Tonsefe tikudziwa bwino lomwe kuti dziko laukadaulo lotizungulira ndi la digito, kapena likulimbikira. Kuwulutsa kwapawayilesi pakompyuta sikunakhale kwatsopano, koma ngati simunachite nawo chidwi, matekinoloje omwe ali nawo angakhale odabwitsa kwa inu.
Zamkatimu zankhani
- Gawo 4: Digital gawo la chizindikiro
- Gawo 5: Coaxial Distribution Network
- Gawo 6: RF Amplifiers
- Gawo 7: Optical Receivers
- Gawo 8: Optical backbone network
- Gawo 9: Mutu
- Gawo 10: Troubleshooting pa chingwe TV maukonde
Kupanga chizindikiro cha digito chawayilesi
Chizindikiro cha kanema wawayilesi wa digito ndi mayendedwe amitundu yosiyanasiyana ya MPEG (nthawi zina ma codec ena), omwe amafalitsidwa ndi siginecha yawayilesi pogwiritsa ntchito QAM yamitundu yosiyanasiyana. Mawu awa ayenera kukhala omveka bwino ngati tsiku kwa wowonetsa aliyense, kotero ndingopereka gif kuchokera , zomwe, ndikuyembekeza, zidzapereka chidziwitso cha zomwe zili kwa iwo omwe sanachite chidwi:
Kusinthasintha kotereku kwamtundu umodzi sikugwiritsidwa ntchito kokha pa "anachronism ya kanema", komanso machitidwe onse otumizira deta pachimake chaukadaulo. Liwiro la mtsinje wa digito mu chingwe cha "mlongoti" ndi mazana a megabits!
Digital chizindikiro magawo
Pogwiritsa ntchito Deviser DS2400T m'njira yowonetsera magawo azizindikiro za digito, titha kuwona momwe izi zimachitikira:
Maukonde athu ali ndi zizindikiro za mfundo zitatu nthawi imodzi: DVB-T, DVB-T2 ndi DVB-C. Tiyeni tiyang'ane pa iwo mmodzimmodzi.
DVB-T
Muyezo uwu sunakhale waukulu m'dziko lathu, ukupereka njira yachiwiri, koma ndi yoyenera kugwiritsidwa ntchito ndi wogwiritsa ntchito chifukwa chakuti olandila DVB-T2 ali m'mbuyo amagwirizana ndi chikhalidwe cha m'badwo woyamba, kutanthauza kuti olembetsa. amatha kulandira chizindikiro choterocho pafupifupi pa TV iliyonse ya digito popanda zowonjezera zowonjezera. Kuphatikiza apo, mulingo womwe umafunidwa kuti upatsidwe mlengalenga (chilembo T chikuyimira Terrestrial, ether) chimakhala ndi chitetezo chabwino cha phokoso komanso redundancy kotero kuti nthawi zina zimagwira ntchito pomwe, pazifukwa zina, chizindikiro cha analogi sichingalowe.
Pazenera la chipangizochi titha kuwona momwe gulu la nyenyezi la 64QAM likupangidwira (muyezo umathandizira QPSK, 16QAM, 64QAM). Zitha kuwoneka kuti m'mikhalidwe yeniyeni mfundozo siziphatikizana, koma zimabwera ndi kumwaza kwina. Izi ndizabwinobwino bola ngati decoder imatha kudziwa kuti malo ofikirawo ndi ati, koma ngakhale pachithunzichi pali madera omwe ali pamalire kapena pafupi nawo. Kuchokera pa chithunzichi mungathe kudziwa mwamsanga mtundu wa chizindikiro "ndi diso": ngati amplifier sikugwira ntchito bwino, mwachitsanzo, madontho ali ndi chipwirikiti, ndipo ma TV sangathe kusonkhanitsa chithunzi kuchokera ku deta yolandiridwa: "pixelates" , kapena kuzizira kwathunthu. Pali nthawi zina pamene purosesa ya amplifier "imayiwala" kuwonjezera chimodzi mwa zigawo (makulitsidwe kapena gawo) ku chizindikiro. Zikatero, pazenera la chipangizochi mutha kuwona bwalo kapena kulira kukula kwa gawo lonselo. Mfundo ziwiri kunja kwa gawo lalikulu ndi mfundo za wolandira ndipo sizinyamula zambiri.
Kumanzere kwa chinsalu, pansi pa nambala ya tchanelo, tikuwona magawo ochulukira:
Mulingo wa siginecha (P) mu dBΒ΅V yomweyo monga analogi, komabe, kwa chizindikiro cha digito GOST imayang'anira 50 dBΒ΅V yokha pakulowetsa kwa wolandila. Ndiko kuti, m'madera omwe ali ndi vuto lalikulu, "digito" idzagwira ntchito bwino kuposa analogue.
Mtengo wa zolakwika zosinthira (MER) ikuwonetsa momwe chizindikiro chomwe tikulandirira chikusokonekera, ndiko kuti, kutalika kwa malo ofikirako kutha kukhala pakati pa bwalo. Izi ndizofanana ndi chiΕ΅erengero cha ma signal-to-noise kuchokera ku analogi; mtengo wamba wa 64QAM umachokera ku 28 dB. Zitha kuwoneka bwino kuti kupatuka kwakukulu mu chithunzi pamwambapa kumagwirizana ndi khalidwe lomwe lili pamwamba pa chizolowezi: ichi ndi chitetezo cha phokoso la chizindikiro cha digito.
Chiwerengero cha zolakwika mu sigino yolandiridwa (Mtengo CBER) - kuchuluka kwa zolakwika mu siginecha musanakonze ndi ma aligorivimu aliwonse owongolera.
Chiwerengero cha zolakwika pambuyo pa Viterbi decoder (VBER) ndi zotsatira za decoder yomwe imagwiritsa ntchito zidziwitso zosafunikira kuti ipeze zolakwika mu siginecha. Magawo awiriwa amayezedwa mu "zidutswa pa kuchuluka kwatengedwa." Kuti chipangizochi chiwonetse kuchuluka kwa zolakwika zosakwana chimodzi mwa zikwi zana limodzi kapena khumi miliyoni (monga momwe zilili pamwambapa), chikuyenera kuvomereza ma bits mamiliyoni khumi awa, omwe amatenga nthawi pa njira imodzi, kotero zotsatira zake zimayesedwa. sizimawonekera nthawi yomweyo, ndipo mwina zingakhale zoipa poyamba (E -03, mwachitsanzo), koma patapita masekondi angapo mufika chizindikiro kwambiri.
DVB-T2
Muyezo wawayilesi wa digito womwe udakhazikitsidwa ku Russia utha kufalitsidwanso kudzera pa chingwe. Maonekedwe a gulu la nyenyezilo akhoza kukhala odabwitsa poyang'ana koyamba:
Kuzungulira uku kumawonjezera chitetezo chamkokomo, popeza wolandila amadziwa kuti kuwundanako kumayenera kuzunguliridwa ndi ngodya yomwe yaperekedwa, zomwe zikutanthauza kuti imatha kusefa zomwe zimabwera popanda kusintha kosinthika. Zitha kuwoneka kuti pa muyezo uwu zolakwa pang'ono ndi dongosolo la kukula kwake ndipo zolakwika mu siginecha isanakonzedwe sizidutsanso malire, koma zimakhala zenizeni zenizeni 8,6 pa miliyoni. Kuwongolera, decoder imagwiritsidwa ntchito Chithunzi cha LDPC, kotero parameter imatchedwa LBER.
Chifukwa chakusatetezeka kwa phokoso, mulingo uwu umathandizira mulingo wosinthika wa 256QAM, koma pakadali pano 64QAM yokha ndiyo yomwe imagwiritsidwa ntchito powulutsa.
DVB-C
Muyezo uwu udapangidwa kuti utumizidwe kudzera pa chingwe (C - Cable) - sing'anga yokhazikika kwambiri kuposa mpweya, chifukwa chake imalola kugwiritsa ntchito kusinthasintha kwapamwamba kuposa DVB-T, motero imatumiza chidziwitso chochulukirapo popanda kugwiritsa ntchito zovuta. kodi.
Apa tikuwona kuwundana kwa 256QAM. Pali mabwalo ochulukirapo, kukula kwake kwakhala kocheperako. Kuthekera kwa cholakwika kwawonjezeka, zomwe zikutanthauza kuti sing'anga yodalirika (kapena zolemba zovuta kwambiri, monga mu DVB-T2) ndizofunikira kuti zitumize chizindikiro choterocho. Chizindikiro choterocho chikhoza "kumwaza" kumene analogi ndi DVB-T / T2 zimagwira ntchito, koma zimakhalanso ndi malire a chitetezo cha phokoso ndi ma algorithms okonza zolakwika.
Chifukwa chazovuta zambiri, gawo la MER la 256-QAM limasinthidwa kukhala 32 dB.
Kuwerengera kwa ma bits olakwika kwawukanso kukula kwina ndipo tsopano kuwerengera cholakwika chimodzi pa biliyoni, koma ngakhale pali mazana a mamiliyoni aiwo (PRE-BER ~E-07-8), Reed-Solomon decoder yomwe imagwiritsidwa ntchito pano. muyezo udzathetsa zolakwika zonse.
Source: www.habr.com