1、Unit 14 Digital Signal Processing Unit 14 Digital Signal Processing TextKey wordsTechnical termsExpressionsNotes to the textUnit 14 Digital Signal Processing TextWhat is DSP?DSP,or Digital Signal Processing,as the term suggests,is the processing of signals by digital means.A signal in this context c
2、an mean a number of different things.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 anythin
3、g from stock prices to data from a remote-sensing satellite.Unit 14 Digital Signal Processing The term“digital”comes from“digit”,meaning a number,so“digital”literally means numerical.A digital signal consists of a stream of numbers,usually(but not necessarily)in binary form.The processing of a digit
4、al signal is done by performing numerical calculations.Unit 14 Digital Signal Processing Analog and Digital SignalsIn many cases,the signal of interest is initially in the form of an analog electrical voltage or current,produced for example by a microphone or some other type of transducer.In some si
5、tuations,such as the output from the readout system of a CD(compact disc)player,the data is already in digital form.An analog signal must be converted into digital form before DSP techniques can be applied.An analog-to-digital converter or ADC.This generates a digital output as a stream of binary nu
6、mbers whose values represent the electrical voltage input to the device at each sampling instant.Unit 14 Digital Signal Processing Signal 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 electr
7、ical“noise”.The electrodes attached 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.Processing the signal usi
8、ng a filter circuit can 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.Unit 14 Digital Signal Processing Applications of
9、 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 sets and telephones.An important application of DSP is in signal compression and decompressi
10、on.Signal compression is used in digital cellular phones to allow a greater number of calls to be handled simultaneously within each local“cell”.DSP signal compression technology allows people not only to talk to one another but also to see one another on their computer screens,Unit 14 Digital Signa
11、l Processing using small video cameras mounted on the computer monitors,with only a conventional telephone line linking them together.In audio CD systems,DSP technology is used to perform complex error detection and correction on the raw data as it is read from the CD.The architecture of a DSP chip
12、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 sampled and then output the processed signal,for example to a loudspeaker or video display.Unit 14 D
13、igital Signal Processing Key wordsprocessing n.处理originn.起源，由来，起因numerical adj.数字的，用数表示的initially adv.最初，开头microphone n.扩音器，麦克风transducer n.传感器，变频器readout n.读出器，读出contaminatev.污染Unit 14 Digital Signal Processing electroden.电极interferencen.冲突，干涉modemn.计调制解调器cellular adj.细胞的monitorn.监视器，监控器Unit 14 Dig
14、ital Signal Processing Technical termsDSP(Digital Signal Processing)数字信号处理electrical engineering 电子工程radio wave 无线电波a remote-sensing satellite 遥感卫星CD(compact disc)光盘ADC(analog-to-digital converter)模数转换器ECG(Electrocardiograph)心电图signal compression and decompression 信号压缩和解压缩digital cellular phones数字蜂窝
15、电话video camera摄影机Unit 14 Digital Signal Processing Expressionscome from 起源于in many cases 在多数情况下be converted into 将转换为due to因为rather than 胜于real-time实时的Unit 14 Digital Signal Processing Notes to the text1.DSP signal compression technology allows people not only to talk to one another but also to see
16、one another on their computer screens,using small video cameras mounted on the computer monitors,with only a conventional telephone line linking them together.有了数字信号处理的信号压缩技术，人们不但可以互有了数字信号处理的信号压缩技术，人们不但可以互相交谈，而且能通过电脑屏幕看见彼此，这仅需一根普通相交谈，而且能通过电脑屏幕看见彼此，这仅需一根普通的电话线连接，在计算机显示器上安装一个摄像头便可实的电话线连接，在计算机显示器上安装一个摄
17、像头便可实现。现。句中使用了“allows to to”的结构；“mounted on the computer monitors”为过去分词定语后置，修饰“video cameras”；“using”为现在分词作方式状语；“with only a conventional telephone line linking them together”为伴随状语。Unit 14 Digital Signal Processing 2.The architecture of a DSP chip is designed to carry out such operations incredibly
18、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 sampled and then output the processed signal,for example to a loudspeaker or video display.Unit 14 Digital Signal Processing 数字信号处理器具有很快的运算速度，每秒能执行上数字信号
19、处理器具有很快的运算速度，每秒能执行上亿次的采样，能够达到实时效果。也就是说，它能够一边亿次的采样，能够达到实时效果。也就是说，它能够一边采样，一边处理实时信号，并将处理过的信号输出给扩音采样，一边处理实时信号，并将处理过的信号输出给扩音器或视频播放器等设备。器或视频播放器等设备。句中采用了“be designed to,to”的结构，两个“to”引导的不定式作目的状语；“processing hundreds of millions of samples every second”为插入语，承前起补充说明的作用；“live”可翻译为“real-time”；“that is”可译为意即、也就是说，其后的长句阐释了主句所表达的意思。
