Software Defined Radio inzira yekutsiva basa resimbi (rinonyanyonakira hutano hwako) nemusoro wekuronga zvirongwa. SDRs inofanotaura ramangwana rakanaka uye mukana mukuru unoonekwa sekubviswa kwezvirambidzo mukuitwa kweredhiyo protocol. Muenzaniso ndeye OFDM (Orthogonal frequency-division multiplexing) modulation nzira, iyo inogoneka chete neiyo SDR nzira. Asi SDR zvakare ine imwezve, mukana weinjiniya chete - kugona kudzora uye kuona chiratidzo pane chero nzvimbo yekupokana nekuedza kushoma.
Imwe yeanonakidza kutaurirana mwero ndeye terrestrial terevhizheni DVB-T2.
Yechii? Ehe, iwe unogona kungovhura TV usingasimuke, asi hapana zvachose chekuona ipapo uye aya haasisiri maonero angu, asi chokwadi chekurapa.
Zvakakomba, DVB-T2 yakagadzirwa nehunyanzvi hwakakura kwazvo, kusanganisira:
- indoor application
- modulation kubva kuQPSK kuenda ku256QAM
- bandwidth kubva 1,7MHz kusvika 8MHz
Ndine ruzivo mukugamuchira terevhizheni yedhijitari ndichishandisa iyo SDR musimboti. Iyo DVB-T chiyero iri mune inozivikanwa GNURadio chirongwa. Kune gr-dvbs2rx block yeDVB-T2 standard (ese kune imwecheteyo GNURadio), asi inoda yekutanga chiratidzo kuwiriranisa uye inokurudzira (yakanyanya kutenda kuna Ron Economos).
Zvatinazvo.
Iko kune ETSI EN 302 755 yakajairwa iyo inotsanangura kutapurirana, asi kwete kugamuchira.
Chiratidzo chiri pamhepo ine sampling frequency ye9,14285714285714285714 MHz, yakagadziridzwa neCOFDM ine 32768 vatakuri, mubhendi re8 MHZ.
Zvinokurudzirwa kugashira masaini akadaro nekaviri sampling frequency (kuitira kuti usarasikirwe chero chinhu) uye panguva yepakati frequency ine yakawanda bandwidth (superheterodyne reception), kubvisa yakananga ikozvino (DC) offset uye "kudonha" kwenzvimbo. oscillator (LO) kune iyo inogamuchira yekupinda. Midziyo inogutsa mamiriro aya inodhura zvakanyanya pakuda kuziva.
SdrPlay ine 10Msps 10bit kana AirSpy ine maitiro akafanana yakachipa zvakanyanya. Iko hakuna mubvunzo wekupeta sampling frequency pano uye kugamuchira kunogona kuitwa chete nekutendeuka kwakananga (Zero IF). Naizvozvo (nekuda kwezvikonzero zvemari) tiri kuchinjika kudivi revateveri ve "pure" SDR ine hushoma hwekushandurwa kwehardware.
Zvaive zvakakodzera kugadzirisa matambudziko maviri:
- Synchronization. Tsvaga iyo chaiyo chikamu-chaiyo RF kutsauka uye sampling frequency kutsauka.
- Nyora zvakare DVB-T2 chiyero kumashure.
Basa rechipiri rinoda kodhi yakawanda, asi inogona kugadziriswa nekutsungirira uye inogona kusimbiswa nyore nyore uchishandisa zviratidzo zvekuedza.
Masaini ekuedzwa anowanikwa paBBC server ftp://ftp.kw.bbc.co.uk/t2refs/ ine mirairo yakazara.
Mhinduro yedambudziko rekutanga inoenderana zvakanyanya nehunhu hweiyo SDR mudziyo uye kugona kwayo kutonga. Kushandisa yakakurudzirwa frequency control function, sezvavanotaura, haina kubudirira, asi yakapa ruzivo rwakawanda kuverenga idzo. zvinyorwa, kuronga, kutarisa TV series, kugadzirisa mibvunzo yefilosofi ..., muchidimbu, zvakanga zvisingaiti kusiya basa racho.
Kutenda mu "pure SDR" kwakangowedzera kusimba.
Isu tinotora chiratidzo sezvazviri, tinochidudzira kunenge kune analogue uye totora discrete, asi yakafanana neicho chaicho.
Synchronization block diagram:
Zvese zviri pano zvinoenderana nebhuku. Zvinotevera zvishoma zvakaoma. Kutsauka kunoda kuverengerwa. Kune akawanda mabhuku uye zvinyorwa zvekutsvagisa achienzanisa zvakanakira nekuipira nzira dzakasiyana. Kubva kumakirasi - uyu ndi "Michael Speth, Stefan Fechtel, Gunnar Fock, Heinrich Meyr, Optimum Receiver Dhizaini yeOFDM-Yakavakirwa Broadband Transmission - Chikamu I uye II." Asi ini handisati ndasangana neinjiniya mumwe anogona uye anoda kuverenga, saka nzira yeinjiniya yakashandiswa. Uchishandisa nzira imwechete yekuyananisa, detuning yakaunzwa muchiratidzo chekuyedza. Nekuenzanisa ma metrics akasiyana nekutsauka kunozivikanwa (akazvizivisa iye), iwo akanakisa akasarudzwa kuita uye nyore kuita. Reception frequency deviation inoverengerwa nekuenzanisa nguva yevarindi uye chikamu chayo chekudzokorora. Chikamu chekugamuchira frequency uye sampling frequency inofungidzirwa kubva pachikamu chekutsauka kwechiratidzo chekutyaira uye izvi zvinoshandiswawo mune yakapusa, mutsara yakaenzana yechiratidzo cheOFDM.
Equalizer maitiro:
Uye izvi zvose zvinoshanda zvakanaka kana uchiziva apo DVB-T2 furemu inotanga. Kuti uite izvi, chiratidzo chekutanga P1 chinoparidzirwa muchiratidzo. Iyo nzira yekuona uye decoding chiratidzo cheP1 inotsanangurwa muTechnical Specification ETSI TS 102 831 (kune zvakare akawanda anobatsira mazano ekugamuchira).
Autocorrelation yeP1 chiratidzo (iyo yepamusoro nzvimbo pakutanga kwefuremu):
Mufananidzo wekutanga (kwasara mwedzi mitanhatu chete kusvika mufananidzo unofamba...):
Uye apa ndipo patinodzidza kuti IQ kusaenzana, DC inobvisa uye LO leakage chii. Semutemo, kubhadharwa kweizvi kukanganisa kwakananga kutendeuka kwakananga kunoitwa mune SDR mudziyo mutyairi. Naizvozvo, zvakatora nguva yakareba kuti tinzwisise: kugogodza kunze nyeredzi kubva kune hushamwari QAM64 boka renyeredzi ibasa remuripo mabasa. Ndakatozodzima zvese ndonyora bhasikoro rangu.
Uye ipapo mufananidzo wakafamba:
QAM64 modulation ine chaiyo nyeredzi kutenderera muDVB-T2 chiyero:
Muchidimbu, ichi ndicho chikonzero chekupfuudza nyama yakakanyiwa zvakare kuburikidza neguyo renyama. Chiyero chinopa marudzi mana ekusanganisa:
- bit interleaving
- cell interleaving (kusanganisa masero mubhokisi rekodhi)
- nguva yekupinda (iri zvakare muboka remabhuroko encoding)
- frequency interleaving (frequency kusanganiswa muchiratidzo cheOFDM)
Nekuda kweizvozvo, isu tine chiratidzo chinotevera pakuiswa:
Zvese izvi kurwira kudzivirira ruzha rweiyo encoded chiratidzo.
Mugumisiro
Iye zvino hatigone kuona kwete chete chiratidzo pachayo uye chimiro chayo, asiwo ruzivo rwebasa.
Kune maviri akawanda mumhepo. Imwe neimwe ine nzira mbiri dzemuviri (PLP).
Chinhu chimwe chisinganzwisisike chakaonekwa mune yekutanga kuwanda - yekutanga PLP yakanyorwa kuti "multiple", zvine musoro, sezvo pane inodarika imwe mumultiplex, uye yechipiri PLP yakanzi "single" uye uyu mubvunzo.
Kunyanya kunakidza ndeyechipiri isinganzwisisiki mune yechipiri multiplex - mapurogiramu ose ari mu PLP yekutanga, asi mune yechipiri PLP pane chiratidzo chechimiro chisingazivikanwi pane zvishoma. Zvirinani iyo VLC inoridza, iyo inonzwisisa makumi mashanu emavhidhiyo mafomati uye huwandu hwakafanana hweodhiyo, haazvizive.
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Iyo purojekiti yakagadzirwa nechinangwa chekuona mukana chaiwo wekudhikodha DVB-T2 uchishandisa SdrPlay (uye ikozvino AirSpy.), saka iyi haisi kunyange alpha vhezheni.
PS Pandakanga ndichinyora chinyorwa nekunetseka, ndakakwanisa kubatanidza PlutoSDR muprojekti.
Mumwe munhu anobva angotaura kuti pane chete 6Msps yeIQ siginecha pa USB2.0 inobuda, asi iwe unoda inokwana 9,2Msps, asi iyi inyaya yakasiyana.
Source: www.habr.com