Nisa tsakanin sadarwa da tsarin sadarwa mara waya zai iya samu yana faruwa ne ta hanyar abubuwa daban-daban kamar na'urori daban-daban da suka samar da tsarin da kuma yanayin sadarwa. Alaƙar da ke tsakaninsu za a iya bayyana ta ta hanyar lissafin nisan sadarwa mai zuwa.
Idan ƙarfin watsawa na na'urar watsawa ta tsarin sadarwa shine PT, ribar eriya ta watsawa shine GT, kuma tsawon aikin shine λ. Jin daɗin mai karɓar na'urar karɓa shine PR, ribar eriya mai karɓa shine GR, kuma nisan da ke tsakanin eriya mai karɓa da mai watsawa shine R, a cikin nisan gani da kuma a cikin yanayi ba tare da tsangwama na lantarki ba, akwai alaƙa mai zuwa:
PT(dBm)-PR(dBm)+GT(dBi)+GR(dBi)=20log4pr(m)/l(m)+Lc(dB)+ L0(dB) A cikin dabarar, Lc shine asarar shigar da mai ciyarwa na eriya mai watsa tashar tushe; L0 shine asarar raƙuman rediyo yayin yaɗuwa.
Lokacin tsara tsarin, ya kamata a bar isasshen iyaka don abu na ƙarshe, asarar yaɗuwar raƙuman rediyo L0.
Gabaɗaya, ana buƙatar gefen 10 zuwa 15 dB lokacin wucewa ta cikin dazuzzuka da gine-ginen farar hula; ana buƙatar gefen 30 zuwa 35 dB lokacin wucewa ta cikin gine-ginen siminti masu ƙarfi.
Ga tashoshin mitar 800MH, 900ZMHz da GSM, gabaɗaya ana kyautata zaton cewa matakin matakin karɓa na wayoyin hannu ya kai kusan -104dBm, kuma ainihin siginar da aka karɓa ya kamata ta kasance aƙalla 10dB mafi girma don tabbatar da rabon sigina-zuwa-amo da ake buƙata. A gaskiya ma, domin a ci gaba da sadarwa mai kyau, ana ƙididdige ƙarfin da aka karɓa sau da yawa a matsayin -70 dBm. A ɗauka cewa tashar tushe tana da sigogi masu zuwa:
Ƙarfin watsawa shine PT = 20W = 43dBm; ƙarfin karɓa shine PR = -70dBm;
Asarar mai ciyarwa shine 2.4dB (kimanin mai ciyarwa 60m)
Karuwar eriya mai karɓar wayar hannu GR = 1.5dBi;
Tsawon tsayin aiki λ = 33.333cm (daidai da mita f0 = 900MHz);
Tsarin sadarwa da ke sama zai zama:
43dBm-(-70dBm)+ GT(dBi)+1.5dBi=32dB+ 20logr(m) dB +2.4dB + asarar yaɗuwa L0
114.5dB+ GT(dBi) -34.4dB = 20logr(m)+ asarar yaɗuwa L0
80.1dB+ GT(dBi) = 20logr(m)+ asarar yaɗuwa L0
Idan ƙimar da ke gefen hagu na dabarar da ke sama ta fi ƙimar da ke gefen dama, to wannan shine:
GT(dBi) > 20logr(m)-80.1dB+rashin yaduwa L0. Idan rashin daidaito ya kasance, za a iya la'akari da cewa tsarin zai iya kiyaye kyakkyawar sadarwa.
Idan tashar tushe tana amfani da eriya mai watsawa ta hanya mai kusurwa huɗu tare da ribar GT=11dBi kuma nisan da ke tsakanin eriya mai watsawa da karɓa shine R=1000m, lissafin sadarwa ya ƙara zama 11dB>60-80.1dB+rashin yaduwa L0, wato, lokacin da asarar yaduwa L0<31.1dB, ana iya kiyaye kyakkyawar sadarwa a cikin nisan kilomita 1.
A ƙarƙashin yanayin asarar yaɗuwa kamar yadda aka ambata a sama, idan eriya mai watsawa ta sami GT = 17dBi, wato, ƙaruwar 6dBi, za a iya ninka nisan sadarwa sau biyu, wato, r = kilomita 2. Wasu kuma za a iya cire su ta wannan hanyar. Duk da haka, ya kamata a lura cewa eriya mai tushe mai riba ta GT na 17dBi za ta iya samun murfin katako mai siffar fanka kawai tare da faɗin katako na 30°, 65° ko 90°, da sauransu, kuma ba za ta iya kiyaye ɗaukar hoto mai kusurwa-da-gefe ba.
Bugu da ƙari, idan ribar eriya mai watsawa GT=11dBi ta kasance ba ta canzawa a cikin lissafin da ke sama, amma yanayin yaɗuwa ya canza, asarar yaɗuwa L0=31.1dB-20dB=11.1dB, to raguwar asarar yaɗuwa 20dB zai ƙara nisan sadarwa ninki goma, wato, r=kilomita 10. Kalmar asarar yaɗuwa tana da alaƙa da yanayin lantarki da ke kewaye. A yankunan birane, akwai gine-gine masu tsayi da yawa kuma asarar yaɗuwa tana da yawa. A yankunan karkara na birni, gidajen gona suna da ƙasa kuma ba su da yawa, kuma asarar yaɗuwa ƙarama ce. Saboda haka, ko da saitunan tsarin sadarwa iri ɗaya ne, ingantaccen kewayon ɗaukar hoto zai bambanta saboda bambancin yanayin amfani.
Saboda haka, lokacin zabar eriya mai jagora, mai jagora da kuma nau'ikan eriya masu riba ko ƙarancin riba, ya zama dole a yi la'akari da amfani da eriya mai tushe iri daban-daban da ƙayyadaddun bayanai bisa ga takamaiman yanayin hanyar sadarwa ta wayar hannu da yanayin aikace-aikacen.
Don ƙarin koyo game da eriya, da fatan za a ziyarci:
Lokacin Saƙo: Yuli-25-2025
