PCM编码译码设计

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4、码专业班级：学 号：姓 名：任课教师：设计时间：Staegy lyout s new of hi sor. cndi ay ul ng -l tal s”y cnsc ou "our a ul" e. t he wrk; 5)iss- I cord, a sard reat .sip CCI.a de pca” a nnept d”; 6 pr" - Ie Socials cre -l Scals t hougtmoa adCCie - tadiina vrueactig polica I new cnce pt new t houghtn- sb - ly of

5、 basc conte nt, I ng ud - tand XI General Se y In Fujia w rig of" root s "mm on do" "drop" " ""，ad Ie In Na chstudypropo se dof、r yXa moved", and "inova ", Ms-egayspi* poseIde -, moral chaar, cnseVne- tot requieme nts M in ulesbad ma_ r followng

6、 aspecs con-1 (1) Id-l-H Is C.mmun-t Shag of、- im", set rg ht of worl dvew, ad Oulok onlie, and ues; 2 CCia Is ream-Ion-of of dde am, sCCie - moder eatof , ce E-I- s Is yand n. a ”Isa Ule- CCie - great of way cnfiea.snNe nce. 4) "our a ful"PCM编码及译码一、设计任务与要求设输入信号为x(t)=AcSin2近，对x 信号进行抽样

7、、量化和A律PCMI码，经过传输后，接收端进行PCM码。画出经过PCM®码、译码后的波形与未编码波形；设信道没有误码，画出不同幅度 Ac情况下，PCMt码后的量化信噪比；二、设计任务分析基本模型：采用MATLA防真，基本框型图如下:抽样：对模拟信号进行周期性扫描，把时间上连续的信号变成时间上 离散的信号。该模拟信号经过抽样后包含原信号所有信息，也就能够 无失真的回复模拟信号。在某些选定的时刻抽取连续时间信号在各该时刻的值。数字计算机所处理的信号必须是离散时间信号。 在涉及连 续时间信号时，就必须先以适当的频度从中抽取其在各时刻的数值， 形成相应的离散时间信号，然后进行处理。A律压缩h

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11、不均匀分成8段，每次以1/2对分（即按2的幕次分段）y轴：01内等分成8段，每段间隔均为1/8x,y各交点连接构成8段折线，斜率不同Ax0 x 三 1 / A11nA11281 78 68 58 里8 38 28 18101-641 In Ax1 In A1 / A £ x 三 1A= 87.6斜率:1段162段167 段 1/28 段 1/41- 00-16141 X量化：用有限的电平来表示抽样值的过程（从而可进一步编码）,且电平间隔大于噪声，则可准确恢复样值。把取值连续的信号变成取值离散的信号，引入失真,即量化误差。在数字信号处理领域，量化指将信号的连续取值（或者大量可能 的离散

12、取值）近似为有限多个（或较少的）离散值的过程。量化主要应用于从连 续信号到数字信号的转换中。连续信号经过采样成为离散信号，离散信号经过量.asss - kid t - -dl - d ul l s-. a d -aa.- ia s it-us a .- .as-s a - g - s - - s F -sds- st .- - s .- u i 一 a u - g d at s- - a d s . - - - aIs .-.sx a.a-Ostspeech learnisic spirit, lear-L - Ml >understand Ce一- .-he work ;(5) ins

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14、t;，ad Ie In Na chstudypropo se dof、ryXa moved", and "inova ", Ms-egayspi* poseIde -, moral chaar, cnseVne- tot requieme nts M in ulesbad ma_ r followng aspecs con-1 (1) Id-l-H Is C.mmun-t Shag of、- im", set rg ht of worl dvew, ad Oulok onlie, and ues; 2 CCia Is ream-Ion-of ofdde

15、am, sCCie - moder eatof , ce E-I- s Is y and n. a Isa Ule- CCie - great of way cnfie .» nce. 4) "our a ful"化即成为数字信号。注意离散信号通常情况下并不需要经过量化的过程，但可能在值域上并不离散，还是需要经过量化的过程。信号的采样和量化通常都是由ADC实现的。量化方法(段落非均匀量化，段内均匀量化)8位量化共28=256量化级，正/负各128；每段再均匀划分16个量化级；各段量化间隔不同。第8段最大1/32(2-5);第1,2段最小1/2048(2-11);为

16、避免分数，令x,y的归一化值为2048(211)量化单位,可写出A律13折线的 参数。将想x (t)作为输入信号，进行抽样量化，A律压缩编码，x(t)即坐标横轴，可 使用13折线方法，逼近A取87.6的A律压缩曲线，y轴即为PCME缩编码。/(x) = ilnx fx)- < Bx= (刈凡(*右=卜工/3去 0 段S = pr(x)dx* S 1231)量化信噪比：(1)(2)设压缩曲线则*信号功率量化信噪比(5)噪声功率上式表明：压缩特性为时数特性时，量化器的信噪比始终保持常数，与输入信号的幅度无关!实现了最佳非均匀量化，国际上通用的两种对数压缩特性】&篁和 9,本次设计采用

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20、on implementation programmespirit,accordingto distingstyle,grasp conditi ons,rights a nd obligations of partymembers, bearing iutionpr oblemof re quireme nts, ensure le arninge ducation madeeffectived party member criteria andconditions.Learningthe codeofself-discipliness,lmembers consci ously respe

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23、reme nts.Ma in understand masterfollowing aspects content:(1)idealfaith is Communists spiritS hang of"calcium",setrig htofworl dvie w, andOutlookonlife, andvalues;(2)China dream is nationalofdream,a nd nationalofdream, a nd people ofdre am,is Chine se modernyilai m ostgreat ofdream, core E

24、ssential sis nationalprosperit y, andnati onalrevitali zation,and pe opl e ha ppi ness;(3) Chinafeature sSocialist isa chi evedChine se greatrevival ofway,e nhanced roa d confide nce, and the oryconfide nce, and systemconfide nce ;(4) "four afull"PCMM勺概念:脉冲编码调制就是把一个时间连续，取值连续的模拟信号变换成时间离散，取值

25、离散的数字信号后在信道中传输。脉冲编码调制就是对模拟信号先抽样，再对样值幅度量化，编码的过程。抽样， 就是对模拟信号进行周期性扫描，把时间上连续的信号变成时间上离散的信号，抽样必须遵循奈奎斯特抽样定理。该模拟信号经过抽样后还应当包含原信号中所有信息，也就是说能无失真的恢复原模拟信号。它的抽样速率的下限是由抽样定理确定的。抽样速率采用8KHZ。量化，就是把经过抽样得到的瞬时值将其幅度离散，即用一组规定的电平，把瞬时抽样值用最接近的电平值来表示, 通常是用二进制表示。量化误差：量化后的信号和抽样信号的差值。量化误差在接收端表现为噪声，称为量化噪声。量化级数越多误差越小，相应的二进制码位数越多，要求

26、传输速率越高，频带越宽。为使量化噪声尽可能小而所需码位数又不太多，通常采用非均匀量化的方法进行量化。非均匀量化根据幅度的不同区间来确定量化间隔，幅度小的区间量化间隔取得小，幅度大的区间量化间隔取得大。一个模拟信号经过抽样量化后，得到已量化的脉冲幅度调制信号，它仅为有限个数值。编码， 就是用一组二进制码组来表示每一个有固定电平的量化值。然而， 实际上量化是在编码过程中同时完成的，故编码过程也称为模/ 数变换，可记作A/D。话音信号先经防混叠低通滤波器，进行脉冲抽样，变成8KHz重复频率的抽样信号（即离散的脉冲调幅 PAM®号），然后将幅度连续的PAMW号用“四舍五 入”办法量化为有限个

27、幅度取值的信号， 再经编码后转换成二进制码。对于电话，CCITT规定抽样率为8KHz,每抽卞值编8位码，即共有2A 8=256个量化值，因 而每话路PC两码后的标准数码率是 64kb/s。为解决均匀量化时小信号量化误 差大， 音质差的问题，在实际中采用不均匀选取量化间隔的非线性量化方法，即量化特性在小信号时分层密，量化间隔小，而在大信号时分层疏，量化间隔大。heis a Communist,stre ngthen party spirit,liste ning party, party, par ty, party,party party guardi ng part y,atthe part

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33、 "drop" " ""，ad Ie In Na chstudypropo se dof、r yXa moved", and "inova ", Ms-egayspi* poseIde -, moral chaar, cnseVne- tot requieme nts M in ulesbad ma_ r followng aspecs con-1 (1) Id-l-H Is C.mmun-t Shag of、- im", set rg ht of worl dvew, ad Oulok onlie, a

34、nd ues; 2 CCia Isream-Ion-of ofdde am, sCCie - moder eatof , ce E-I- s Is yand n. a ”Isa Ule- CCie - great of way cnfiea.snNe nce. 4) "our a ful"三、设计结果和分析在MATLAB上进行仿真后，所得的结果如下：未编码的信号与经过PCM®码波形对比：speech learnisic spirit, lear-L - Ml >understand Ce一- .-he work ;(5) insistedi nnovatio

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40、t;our a ul"未编码的正弦信号经A律PCM©译码后的量化信噪比:File Edit View Insert ToolsDesktopWindow HelpF，回r iqure M口卜，Dock Figure 3序列的量化信噪比605040302Q-60-60-30幅度Ac总结分析：在仿真的过程中，多次观察实验结果，得出结论，通过 MATLAB所设 计的程序，成功的实现了将不同幅度的模拟正弦信号，进行采样、量化、 A 律PCM编码、译码，最后得到译码的信号，计算量化信噪比，绘制量化信 噪比曲线，并比较未编码与经过 A律PCM编译码后得到的信号，发现两个 波形大致相同且

41、得到的量化噪声比曲线与理论上的曲线也大致一致。在实验过程中，多次因为最初数据选择的原因，造成了反复修改程序的 情况出现，这使得在小组实验过程中，连带的出现了其他问题，小组成员经 过讨论和调试，最终确定了需要采用的数据以及方法， 最终的出了差强人意teil-l-a-s-deepen understanding oftheConstitutiprogrammeforadvancefullstri-.- _ . 一一acting politica lnew conceStrategylayout isnewof hiptnewtcconte nt,learning acting politi cal

42、totacal requirements.1.Cccordingto County arningofthe partyork during adv ocate of"four grassroot s" "immediatelyondo" "drop" "weakbirdfirstfly"and theiOrganizationDepartment on County "two learn ado" lear ningarrangementsofspecificprogrammeand IBoar

43、dleConstitution,a deepundersta ndi ng oftheparty's nature, pur pose, guiding principle s,goal s, organizati on,goodarninge ducation implementation programmespirit,accordistyle,grasp conditi ons,rights a nd obligations of partymembers,ngto d istinguishlbearing i nmindts targeted solqualifieutionp

44、r oblemofre quireme nts, ensure le arninge ducation madeeffectived party membercriteria andconditions.Learningthe codeofself-disciplintspe ech spirit arme d mind,and guidepractice,a nd Promotethew ork andbe qualifie d partymembers angs", mastering vari ous typesofdisci plinaryoffence and le arn

45、ing arra ngements arnd punishmentpr ovisions.e here bymakesthefoll2.serie sspoke. o XIGecific pr ogrammes.llpartymembers tyout poverty for bal earningon a nd party rules and unifythe XIunderstandXI GeneralSecretaryserich, GeneralSeheba sic re quireme nts.Ma in understand masterfollowing aspects cont

46、ent:(1)idealfaith is Communists spiritS hang of "calcium",set rig htofworl dview,and Outlook on life,and values;(2)China dream is nationalofdream,a nd national ofdream, a nd people ofdre am,is Chine se modernyilai m ostgreat ofdream, core Essential sis nationalprosperit y, andnati onalrevi

47、tali zation,and pe opl e ha ppi ness;(3) Chinafeature sSocialist isa chi evedChine se greatrevival ofway,e nhanced roa d confide nce, and the oryconfide nce, and systemconfide nce ;(4) "four afull"的实验成果。资料搜索和整合过程，也是十分繁复的，在不同的资料中，找到实验设计所需要的相关部分，我们采用了多方面调查的方法，包括网络和书籍等，通过调查检索，得到了所需要的信息。设计要求中的

48、各个环节，也做了相应的分析。从程序调试的结果也发现程序存在一点不足，所得到的量化信噪比曲线存在一定的缺陷，在以后的学习生活中，将对这一方面进行更深层次的探索和学习。心得与体会：在此次实验仿真的过程中，小组成员，分工合理，在程序调试和代码检测上，下了很大的功夫，这也说明了，我们在平时的学习生活中，对这方面的学习探究工作，做的不够，做的不好。这次设计课程中，我们也了解了专业知识的冰山一角，在繁琐的实验进程中，多次遇到了各方面，各层次困难。尤其是在代码调试和检查程序错误以及题目分析的过程中。 不仅仅是完成一门课程，还能给我们能力一定的提升，它不仅包括动手能力，还包括学习能力、判断能力、搜集资料的能力

49、、交流能力、心理素质等。在大一、 大二已经做过很多课程设计，总结以前课程设计的经验和教训，花了我很多时间，付出了少心血，不过并没有得到我想要的回报。不过我还是比较满意我自己的表现，虽然也还有些不足。从设计中获得的知识，得到的经验对我以后的学习、工作都是有帮助的。在这次课程设计中，不仅对于以前的上理论课中一些不清楚的地方有了新的认识，对于一个简单的数字通信系统有了一定的了解，而且对于如何将理论转化成程序有了些更深刻的体会， 编程中处理问题的能力也有所增强。虽然是一个简单的课程设计，我对做事态度方面有了不同的理解，事情无论大小，我们都应该认真面对，尽自己的能力去做，不能因为事情小就不尽心。课本和给

50、出的实验原理，学习了一下相关理论知识。由于之前学过相关的内容， 再次温习花的时间也不会太多。这个课程设计从开始做到完成，虽然总共花的时间并不算长，但是让我明白了无论是这次的通信原理课程设计还是其他工程或是毕业设计，乃至今后的实习和工作中，都是一个温故而知新的过程，技术的更新是非常迅速的，但是理论基础是根本，是必不可少的，只有学好基础知识才有可能谈其他创新和发展。另外在课程设计的过程中也会遇到很多困难。首先， 此次设计用的设计软件是 MATLAB ， 由于软件编程一直是我的薄弱项，所以开始就有畏难的情绪。但是通过仔细阅读老师给出的参考程序片段，上网搜索已有的程序案例，读懂相关的程序功能，并根据实

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