I-Software Defined Radio iyindlela yokushintsha umsebenzi wensimbi (okuyinto elungele impilo yakho) nekhanda elibuhlungu lokuhlela. Ama-SDR abikezela ikusasa elihle futhi inzuzo enkulu ibhekwa njengokususwa kwemikhawulo ekusetshenzisweni kwezivumelwano zomsakazo. Isibonelo indlela yokushintshashintsha ye-OFDM (Orthogonal frequency-division multiplexing), eyenziwa yenzeke kuphela indlela ye-SDR. Kodwa i-SDR iphinde ibe nethuba elilodwa, elimsulwa lobunjiniyela - amandla okulawula nokubona isiginali kunoma iyiphi indawo engafanele ngomzamo omncane.
Enye yezindinganiso zokuxhumana ezithakazelisayo ithelevishini yasemhlabeni i-DVB-T2.
Kwani? Yiqiniso, ungamane uvule i-TV ngaphandle kokusukuma, kodwa akukho lutho ongakubuka lapho futhi lokhu akusewona umbono wami, kodwa iqiniso lezokwelapha.
Ngokujulile, i-DVB-T2 yakhelwe ngamakhono abanzi kakhulu, kufaka phakathi:
- isicelo sangaphakathi
- ukuguqulwa kwe-QPSK kuye ku-256QAM
- umkhawulokudonsa kusuka ku-1,7MHz ukuya ku-8MHz
Nginolwazi lokuthola umabonakude wedijithali ngisebenzisa isimiso se-SDR. Izinga le-DVB-T likuphrojekthi eyaziwa kakhulu ye-GNURadio. Kukhona ibhulokhi ye-gr-dvbs2rx yezinga le-DVB-T2 (konke ku-GNURadio efanayo), kodwa idinga ukuvumelanisa kwesignali yokuqala futhi iyakhuthaza (sibonga ngokukhethekile ku-Ron Economos).
Esinakho.
Kunezinga le-ETSI EN 302 755 elinemininingwane yokudluliselwa, kodwa hhayi ukwamukelwa.
Isignali isemoyeni ngemvamisa yesampula engu-9,14285714285714285714 MHz, elungiswe yi-COFDM enabathwali abangu-32768, ebhendini engu-8 MHZ.
Kunconywa ukuthola amasiginali anjalo ngokuphindwe kabili imvamisa yesampula (ukuze ungalahlekelwa lutho) kanye nemvamisa emaphakathi umkhawulokudonsa owengeziwe (ukwamukelwa kwe-superheterodyne), ukuqeda i-offset yamanje (DC) eqondile kanye "nokuvuza" kwe-oscillator yendawo. (LO) kokokufaka komamukeli. Amadivayisi anelisa lezi zimo abiza kakhulu ngelukuluku nje.
I-SdrPlay ene-10Msps 10bit noma i-AirSpy enezici ezifanayo ishibhe kakhulu. Akukho mbuzo wokuphinda kabili imvamisa yesampula lapha futhi ukwamukela kungenziwa kuphela ngokuguqulwa okuqondile (Zero IF). Ngakho-ke (ngenxa yezizathu zezimali) sishintshela ohlangothini lwabalandeli be-SDR "ehlanzekile" enokuguqulwa okuncane kwehadiwe.
Kwakudingeka ukuxazulula izinkinga ezimbili:
- Ukuvumelanisa. Thola ukuchezuka kwe-RF okunembe kakhulu kwesigaba kanye nokuchezuka kwefrikhwensi yesampula.
- Phinda ubhale i-DVB-T2 indinganiso uye emuva.
Umsebenzi wesibili udinga ikhodi eningi kakhulu, kodwa ingaxazululwa ngokuphikelela futhi ingaqinisekiswa kalula kusetshenziswa izimpawu zokuhlola.
Amasignali okuhlola ayatholakala kuseva ye-BBC ftp://ftp.kw.bbc.co.uk/t2refs/ enemiyalo enemininingwane.
Isixazululo senkinga yokuqala sincike kakhulu ezicini zedivayisi ye-SDR namandla ayo okulawula. Ukusebenzisa imisebenzi yokulawula imvamisa enconyiwe, njengoba besho, akuphumelelanga, kodwa kunikeza ulwazi oluningi lokufunda lezo. imibhalo, ukuhlela, ukubuka uchungechunge lwe-TV, ukuxazulula imibuzo yefilosofi..., ngamafuphi, kwakungenakwenzeka ukuyeka iphrojekthi.
Ukukholwa “ku-SDR ehlanzekile” kuye kwaqina nakakhulu.
Sithatha isignali njengoba injalo, siyifake ku-analogue futhi sikhiphe eyodwa, kodwa efana neyangempela.
Umdwebo webhulokhi yokuvumelanisa:
Konke lapha ngokwencwadi yokufunda. Okulandelayo kuyinkimbinkimbi ngokwengeziwe. Ukuchezuka kumele kubalwe. Kunenqwaba yemibhalo nemibhalo yocwaningo eqhathanisa izinzuzo nezingozi zezindlela ezahlukene. Kusukela kweyakudala - lena "uMichael Speth, uStefan Fechtel, u-Gunnar Fock, u-Heinrich Meyr, Idizayini ye-Optimum Receiver Ye-OFDM-Based Broadband Transmission - Ingxenye I no-II." Kodwa angikaze ngihlangane nonjiniyela oyedwa okwaziyo futhi ofuna ukubala, ngakho kwasetshenziswa indlela yobunjiniyela. Kusetshenziswa indlela yokuvumelanisa efanayo, ukukhipha kwethulwa kusignali yokuhlola. Ngokuqhathanisa amamethrikhi ahlukene nokuchezuka okwaziwayo (wazethula yena), angcono kakhulu akhethelwa ukusebenza kanye nokuwasebenzisa kalula. Ukuchezuka kwefrikhwensi yokwamukela kubalwa ngokuqhathanisa isikhawu sonogada kanye nengxenye ephindayo. Isigaba sefrikhwensi yokwamukela kanye nemvamisa yesampula kulinganiselwa kusukela ekuchezukeni kwesigaba samasiginali wokuhlola futhi lokhu kuphinda kusetshenziswe kusilinganisi esilula, esilandelanayo sesiginali ye-OFDM.
Isici se-Equalizer:
Futhi konke lokhu kusebenza kahle uma wazi lapho uhlaka DVB-T2 iqala. Ukuze wenze lokhu, uphawu lwesethulo P1 ludluliselwa kusiginali. Indlela yokuthola nokuqopha uphawu lwe-P1 ichazwe ku-Technical Specification ETSI TS 102 831 (kukhona nezincomo eziningi eziwusizo zokwamukela).
Ukuhlanganiswa okuzenzakalelayo kwesiginali ye-P1 (iphuzu eliphakeme kakhulu ekuqaleni kohlaka):
Isithombe sokuqala (kusele izinyanga eziyisithupha kuphela kuze kufike isithombe esinyakazayo...):
Futhi kulapho sifunda khona ukuthi kuyini ukungalingani kwe-IQ, i-DC offset kanye nokuvuza kwe-LO. Njengomthetho, isinxephezelo salokhu kuhlanekezela okuqondene nokuguqulwa okuqondile sisetshenziswa kumshayeli wedivayisi ye-SDR. Ngakho-ke, kwathatha isikhathi eside ukuqonda: ukukhipha izinkanyezi kumlaza we-QAM64 enobungane kuwumsebenzi wemisebenzi yesinxephezelo. Kwadingeka ngicime yonke into futhi ngibhale ibhayisikili lami.
Sabe sesinyakaza isithombe:
Ukuguquguquka kwe-QAM64 ngokuzungezisa okuthile komlaza kuzinga le-DVB-T2:
Ngamafuphi, lokhu kuwumphumela wokudlulisa inyama egayiwe emuva nge-grinder yenyama. Izinga lihlinzeka ngezinhlobo ezine zokuxuba:
- kancane ukushiyana
- iseli interleaving (ukuxuba amaseli ebhodini lekhodi)
- ukushiya isikhathi (kukhona futhi eqenjini lamabhulokhi wombhalo wekhodi)
- i-frequency interleaving (ukuxuba imvamisa kuphawu lwe-OFDM)
Njengomphumela, sinesignali elandelayo kokokufaka:
Konke lokhu kungumzabalazo wokungavikeleki komsindo wesiginali efakwe ikhodi.
Umphumela
Manje asikwazi ukubona kuphela isignali ngokwayo kanye nesimo sayo, kodwa futhi nolwazi lwesevisi.
Kukhona ama-multiplex amabili emoyeni. Ngayinye ineziteshi ezimbili zomzimba (PLP).
Okukodwa okuyinqaba kwaqashelwa ku-multiplex yokuqala - i-PLP yokuqala ibhalwe ukuthi “multiple”, okunengqondo, njengoba kukhona okungaphezu kokukodwa ku-multiplex, kanti eyesibili i-PLP ibhalwe ukuthi “okukodwa” futhi lona umbuzo.
Okuthakazelisayo nakakhulu ukungaqondakali kwesibili ku-multiplex yesibili - zonke izinhlelo zise-PLP yokuqala, kodwa ku-PLP yesibili kukhona isignali yemvelo engaziwa ngesivinini esiphansi. Okungenani isidlali se-VLC, esiqonda mayelana namafomethi wevidiyo angamashumi amahlanu nenani elifanayo lomsindo, asiyiboni.
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Iphrojekthi yadalwa ngenhloso yokunquma ukuthi kungenzeka yini ukuqopha i-DVB-T2 kusetshenziswa i-SdrPlay (futhi manje i-AirSpy.), ngakho lokhu akulona ngisho inguqulo ye-alpha.
PS Ngenkathi ngibhala isihloko ngobunzima, ngakwazi ukuhlanganisa i-PlutoSDR kuphrojekthi.
Othile uzosho ngokushesha ukuthi kukhona kuphela i-6Msps yesiginali ye-IQ ekuphumeni kwe-USB2.0, kodwa udinga okungenani u-9,2Msps, kodwa lesi isihloko esihlukile.
Source: www.habr.com