【本科優(yōu)秀畢業(yè)設(shè)計】簡易調(diào)幅發(fā)射機

畢業(yè)設(shè)計論文簡易調(diào)幅發(fā)射機摘要本系統(tǒng)為簡易調(diào)幅發(fā)射機，主要是由調(diào)幅信號源、幅度調(diào)制模塊和高頻高效功率放大器組成，本設(shè)計中運用了鎖相環(huán)頻率合成和反相功率合成原理。調(diào)制信號源部分是由LC振蕩電路產(chǎn)生正弦波，鎖相環(huán)芯片MC145152和雙模分頻器MC12017組成鎖相環(huán)路，并且經(jīng)過環(huán)路濾波器，最終將載波頻率精確的鎖定在15MHZ。調(diào)制模塊主要是運用模擬乘法器進行調(diào)幅，本設(shè)計中使用MC1496進行調(diào)幅。高頻高效功率放大級應(yīng)用了功率合成技術(shù)，采用反相推挽功率合成電路，負載50輸出功率大于60MW。本文中首先對調(diào)幅發(fā)射機的發(fā)展情況及面臨的問題進行了說明，其次對調(diào)幅通信系統(tǒng)原理做了相應(yīng)的說明，最后對電路進行具體設(shè)計。關(guān)鍵詞調(diào)幅發(fā)射機；鎖相環(huán)；功率合成器ABSTRACTSUMMARYOFTHESYSTEMFORAMTRANSMITTERS,MAINLYFROMTHEAMSIGNALSOURCE,AMPLITUDEMODULATIONMODULEANDHIGHFREQUENCYPOWERAMPLIFIEREFFICIENTCOMPONENTS,THEDESIGNUSEDPLLFREQUENCYSYNTHESIZERANDRPPOWERSYNTHESISTHEORYMODULATIONSIGNALSOURCEPARTBYTHELCOSCILLATORCIRCUITISMYSTERIOUSWAVE,MC145152PLLCHIPDUALFREQUENCYDIVIDERANDMC12017PLLCOMPONENTS,ANDHASGONETHROUGHALOOPFILTER,WHICHWILLULTIMATELYCARRIERFREQUENCYPRECISELOCKIN15MHZMODULATIONMODULEISMAINLYUSEDFORAMANALOGMULTIPLIER,THEDESIGNFORUSEMC1496AMHIGHFREQUENCYPOWERAMPLIFIEREFFICIENTUSEOFPOWERLEVELSYNTHESISTECHNOLOGY,RPPOWERPUSHPULLCIRCUIT,50LOADOUTPUTPOWEROFGREATERTHAN60MWTHISARTICLEFIRSTAMTRANSMITTERTOTHEDEVELOPMENTANDTHEPROBLEMSFACINGTHENOTE,SECOND,COMMUNICATIONSYSTEMSTHEORYAMDONEACORRESPONDINGNOTE,THELASTPAIROFCIRCUITDESIGNKEYWORDSAMPLITUDEMODULATEDTRANSMITTERLOCKAPPEARANCERINGPOWERSYNTHESIZER目錄摘要IABSTRACTII第1章緒論111課題背景112本課題發(fā)展狀況3121課題的國內(nèi)外發(fā)展現(xiàn)狀3122研究成果3123發(fā)展趨勢3124存在的問題4第2章調(diào)幅通信系統(tǒng)原理分析521調(diào)幅電路的原理522LC振蕩電路的原理523鎖相環(huán)路的組成及工作原理7231環(huán)路濾波器的原理8232壓控振蕩器的原理924鎖相環(huán)頻率合成器原理1025功率放大器的原理1126反相功率合成原理1327本章小結(jié)14第3章系統(tǒng)框圖與電路設(shè)計1531系統(tǒng)框圖1532LC振蕩電路的設(shè)計1533鎖相環(huán)路的設(shè)計17331集成數(shù)字鎖相環(huán)路的設(shè)計17332環(huán)路濾波器的設(shè)計1734調(diào)幅調(diào)制電路的設(shè)計1935高效高頻功率放大電路的設(shè)計2036本章小結(jié)22結(jié)論23參考文獻25附錄127附錄233附錄337附錄455致謝57第1章緒論11課題背景面對各種新的廣播制式的競爭，傳統(tǒng)的AM廣播播處于明顯的劣勢地位，歐洲許多國家，正逐漸減少中波廣播。為了擺脫困境，國外的廣播和與其相關(guān)的研究機構(gòu)，努力尋求新的途徑，使AM廣播獲得新生。將現(xiàn)有的AM廣播進行數(shù)字化改造，是一條必由之路。我國的廣播和工業(yè)界也逐漸開始關(guān)注數(shù)字AM，希望能找到一個行之有效的系統(tǒng)，改造我國大量存在的傳統(tǒng)AM廣播。數(shù)字AM是一種新的廣播體制，技術(shù)還在不斷發(fā)展，各國都在研究。1998年3月在廣州召開了世界數(shù)字AM成立大會，經(jīng)過3年多的努力，2001年國際電信聯(lián)盟ITU已通過了數(shù)字調(diào)幅廣播的國際標準，這將推動數(shù)字調(diào)幅廣播的進一步廣泛應(yīng)用。世界數(shù)字廣播公司總裁彼得申格稱，數(shù)字調(diào)幅廣播為沉悶的調(diào)幅廣播市場帶來了新鮮空氣。國際電聯(lián)的決定具有劃時代的意義，全世界的廣播聽眾將獲得價廉物美的高質(zhì)量數(shù)字廣播服務(wù)，這是半導體發(fā)明以來廣播事業(yè)最大的進步。由于數(shù)字AM是在現(xiàn)有的AM波段中進行播出，考慮到現(xiàn)階段我國的國情，發(fā)展數(shù)字AM必須考慮以下幾方面的問題。根據(jù)國內(nèi)外已公開的研究結(jié)果和資料表明，為了不影響現(xiàn)有的模擬AM廣播，不變動原有的頻率分配，限制數(shù)字AM帶寬，應(yīng)保持現(xiàn)有中、短波廣播帶寬如9KHZ。有限的帶寬必然限制了新系統(tǒng)可能達到的聲音質(zhì)量和數(shù)據(jù)傳送能力，應(yīng)用目前的音頻數(shù)字壓縮技術(shù)，9KHZ帶寬的數(shù)字AM系統(tǒng)質(zhì)量可達FM水平同時提供1KB/S的數(shù)據(jù)業(yè)務(wù)。利用29KHZ的帶寬，聲音質(zhì)量可接近CD質(zhì)量。應(yīng)利用現(xiàn)有發(fā)射設(shè)備并保持高效率為了擴大覆蓋范圍和提高效率，繼脈沖寬度調(diào)制PDM發(fā)射機之后，又出現(xiàn)了脈沖階梯調(diào)制PSM大功率發(fā)射機。與國外一樣，我國中短波發(fā)射臺的發(fā)射機已經(jīng)或正在更換為這種新型的發(fā)射機。如果未來的數(shù)字聲音廣播系統(tǒng)不再繼續(xù)使用這些昂貴的大功率、高效率的發(fā)射設(shè)備，那將造成極大的浪費，是十分可惜的。鑒于此，國外正在試驗新的數(shù)字傳輸系統(tǒng)仍然使用現(xiàn)代發(fā)射機的調(diào)制器和高頻前級、末級被調(diào)級功率放大器。此外，繼續(xù)保持這些發(fā)射機高的效率是非常重要的。要留住原有的聽眾群就應(yīng)有較長的過度期我國有數(shù)億臺調(diào)幅接收機，如果一個模擬AM電臺從某一天起改為數(shù)字聲音廣播運行，那么經(jīng)常收聽該電臺廣播而沒有數(shù)字聲接收機的聽眾就不可能再用包絡(luò)檢波的接收機收聽該臺的廣播。考慮到絕大多數(shù)聽眾是在農(nóng)村和偏遠地區(qū)，盡快擁有數(shù)字聲接收機不太現(xiàn)實，為了不失去已有的聽眾，就需要較長時間的過渡期。在過渡期間內(nèi)，應(yīng)做到模擬、數(shù)字之間相互無影響，也叫兼容。AM波段的廣播，由模擬制向數(shù)字制過渡是逐步完成的，就像黑白電視向彩色電視過度一樣。采用目前已成熟的技術(shù)，在發(fā)射機進行固態(tài)化改造的同時，采用最先進的數(shù)字調(diào)幅技術(shù)將原有發(fā)射機進一步改造成數(shù)字調(diào)幅發(fā)射機，作為數(shù)字化進程中的一種階段性技術(shù)加以應(yīng)用，不時為一個較好的辦法。運用數(shù)字調(diào)幅技術(shù)的數(shù)字調(diào)幅發(fā)射機即DAM發(fā)射機，它最早是由美國哈里斯HARRIS公司于上世紀80年代后期發(fā)明的新式發(fā)射機，其發(fā)射后的收聽效果可接近調(diào)頻廣播的質(zhì)量。盡管這樣改造后的反射機還不是真正意義上的數(shù)字AM系統(tǒng)沒有數(shù)據(jù)傳送，但比起PDM、PSM發(fā)射機的各項指標已經(jīng)有了很大的進步，經(jīng)過上述數(shù)字化的改造作為過度，可為今后發(fā)展和使用真正的數(shù)字AM系統(tǒng)，作好技術(shù)準備。下面結(jié)合我臺即將投入使用的DAM數(shù)字調(diào)幅發(fā)射機對DAM數(shù)字調(diào)幅發(fā)射技術(shù)應(yīng)用作一簡要介紹。DAM數(shù)字調(diào)幅發(fā)射機取消了傳統(tǒng)的高電平音頻功率放大器，直接用數(shù)字化音頻控制信號在射頻功率放大器末級實行高電平調(diào)幅，它把主振、調(diào)制器、和射頻功放三合一，是整機性的脈沖階梯調(diào)制，DAM發(fā)射機實際上是大功率射頻A/D與D/A轉(zhuǎn)換器。DAM數(shù)字調(diào)幅發(fā)射機克服了以往各種模擬調(diào)制難于避免的各種非線性失真，有極好的動態(tài)響應(yīng)，各項電聲技術(shù)指標遠優(yōu)于其它各類模擬調(diào)制的廣播發(fā)射機。另外，我們還可以采用數(shù)字調(diào)幅廣播技術(shù)對現(xiàn)有的中短波廣播發(fā)射機進行改造，充分利用現(xiàn)有設(shè)備和現(xiàn)有的中短波頻譜資源。DAM數(shù)字調(diào)幅發(fā)射機的工作原理是這樣的，音頻信號先經(jīng)數(shù)字處理，變換為12比特數(shù)字流，并進行編碼，用來控制各射頻功率放大器的開關(guān)。通過接通射頻功率放大器的數(shù)量多少，來控制發(fā)射機輸出射頻電平。經(jīng)帶通濾波器光滑處理濾除量化臺階和不需要的頻譜分量后，就得到通常所說的幅度調(diào)制的射頻已調(diào)波輸出，最后經(jīng)饋線、調(diào)配室傳送到天線系統(tǒng)發(fā)射出去。有限的帶寬必然限制了新系統(tǒng)可能達到的聲音質(zhì)量和數(shù)據(jù)傳送能力，應(yīng)用目前的音頻數(shù)字壓縮技術(shù)，9KHZ帶寬的數(shù)字AM系統(tǒng)質(zhì)量可達FM水平同時提供1KB/S的數(shù)據(jù)業(yè)務(wù)。12本課題發(fā)展狀況121課題的國內(nèi)外發(fā)展現(xiàn)狀現(xiàn)代廣播技術(shù)由調(diào)幅AM廣播、調(diào)頻FM廣播、調(diào)頻立體聲廣播到目前已經(jīng)試播的數(shù)字音頻廣播DAB，以及數(shù)字多媒體廣播DMB。面對各種新的廣播制式的競爭，傳統(tǒng)的AM廣播處于明顯的劣勢地位，歐洲許多國家，正逐漸減少中波廣播。為了擺脫困境，國外的廣播和與其相關(guān)的研究機構(gòu)，努力尋求新的途徑，使AM廣播獲得新生。將現(xiàn)有的AM廣播進行數(shù)字化改造，是一條必由之路。我國的廣播和工業(yè)界也逐漸開始關(guān)注數(shù)字AM，希望能找到一個行之有效的系統(tǒng)，改造我國大量存在的傳統(tǒng)AM廣播。調(diào)幅廣播正面臨著來自電視、互聯(lián)網(wǎng)、通訊等的巨大挑戰(zhàn)。同傳統(tǒng)的廣播機相比較，數(shù)字調(diào)幅廣播發(fā)射機整機的可靠性、穩(wěn)定性、抗干擾能力有大大的提高，其音色、音質(zhì)可與調(diào)頻機相媲美。2122研究成果數(shù)字調(diào)幅發(fā)射機是一種高效率的設(shè)備，比目前國內(nèi)廣泛使用的同功率中波機效率高出2030。目前已經(jīng)開發(fā)出10KW、25KW、50KW、100KW等多種規(guī)格和數(shù)字廣播發(fā)射機系列產(chǎn)品，全固態(tài)中波數(shù)字調(diào)幅發(fā)射機，并且雷達系統(tǒng)中也有著廣泛的應(yīng)用。3123發(fā)展趨勢數(shù)字AM技術(shù)和DAM發(fā)射機是AM廣播今后發(fā)展的必由之路，發(fā)展新系統(tǒng)我國已明顯落后，但在改造舊系統(tǒng)的進程中，我國雖有一批廣播發(fā)射臺的發(fā)射機經(jīng)技術(shù)升級改造成全固態(tài)的PDM、PSM或DAM等發(fā)射機，但仍有數(shù)以千計的大小發(fā)射臺還等待著這一設(shè)備更新時代的到來，作為工作在發(fā)射臺的技術(shù)人員，非常有必要經(jīng)常充電，迅速提高自身的業(yè)務(wù)能力和技術(shù)水平，盡快掌握DAM發(fā)射機的工作原理和使用維護技術(shù)，以迎接新的挑戰(zhàn)。124存在的問題發(fā)射設(shè)備，尤其是調(diào)幅發(fā)射機設(shè)備的復雜性，直接影響一項新技術(shù)、新系統(tǒng)的推廣應(yīng)用。從長遠來看，數(shù)字調(diào)幅廣播將會逐步取代模擬調(diào)幅廣播。但由于數(shù)字調(diào)幅廣播發(fā)射機要比模擬調(diào)幅廣播發(fā)射機復雜得多，只有采用高度集成的微電子技術(shù)才能實現(xiàn)。并且在大批量生產(chǎn)的情況下，價格才有可能降下來。第2章幅通信系統(tǒng)原理分析21調(diào)幅電路的原理調(diào)幅就是使載波的振幅隨調(diào)制信號的變化規(guī)律而變化。實現(xiàn)調(diào)幅的方法有低電平調(diào)幅和高電平調(diào)幅，其中低電平調(diào)幅包括平方律調(diào)幅和斬波調(diào)幅，高電平調(diào)幅包括集電極調(diào)幅和基極調(diào)幅。調(diào)幅波的特點是載波的振幅受調(diào)制信號的控制作周期性的變化。這個變化的周期與調(diào)制信號的周期相同，而振幅變化則與調(diào)制信號的振幅成正比。為簡化分析手續(xù)起見，假定調(diào)制信號是簡諧振蕩，其表達式為21TVVCOS如果用它來對載波進行調(diào)幅，那么，在理想的情況下，已調(diào)TV0COS波的振幅為22TVKATCOS0式中，為比例常數(shù)。因此，已調(diào)波可以用下式表示AKTVTT023M0S122LC振蕩電路的原理成一個振蕩器必須具備的條件是有一套振蕩回路，包含兩個或兩個以上儲能元件。在這兩個元件中，當一個釋放能量時，另一個就接收能量。有一個能量來源，可以補充由振蕩回路電阻所產(chǎn)生的能量損失。有一個控制設(shè)備，可以使電源功率在正確的時刻補充電路的能量損失，以維持等幅振蕩。反饋型LC振蕩器有許多形式。按照反饋耦合元件可以分成互感耦合振蕩器、電感反饋式振蕩器與電容反饋式振蕩器等。當要求電容三點式振蕩電路的振蕩頻率更高時，則應(yīng)使電容C1、C2的值較小。由于C1并接在三極管的C、E極之間，C2并接在三極管的B、E極之間，當管子的極間電容隨溫度等因素的變化而變化時，將對振蕩頻率產(chǎn)生顯著影響，造成振蕩頻率的不穩(wěn)定。為了減小極間電容的影響，提高電路頻率的穩(wěn)定性，對電容三點式振蕩電路進行適當改進就形成了改進型電容三點式振蕩電路，如圖21所示。該電路稱為串聯(lián)型電容三點式振蕩電路，又稱克拉潑振蕩電路。圖21串聯(lián)型電容三點式振蕩器由圖可知，這種電路是在電容三點式振蕩電路的電感支路上串進了一個小電容C而構(gòu)成的C3對交流短路，屬共基組態(tài)。C1、C2、C及L組成諧振回路，當C2的情形，所以每個M符號都由兩個或兩個以上比特構(gòu)成與DCS中這種有限碼元集不同，模擬系統(tǒng)的信號波形是無限的。對于采用信道編碼糾錯編碼的系統(tǒng)而言，消息碼元序列轉(zhuǎn)變成了信道碼元編碼碼元序列，每個信道碼元標識為UI。由于每個消息碼元或信道碼元由1個或1組比特構(gòu)成，這樣的碼元序列也成為比特流BITSTREAM。對于DCS，關(guān)鍵信號處理過程僅包括的格式化、調(diào)制、解調(diào)/檢測和同步。格式化把源信息轉(zhuǎn)換成數(shù)字比特，以保證在DCS內(nèi)信息與信號處理的一致性。脈沖調(diào)制方框之前的信息仍是比特流的形式。調(diào)制過程將消息碼元或信道碼元采用信道編碼轉(zhuǎn)換成與傳輸信道特性匹配的波形。脈沖調(diào)制是必不可少的步驟，因為要傳送每個符號必須先將其二進制數(shù)代碼轉(zhuǎn)換成基帶波形。術(shù)語基帶是指從直流延伸到某個有限值的信號頻譜，這個值通常是小于幾MHZ的有限數(shù)。脈沖調(diào)制方框通常包括使傳輸帶寬最小化的濾波器。當對二進制數(shù)符號應(yīng)用脈沖時，產(chǎn)生的二進制數(shù)波形就稱為脈沖編碼調(diào)制波形。PCM波形有幾種類型，在電話通信中這些波形常稱多址接入格式化信源編碼加密信道編碼碼多路復用帶通調(diào)制頻率擴展多址接入頻率擴展帶通調(diào)制脈沖調(diào)制多路復用信道編碼加密信源編碼格式化為線路碼。當脈沖調(diào)制用于非二進制符號時，產(chǎn)生的二進制數(shù)波形就稱為脈沖編碼調(diào)制波形。每個消息碼元或信道碼元都轉(zhuǎn)變?yōu)榛鶐Рㄐ蔚男问?。在任何電子設(shè)備中，脈沖調(diào)制之前的比特流都用電壓電平表示。INTRODUCTIONCOMMUNICATIONWASONEOFTHEFIRSTAPPLICATIONSOFELECTRICALTECHNOLOGYTODAY,INTHEAGEOFFIBEROPTICSANDSATELLITETELEVISION,FACSIMILEMACHINESANDCELLULARTELEPHONES,COMMUNICATIONSYSTEMSREMAINATTHELEADINGEDGEOFELECTRONICSPROBABLYNOOTHERBRANCHOFELECTRONICSHASASPROFOUNDANEFFECTONPEOPLESEVERYDAYLIVES,THERE,WEWILLCONSIDERTHEBASICELEMENTSTHATARECOMMONTOANYSUCHSYSTEMATRANSMITTER,ARECEIVER,ANDACOMMUNICATIONCHANNELFIRSTOFALL,LETUSREVIEWSOMEOFTHEFUNDAMENTALSTHATYOUWELLNEEDFORLATERSTUDYANDINTRODUCEYOUTOSOMEOFTHECIRCUITSTHATARECOMMONLYFOUNDINRADIOFREQUENCYSYSTEMATRANSMITTER,ARECEIVER,ANDACOMMUNICATIONCHANNELWEBEGINWITHANALOGSYSTEMSTHEREADERWHOISIMPATIENTTOGETONTODIGITALSYSTEMSSHOULDREALIZETHATMANYDIGITALSYSTEMSALSOREQUIREANALOGTECHNOLOGYTOFUNCTIONTHEMODERNTECHNOLOGISTNEEDSTOHAVEATLEASTABASICUNDERSTANDINGOFBOTHANALOGANDDIGITALSYSTEMSBEFORESPECIALIZINGINONEORTHEOTHERITISOFTENSAIDTHATWEARELIVINGINTHEINFORMATIONAGECOMMUNICATIONTECHNOLOGYISABSOLUTELYVITALTOTHEGENERATION,STORAGE,ANDTRANSMISSIONOFTHISINFORMATIONELEMENTSOFACOMMUNICATIONSYSTEMANYCOMMUNICATIONSYSTEMMOVESINFORMATIONFROMASOURCETOADESTINATIONTHROUGHACHANNELFIGURE111ILLUSTRATESTHISVERYSIMPLEIDEATHEINFORMATIONFROMTHESOURCEWELLGENERALLYNOTBEINAFORMTHATCANTRAVELTHROUGHTHECHANNEL,SOADEVICECALLEDATRANSMITTERWILLBEEMPLOYEDATONEANDARECEIVERATTHEOTHERTHESOURCETHESOURCEORINFORMATIONSIGNALCANBEANALOGORDIGITALCOMMONEXAMPLESAREANALOGAUDIO,VIDEOSIGNALSANDDIGITALDATASOURCESAREOFTENDESCRIBEDINTERMSOFTHEFREQUENCYRANGETHATTHEYOCCUPYTELEPHONEQUALITYANALOGVOICESIGNALS,FORINSTANCE,CONTAINFREQUENCIESFROM300HZTO3KHZ,WHILEANALOGHIGHFIDELITYMUSICNEEDSAFREQUENCYRANGEOFAPPROXIMATELY20HZTO20KHZVIDEOREQUIRESAMUCHLARGERFREQUENCYRANGETHANAUDIOANANALOGVIDEOSIGNALOFTELEVISIONBROADCASTQUALITYNEEDSAFREQUENCYRANGEFROM6MHZTOABOUT8MHZTVSIGNALSOVERTHEAUDIOSIGNALOFTHENEEDFORHIGHERFREQUENCYRANGEQUALITYOFATELEVISIONVIDEOSIGNALNEEDS68MHZFREQUENCYRANGEDIGITALSIGNALFROMANAUDIOORVIDEOSIGNAL,ORDATACOMPONENTSEG,TEXTFIGURESANDCHARACTERSDIGITALSIGNALFROMARBITRARYBANDWIDTH,THISDEPENDSONTHE489,000BITSANDTHENUMBEROFBINARY1AND0SIGNALCONVERSIONMETHODTHECHANNELCOMMUNICATIONCHANNELCANBEANYMEDIUMACONDUCTOR,AFIBEROROURFREEDOMTOLIVEIN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