Isiginali ye-baseband yedijithali yindlela yamaza ombane emele ulwazi lwedijithali, olunokuthi lumelwe ngamanqanaba ahlukeneyo okanye iipulses. Kukho iintlobo ezininzi zemiqondiso ye-baseband yedijithali (emva koku kuthiwa yimiqondiso ye-baseband). Umzobo 6-1 ubonisa iifomati ezimbalwa zesiseko sophawu lwamaza, kwaye siya kusebenzisa ipulse yoxande njengomzekelo.
1. Unipolar waveform
Njengoko kubonisiwe kwi-Figure 6-1 (a), le yeyona ndlela ilula ye-baseband signal waveform. Isebenzisa inqanaba elilungileyo kunye nenqanaba elingu-zero ukumela amanani okubini "1" kunye "0," okanye isebenzisa ubukho okanye ukungabikho kweepulses ukumela "1" kunye "0" kwixesha lesimboli.Iimpawu zolu hlobo lwamaza kukuba akukho sithuba phakathi kwee-pulses zombane, i-polarity inye, kwaye yenziwa lula yi-TTL kunye neesekethe ze-CMOS. Inokuthunyelwa ngaphakathi kwikhompyuter okanye phakathi kwezinto ezisondele kakhulu, njengebhodi yesekethe eprintiweyo kunye ne-chassis.
2. I-bipolar waveform
Isebenzisa i-pulses yezinga eli-positive kunye ne-negative level ukumela amanani okubini "1" kunye no-"0," njengoko kubonisiwe kuMfanekiso 6-1(b).Ngenxa yokuba amanqanaba alungileyo kunye ne-negative ane-amplitudes elinganayo kunye ne-polarities ezichaseneyo, akukho candelo le-DC amathuba okuba "1" kunye no "0" avele, okulungele ukuhanjiswa kwijelo, kunye nenqanaba lesigqibo sokubuyisela umqondiso ekupheleni kokufumana ngu-zero, ngoko ke, ayichatshazelwa lutshintsho lweempawu zetshaneli, kwaye isakhono sokuchasa ukungenelela sinamandla. Umgangatho wojongano lwe-ITU-T's V.24 kunye ne-American Electrotechnical Association's (EIA) RS-232C umgangatho wojongano olusemgangathweni zombini zisebenzisa ii-bipolar waveforms.
3. Unipolar ukubuya-to-zero waveform
Ububanzi be-pulse esebenzayo ye-return-to-zero (RZ) ingaphantsi kobubanzi besimboli T, okuthetha ukuba amandla ombane wesignali ahlala ebuyela ku-zero phambi kwexesha lokupheliswa kwesimboli, njengoko kubonisiwe kuMfanekiso 6-1(c). ).bonisa. Ngokuqhelekileyo, i-return-to-zero waveform isebenzisa ikhowudi yesiqingatha, oko kukuthi, umjikelezo womsebenzi (T / TB) ngu-50%, kwaye ulwazi lwexesha lunokukhutshwa ngokuthe ngqo kwi-unipolar waveform ye-RZ. inguqu yamaza.
ehambelana nokubuyela-ku-zero. I-unipolar kunye ne-bipolar waveforms ngasentla zeze-non-return-to-zero (NRZ) iifom zamaza ezinomjikelezo womsebenzi we.
4.I-Bipolar ibuyela-kwi-zero waveform
Yindlela yokubuyela kwi-zero ye-bipolar waveform, njengoko kuboniswe kuMfanekiso 6-1 (d). Idibanisa iimpawu ze-bipolar kunye ne-return-to-zero waveforms. Ngenxa yokuba kukho isithuba esinguziro esinokubakho phakathi kwee-pulses ezikufutshane, umamkeli unokuchonga ngokulula isiqalo nesiphelo sexesha lesimboli nganye, ukuze umthumeli kunye nomamkeli bakwazi ukugcina ungqamaniso lwebit oluchanekileyo. Olu ncedo lwenza ukuba i-bipolar nulling waveforms ibe luncedo.
5. Ulwahlulo lwamaza
Olu hlobo lwamaza luvakalisa umyalezo ngotshintsho kunye notshintsho lwenqanaba lesimboli esikufutshane, kungakhathaliseki ukuba yintoni na okanye i-polarity yesimboli ngokwayo, njengoko kubonisiwe kuMfanekiso 6-1 (e). Kumfanekiso, "1" imelwe kukutsiba kwinqanaba, kwaye "0" imelwe kwinqanaba elingatshintshwanga. Kakade ke, la malungiselelo angasentla nawo anokuguqulwa. Kuba i-wave wave umahluko imele umyalezo ngotshintsho oluhambelanayo lwamanqanaba e-pulse akufuphi, ikwabizwa ngokuba yikhowudi ye-waveform kwaye ngokuhambelanayo, i-unipolar okanye i-bipolar waveform yangaphambili ibizwa ngokuba yi-absolute code waveform. Ukusebenzisa ulwahlulo lwamaza ukuhambisa imiyalezo kunokuphelisa umphumo wemeko yokuqala yesixhobo, ngakumbi kwiinkqubo zomodareyitha wesigaba. Ingasetyenziselwa ukusombulula ingxaki yokungacaci kwesigaba somthwali.
6. Amanqanaba amaninzi amaza
Kukho amanqanaba amabini kuphela kwezi fom zamaza zingentla, oko kukuthi, isimboli enye yokubini ihambelana ne-pulse enye. Ukuze kuphuculwe ukusetyenziswa kwebhendi ye-frequency, i-multi-level waveform okanye i-multi-value waveform ingasetyenziswa. Umzobo 6-1(f) ubonisa i-2B1Q enemigangatho emine (iisuntswana ezimbini zimelwe ngomnye wamanqanaba amane), apho i-11 imele +3E, i-10 imele + E, i-00 imele u-E, kwaye i-01 imele -3E. I-multi-level waveform isetyenziswa kwiinkqubo zothumelo lwedatha yesantya esiphezulu kunye neebhendi ezilinganiselweyo. Ekubeni i-pulse enye ye-multi-level waveform ihambelana neekhowudi ezininzi zebhinari, i-bit rate yonyuka phantsi kwemeko yezinga elifanayo le-baud (i-bandwidth efanayo). Isetyenziswe ngokubanzi.
Kufuneka kuqatshelwe ukuba i-waveform ye-pulse enye emele isimboli yolwazi ayifuni ukuba ixande. Ngokweemfuno zangempela kunye neemeko zetshaneli, ezinye iifom ezifana ne-Gaussian pulse, i-cosine pulse ephakanyisiweyo, njl. Kodwa kungakhathaliseki ukuba yeyiphi na ifom ye-waveform esetyenzisiweyo, isignali ye-baseband yedijithali inokumelwa ngokwezibalo. Ukuba iifom zamaza ezimele iisimboli ziyafana kodwa amaxabiso amanqanaba ahlukile.
Le "Intshayelelo kwi-Digital Baseband Signal Waveforms" eziswe kuwe nguShenzhen HDV Phoelectron Technology Co., Ltd., Ndiyathemba ukuba eli nqaku linokukunceda ukwandisa ulwazi lwakho. Ngaphandle kweli nqaku ukuba ujonge inkampani elungileyo yomenzi wezixhobo zonxibelelwano lwefiber onokuthi uyithathele ingqalelongathi.
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