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1、信息科学与电子工程专业英语Technical EnglishFor Information Science and Electronic Engineering信息科学与电子工程专业英语Unit 9Electronics:Digital Signals and Signal Processing信息科学与电子工程专业英语Part IDigital Signal Processing 3New Wordssub-field sub-field 分领域，子领域分领域，子领域分领域，子领域分领域，子领域sonar sonar 声呐声呐声呐声呐sensor array sensor array 传感器
2、阵列传感器阵列传感器阵列传感器阵列biomedical biomedical 生物特征的生物特征的生物特征的生物特征的algorithm algorithm 算法算法算法算法abbreviate abbreviate 缩写，缩略缩写，缩略缩写，缩略缩写，缩略purpose-designed purpose-designed 针对目的设计的针对目的设计的针对目的设计的针对目的设计的application-specific application-specific 面向应用的面向应用的面向应用的面向应用的integrated circuits integrated circuits 集成电路集成电
3、路集成电路集成电路autocorrelation autocorrelation 自相关自相关自相关自相关wavelet wavelet 小波小波小波小波baseband baseband 基带基带基带基带informed informed 有知识的，有见闻的有知识的，有见闻的有知识的，有见闻的有知识的，有见闻的spatial domain spatial domain 空间域空间域空间域空间域cross-correlation cross-correlation 互相关互相关互相关互相关interval interval 间隔间隔间隔间隔discretization discretizati
4、on 离散化离散化离散化离散化quantization quantization 量化量化量化量化partition partition 分割，分区分割，分区分割，分区分割，分区finite set finite set 有限的集有限的集有限的集有限的集5New WordsFIR(finite impulseresponse filter)FIR(finite impulseresponse filter)有限冲击响应滤波器有限冲击响应滤波器有限冲击响应滤波器有限冲击响应滤波器IIR(infinite impulse response filter)IIR(infinite impulse r
5、esponse filter)无限冲击响应滤波器无限冲击响应滤波器无限冲击响应滤波器无限冲击响应滤波器field-programmablegate array field-programmablegate array(FPGA)(FPGA)现场可编程门阵列现场可编程门阵列现场可编程门阵列现场可编程门阵列computer aidedtomography(CAT)computer aidedtomography(CAT)计算机断层扫描计算机断层扫描计算机断层扫描计算机断层扫描seismology seismology 地震学地震学地震学地震学equalization equalization 均衡
6、均衡均衡均衡hifi(high fidelity)hifi(high fidelity)高保真（音乐）高保真（音乐）高保真（音乐）高保真（音乐）reinforcement reinforcement 加强加强加强加强animation animation 动画动画动画动画loudspeaker loudspeaker 扬声器扬声器扬声器扬声器floating point floating point 浮点浮点浮点浮点arithmetic arithmetic 算术算术算术算术magnetic resonanceimaging(MRI)magnetic resonanceimaging(MRI)
7、磁共振成像磁共振成像磁共振成像磁共振成像fixed-point arithmeticfixed-point arithmetic定点运算，整数运算定点运算，整数运算定点运算，整数运算定点运算，整数运算61Digital signal processing(DSP)is the study of signals in a Digital signal processing(DSP)is the study of signals in a digital representation and the processing methods of these digital representatio
8、n and the processing methods of these signals.DSP and analog signal processing are sub-fields of signals.DSP and analog signal processing are sub-fields of signal processing.DSP includes sub-fields like signal processing.DSP includes sub-fields like audio and audio and speech signal processing,sonar
9、 and radar signal processing,speech signal processing,sonar and radar signal processing,sensor array processing,spectral estimation,statistical signal sensor array processing,spectral estimation,statistical signal processing,image processing,signal processing for processing,image processing,signal p
10、rocessing for communications,biomedical signal processingcommunications,biomedical signal processing,etc.,etc.音频及语音信号处理、声纳和雷达信号处理、音频及语音信号处理、声纳和雷达信号处理、音频及语音信号处理、声纳和雷达信号处理、音频及语音信号处理、声纳和雷达信号处理、传感器阵列处理、谱估计、统计信号处理、图传感器阵列处理、谱估计、统计信号处理、图传感器阵列处理、谱估计、统计信号处理、图传感器阵列处理、谱估计、统计信号处理、图像处理、通信信号处理、生物医学信号处理像处理、通信信号处理、
11、生物医学信号处理像处理、通信信号处理、生物医学信号处理像处理、通信信号处理、生物医学信号处理72Since the goal of DSP is usually to measure or filter continuous Since the goal of DSP is usually to measure or filter continuous real-world analog signalsreal-world analog signals,the first step is usually to convert,the first step is usually to conve
12、rt the signal from an analog to a digital form,by using an analog the signal from an analog to a digital form,by using an analog to digital converter.Often,the required output signal is to digital converter.Often,the required output signal is another analog output signal,which requires a digital to
13、another analog output signal,which requires a digital to analog converter.analog converter.数字信号处理的目标通常是数字信号处理的目标通常是数字信号处理的目标通常是数字信号处理的目标通常是测量连续的真实世界的模拟测量连续的真实世界的模拟测量连续的真实世界的模拟测量连续的真实世界的模拟信号或对其滤波信号或对其滤波信号或对其滤波信号或对其滤波93When flexibility and rapid development are more important When flexibility and rapi
14、d development are more important than unit costs at high volume,DSP algorithms may also be than unit costs at high volume,DSP algorithms may also be implemented using field-programmable gate arrays(FPGAs).implemented using field-programmable gate arrays(FPGAs).2 2当灵活性和快速开发比大批量生产的当灵活性和快速开发比大批量生产的当灵活性
15、和快速开发比大批量生产的当灵活性和快速开发比大批量生产的成本更重要时，成本更重要时，成本更重要时，成本更重要时，DSPDSP算法也可以用现场算法也可以用现场算法也可以用现场算法也可以用现场可编程门阵列来实现。可编程门阵列来实现。可编程门阵列来实现。可编程门阵列来实现。104 DSP domainsIn DSP,engineers usually study digital signals in one of the In DSP,engineers usually study digital signals in one of the following domains:time domain
16、(one-dimensional signals),following domains:time domain(one-dimensional signals),spatial domain(multidimensional signals),frequency domain,spatial domain(multidimensional signals),frequency domain,autocorrelation domain,and wavelet domains.autocorrelation domain,and wavelet domains.They choose They
17、choose the domain in which to process a signal by making an the domain in which to process a signal by making an informed guess(or by trying different possibilities)as to which informed guess(or by trying different possibilities)as to which domain best represents the essential characteristics of the
18、 domain best represents the essential characteristics of the signal.signal.3 3 他们按某些依据来猜测（或试验不同的可能他们按某些依据来猜测（或试验不同的可能他们按某些依据来猜测（或试验不同的可能他们按某些依据来猜测（或试验不同的可能性）那一个域能够最好地表示信号的本质特性）那一个域能够最好地表示信号的本质特性）那一个域能够最好地表示信号的本质特性）那一个域能够最好地表示信号的本质特性来选择在其中进行信号处理的域。性来选择在其中进行信号处理的域。性来选择在其中进行信号处理的域。性来选择在其中进行信号处理的域。125 S
19、ignal samplingWith the increasing use of computers the usage and need of With the increasing use of computers the usage and need of digital signal processing has increased.In order to use an digital signal processing has increased.In order to use an analog signal on a computer it must be digitized w
20、ith an analog signal on a computer it must be digitized with an analog to digital converter(ADC).analog to digital converter(ADC).Sampling is usually carried Sampling is usually carried out in two stages,discretization and quantizationout in two stages,discretization and quantization.采样通常分两步实现：采样通常分
21、两步实现：采样通常分两步实现：采样通常分两步实现：离散化和量化离散化和量化离散化和量化离散化和量化146In order for a sampled analog signal to be exactly In order for a sampled analog signal to be exactly reconstructed,the Nyquist-Shannon sampling theorem must reconstructed,the Nyquist-Shannon sampling theorem must be satisfied.be satisfied.This the
22、orem states that the sampling frequency This theorem states that the sampling frequency must be greater than twice the bandwidth of the signalmust be greater than twice the bandwidth of the signal.定理规定：采样频率必须定理规定：采样频率必须定理规定：采样频率必须定理规定：采样频率必须大于两倍的信号带宽大于两倍的信号带宽大于两倍的信号带宽大于两倍的信号带宽156In practice,In pract
23、ice,the sampling frequency is often significantly more the sampling frequency is often significantly more than twice the required bandwidththan twice the required bandwidth.The most common.The most common bandwidth scenarios are:DCBW(“baseband”);and bandwidth scenarios are:DCBW(“baseband”);and fcfc
24、BW,BW,a frequency band centered on a carrier frequency(“direct a frequency band centered on a carrier frequency(“direct demodulation”).demodulation”).采样频率通常远大于信号采样频率通常远大于信号采样频率通常远大于信号采样频率通常远大于信号带宽的两倍带宽的两倍带宽的两倍带宽的两倍178 Time and space domainsThe most common processing approach in the time or space The
25、 most common processing approach in the time or space domain is enhancement of the input signal through a method domain is enhancement of the input signal through a method called filtering.called filtering.Filtering generally consists of some Filtering generally consists of some transformation of a
26、number of surrounding samples around transformation of a number of surrounding samples around the current sample of the input or output signalthe current sample of the input or output signal.There are.There are various ways to characterize filters;for example:various ways to characterize filters;for
27、 example:滤波通常由在输入或输出信号当前样本滤波通常由在输入或输出信号当前样本滤波通常由在输入或输出信号当前样本滤波通常由在输入或输出信号当前样本周围的许多样本的某种变换组成周围的许多样本的某种变换组成周围的许多样本的某种变换组成周围的许多样本的某种变换组成188-A“linear”filter is a linear transformation of input A“linear”filter is a linear transformation of input samples;other filters are“non-linear.”samples;other filters
28、 are“non-linear.”Linear filters satisfy Linear filters satisfy the superposition condition,i.e.,if an input is a weighted the superposition condition,i.e.,if an input is a weighted linear combination of different signals,the output is an linear combination of different signals,the output is an equal
29、ly weighted linear combination of the corresponding equally weighted linear combination of the corresponding output signals.output signals.6 6 线性滤波器满足叠加条件，就是说，如果输入线性滤波器满足叠加条件，就是说，如果输入线性滤波器满足叠加条件，就是说，如果输入线性滤波器满足叠加条件，就是说，如果输入是不同信号的加权线性组合，输出就是（各信是不同信号的加权线性组合，输出就是（各信是不同信号的加权线性组合，输出就是（各信是不同信号的加权线性组合，输出就是
30、（各信号）相应输出的同样加权线性组合。号）相应输出的同样加权线性组合。号）相应输出的同样加权线性组合。号）相应输出的同样加权线性组合。198-A“causal”filter uses only previous samples of the input or A“causal”filter uses only previous samples of the input or output signals;while a“non-causal”filter uses future input output signals;while a“non-causal”filter uses future
31、 input samples.A non-causal filter can usually be changed into a samples.A non-causal filter can usually be changed into a causal filter by adding a delay to it.causal filter by adding a delay to it.-A“time-invariant”filter has constant properties over time;A“time-invariant”filter has constant prope
32、rties over time;other filters such as adaptive filters change in timeother filters such as adaptive filters change in time.“时不变时不变时不变时不变”滤波器对时间具有不变的性质，滤波器对时间具有不变的性质，滤波器对时间具有不变的性质，滤波器对时间具有不变的性质，诸如自适应滤波器等其它滤波器随时间而诸如自适应滤波器等其它滤波器随时间而诸如自适应滤波器等其它滤波器随时间而诸如自适应滤波器等其它滤波器随时间而改变改变改变改变208-Some filters are“stable
33、”,others are“unstable”.Some filters are“stable”,others are“unstable”.A stable A stable filter produces an output that converges to a constant value filter produces an output that converges to a constant value with time,or remains bounded within a finite intervalwith time,or remains bounded within a
34、finite interval.An.An unstable filter produces output which diverges.unstable filter produces output which diverges.稳定的滤波器产生的输出随时间收敛于一个稳定的滤波器产生的输出随时间收敛于一个稳定的滤波器产生的输出随时间收敛于一个稳定的滤波器产生的输出随时间收敛于一个不变的值，或在有限的时间间隔内保持有界不变的值，或在有限的时间间隔内保持有界不变的值，或在有限的时间间隔内保持有界不变的值，或在有限的时间间隔内保持有界218-A“finite impulse response”(F
35、IR)filter uses only the input A“finite impulse response”(FIR)filter uses only the input signal,signal,while an“infinite impulse response”filter(IIR)uses while an“infinite impulse response”filter(IIR)uses both the input signal and previous samples of the output both the input signal and previous samp
36、les of the output signalsignal.FIR filters are always stable,while IIR filters may.FIR filters are always stable,while IIR filters may be unstable.be unstable.而无限脉冲响应（而无限脉冲响应（而无限脉冲响应（而无限脉冲响应（IIRIIR）滤波器）滤波器）滤波器）滤波器同时使用输入信号和以前的输出同时使用输入信号和以前的输出同时使用输入信号和以前的输出同时使用输入信号和以前的输出信号样本信号样本信号样本信号样本239The output o
37、f an FIR filter to any given input may be The output of an FIR filter to any given input may be calculated by convolving the input signal with the impulse calculated by convolving the input signal with the impulse response.response.Filters can also be represented by block diagrams Filters can also b
38、e represented by block diagrams which can then be used to derive a sample processing which can then be used to derive a sample processing algorithm to implement the filter using hardware instructionsalgorithm to implement the filter using hardware instructions.滤波器还可以用结构图来表示，它能滤波器还可以用结构图来表示，它能滤波器还可以用
39、结构图来表示，它能滤波器还可以用结构图来表示，它能用来推导样本处理算法，以便使用硬用来推导样本处理算法，以便使用硬用来推导样本处理算法，以便使用硬用来推导样本处理算法，以便使用硬件指令实现滤波器件指令实现滤波器件指令实现滤波器件指令实现滤波器2410 Frequency domainSignals are converted from time or space domain to the Signals are converted from time or space domain to the frequency domain usually through the Fourier tra
40、nsform.frequency domain usually through the Fourier transform.The The Fourier transform converts the signal information to a Fourier transform converts the signal information to a magnitude and phase component of each frequencymagnitude and phase component of each frequency.Often the.Often the Fouri
41、er transform is converted to the power spectrum,which Fourier transform is converted to the power spectrum,which is the magnitude of each frequency component squared.is the magnitude of each frequency component squared.FourierFourier变换将信号信息变换成每个变换将信号信息变换成每个变换将信号信息变换成每个变换将信号信息变换成每个频率的幅度和相位成分频率的幅度和相位成
42、分频率的幅度和相位成分频率的幅度和相位成分2511The most common purpose for analysis of signals in the The most common purpose for analysis of signals in the frequency domain is analysis of signal properties.The frequency domain is analysis of signal properties.The engineer can study the spectrum to get information of whi
43、ch engineer can study the spectrum to get information of which frequencies are present in the input signal and which are frequencies are present in the input signal and which are missing.missing.2713 ApplicationsThe main applications of DSP are audio signal processing,The main applications of DSP ar
44、e audio signal processing,audio compression,digital image processing,video audio compression,digital image processing,video compression,speech processing,speech recognition,digital compression,speech processing,speech recognition,digital communications,radar,sonar,seismology,and munications,radar,so
45、nar,seismology,and biomedicine.2813Specific examples are speech compression and transmission in Specific examples are speech compression and transmission in digital mobile phones,room matching equalization of sound in digital mobile phones,room matching equalization of sound in HiFi and sound reinfo
46、rcement applications,weather HiFi and sound reinforcement applications,weather forecasting,economic forecasting,seismic data processing,forecasting,economic forecasting,seismic data processing,analysis and control of industrial processes,computer-analysis and control of industrial processes,computer
47、-generated animations in movies,medical imaging such as CAT generated animations in movies,medical imaging such as CAT scans and MRI,image manipulation,high fidelity loudspeaker scans and MRI,image manipulation,high fidelity loudspeaker crossovers and equalization,and audio effects for use with cros
48、sovers and equalization,and audio effects for use with electric guitar amplifiers.electric guitar amplifiers.3014For faster applications FPGAs might be used.Beginning in For faster applications FPGAs might be used.Beginning in 2007,multicore implementations of DSPs have started to 2007,multicore imp
49、lementations of DSPs have started to emerge.For faster applications with vast usage,ASICs might emerge.For faster applications with vast usage,ASICs might be designed specifically.For slow applications,a traditional be designed specifically.For slow applications,a traditional slower processor such a
50、s a microcontroller can cope.slower processor such as a microcontroller can cope.信息科学与电子工程专业英语Part IIGeneral Concepts of Digital Signal Processing 32New Wordsspecial-purposespecial-purpose专用专用专用专用terminology terminology 术语术语术语术语sinusoidal sinusoidal 正弦的正弦的正弦的正弦的contextcontext上下文，背景上下文，背景上下文，背景上下文，背景