通信信号处理第三章2012概要
无线通信原理与应用第三章
(a) 信噪比（SNR: Signal to Noise Ratio ）
SNR = 信号的平均功率/噪声平均功率 = S/N. (b) 数字通信系统中的信噪比Eb/N0
Eb为每比特能量，N0是白噪声单边功率谱密度。 2017/8/1
9
第三章数字调制解调
【注】：SNR是功率之比；Eb/N0是能量之比。两者 都无量纲。两者实质上都是信噪比的概念， SNR多用 于模拟通信系统；而Eb/N0则只用于数字通信系统。
2017/8/1 9
第三章数字调制解调
(a) 传码率R
单位时间所传输的码元个数，单位为B（Baud）。 R = 1/T （3-3） T 为码元间隔，单位为S(秒) 。 R是数字通信系统中的一个基本指标。 (b) 传信率Rb 单位时间传输的比特数，单位为bit/s（比特/每秒）。
log 2 M k Rb R log 2 M T T
量纲为Hz或rad/s。它表明了信号和通信系统对频率
资源的绝对占用和分配情况。 带宽分为:调制信号带宽、已调波信号带宽、系统带宽。 2017/8/1
9
第三章数字调制解调
(d) 频谱效率（频带利用率） 数字通信系统中，单一的传码率（或传信率）或 带宽不能全面反映系统的有效性，例如某系统的传码 率虽然很高，但占用的频带却也很高，其有效性并不 高，因此将这两类指标结合起来，对系统的有效性进 行综合地分析，这个指标就是频谱效率或频谱利用率。
（2）分类 相干解调（coherent demodulation）
非相干解调（noncoherent demodulation）
2017/8/1 9
第三章数字调制解调
(a) 相干解调
充分利用了原始载波信号的信息，包括相位和频 率，得到最佳或最大似然解调。但其结构较为复杂 ，尤其是在移动的变参信道中，实现完全的同频、 同相较为困难。
第三章信号转换与处理电路
前述的电桥放大器中，只有当δ很小 时 Vo 与δ才成线性关系。当δ很大时， 非线性就很明显，以致给实际测量 带来不便。图3.20采用负反馈技术， 能使δ在很大范围内变化时，电路输 出电压的非线性偏差保持在0.1%以 内。
第三章：信号转换与处理电路
3、交流放大器
其中电容C1、C2及C3 为隔直电容，因此交流 电压放大器无直流增益
第三章：信号转换与处理电路
改进电路：
输入阻抗
Vi Rr R Rin I i R Rr
上式表明：只要R稍大于Rr，就能获 得很高的输入阻抗，可高达100M。 但R绝对不能小于Rr，否则输入阻抗为 负，会产生严重自激。
高输入阻抗反相放大器 A’提供补偿电流，减小A从信号源吸 取的电流，可以大幅度地提高主放大 器的等效输入阻抗Rin
2. 调幅波的解调 从已调信号中检出调制信号的过程称为解调或检波，因此解调的目的是为了恢 复被调制的信号。为了解调可以使调幅波和载波相乘，再通过低通滤波器滤波。
包络检波
若所加的偏置电压未能使 信号电压都在零线的一侧， 则对调幅波只是简单地整 流就不能恢复原调制信号， 如图4(b)所示，这就需要 采用相敏检波技术。
第三章：信号转换与处理电路
在信号调制中常以一
调制分类：
个高频正弦信号作为
载波信号。一个正弦 信号有幅值、频率、 相位三个参数，可以 对这三个参数进行调
制，分别称为调幅、
调频和调相。
载波、调制信号及调幅、调频波
第三章：信号转换与处理电路
一. 幅值调制与解调
1. 调幅原理 调幅是将一个高频简谐信号(载波信号)与测试信号(调制信号)相乘， 使载波信号随测试信号的变化而变化。调幅的目的是为了便于缓变信 号的放大和传送。常用的方法是线性调幅，即让调幅波的幅值随调制 信号x按线性规律变化。调幅波的表达式可写为
通信信号处理资料
通信信号处理摘要：在这通信信号处理这门课程中，老师给我们讲解了通信系统中的一些基本知识和一些关键技术，比如多输入多输出（MIMO，multiple-input multiple-output）、正交频分复用（OFDM，orthogonal frequency division multiplexing）以及比特交织编码调制（BICM，bit-interleaved coded modulation）等技术。
这篇文章的主要内容就是对本课程内容的总结以及自己的理解。
一、基本知识1.多径衰落（1）概念在通信系统中，由于通信地面站天线波束较宽，受地物、地貌和海况等诸多因素的影响，使接收机收到经折射、反射和直射等几条路径到达的电磁波，这种现象就是多径效应。
这些不同路径到达的电磁波射线相位不一致且具有时变性，导致接收信号呈衰落状态；这些电磁波射线到达的时延不同，又导致码间干扰。
若多射线强度较大，且时延差不能忽略，则会产生误码，这种误码靠增加发射功率是不能消除的，而由此多径效应产生的衰落叫多径衰落，它也是产生码间干扰的根源。
对于数字通信、雷达最佳检测等都会产生十分严重的影响。
（2）分类主要可以分为两种,频率选择性衰落和频率非选择性衰落（平坦型衰落）。
如果各条路径传输时延差别较大，传输波形的频谱较宽（或数字信号传输速率较高），则信道对传输信号中不同频率分量强度和相位的影响各不相同。
此时，接收点合成信号不仅强度不稳定而且产生波形失真，数字信号在时间上有所展宽，这就可能千万前后码元的波形重叠，出现码间（符号间）干扰。
这种衰落称为频率选择性衰落，有时也简称选择性衰落。
如果各条路径传输时延差别不大，而传输波形的频谱较窄（数字信号传输速率较低），则信道对信号传输频带内各频率分量强度和相位的影响基本相同。
此时，接收点的合成信号只有强度的随机变化，而波形失真很小。
这种衰落称为一致性衰落，或称平坦型衰落。
瑞利信道（包络的一维统计特性服从瑞利分布）就是典型的平坦型衰落信道。
现代通信系统的信号处理方法研究
现代通信系统的信号处理方法研究第一章：引言随着现代通信技术的不断发展和普及，越来越多的通信设备、网络和系统被广泛应用于各个领域，如无线通信、卫星通信、光纤通信、数字电视等。
信号处理作为现代通信系统中的重要一环，对于实现高效、稳定、高品质的通信具有至关重要的作用。
本文将对现代通信系统的信号处理方法进行研究，分析和探讨其在实际应用中的优缺点以及未来的发展方向。
第二章：通信信号处理的基本概念通信信号处理是指对传输信号进行处理的一系列技术，包括信号采样、滤波、数据压缩、信道编码和解码等工作。
其中，信号采样是将连续时间信号转化为离散时间信号的过程。
滤波是对信号进行波形修正，去除无用的频率成分的过程。
数据压缩是将信号的冗余部分压缩以减少信号传输的数据量。
信道编码和解码是对传输信号进行编码和解码以提高传输可靠性和数据安全性。
第三章：现代通信系统的信号处理方法3.1 数字信号处理技术数字信号处理技术是将信号转化为数字信号进行处理的技术，主要包括数字滤波、数字信号处理、数字信号编码和解码等。
数字信号处理技术具有精度高、可重复、可编程、抗干扰能力强等优点，可以实现信号传输质量的稳定、高效、快速等特点。
3.2 常用的信号处理方法常用的信号处理方法包括模拟信号处理和数字信号处理两种。
模拟信号处理是将连续时间信号进行处理的技术，主要包括模拟滤波、模拟信号处理、模拟信号编码和解码等。
模拟信号处理技术具有处理速度快、实时性好等优点，但受到噪声干扰影响较大，容易出现误差和失真等问题。
数字信号处理技术具有处理精度高、可重复、可编程、抗干扰能力强等优点，但对处理器要求较高，处理速度较慢。
3.3 现代通信系统中的信号处理方法现代通信系统中的信号处理方法包括数字信号处理、模拟信号处理、混合信号处理等。
其中，数字信号处理技术被广泛应用于无线通信、卫星通信、光纤通信和数字电视等领域。
而模拟信号处理技术则主要应用于音频信号处理、图像处理和电力信号处理等领域。
《数字通信原理》第3章 模拟信号的数字编码
Unit EightText II. Writing SkillsThis is a short, simple and straightforward piece of persuasive writing, informal style is used.nguage Points1.enjoy①enjoy (v.)②enjoyable (adj.)③enjoyment (n.)eg: We enjoy books very much.Books are enjoyable.We find great enjoyment in books.He is enjoying a book.Wrong: 1. Books are enjoying.2. We are enjoyed at the books.2. be aware of ----realizebe unaware ofPar:1) He knows very well the danger.2) He doesn't realize the danger he is facing.3) Do you know the result of the matter?4) She didn't know what was happing.3.resistible①resistible (adj.) -- that can be resistedeg: This wish to get more money is resistible.irresistible --- that can not be resistedeg: His wish to get more money is resistible, so he tries to steal.②resist (v.)--- oppose; keep oneself back frombe undamaged or unaffected by抵抗; 对抗; 不屈服于, 忍耐; 不受…的影响a)opposeeg: The country was unable to resist the invasion.She can't resist the temptation. …的诱惑They have the right to resist.b) keep oneself back fromeg: She could not resist his charms.I can't resist the wish to see him.c) undamaged or unaffected by…eg: This material resists fire.③resistance (n.) --- [u] power of resisting ; opposing power 抵抗; 抵抗力; 阻力;eg: The enemy offered very little resistance.The enemy's resistance was completely destroyed.There is much resistance to the new law.Copper has less resistance to electricity than many other metals.Healthy people have more resistance to disease than weak people.④resistant (adj.) --- offering resistance 抵抗的; 有抵抗力的; 反抗的;be resistant to…eg: Some insects are resistant to DDT.She is not resistant to disease.4.end up with --- finish ... in the end.Par:In the end, I failed in the exam. (I ended up with failure in the exam.In the end, I left much work undone. (I ended up with much work undone.)5.engross①engross (v.) --- take up all the time or attention of 花费所有的时间和精力(usu. used in passive.) 通常用于被动be engrossed in... 全神贯注于...eg: He is engrossed in his work.Par: He is reading a book attentively.We should concentrate ourselves on English study.②engrossing --- attractive 引人入胜的eg: It is an engrossing story.6. reality n. [u] [c] --- the quality of being real; real existence; sth real;sth actually seen.eg: Don't escape realities of our every day life.in reality--- in fact; reallyeg; In reality, he is a good teacher.7.content①content n. [u] the condition of being satisfied 满足live in content 心满意足eg: Now she is living in content.Do you live in content?to one's heart's content --- being completely satisfied.eg: We can swim in the river to our heart's content.The children enjoyed themselves to their heart's content.Par: When children are allowed to watch TV, they are completely satisfied to watch TV. (Children are allowed to watch TV to their heart's content.)Children are eating happily.The boys are dancing happily.②content (adj.) (不做定语) --- satisfied with what one has 满足的; 满意的be content with...eg: I'm content with my salary now.He is not content with beautiful dreams, he wants beautiful realities.be content to do sth.eg: He is content to eat the leftovers.I'm content to stay here.③content (v.) --- make content; satisfy 使满足to content sb.eg: Simple praise can content him.Par:60 marks can satisfy him.Nothing can make her satisfied.* content oneself with --- be satisfied with ...= be contented withPar:We are satisfied with our success.He is satisfied with his job.④contented adj. --- satisfied; showing or feeling satisfied满足的; 表示满意的;* 做定语:eg: He was speaking with a contented look.(smile)* 做表语: be contented (with)... --- be satisfied = be content witheg; Some people are never contented.He seems quite contented with his with his life.⑤contentedly (adv.) --- happilyeg: He went to bed contentedly.c.f. `content the content of the bag8. inevitable①inevitable (adj.) --- that can not be avoided; that is sure to happen 不可避免的eg: When you break a bone, what is inevitable? (Pain is inevitable)Par:Accident will sooner or later happen if you drive carelessly.Traffic delays always occur at week-ends.Mistake can not be avoided in dictations.②inevitably (adv.)eg: Mistakes occur inevitably in our study.9. browse①browse (vi.) --- read parts of the books without any definite plan,for interest or enjoyment 浏览书籍, 随便阅读eg: Do you browse through/among books in a bookstore?I often browse among books in a bookstore?②browse (n.) (act, period of) browsing 浏览, 浏览的啪have a good browsing (among books)浏览很长时间eg: Do you have a good browse when you go to a bookshop?10. discreet①discreet (adj.) --- careful, tactful, prudent 小心的, 懂读的;eg: a discreet personHe kept a discreet silence. (保持深重的沉默)②discreetly (adv.)eg: He drives discreetly.11. illustrate①illustrate (vt.)a) explain by examples or pictures (通过距离或图表说明)Par:The teacher explained the sentence striationHe illustrated his point by relating his own experience.He tried to explained his meaning.How he did explain his kindness.b) supply ((a book, article) with pictures or diagramseg: The artist illustrated the book with pen-and-ink drawings.(给书等配入插图) Par:I'll illustrate the book with picture.This book is well-supplied with pictures.It is a well illustrated text-book.②illustration (n.)a) illustrating or being illustrated; explanation with picturesPar: Give me an explanation (Give me an illustrator)以图表距离说明The teacher said it as an explanation (illustration) of the boy's poor work.He gave me an explanation(illustration) of the sentence pattern.in illustration of... --- in order to illustrate...Par: In order to illustrate the story, he used some examples.In order to illustrate the theory, he used some pictures.b) [c] sth. or pictures or diagrams that illustration 例子, 插图, 图表eg: Are there any illustrations on this page?I like magazines full of illustrations.by way of illustration作为...的例子eg: I mentioned it by ways of illustration.③illustrative (adj.) --- as an explanation or example of sth. 说明的, 作为例证的These words are illustrative.There are illustrative examples.12. indulgent①indulgent (adj.)--- inclined to give kind to (对...放纵; 溺爱)eg: He is an indulgent father.Indulgent parents are those who easily agree to let children do what they like.Is an indulgent teacher a good teacher?②indulge(vt.) --- gratify; give way to and satisfy(使满足; 纵容; 耽溺; 纵情; 顺从)eg: Do you think it is necessary to indulge a child?Is a teacher who indulges students a good teacher?Many rich people indulge their children.I indulge my interest in flowers. (Do I resist my interest?)indulge (oneself) in --- allow (oneself) to enjoy容许自己享受, 尽情eg: He sometimes indulges himself in a cigarette.Par:He allowed himself to have an expensive meal.We allow ourselves to have a long sheep on Sunday.(vi.)indulge ineg: He indulges in gambling.③indulgence (n.)[u] indulging; the state of being indulged 放纵; 沉溺; 纵容eg: Indulgence in smoking/drink can harm your health.Indulgence in gambling will spoil you.[c] sth one allow him to enjoy 允许自己享受的东西eg: One of my indulgences is having breakfast in bed.What is you indulgence?13. beckon v. --- call sb's attention by a movement of the hand or arm, usu.to show that he is to come nearer or to follow招手令他人走近或跟着来beckon sb. to do sth. 招手让...做...eg: The teachers beckoned others to follow him.Par:The police made a signal to ask the man to go quicker.The teacher made a signal to show the student to stop reading.beckon sb. in/on/out/forward/to sb's sideeg: He beckoned me in.He stood waiting until the policeman beckoned him on.Par: The teacher signaled me to come in.The man signaled the woman to walk forward.The policeman signaled me to go out.The man signaled me to go to his side.14. tell sb. off (for...) --- scold sbeg: He told me off for taking away the newspaper.15. tuck①tuck (v.)a) tuck (away) --- store in a safe place 将...藏起来Par: She put her dress at the button of the case.Grandfather had may old bottles put in the cellar.The map is put in the pocket.b). ---- to draw together into a small space; put into a desired or convenientplace. 缩拢; 塞置于方便之处eg: He tucked up his sleeves.When you swim, you tuck the end of your hair into your bathing-hat.Do you often tuck your shirt into your trousers?②tuck (n.) stitched fold of material in a garment (衣服的)摺等She is making a tuck in a dress.(打褶)Her dress has tucks in the sleeves.III. Questions on Text I1. Is the time spent in a bookshop very pleasant?2. Why is the time spent in a bookshop enjoyable?3. What kind of place can make people escape the realities of everyday life?4. What can people do in a bookshop or a music shop?5. Is it necessary for the assistants to greet the people who enter the bookshop?6. When do people need an assistant in a bookshop?7. Is it easy for people to become engrossed in books?8. Are people easily tempted to buy books?9. Must book sellers be patient and kind?10. Do people rend books in a bookshop?11. What kind of people often rend books in a bookshop?12. Was the book seller very kind to the identical student in this text?13. Was the book seller so kind that he kept the book in safe place in order that nobodywould buy it? (for the medical student to read?)14. Had the medical student expected to be treated with such kindness?VI. Translation1. 请你把自行车放到走廊里, 以免日晒雨淋. (get shelter from)2. 有时候, 想买某种东西的愿望是压抑不住的.3. 当你参观中国出口商品交易会的时候, 你可以欣赏各种商品, 直到心满意足为止.4. 沉迷于赌博的人是不会有所作为的.5. 请把这本书房在较安全的地方, 以免读者们随意拿走.6. 为了解释这个问题, 老师举了很多例子.(in illustration of)7. 我已经很满足现在的生活.8. 他唱着歌, 脸上挂着满意的笑容. (with a contented smile on his face)9. 在我们的学习和生活中, 犯错误是不可避免的, 最重要的认识错误和改正错误.10. 我很喜欢在星期天到广州各大书店浏览各种书籍, 这也可以说是一种我允许自己享受的东西.(Suggested key:)1.Please put your bike in the corridor to get shelter from the sun and the rain.2.Sometimes the temptation to buy something is irresistible.3.When you visit the Chinese Export Commodities Fair, you can enjoy all kinds of products toyour heart’s content.4.Those who indulge in gambling will never be promising.5.Please tuck away the book in a safe place in case the readers take it away at will.6.In illustration of this matter/issue, the teacher gave a lot of examples.7.I am content/contented with the present life.8.He is singing, with a contented smile on his face.9.In our study and daily life, it is inevitable for us to make mistakes. The most important thingis to realize the mistakes and correct them.10.I like to browse among books in big bookshops on Sundays and this is one of myindulgences.)VII. Questions on Text II:1.Are those people who buy second-hand goods mean?2.Why do people usually buy second-hand goods?3.Which book can tell you the markets of second-hand goods? (beginners guide)4.Do second-hand goods have a guarantee?5.What kind of second-hand books worth keeping?。
通信原理第三章PPT课件
调制的分类
调制方式往往能决定一个通信系统的性能。 通常调制分为模拟调制和数字调制两大类： 1、在模拟调制中，调制信号是模拟信号； 2、而在数字调制中，调制信号是数字信号。 由于模拟调制是其他调制方式的基础，故本
章首先讨论模拟调制的基本原理。
3.1 幅度调制
幅度调制的基本作用: 实现频率搬移，其目的是进行频率变换，使
因此，式（3．9）可写为
式中
已调波的效率AM 定义为边带功率与总平均
功率之比，即
[例 3－2]设用峰一峰值为 2A 且不含直流的方波对振幅为 A
m
0
的载波进行标准调幅。试求已调波的功率和效率。
解
在不过调制的情况下，A 的最大值等于 A 。这时最大可能的
m
0
效率是 50％。由式（3.13）可以看出，所有不含直流分量的
调制是用基带信号 f (t)去控制载波的某个（或某 些）参数，使该参数按照信号 f (t) 的规律变化的
过程。载波可以是正弦波，也可以是脉冲序列。 以正弦信号作载波的调制叫连续波（CW）调制。
RF 频谱分配
ELF 30-300Hz EXTREMELY LOW F VF 0.3-3KHZ VOICE F VLF 3-30KHZ VERY LOW F LF 30-300KHZ LOW MF 0.3-3MHZ MEDIUM F HF 3-30MHZ HIGH VHF 30-300MHZ VERY HIGH UHF 0.3-3GHZ ULTRA HIGH SHF 3-30GHZ SUPER HIGH EHF 30-300GHZ EXTREMELY HIGH INFRARED,VISIBLE LIGHT 103-107GHZ
信号进行标准调制（不过调制），其效率都不会超过 50％。
移动通信的信号处理技术
第三章移动通信的信号处理技术（本章部分内容为教材第四章）第一节、语音编码技术第二节、均衡技术第三节、分集技术第四节、交织与信道编码技术第一节、语音编码技术一. 语音编码概念二.波形编码基本原理三.参量编码基本原理四.混合编码技术“我爱北京天安门”波形语音波形“中国”语音波形语音波形“国”字语音波形语音波形“国”部分语音波形●语音、图像属模拟信号范畴。
●语音、图像通过编码实现数字化是必然趋势。
●数字化的语音和图像需要用较高的数码率，需占用较大的带宽和存储空间。
●压缩数字化语音和图像信号的数码率是实现语音和图像通信数字化的关键。
●编码技术的核心就是研究压缩编码算法．用尽可能低的数码率获得尽可能好的语音和图像质量。
人耳听觉特性-2人耳听觉特性-3一. 语音编码概念移动通信对语音编码的要求是：(1) 编码的速率要适合在移动信道内传输，纯编码速率应低于16kbit/s。
(2) 在一定编码速率下语音质量应尽可能高，即解码后的复原语音的保真度要高，主观评分MOS（Mean Opinion Score）应不低于3.5分（按长途语音质量要求）。
(3) 编解码时延要短，总时延不得超过65ms。
(4) 要能适应衰落信道的传输，即抗误码性能要好，以保持较好的语音质量。
(5) 算法的复杂程度要适中，应易于大规模电路集成。
（6）功耗小，便于应用于手持机语音评价客观评定方法用客观测量的手段来评价语音编码的质量，常用的方法有信噪比、加权信噪比、平均分段信噪比等。
主观评定方法是主观评定等级（Subjective Opinion Scale ），或称平均评定得分（MOS ）。
MOS 得分采用五级评分标准，其方法是由数十名试听者在相同信道环境中试听并给予评分，然后对评分进行统计处理，求出平均得分。
即使努力去听，也很难听懂1劣需要集中注意力2差中等程度的注意力3满意(正常)需要注意，但不需要明显集中注意力4良可完全放松，不需要注意力5优收听注意力等级分数质量等级主观评定等级语音编码：为信源编码，移动通信数字化的基础第1/2代蜂窝系统的根本区别语音压缩编码的目的：在保持一定复杂程度和通信时延的前提下，使用尽可能少的信道容量，传送尽可能高质量的语音。
【2021】通信信号处理.完整资料PPT
改善蜂窝和个人通信服务系统 结构的矩阵信道的盲算法研究和应用开辟了一条新的途径.
如果信道延迟扩展比循环前缀长度短，就可以完全避免ISI，从而省去了陡截的滤波器和需大量复数乘加的均衡器，使系统实现效率更 高，更具明显优势.
延迟时间
滞后相位
阵列流形（２）
阵列信号总是变换到基带再进行处理的 将阵列信号用向量形式表示
s(t)[s1(t),s2(t),,sM(t)]T
s(t)[ej1rTk,ejr2Tk,,ejrM Tk]T
方向向量与空间角向量有关，
记作： a( )
方向向量
阵列流形（３）
阵列流形A与频率相关， 当有多个信代源表时了，相到对空间结构，
通信信号处理
阵列信号处理
January 19, 2005
School of Communication and Information Engineering
总述
概述 阵列的基本知识（阵列流形） 波束形成 文献分析
什么是阵列信号处理
阵列信号处理： 将一组传感器在空间的不
同位置按一定的规则布置形成的 传感器阵列，用传感器阵列发射 能量和接收空间信号，获得信号 源的观测数据并加以处理。
达 用波a的(有i方) 助表向于示向方，量向i分=向别1,量 a(i) 的确定。
2,3,…..p
阵列的方向矩阵（表示信源的方向）为
A [a (1 )a ,(2 ) ,,a (P )]
阵列流形
移动通信系统面临的问题
频谱资源紧张、远近效应、共信 道干扰、多径衰落、越区切换以 及移动台电池容量问题带来的功 率受限等。