【正文】 一個(gè)復(fù)用器可以容納 25Mbps的數(shù)據(jù)速率，現(xiàn)在考慮一路節(jié)目給它多高的數(shù)據(jù)速率。 調(diào)制 速率 16QAM調(diào)制中，一個(gè)符號用 4個(gè)比特來表示； 64QAM調(diào)制中，一個(gè)符號用 6個(gè)比特來表示； 256QAM調(diào)制中，一個(gè)符號用 8個(gè)比特來表示。 QAM調(diào)制原理框圖如下： 圖 27 QAM調(diào)制原理框圖 QA M星座圖 圖 28 QA M星座圖 利用星座圖分析故障 （ 1）理想星座圖 符號點(diǎn)均在決策邊框內(nèi)的中心點(diǎn)，說明有良好的相位噪聲、熱噪聲等，因此 MER值好。 數(shù)字電視前端系統(tǒng) 畢業(yè)設(shè)計(jì) 13 3）在 TS流中插入 EMM（授權(quán)管理信息） 和 ECM（授權(quán)控制信息）數(shù)據(jù)流。 dBμV。這些信息包含在表中：節(jié)目群信息表（ BAT）、業(yè)務(wù)描述表（ SDT）、事件信息表（ EIT）、時(shí)間日期表（ TDT）、運(yùn)行狀態(tài)表（ RST）等。 TableID： 0x4A 業(yè)務(wù)描述表（ SDT） 描述系統(tǒng)中業(yè)務(wù)的名稱、業(yè)務(wù)提供者、是否有相應(yīng)的事件描述、起始時(shí)間、持續(xù)時(shí)間等； SDT可以描述當(dāng)前 TS流的相應(yīng)信息，也可以描述其它 TS流的相應(yīng)信息，這由 SDT的表標(biāo)識符（ TableID）來區(qū)分。 解密操作在接收機(jī)端進(jìn)行。 解擾是加擾的逆過程，在用戶接收端的解擾器中完成。在接收端， EMM 也用于控制解擾。 ECM 是在前端形成的。 加擾的方 法是由偽隨機(jī)碼發(fā)生器產(chǎn)生的偽隨機(jī)序列與原始的傳輸流進(jìn)行 XOR運(yùn)算，改變被傳輸信息的特征，使信號變?yōu)椴豢深A(yù)測的數(shù)據(jù)流。 CW由前端加密后經(jīng)過網(wǎng)絡(luò)傳送到用戶機(jī)頂盒的智能卡上，經(jīng)解密后產(chǎn)生密鑰。 這種方式便于多級運(yùn)營管理，為多級運(yùn)營商選擇 CA 系統(tǒng)提供靈活性（不必大家都使用同一 CA 系統(tǒng)）。是針對接收端機(jī)頂盒而言的。從而實(shí)現(xiàn)機(jī)卡分離。在用戶端，智能卡通過 PDK 對 EMM和 ECM 解密，取出CW，實(shí)現(xiàn)對加擾傳輸流的解擾。加密器 A接收到控制字（ CW）之后，根據(jù)用戶授權(quán)系統(tǒng)提供的業(yè)務(wù)密鑰對控制字進(jìn)行加密運(yùn)算。加密器 B的輸出結(jié)果就是加了密的業(yè)務(wù)密鑰，稱為數(shù)字電視前端系統(tǒng) 畢業(yè)設(shè)計(jì) 18 授權(quán)管理信息（ EMM）。 恢復(fù)控制字的過程非常短暫，一旦恢復(fù)出正確的控制字后，解擾器便能正常解擾，把加擾 TS流變成正常的 TS流 DVBCA的應(yīng)用模式 基本功能 條件接收（ CA）系統(tǒng)是指用來控制用戶對廣播電視節(jié)目或服務(wù)進(jìn)行接收的系統(tǒng)，即用戶只能收看經(jīng)過授權(quán)的廣播電視節(jié) 目或服務(wù)；它是實(shí)現(xiàn)個(gè)性化服務(wù)的關(guān)鍵，其基本目的是在數(shù)字電視系統(tǒng)中對用戶進(jìn)行授權(quán)控制及授權(quán)管理，從而實(shí)現(xiàn)有償服務(wù)。 解密模式的條件接收系統(tǒng)結(jié)構(gòu)如下圖所示： 數(shù)字電視前端系統(tǒng) 畢業(yè)設(shè)計(jì) 19 圖 32 解密模式的條件接收系統(tǒng)結(jié)構(gòu)圖 不解密模式中，當(dāng)節(jié)目平臺和服務(wù)平臺采用相同的 CA系統(tǒng)時(shí)，節(jié)目平臺的節(jié)目碼流傳送到服務(wù)平臺后不解擾，直接傳送到用戶。 在同密的 CA系統(tǒng)中，存在兩種或兩種以上的 ECMG和 EMMG，分別生成各自的 ECM和 EMM信息。 用戶終端中采用分區(qū)的智能卡，節(jié)目平臺 CA系統(tǒng)的密鑰和服務(wù)平臺 CA系統(tǒng)的密鑰分?jǐn)?shù)字電視前端系統(tǒng) 畢業(yè)設(shè)計(jì) 20 別被植入到不同的智能卡分區(qū)中，用戶終端根據(jù)加擾節(jié)目碼流中的 CA系統(tǒng)標(biāo)識決定采用哪個(gè)密鑰進(jìn)行解擾。 服務(wù)平臺收到節(jié)目平臺的加擾 節(jié)目碼流，插入用戶的收視授權(quán)后，轉(zhuǎn)播到用戶。此次我們的設(shè)計(jì)也接近尾聲。在動(dòng)手設(shè)計(jì)之前我就已經(jīng)著手準(zhǔn)備相關(guān)資料，凡是估計(jì)能在設(shè)計(jì)中用得著的我都找來閱讀過，了解了全自動(dòng)洗衣機(jī)的工作原理后才開始動(dòng)手設(shè)計(jì)。有時(shí)不得不自我反省，同時(shí)，我也得出了這樣一條結(jié)論：光是學(xué)習(xí)和思考書本和課堂上所學(xué)的知識是遠(yuǎn)遠(yuǎn)不夠應(yīng)對以后的工作的，要有一個(gè)預(yù)見能力，即為以后考慮能力，也為以后把學(xué)習(xí)、思考和具體的實(shí)踐結(jié)合起來用于實(shí)踐，這樣才能把知識和本領(lǐng)掌握牢固，也只有這樣才能真正達(dá)到學(xué)以致用的目的。細(xì)心與認(rèn)真是做好每一件事情的必要條件，只要細(xì)心認(rèn)真地做事才能保證前面所做的事情是對的是正確的，下面的方案才有可能順利進(jìn)行。通過不斷地自我學(xué)習(xí)、向他人學(xué)習(xí)以及對現(xiàn)實(shí)社會現(xiàn)象觀察與思考，是自己保持一種積極上進(jìn)地思想態(tài)度，同時(shí)也養(yǎng)成了一種勤于觀察和思考的生活態(tài)度。 我深知自己存在諸多不足。另外，可以肯定的是，我自身一定還存在著其它的我尚未意識到的不足。s Zhangye city during their journey to Kazakhstan, May 5, 2021. The caravan, consisting of more than 100 camels, three horsedrawn carriages and four support vehicles, started the trip from Jingyang county in Shaanxi on Sept 19, 2021. It will pass through Gansu province and Xinjiang Uygur autonomous region, and finally arrive in Almaty, formerly known as AlmaAta, the largest city in Kazakhstan, and Dungan in Zhambyl province. The trip will cover about 15,000 kilometers and take the caravan more than one year to plete. The caravan is expected to return to Jingyang in March 2021. Then they will e back, carrying specialty products from Kazakhstan A small art troupe founded six decades ago has grown into a household name in the Inner Mongolia autonomous region. In the 1950s, Ulan Muqir Art Troupe was created by nine young musicians, who toured remote villages on horses and performed traditional Mongolian music and dances for nomadic families. The 54yearold was born in Tongliao, in eastern Inner Mongolia and joined the troupe in says there are 74 branch troupes across Inner Mongolia and actors give around 100 shows every year to local nomadic people. I can still recall the days when I toured with the troupe in the early 39。t just about sharing art with nomadic families but also about gaining inspiration for the music and dance. Ulan Muqir literally translates as red burgeon, and today39。s president, who is also a renowned tenor, tells China Daily. During a tour in 1985, he went to a village and met an elderly local man, who told him a story about his friendship with a solider from Shenyang, capital of Northeast China39。s to e and recapping the key points. This device, not used in the original, is culturally understandable but artistically mediocre. What puzzles me is the two new songs for the opening and end credits. They were written in Englis h, but sung by Chinese with an unfortable accent. They were obviously designed to appeal to an Englishspeaking base, but do not jibe with the Chinese dialogue. Speaking of the dialogue, the English translation, picked apart by some Chinese, is too literal for my taste. I can imagine a typical American hit by a flurry of royal ranks, addresses and greetings, even multiple names and titles for the same person. The first half hour must be a swamp to wade through, very much like my experience of getting through a Tolstoy tome with its endless inflections of names transliterated into lengthy Chinese. I see the choice of verbatim translation as an effort for conveying exotica. It is fairly petent, with no error that I could detect, but fails to rise above words or capture the essence of the language. A cultural product usually crosses over to a foreign territory first by an emphasis on the monalities. But whether inside or outside China, the temptation to sell it for the differences is just too great. Sure, the sumptuous sets and costumes are a big attraction, but the narrative technique has bee－ how shall I put it?－ a bit anglicized, which is necessary for cultural export. Judging by the responses, this legend, which, contrary to the claim of the English trailer, is totally fictitious, has departed from China but not yet landed on American shores. I am a big fan of Ralph Waldo Emerson39。 he wondered how in the world he came to belong there. Indeed his penning and publishing this essay caused his exmunication from high society and also caused him a lot of legal trouble. The legal trouble came as a result of the fact that he was speaking out against the government. I like to reference such texts from time to time as an example both of the fact that history does repeat itself and that this world is not so big that what applies to one society does not in any way touch another society. On a much smaller scale,Emerson39。 names and figuring out what to do with them for the brief time each week that I stand in front of them. I do not consider the challenges of learning to live