电子与通信工程专业英语Unit-11--Introduction-to-Digital-Signal-Processing 课件

1、1 1电子与通信工程专电子与通信工程专业英语业英语Unit-11-Unit-11-Introduction-to-Introduction-to-Digital-Signal-Digital-Signal-ProcessingProcessing2 21What is DSP?DSP, or Digital Signal Processing, as the term suggests, is the processing or signals by digital means. A signal in this context can mean a number of different t

2、hings. Historically the origins of signal processing are in electrical engineering, and a signal here means an electrical signal carried by a wire or telephone line, or perhaps by a radio wave. More generally, however, a signal is a stream of information representing anything from stock prices to da

3、ta from a remote-sensing satellite.3 3The term “digital comes from “digit, meaning a number (you count with your fingersyour digits), so “digital literally means numerical; the French word for digitalis numrique. A digital signal consists of a stream of numbers, usually (but not necessarily) in bina

4、ry form. The processing of a digital signal is done by performing numerical calculations.4 45 56 63Signal processingSignals commonly need to be processed in a variety of ways. For example, the output signal from a transducer may well be contaminated with unwanted electrical “noise. The electrodes at

5、tached to a patients chest when an ECG is taken measure tiny electrical voltage changes due to the activity of the heart and other muscles. The signal is often strongly affected by “mains pickup due to electrical interference from the mains supply. 7 7Processing the signal using a filter circuit can

6、 remove or at least reduce the unwanted part of the signal. Increasingly nowadays, the filtering of signals to improve signal quality or to extract important information is done by DSP techniques rather than by analog electronics 2.8 84Digital signal processors (DSPs)The introduction of the micropro

7、cessor in the late 1970s and early 1980s made it possible for DSP techniques to be used in a much wider range of applications. However, general-purpose microprocessors such as the Intel x86 family are not ideally suited to the numerically-intensive requirements of DSP, and during the 1980s the incre

8、asing importance of DSP led several major electronics manufacturers (such as Texas Instruments, Analog Devices and Motorola) to develop Digital Signal Processor chips-specialised microprocessors with architectures designed specifically for the types of operations required in digital signal processin

9、g3. 9 9Note that the acronym DSP can variously mean Digital Signal Processing, the term used for a wide range of techniques for processing signals digitally, or Digital Signal Processor, a specialised type of microprocessor chip. Like a general-purpose microprocessor, a DSP is a programmable device,

10、 with its own native instruction code. DSP chips are capable of carrying out millions of floating point operations per second, and like their better-known general-purpose cousins, faster and more powerful versions are continually being introduced4. DSPs can also be embedded within complex “system-on

11、-chip devices, often containing both analog and digital circuitry.10 105Applications of DSPDSP technology is nowadays commonplace in such devices as mobile phones, multimedia computers, video recorders, CD players, hard disc drive controllers and modems, and will soon replace analog circuitry in TV

12、sets and telephones. An important application of DSP is in signal compression and decompression. Signal compression is used in digital cellular phones to allow a greater number of calls to be handled simultaneously within each local “cell. 11 11DSP signal compression technology allows people not onl

13、y to talk to one another but also to see one another on their computer screens, using small video cameras mounted on the computer monitors, with only a conventional telephone line linking them together5. In audio CD systems, DSP technology is used to perform complex error detection and correction on

14、 the raw data as it is read from the CD.12 12Although some of the mathematical theory underlying DSP techniques, such as Fourier and Hilbert Transforms, digital filter design and signal compression, can be fairly complex, the numerical operations required actually to implement these techniques are v

15、ery simple, consisting mainly of operations that could be done on a cheap four-function calculator6. The architecture of a DSP chip is designed to carry out such operations incredibly fast, processing hundreds of millions of samples every second, to provide real-time performance:13 13that is, the ab

16、ility to process a signal “live as it is sampled and then output the processed signal, for example to a loudspeaker or video display7. All of the practical examples of DSP applications mentioned earlier, such as hard disc drives and mobile phones, demand real-lime operation.14 146The Roots of DSPDig

17、ital Signal Processing is distinguished from other areas in computer science by the unique type of data it uses: signals. In most cases, these signals originate as sensory data from the real world: seismic vibrations, visual images, sound waves, etc. DSP is the mathematics, the algorithms, and the t

18、echniques used to manipulate these signals after they have been converted into a digital form. This includes a wide variety of goals, such as: enhancement of visual images, recognition and generation of speech, compression of data for storage and transmission, etc. 15 15Suppose we attach an analog-t

19、o-digital converter to a computer and use it to acquire a chunk of real world data. DSP answers the question: What next?The roots of DSP are in the 1960s and 1970s when digital computers first became available. Computers were expensive during this era, and DSP was limited to only a few critical appl

20、ications. Pioneering efforts were made in four key areas: radar & sonar, where national security was at risk; oil exploration, where large amounts of money could be made; space exploration, where the data were irreplaceable; 16 16and medical imaging, where lives could be saved. The personal comp

21、uter revolution of the 1980s and 1990s caused DSP to explode with new applications. Rather than being motivated by military and government needs, DSP was suddenly driven by the commercial marketplace. Anyone who thought they could make money in the rapidly expanding field was suddenly a DSP vendor.

22、DSP reached the public in such products as: mobile telephones, compact disc players, and electronic voice mail. Fig 11.1 illustrates a few of these varied applications.17 17Fig 11.1 The application of DSP18 18This technological revolution occurred from the top-down. In the early 1980s, DSP was taugh

23、t as a graduate level course in electrical engineering. A decade later, DSP had become a standard part of the undergraduate curriculum. Today, DSP is a basic skill needed by scientists and engineers in many fields. As an analogy, DSP can be compared to a previous technological revolution: electronic

24、s. While still the realm of electrical engineering, nearly every scientist and engineer has some background in basic circuit design. Without it, they would be lost in the technological world. DSP has the same future.19 19NEW WORDS AND PHRASEStransducern.传感器，变频器，变换器digitizevt.数字化converter n.转换器electr

25、odesn.电极microprocessorn.微(型)处理器sonarn.声呐，声波定位器curriculumn.课程acronym n.缩写字，字头语2020cousinn.同族，同类multimedian.多媒体substantialn.重要局部，本质adj.实质上的，有内容的compressionn.压缩，压榨，缩小decompressionn.复原，解压vendorn.厂商，卖主curiosity adj.好奇，好奇心tremendousadj.巨大的，惊人的obscureadj.微暗的，难解的21 21vt.使阴暗、隐藏，使模糊bafflevt. 困惑，阻碍，为难crunchvt.

26、, vi. 嘎吱嘎吱地咬嚼，压碎spectrum n.谱，光谱numerically-intensive高强度数字运算floating point operation浮点操作，浮点运算seismic vibrations地震颤抖2222NOTES1 This generates a digital output as a stream of binary numbers whose values represent the electrical voltage input to the device at each sampling instant.句中“this指“模/数转换器；“whose

27、 values represent the electrical voltage input to the device at each sampling instant修饰“a stream of binary numbers。本句可译为：这个器件(模/数转换器)以二进制数码流的方式输出数据，这些二进制数码流的值表示每次采样时输入这个器件模拟电压的大小。23232 Increasingly nowadays, the filtering of signals to improve signal quality or to extract important information is do

28、ne by DSP techniques rather than by analog electronics.句中“to improve signal quality or to extract important information修饰“the filtering of signals。本句可译为：现在，提高信号质量或提取信号重要局部的滤波处理，越来越多地采用DSP技术实现，而不采用模拟电子技术。24243 However, general-purpose microprocessors such as the Intel x86 family are not ideally suite

29、d to the numerically-intensive requirements of DSP, and during the 1980s the increasing importance of DSP led several major electronics manufacturers (such as Texas Instruments, Analog Devices and Motorola) to develop Digital Signal Processor chips-specialised microprocessors with architectures desi

30、gned specifically for the types of operations required in digital signal processing.2525句中“with architectures designed specifically for the types of operations required in digital signal processing修饰“specialised microprocessors。本句可译为：然而，如Intel x86系列这类通用处理器难以满足数字信号处理技术的高要求。在 20 世纪 80 年代，数字信号处理日益重要，这促

31、使几个知名的电子产品制造商开发数字信号处理器芯片，这些厂家包括德州仪器公司(TI)、模拟器件公司(AD)和摩托罗拉公司(Motorola)。数字信号处理芯片是一类专用的微处理器，这类处理器具有数字信号处理所要求的特殊架构。26264 DSP chips are capable of carrying out millions of floating point operations per second, and like their better-known general-purpose cousins, faster and more powerful versions are cont

32、inually being introduced.句中“cousins的原意为“堂兄弟姊妹，表兄弟姊妹；同族者；同类者；同辈，这里指与DSP具有相同功能的同类芯片。本句可译为：DSP芯片每秒能够执行数百万次的浮点运算。像众所周知的其他多用途芯片一样，速度更快、性能更强版本的DSP芯片也被陆续推出。27275 DSP signal compression technology allows people not only to talk to one another but also to see one another on their computer screens, using smal

33、l video cameras mounted on the computer monitors, with only a conventional telephone line linking them together.句中“using small video cameras mounted on the computer monitors作为“see one another on their computer screens的后置定语；“with only a conventional telephone line linking them together是全句的后置定语。2828本句

34、可译为：在计算机显示器上安装一台小摄像头，仅用一根普通的 线相互连接，依靠DSP信号压缩技术，我们不但可以与对方交谈，而且可以在计算机显示器中看见对方。6 Although some of the mathematical theory underlying DSP techniques, such as Fourier and Hilbert Transforms, digital filter design and signal compression, can be fairly complex, the numerical operations required actually to

35、 implement these techniques are very simple, consisting mainly of operations that could be done on a cheap four-function calculator.2929句中“consisting mainly of operations that could be done on a cheap four-function calculator作为后置定语用来补充说明“very simple。本句可译为：尽管支持DSP技术的数学理论，如Fourier和Hilbert变换、数字滤波器设计、信号

36、压缩等都很复杂，但实现这些理论的数学运算却十分简单，主要的算法可以用简单的四功能(加、减、乘、除)计算器就能完成。30307 The architecture of a DSP chip is designed to carry out such operations incredibly fast, processing hundreds of millions of samples every second, to provide real-time performance: that is, the ability to process a signal “live as it is s

37、ampled and then output the processed signal, for example to a loudspeaker or video display.句中“hundreds of millions意为“上亿次。本句可译为：DSP芯片采用的设计架构使其具有极快的运算速度，每秒能执行上亿次的采样，具有实时性，也就是说，当信号采样后，它可以实时处理并将处理过的信号即刻输出到相关的设备，如扩音器或视频显示设备。31 31EXERCISES. True or False.(1) Before applying DSP, an analog signal must be c

38、onverted into digital form. ( )(2) The filtering of signals to improve signal quality done by analog electronics. ( )(3) Some complex “system-on-chip devices can embedded DSPs. ( )(4) In I 960s, DSP was driven by the commercial marketplace. ( )3232(5) In audio CD systems, DSP technology is used to p

39、erform complex error detection. ( ). Answer the following question briefly.Please indicate the main application of DSP.3333参考译文第十一单元 数字信号处理概述1什么是DSP？DSP即数字信号处理(Digital Signal Processing)，正如字面意思所描述，是通过数字方法对信号的处理。这里的“信号可能指许多不同的东西。历史上，信号处理起源于电气工程，电气工程中的信号指在导线、 线或无线电波上传输的信号。更一般地讲，信号就是表示任何事物的一组信息流，这些信息表示

40、的可能是股票价格，也可能是来自遥感卫星的数据。术语“digital源自“digit，意为一个数字(你用你的手指计数这就是你的数字)，3434所以“digital的字面意义为“用数字表示的；法语中的“digital是numrique。数字信号由数字流组成，通常(但不是必要)是二进制形式。数字信号的处理是通过执行数字运算完成的。35352模拟信号和数字信号许多情况下，如由麦克风或其他传感器产生的信号，我们首先关注的是信号形式，是模拟电压还是电流。在一些情况下，如CD播放器读出系统的输出，数据已经是数字形式。模拟信号必须首先转换为数字信号后，才能被DSP处理。例如，模拟电压信号可以通过模/数转换器(

41、ADC)进行数字化。这个器件(模/数转换器)以二进制数码流的方式输出数据，这些二进制数码流的值表示每次采样时输入这个器件模拟电压的大小。36363信号处理信号通常需要经过多种方法处理。例如，传感器输出的信号很可能包含有我们不想要的电子“噪声。当做心电图时，贴到病人胸部的电极将测量由心脏和其他肌肉产生的微小电压变化。这些微小电压经常受到由市电电源造成的“电源拾波的强烈干扰。采用滤波电路对信号进行处理后，能去除或减少信号中的有害局部。现在，提高信号质量或提取信号重要局部的滤波处理越来越多地采用DSP技术实现，而不采用模拟电子技术。37374数字信号处理器(DSP)20世纪70年代后期，随着微处理器

42、的出现和开展，到80年代初期，使得数字信号处理技术广泛应用成为可能。然而，如Intel x86系列这类通用处理器难以满足数字信号处理技术的高要求。在 20 世纪 80 年代，数字信号处理日益重要，这促使几个知名的电子产品制造商开发数字信号处理器芯片，这些厂家包括德州仪器公司、仿真器件公司和摩托罗拉公司。数字信号处理芯片是一类专用的微处理器，这类处理器具有数字信号处理所要求的特殊架构。3838同通用微处理器一样，数字信号处理器也是一种可编程器件，并使用自己特有的指令代码。DSP芯片每秒能够执行数百万次的浮点运算，像众所周知的其他多用途芯片一样，速度更快、性能更强版本的DSP芯片也被陆续推出。数字

43、信号处理器也能嵌入到复杂的“片上系统器件中，通常都包含模拟和数字两种电路。39395DSP的应用当今，DSP在设备中的应用很常见，如移动 、多媒体计算机、录像机、CD播放器、硬盘驱动控制器和调制解调器，不久电视机和 机中的模拟电路也会被DSP取代。DSP最重要的应用领域是信号压缩和解压缩。数字蜂窝 就使用了信号压缩，从而能在每一个本地蜂窝网同时允许大量移动 用户通话。在计算机显示器上安装一台小摄像头，仅用一根普通的 线相互连接，依靠DSP信号压缩技术，我们不但可以与对方交谈，而且可以在计算机显示器中看见对方。在音频CD系统中，DSP技术用来对从CD上读出的原始数据进行复杂的过失检测和纠错。40

44、40尽管支持DSP技术的数学理论，如Fourier和Hilbert变换、数字滤波器、信号压缩等都很复杂，但实现这些理论的数学运算却十分简单，主要的算法可以用简单的四功能(加、减、乘、除)计算器就能完成。DSP芯片采用的设计架构使其具有极快的运算速度，每秒能执行上亿次的采样，具有实时性，也就是说，当信号采样后，它可以实时处理并将处理过的信号即刻输出到相关的设备，如扩音器或视频显示设备。如前所述的DSP应用的所有实例，如硬盘驱动和移动 都需要实时处理能力。41 416DSP的起源数字信号处理与计算机科学其他领域的最大区别在于，它采用了独特的数据类型信号。在大多数情况下，这些信号从现实世界的传感数据

45、获得，如地震的震动、可视图像、声波等。当这些信号被转换为数字形式后，DSP就是处理这些信号的数学、算法和技术。这种处理目的多种多样，例如可见图像的增强、语音的识别和再生、数据的压缩以方便其存储和传输，等等。假设我们给计算机配备一个模/数转换器，并通过它获得大量现实世界数据，那么接下来的工作就由DSP来完成了。4242DSP起源于20世纪60到70年代，当时数字计算机刚问世。在那个年代，计算机价格不菲，DSP局限于少数的关键应用。DSP的先驱者致力于四个关键领域：雷达和声呐维护国家平安；石油勘测获得更多财富；空间探测获得独一无二的数据；医学成像救死扶伤。20世纪80到90年代，个人计算机革命促使

46、DSP的新应用获得爆发式增长。DSP的开展突然由商业市场推动，而不再是军队和政府需求推动。所有认为可以在这个迅速扩张的领域中获得财富的人都迅速成为了DSP售卖者。DSP已拓展到民用产品，如移动 、CD播放器和电子语音邮件。图11.1所示为DSP各种各样的应用。4343图11.1 数字信号处理的应用4444DSP技术革新是自顶向下进行的。在20世纪80年代初期，DSP是电子工程专业研究生的课程。十年后，DSP已变为大学生的根本课程。如今，DSP已成为许多领域科学家和工程师的必备根本技能。DSP的革命就如同以前电子技术的革命。当然，几乎每一个电子工程领域的科学家和工程师都具备一定的根底电路设计能力

47、。假设没有这种能力，他们就无法承担该领域的研究工作。DSP具有同样的未来。4545EXTENSIVE TEXTDigital Signal ProcessorsDigital signal processing tasks can be performed by all processors. Specialized digital signal processors (DSP), however, perform these tasks most efficiently and most quickly. While traditional processors follow the Von

48、 Neumann architecture model, which assumes a shared single memory to be used for both program instructions and data, DSPs use the Harvard or modified Harvard architecture, which includes multiple program and data memories, along with multiple buses to access them. 4646This arrangement means that muc

49、h less waiting is required when instructions or numbers are fetched from memory. In fact at least one of each can be fetched simultaneously. Such overlapping of tasks is called pipelining. In addition to multiple memories and buses, all DSPs have fast multipliers, accumulators, and shifters, and man

50、y have hardware support for circular buffers. Address generators can speed up accesses to memory locations referenced by registers.4747DSPs are available in two major classes: fixed point and floating point. The fixed point class represents real numbers in a fixed number of bits. The position of the

51、 binary point (similar to the decimal paint) can be controlled by the programmer, and determines the range of numbers that can be represented. As the range increases, though, the available precision goes down, since fewer bits lie to the right of the binary point. In 16 bits, the formats 16.0, 15.1,

52、 l4.2, 13.3, 12.4, 11.5, 10.6, 9.7, 8.8, 7.9, 6.10, 5.11, 4.12, 3.13, 2.14, and 1.15 are possible. The dynamic range, calculated as 20log (Full Scale Range/Smallest Resolvable Difference), remains the same for all 16-hit formats, 20log216 = 96.3 dB.4848Floating point DSPs represent real numbers usin

53、g a mantissa and an exponent, similar to scientific notation; many combine mantissa and exponent into a 32-bit number. The dynamic range for floating point devices is calculated from the largest and smallest multipliers 2E, where E is the exponent. Thus, for a representation that uses 24 bits for th

54、e mantissa and 8 bits for the signed exponent, the dynamic range is 20log(2127/2-128dB. A large dynamic range means the system has great power to represent a wide range of input signals, from very small to very large.4949Assembly language is the command language far DSPs. DSPs often have specialized

55、 instructions that make programming for common DSP tasks more convenient and more efficient. For example, most DSPs offer multi-function instructions that exploit their parallel architecture. Other constructs that are frequently offered are efficient looping schemes, since so many DSP operations involve a great deal of repetition.5050Choosing a DSP for a particular application is not always easy. The first decision is on whether to choose a fixed point or a floating point device. Generally, fixed point device