Software Defined Radio hanya ce ta maye gurbin aikin karfe (wanda yake da kyau ga lafiyar ku) tare da ciwon kai na shirye-shirye. SDRs sun yi hasashen makoma mai girma kuma babban fa'ida ana ɗauka shine kawar da hane-hane a cikin aiwatar da ka'idojin rediyo. Misali shine hanyar daidaitawa ta OFDM (Orthogonal mita-division multiplexing), wanda ya zama mai yiwuwa kawai tare da hanyar SDR. Amma SDR kuma yana da ƙarin, damar injiniya zalla - ikon sarrafawa da hango sigina a kowane lokaci na sabani tare da ƙaramin ƙoƙari.
Ɗaya daga cikin ƙa'idodin sadarwa mai ban sha'awa shine gidan talabijin na ƙasa na duniya DVB-T2.
Don me? Tabbas, zaku iya kunna TV kawai ba tare da tashi ba, amma babu komai don kallo a can kuma wannan ba ra'ayina bane, amma gaskiyar likita.
Mahimmanci, DVB-T2 an ƙera shi tare da fa'ida sosai, gami da:
- aikace-aikacen cikin gida
- Modulation daga QPSK zuwa 256QAM
- bandwidth daga 1,7MHz zuwa 8MHz
Ina da gogewa wajen karɓar talabijin na dijital ta amfani da ka'idar SDR. Ma'aunin DVB-T yana cikin sanannen aikin GNURadio. Akwai toshe gr-dvbs2rx don ma'aunin DVB-T2 (duk don GNURadio iri ɗaya), amma yana buƙatar aiki tare da siginar farko kuma yana da ban sha'awa (godiya ta musamman ga Ron Economos).
Abin da muke da shi.
Akwai ma'aunin ETSI EN 302 755 wanda ke ba da cikakken bayani game da watsawa, amma ba liyafar ba.
Sigina yana kan iska tare da mitar samfurin 9,14285714285714285714 MHz, wanda COFDM ya daidaita tare da masu ɗaukar kaya 32768, a cikin rukunin 8 MHZ.
Ana ba da shawarar karɓar irin waɗannan sigina tare da mitar samfur sau biyu (don kada a rasa wani abu) kuma a matsakaicin mitar ƙarin bandwidth ( liyafar superheterodyne), don kawar da diyya kai tsaye (DC) da kuma "leakage" na oscillator na gida. (LO) zuwa shigar da mai karɓa. Na'urorin da suka gamsar da waɗannan sharuɗɗan suna da tsada sosai don son sani kawai.
SdrPlay tare da 10Msps 10bit ko AirSpy tare da halaye iri ɗaya ya fi rahusa. Babu tambaya sau biyu mitar samfur anan kuma ana iya yin liyafar tare da juyawa kai tsaye (Zero IF). Don haka (saboda dalilai na kuɗi) muna canzawa zuwa gefen masu bin “tsaftataccen” SDR tare da ƙaramin juzu'in kayan aikin.
Wajibi ne a magance matsaloli guda biyu:
- Aiki tare. Nemo ainihin madaidaicin saɓanin RF na lokaci-lokaci da karkacewar mitar samfur.
- Sake rubuta ma'aunin DVB-T2 baya.
Aiki na biyu yana buƙatar ƙarin lamba, amma ana iya magance shi tare da juriya kuma ana iya tabbatar da shi cikin sauƙi ta amfani da siginar gwaji.
Ana samun siginar gwaji akan sabar BBC ftp://ftp.kw.bbc.co.uk/t2refs/ tare da cikakkun bayanai.
Maganin matsalar farko ya dogara sosai akan halayen na'urar SDR da ikon sarrafawa. Yin amfani da ayyukan sarrafa mitar da aka ba da shawarar, kamar yadda suke faɗa, bai yi nasara ba, amma ya ba da ƙwarewa da yawa na karanta waɗannan. takardun shaida, shirye-shirye, kallon jerin talabijin, warware tambayoyin falsafa ..., a takaice, ba zai yiwu a yi watsi da aikin ba.
Bangaskiya a cikin “SDR mai tsafta” ya ƙara ƙarfi ne kawai.
Muna ɗaukar siginar yadda take, mu haɗa shi kusan zuwa analog kuma mu fitar da mai hankali, amma kama da ainihin.
Tsarin toshe aiki tare:
Komai anan shine bisa ga littafin koyarwa. Na gaba yana da ɗan rikitarwa. Ana buƙatar ƙididdige ɓarna. Akwai wallafe-wallafe da labaran bincike da yawa waɗanda ke kwatanta fa'idodi da rashin amfanin hanyoyin daban-daban. Daga litattafan litattafai - wannan shine "Michael Speth, Stefan Fechtel, Gunnar Fock, Heinrich Meyr, Mafi kyawun Tsarin Mai karɓa don watsa Watsa Labarai na tushen OFDM - Sashe na I da II." Amma ban sadu da injiniya ɗaya da zai iya ƙidaya kuma yana son ƙidaya, don haka aka yi amfani da hanyar injiniya. Yin amfani da hanyar daidaitawa iri ɗaya, an gabatar da ɓarna a cikin siginar gwaji. Ta hanyar kwatanta ma'auni daban-daban tare da sauye-sauye da aka sani (ya gabatar da su da kansa), an zaɓi mafi kyau don yin aiki da sauƙi na aiwatarwa. Ana ƙididdige juzu'in mitar liyafar ta hanyar kwatanta tazarar mai gadi da sashin maimaitawarsa. An ƙididdige lokacin mitar karɓa da mitar samfur daga karkacewar lokaci na siginar matukin kuma ana amfani da wannan a cikin sauƙi, daidaita madaidaicin siginar OFDM.
Siffar mai daidaitawa:
Kuma duk wannan yana aiki da kyau idan kun san lokacin da tsarin DVB-T2 ya fara. Don yin wannan, ana watsa alamar preamble P1 a cikin siginar. Hanyar ganowa da yanke alamar P1 an kwatanta shi a cikin Ƙayyadaddun Fasaha ETSI TS 102 831 (akwai shawarwari masu amfani da yawa don liyafar).
Daidaita kai da siginar P1 (mafi girman matsayi a farkon firam):
Hoto na farko (watanni shida kacal ya rage har zuwa hoton da ke motsawa...):
Kuma wannan shine inda muke koyan menene rashin daidaituwar IQ, rashin daidaituwa na DC da leakawar LO. A matsayinka na mai mulki, ana aiwatar da ramuwa don waɗannan murɗaɗɗen ƙayyadaddun juyawa kai tsaye a cikin direban na'urar SDR. Saboda haka, ya ɗauki lokaci mai tsawo don fahimta: ƙwanƙwasa taurari daga ƙungiyar abokantaka ta QAM64 shine aikin ayyukan ramuwa. Dole na kashe komai na rubuta babur na.
Sannan hoton ya motsa:
Tsarin QAM64 tare da takamaiman jujjuyawar taurari a cikin ma'aunin DVB-T2:
A takaice dai, wannan shine sakamakon mayar da nikakken naman ta cikin injin niƙa. Ma'auni ya tanadi nau'ikan hadawa guda huɗu:
- bit interleaving
- interleaving cell (haɗuwar sel a cikin toshe codeing)
- interleaving lokaci (shima yana cikin rukunin ɓoyayyen tubalan)
- mitar interleaving (yawan mitar a cikin alamar OFDM)
Sakamakon haka, muna da sigina mai zuwa a wurin shigarwa:
Duk wannan gwagwarmaya ce don rigakafin amo na siginar da aka ɓoye.
Sakamakon
Yanzu za mu iya ganin ba kawai siginar kanta da siffarsa ba, har ma bayanan sabis.
Akwai nau'i-nau'i guda biyu akan iska. Kowane yana da tashoshi na zahiri guda biyu (PLP).
An lura da wani abin ban mamaki a cikin maɓalli na farko - PLP na farko an lakafta shi "mafi yawa", wanda yake da ma'ana, tun da akwai fiye da ɗaya a cikin multiplex, kuma PLP na biyu an lakafta shi "guda" kuma wannan tambaya ce.
Ko da mafi ban sha'awa shine rashin daidaituwa na biyu a cikin mahara na biyu - duk shirye-shiryen suna cikin PLP na farko, amma a cikin PLP na biyu akwai siginar yanayin da ba a sani ba a cikin ƙaramin sauri. Aƙalla na'urar VLC, wanda ke fahimtar tsarin bidiyo kusan hamsin da adadin sauti iri ɗaya, bai gane shi ba.
.
An halicci aikin tare da manufar ƙayyade yiwuwar ƙaddamar da DVB-T2 ta amfani da SdrPlay (kuma yanzu AirSpy.), Don haka wannan ba ma wani alpha version ba ne.
PS Yayin da nake rubuta labarin da wahala, na sami damar haɗa PlutoSDR cikin aikin.
Nan da nan wani zai ce akwai 6Msps kawai don siginar IQ a fitarwa na USB2.0, amma kuna buƙatar aƙalla 9,2Msps, amma wannan batu ne daban.
source: www.habr.com