filter (BPF)(4) to prevent filter (BSF)The following chart dotted line for the ideals of the filter frequency characteristics :A(f) A(f) 1 1 0 f f
18、0 f f (a) (b)A(f) A(f) 1 12、Digital filter designDigital filter design of the basic requirementsDigital filter design must go through three steps :(1) Identification of indicators : In the design of a filter, there must be some indicators. These indicators should be determined on the basis of the ap
19、plication. In many practical applications, digital filters are often used to achieve the frequency operation. Therefore, indicators in the form of general jurisdiction given frequency range and phase response. Margins key indicators given in two ways. The first is absolute indicators. It provides a
20、function to respond to the demands of the general application of FIR filter design. The second indicator is the relative indicators. Its value in the form of answers to decibels. In engineering practice, the most popular of such indicators. For phase response indicators forms, usually in the hope th
21、at the system with a linear phase frequency bands human. Using linear phase filter design with the following response to the indicators strengths：it only contains a few algorithms, no plural operations；there is delay distortion, only a fixed amount of delay; the filter length N (number of bands for
22、N-1), the volume calculation for N/2 magnitude.(2) Model approach : Once identified indicators can use a previous study of the basic principles and relationships, a filter model to be closer to the target system.(3) Achieved : the results of the above two filters, usually by differential equations,
23、system function or pulse response to describe. According to this description of hardware or software used to achieve it.3、 MATLAB introducedMATLAB is a matrix laboratory (Matrix Laboratory) is intended. In addition to an excellent value calculation capability, it also provides professional symbols t
24、erms, word processing, visualization modeling, simulation and real-time control functions. MATLAB as the worlds top mathematical software applications, with a strong engineering computing, algorithms research, engineering drawings, applications development, data analysis and dynamic simulation, and
25、other functions, in aerospace, mechanical manufacturing and construction fields playing an increasingly important role. And the C language function rich, the use of flexibility, high-efficiency goals procedures. High language both advantages as well as low level language features. Therefore, C langu
26、age is the most widely used programming language. Although MATLAB is a complete, fully functional programming environment, but in some cases, data and procedures with the external environment of the world is very necessary and useful. Filter design using Matlab, could be adjusted with the design req
27、uirements and filter characteristics of the parameters, visual simple, greatly reducing the workload for the filter design optimization.In the electricity system protection and secondary computer control, many signal processing and analysis are based on are certain types Yeroskipou and the second ha
28、rmonics of the system voltage and current signals (especially at D process), are mixed with a variety of complex components, the filter has been installed power system during the critical components. Current computer protection and the introduction of two digital signal processing software main filt
29、er. Digital filter design using traditional cumbersome formula, the need to change the parameters after recalculation, especially in high filters, filter design workload. Uses MATLAB signal processing boxes can achieve rapid and effective digital filter design and simulation.MATLAB is the basic unit
30、 of data matrix, with its directives Biaodashi mathematics, engineering, commonly used form is very similar, it is used to solve a problem than in MATLAB C, Fortran and other languages End precision much the same thing. The popular MATLAB 5.3/Simulink3.0 including hundreds of internal function with
31、the main pack and 30 types of tool kits (Toolbox). kits can be divided into functional tool kits and disciplines toolkit. MATLAB tool kit used to expand the functional symbols terms, visualization simulation modelling, word processing and real-time control functions. professional disciplines toolkit
32、 is a stronger tool kits, tool kits control, signal processing tool kit, tool kits, etc. belonging to such communicationsMATLAB users to open widely welcomed. In addition to the internal function, all the packages MATLAB tool kits are readable document and the document could be amended, modified or
33、users through Yuanchengxu the construction of new procedures to prepare themselves for kits.中文翻译数字滤波器的仿真与实现随着信息时代和数字世界的到来，数字信号处理已成为当今一门极其重要的学科和技术领域。数字信号处理在通信、语音、图像、自动控制、雷达、军事、航空航天、医疗和家用电器等众多领域得到了广泛的应用。在数字信号处理应用中，数字滤波器十分重要并已获得广泛应用。1、数字滤波器介绍：模拟和数字滤波器 在信号处理、过滤功能是一个不排除部分信息，如随机噪音，提取有用的信号部分，如部分地势在一定的频率范围。
34、有两大类型的过滤，模拟以及数字。他们是完全不同的物理结构，如何工作。类比电子电路模拟用的滤波部分组成，例如由电阻、电容和生产所需的滤波效果。这种滤波器被广泛使用的电路减少噪音等方面的应用，提高视频信号、图像均衡的高科技传真系统等众多领域。有完善的技术标准设计的模拟电路进行滤波的特定要求。在各个阶段，是一个信号，是电机电压和过滤，目前直接的物理模拟量(例如声音或视频信号和变频器生产)处理。数字滤波器用数字进行数值计算处理器的信号抽样值。处理器的可能通用计算机等PC或专业发展计划图(数字信号处理器)芯片。模拟信号必须先投入使用的取样和A/D转换器(模拟到数字转换器)。由此二元多,占抽样连续输入信号
35、的取值传送到处理器,进行数字计算。这些计算通常涉及多方面的投入和增加产品取值的共同因素。如有必要,这些计算结果,现在是抽样信号值的滤波,产出通过D/A转换器来把信号转换回模拟形式。看到一个数字滤波器,信号是由一系列数字组成,而不是电压或电流。滤波器是指用来对输入信号进行滤波的硬件或软件。如果滤波器的输入、输出都是离散信号，则该滤波器的冲击响应也必然是离散的，这样的滤波器定义为数字滤波器。数字滤波器的功能，就是把输入序列X通过一定的运算变换成输出序列Y。根据数字滤波器冲激响应函数的时域特性，可将数字滤波器分为两种，即无限长冲激相应（IIR）滤波器和有限长冲激响应（FIR）滤波器。IIR数字滤波器
36、的优点是可以利用模拟滤波器设计的结果，而模拟滤波器的设计有大量图表可查，方便简单。它的缺点是相位的非线性；若需要线性相位，则要采用全通网络进行相位校正。图象处理以及数据采集传输都要求滤波器具有线性相位特性。而FIR数字滤波器可以实现线性相位，又可具有任意幅度特性。从数字滤波器的单位冲击响应来看，可分为两大类：有限冲击响应（FIR）数字滤波器和无限冲击响应（IIR）数字滤波器。FIR滤波器却可以得到严格的线性相位，然而由于FIR滤波器的系统函数的极点固定在原点，所以只能用较高的阶数来实现其高选择性，对于同样的滤波器设计指标，FIR滤波器所要求的阶数要比IIR高5至10倍，所以成本较高，信号延迟也
37、较大。但是如果要求相同的线性相位，则IIR滤波器就必须加全通网络进行相位校正，同样也要增加滤波器网络的节数和复杂性。FIR滤波器可以用非递归的方法实现，在有限精度下不会产生振荡，同时由于量化舍入以及系数的不确定性所引起的误差的影响要比IIR滤波器小的多，并且FIR滤波器可以采用FFT算法，运算速度快。但是不象IIR滤波器可以借助模拟滤波器的成果，FIR滤波器没有现成的计算公式，必须要用计算机辅助设计软件（如MATLAB）来计算。由此可知，FIR滤波器应用比较广，而IIR滤波器则用在相位要求不是很严格的场合。滤波器从功能上分又可分为如下4类:(1)低通滤波器(LPF)；(2)高通滤波器(HPF
38、)；(3)带通滤波器(BPF )；(4)带阻滤波器(BSF)。A(f) A(f) 1 1 0 f f 0 f f (a) (b)A(f) A(f) 1 1 0 f f f 0 f f f (c) (d)图中四类滤波器的幅频特性(a)低通 (b)高通 (c)带通 (d)带阻2、数字滤波器的设计数字滤波器设计的基本要求，数字滤波器设计要经过三个步骤：（1）确定指标：在设计一个滤波器前，必须有一些指标。这些指标要根据应用确定。在很多实际应用中，数字滤波器常常被用来实现选频操作。因此，指标的形式一般在频域中给出幅度和相位响应。幅度指标主要以两种方式给出。第一种是绝对指标。它提供对幅度响应函数的要求，一
39、般应用于FIR滤波器的设计。第二种指标是相对指标。它以分贝值的形式给出要求。在工程实际中，这种指标最受欢迎。对于相位响应指标形式，通常希望系统在通频带中人有线性相位。运用线性相位响应指标进行滤波器设计具有如下优点：只包含实数算法，不涉及复数运算；不存在延迟失真，只有固定数量的延迟；长度为N的滤波器（阶数为N-1），计算量为N/2数量级。（2）模型逼近：一旦确定了指标，就可利用前面学习过的基本原理和关系式，提出一个滤波器模型来逼近给定的指标体系。（3）实现：上面两步的结果得到的滤波器，通常是以差分方程、系统函数或脉冲响应来描述的。根据这个描述用硬件或者计算机软件来实现它。3、MATLAB介绍：M
40、ATLAB是矩阵实验室（MatrixLaboratory）之意。除具备卓越的数值计算能力外，它还提供了专业水平的符号计算，文字处理，可视化建模仿真和实时控制等功能。MATLAB作为世界顶尖的数学应用软件，以其强大的工程计算、算法研究、工程绘图、应用程序开发、数据分析和动态仿真等功能，在航空航天、机械制造和工程建筑等领域发挥着越来越重要的作用。而C语言功能丰富，使用灵活方便，目标程序效率高。既有高级语言的优点，又有低级语言的特点。因此，C语言是目前应用最广的编程语言。虽然MATLAB是一个完整的、功能齐全的编程环境，但在某些情况下，与外部环境的数据和程序的交互是非常必须而且有益的。利用MATLA
41、B设计滤波器，可以随时对比设计要求和滤波器特性调整参数，直观简便，极大的减轻了工作量，有利于滤波器设计的最优化。在电力系统微机保护和二次控制中，很多信号的处理与分析都是基于正旋基波和某些整次谐波而进行的，而系统电压电流信号（尤其是故障瞬变过程）中混有各种复杂成分，所以滤波器一直是电力系统二次装置的关键部件。目前微机保护和二次信号处理软件主要采用数字滤波器。传统的数字滤波器设计使用繁琐的公式计算，改变参数后需要重新计算，在设计滤波器尤其是高阶滤波器时工作量很大。利用MATLAB信号处理箱可以快速有效地实现数字滤波器的设计与仿真。 MATLAB的基本数据单位是矩阵，它的指令表达式与数学,工程中常用的形式十分相似,故用MATLAB来解算问题要比用C,FORTRAN等语言完相同的事情简捷得多.当前流行的MATLAB 5.3/Simulink3.0包括拥有数百个内部函数的主包和三十几种工具包(Toolbox)。工具包又可以分为功能性工具包和学科工具包.功能工具包用来扩充MATLAB的符号计算,可视化建模仿真,文字处理及实时控制等功能.学科工具包是专业性比较强的工具包,控制工具包,信号处理工具包,通信工具包等都属于此类。开放性使MATLAB广受用户欢迎.除内部函数外,所有MATLAB主包文件和各种工具包都是可读可修改的文件,用户通过对源程序的修改或加入自己编写程序构造新的专用工具包。
