Software Defined Radio ndi njira yosinthira ntchito yachitsulo (yomwe ilidi yabwino ku thanzi lanu) ndi mutu wamapulogalamu. Ma SDR amaneneratu za tsogolo lalikulu ndipo phindu lalikulu limatengedwa kuti ndi kuchotsa zoletsa pakukhazikitsa ma protocol a wailesi. Chitsanzo ndi njira yosinthira ya OFDM (Orthogonal frequency-division multiplexing), yomwe imatheka kokha ndi njira ya SDR. Koma SDR ilinso ndi mwayi winanso waukadaulo - kutha kuwongolera ndikuwona chizindikiro pamalo aliwonse osasunthika mosavutikira.
Chimodzi mwazinthu zosangalatsa zoyankhulirana ndi wailesi yakanema yapadziko lapansi DVB-T2.
Zachiyani? Zachidziwikire, mutha kuyatsa TV osadzuka, koma palibe chilichonse chowonera pamenepo ndipo izi sizilinso lingaliro langa, koma zoona zachipatala.
Zowona, DVB-T2 idapangidwa ndi kuthekera kwakukulu, kuphatikiza:
- m'nyumba ntchito
- kusinthidwa kuchokera ku QPSK kupita ku 256QAM
- bandwidth kuchokera 1,7MHz mpaka 8MHz
Ndili ndi chidziwitso pakulandila kanema wawayilesi wa digito pogwiritsa ntchito mfundo ya SDR. Muyezo wa DVB-T uli mu polojekiti yodziwika bwino ya GNURadio. Pali chipika cha gr-dvbs2rx cha muyezo wa DVB-T2 (zonse za GNURadio yomweyo), koma zimafunikira kulumikizana koyambirira kwazizindikiro ndipo ndizolimbikitsa (zikomo mwapadera kwa Ron Economos).
Zomwe tili nazo.
Pali muyezo wa ETSI EN 302 755 womwe umafotokoza kufalikira, koma osati kulandila.
Chizindikirocho chili pamlengalenga ndi mafupipafupi a sampuli a 9,14285714285714285714 MHz, osinthidwa ndi COFDM ndi onyamula 32768, mu gulu la 8 MHZ.
Ndibwino kuti mulandire zizindikiro zoterezi ndi maulendo awiri a sampuli (kuti musataye kalikonse) komanso pafupipafupi mafupipafupi a bandwidth (kulandila kwa superheterodyne), kuti muchotse zowonongeka (DC) zowonongeka ndi "kutuluka" kwa oscillator wamba. (LO) ku zolowetsa zolandila. Zida zomwe zimakwaniritsa izi ndizokwera mtengo kwambiri chifukwa cha chidwi chabe.
SdrPlay yokhala ndi 10Msps 10bit kapena AirSpy yokhala ndi zofanana ndizotsika mtengo kwambiri. Palibe kukayikira kuwirikiza kawiri kwa zitsanzo pano ndipo kulandila kungatheke kokha ndi kutembenuka kwachindunji (Zero IF). Choncho (chifukwa cha ndalama) tikusinthira kumbali ya omvera a "pure" SDR ndi osachepera kutembenuka kwa hardware.
Zinali zofunikira kuthetsa mavuto awiri:
- Kuyanjanitsa. Dziwani za kupotokola kolondola kwa RF ndi kusanja pafupipafupi.
- Lembaninso muyezo wa DVB-T2 kumbuyo.
Ntchito yachiwiri imafuna ma code ambiri, koma ikhoza kuthetsedwa ndi chipiriro ndipo ikhoza kutsimikiziridwa mosavuta pogwiritsa ntchito zizindikiro zoyesa.
Zizindikiro zoyesa zimapezeka pa seva ya BBC ftp://ftp.kw.bbc.co.uk/t2refs/ ndi malangizo atsatanetsatane.
Njira yothetsera vuto loyamba imadalira kwambiri mawonekedwe a chipangizo cha SDR ndi mphamvu zake zowongolera. Kugwiritsa ntchito zowongolera pafupipafupi, monga akunena, sikunapambane, koma zidapereka chidziwitso chochuluka powerenga izo. zolemba, mapulogalamu, kuyang'ana mndandanda wa TV, kuthetsa mafunso afilosofi ..., mwachidule, sikunali kotheka kusiya ntchitoyi.
Chikhulupiriro mu "SDR yoyera" changokulirakulira.
Timatengera chizindikirocho momwe chilili, timachiphatikiza pafupifupi ku analogue ndikutulutsa china, koma chofanana ndi chenichenicho.
Chithunzi cha block block:
Chilichonse apa ndi molingana ndi buku. Chotsatira ndi chovuta kwambiri. Zopatuka ziyenera kuwerengedwa. Pali zolemba zambiri komanso zolemba zofufuza zomwe zikufanizira zabwino ndi zoyipa za njira zosiyanasiyana. Kuchokera ku classics - iyi ndi "Michael Speth, Stefan Fechtel, Gunnar Fock, Heinrich Meyr, Optimum Receiver Design for OFDM-Based Broadband Transmission - Part I ndi II." Koma sindinakumanepo ndi injiniya mmodzi yemwe angathe ndipo akufuna kuwerengera, kotero njira ya uinjiniya idagwiritsidwa ntchito. Pogwiritsa ntchito njira yofananira yofananira, kutulutsa kudayambika mu chizindikiro choyesera. Poyerekeza ma metrics osiyanasiyana ndi zopatuka zodziwika (adadziwonetsa yekha), zabwino kwambiri zidasankhidwa kuti zigwire ntchito komanso kuti zitheke. Kupatuka kwafupipafupi kolandirira kumawerengedwa poyerekezera nthawi ya alonda ndi gawo lake lobwereza. Gawo la ma frequency olandila ndi ma frequency a sampuli akuyerekezedwa kuchokera pakupatuka kwa ma siginecha oyendetsa ndipo izi zimagwiritsidwanso ntchito munjira yosavuta, yofananira ya chizindikiro cha OFDM.
Makhalidwe a Equalizer:
Ndipo zonsezi ntchito bwino ngati inu mukudziwa pamene DVB-T2 chimango akuyamba. Kuti muchite izi, chizindikiro choyambirira P1 chimaperekedwa mu siginecha. Njira yodziwira ndikuyika chizindikiro cha P1 ikufotokozedwa mu Technical Specification ETSI TS 102 831 (palinso malingaliro ambiri othandiza olandila).
Autocorrelation ya chizindikiro cha P1 (malo apamwamba kwambiri kumayambiriro kwa chimango):
Chithunzi choyamba (miyezi isanu ndi umodzi yokha yatsala kuti chithunzi chikuyenda...):
Ndipo apa ndipamene timaphunzira zomwe kusalinganika kwa IQ, DC offset ndi LO kutayikira kuli. Monga lamulo, kubwezeredwa kwa zosokoneza izi zenizeni kutembenuka kwachindunji kumayendetsedwa mu driver wa chipangizo cha SDR. Chifukwa chake, zidatenga nthawi yayitali kuti timvetsetse: kugwetsa nyenyezi kuchokera kugulu la nyenyezi laubwenzi la QAM64 ndi ntchito yamalipiro. Ndinayenera kuzimitsa zonse ndikulemba njinga yanga.
Kenako chithunzicho chinasuntha:
Kusintha kwa QAM64 ndi kuzungulira kwa nyenyezi mu DVB-T2 muyezo:
Mwachidule, izi ndi zotsatira za kudutsa minced nyama kubwerera mu chopukusira nyama. Muyezo umapereka mitundu inayi yosakanikirana:
- pang'ono interleaking
- cell interleaving (kusakaniza ma cell mu block block)
- nthawi interleaving (ilinso mu gulu la encoding midadada)
- kusakanikirana pafupipafupi (kusakanikirana pafupipafupi mu chizindikiro cha OFDM)
Zotsatira zake, tili ndi chizindikiro chotsatirachi pakulowetsa:
Zonsezi ndikulimbana ndi chitetezo cha phokoso la siginecha yosungidwa.
Zotsatira
Tsopano sitingathe kuwona chizindikiro chokhacho chokha ndi mawonekedwe ake, komanso chidziwitso chautumiki.
Pali ma multiplexes awiri mlengalenga. Iliyonse ili ndi njira ziwiri zakuthupi (PLP).
Chodabwitsa chimodzi chinadziwika mu multiplex yoyamba - PLP yoyamba imatchedwa "multiple", zomwe ziri zomveka, popeza pali zambiri mu multiplex, ndipo PLP yachiwiri imatchedwa "single" ndipo ili ndi funso.
Chochititsa chidwi kwambiri ndi chachiwiri chodabwitsa mu multiplex yachiwiri - mapulogalamu onse ali mu PLP yoyamba, koma PLP yachiwiri pali chizindikiro cha chikhalidwe chosadziwika pa liwiro lochepa. Osachepera VLC wosewera mpira, amene amamvetsa za mavidiyo makumi asanu akamagwiritsa ndi kuchuluka kwa zomvetsera, sadziwa izo.
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Ntchitoyi idapangidwa ndi cholinga chofuna kudziwa momwe mungasinthire DVB-T2 pogwiritsa ntchito SdrPlay (ndipo tsopano AirSpy.), kotero iyi si mtundu wa alpha.
PS Pamene ndinali kulemba nkhaniyi movutikira, ndinakwanitsa kuphatikiza PlutoSDR mu polojekitiyi.
Wina anganene nthawi yomweyo kuti pali 6Msps yokha ya chizindikiro cha IQ pa USB2.0 linanena bungwe, koma muyenera osachepera 9,2Msps, koma iyi ndi mutu wosiyana.
Source: www.habr.com