Iintambo ze-SAS ezikhawulezayo: Izihlanganisi kunye noLungiso lweSignali

Iintambo ze-SAS ezikhawulezayo: Izihlanganisi kunye noLungiso lweSignali

Iinkcukacha zoBulungisa beSignali

Ezinye zezona parameter ziphambili zokuthembeka kwesignali ziquka ukulahleka kokufakwa, i-crosstalk ekufutshane neye-far-end, ukulahleka kokubuya, ukujikajika kwe-skew ngaphakathi kwee-differential pairs, kunye ne-amplitude ukusuka kwi-differential mode ukuya kwi-common mode. Nangona ezi zinto zihambelana kwaye zichaphazela enye kwenye, singaqwalasela into nganye nganye ngexesha ukuze sifunde impembelelo yayo ephambili.
Ukulahleka Kokufakwa
Ukulahleka kokufakwa kukuncipha kwe-amplitude yesignali ukusuka kwisiphelo sokudlulisa ukuya kwisiphelo sokwamkela intambo, kwaye kuhambelana ngqo ne-frequency. Ukulahleka kokufakwa kuxhomekeke kwi-wire gauge, njengoko kubonisiwe kwigrafu yokunciphisa engasezantsi. Kwizinto zangaphakathi ezimfutshane ezisebenzisa iintambo ezingama-30 okanye ezingama-28-AWG, iintambo ezikumgangatho ophezulu kufuneka zibe nokuncipha okungaphantsi kwe-2 dB/m kwi-1.5 GHz. Kwi-6 Gb/s SAS yangaphandle esebenzisa iintambo ezili-10m, kucetyiswa ukusebenzisa iintambo ezine-wire gauge ephakathi engama-24, ezinokuncipha kwe-13 dB kuphela kwi-3 GHz. Ukuba ufuna ukufikelela kwi-signal margin engaphezulu kwizinga eliphezulu lokudluliselwa kwedatha, chaza iintambo ezine-attenuation ephantsi kwi-frequency ephezulu kwiintambo ezinde, ezifana ne-SFF-8482 enentambo ye-POWER okanye i-SlimSAS SFF-8654 8i.

Ingxoxo enqamlezileyo
I-Crosstalk ibhekisa kubungakanani bamandla adluliselwa ukusuka kwisignali enye okanye isibini sokwahluka ukuya kwesinye isignali okanye isibini sokwahluka. Kwiintambo ze-SAS, ukuba i-crosstalk ekufutshane (NEXT) ayincinci ngokwaneleyo, iya kubangela uninzi lweengxaki zekhonkco. Ukulinganiswa kwe-NEXT kwenziwa kuphela kwelinye icala lentambo, kwaye bubungakanani bamandla adluliselwe ukusuka kwisibini sesignali yokudlulisa imveliso ukuya kwisibini sokwamkela i-input. Ukulinganiswa kwe-crosstalk ekude (FEXT) kwenziwa ngokufaka isignali kwisibini sokudlulisa kwelinye icala lentambo kwaye kujongwe ukuba mangakanani amandla asagciniwe kwisignali yokudlulisa kwelinye icala lentambo. I-NEXT kwizixhobo zentambo kunye nezihlanganisi zihlala zibangelwa kukwahlulwa kakubi kwesibini sokwahluka kwesignali, mhlawumbi ngenxa yeesokhethi kunye neeplagi, ukugalelwa okungaphelelanga, okanye ukuphathwa ngendlela engafanelekanga kwendawo yokuphelisa intambo. Abayili beenkqubo kufuneka baqinisekise ukuba abahlanganisi bentambo bajongane nale miba mithathu, njengakwizinto ezifana ne-MINI SAS HD SFF-8644 okanye i-OCuLink SFF-8611 4i.

I-24, 26 kunye ne-28 ziindlela eziqhelekileyo zokulahleka kwentambo ye-100Ω.

Kwiindibano zekhebula ezikumgangatho ophezulu, i-NEXT elinganiswe ngokuhambelana ne-“SFF-8410 – Inkcazo yeeMfuno zoVavanyo lweCopper kunye nokuSebenza kwe-HSS” kufuneka ibe ngaphantsi kwe-3%. Ngokuphathelele i-S-parameter, i-NEXT kufuneka ibe ngaphezulu kwe-28 dB.
Ukulahleka kokubuyisela
Ukulahleka kokubuya kulinganisa ubukhulu bamandla abonakaliswa kwinkqubo okanye kwintambo xa kufakwa isignali. La mandla abonakalisiweyo abangela ukwehla kobukhulu besignali kwisiphelo sokwamkela intambo kwaye kunokukhokelela kwiingxaki zokuthembeka kwesignali kwisiphelo sokudlulisa, nto leyo enokubangela iingxaki zokuphazamiseka kwe-electromagnetic kwinkqubo kunye nabayili benkqubo.
Oku kulahleka kokubuya kubangelwa kukungalingani kwe-impedance kwiinxalenye zekhebula. Kuphela kukuyiphatha ngononophelo le ngxaki apho i-impedance ingatshintshi xa isignali idlula kwiisokhethi, iiplagi, kunye nee-terminals zekhebula, ukuze kuncitshiswe umahluko we-impedance. Umgangatho wangoku we-SAS-4 uhlaziya ixabiso le-impedance ukusuka kwi-±10Ω kwi-SAS-2 ukuya kwi-±3Ω. Iintambo ezisemgangathweni ophezulu kufuneka zigcine imfuneko ngaphakathi kokunyamezelana kwe-nominal 85 okanye i-100 ± 3Ω, njenge-SFF-8639 ene-SATA 15P okanye i-MCIO 74 Pin Cable.

Ukuguqulwa okugobileyo
Kwiintambo ze-SAS, kukho iintlobo ezimbini zokuphambuka kwe-skew: phakathi kwee-differential pairs kunye nangaphakathi kwee-differential pairs (i-signal integrity theory - i-differential signal). Ngokwethiyori, ukuba iisignali ezininzi zifakwa ngaxeshanye kwelinye icala lentambo, kufuneka zifikelele kwelinye icala ngaxeshanye. Ukuba ezi signali azifiki ngaxeshanye, le nto ibizwa ngokuba yi-cable skew distortion, okanye i-delay-skew distortion. Kwii-differential pairs, i-skew distortion ngaphakathi kwe-differential pair kukulibaziseka phakathi kwee-conductors ezimbini ze-differential pair, ngelixa i-skew distortion phakathi kwee-differential pairs kukulibaziseka phakathi kweeseti ezimbini zee-differential pairs. I-skew distortion enkulu ngaphakathi kwe-differential pair inokuwohloka ibhalansi yokwahluka kwesignali edluliselweyo, inciphise ubukhulu besignali, yonyuse i-time jitter, kwaye ibangele iingxaki zokuphazamiseka kwe-electromagnetic. Kwiintambo ezisemgangathweni ophezulu, i-skew distortion ngaphakathi kwe-differential pair kufuneka ibe ngaphantsi kwe-10 ps, ​​njenge-SFF-8654 8i ukuya kwi-SFF-8643 okanye i-Anti-misalignment Insertion cable.
Ukuphazamiseka kwe-electromagnetic
Zininzi izizathu zeengxaki zokuphazamiseka kwe-electromagnetic kwiintambo: ukhuseleko olubi okanye ukungabikho kokhuseleko, indlela engalunganga yokumisa umhlaba, imiqondiso yokwahluka engalinganiyo, kwaye ngaphezulu koko, ukungafani kwe-impedance nako kuyimbangela. Kwiintambo zangaphandle, ukhuseleko kunye nokumisa umhlaba kusenokwenzeka ukuba zezona zinto zimbini zibalulekileyo ekufuneka zijongwe, njenge-SFF-8087 ene-red mesh okanye i-Cooper mesh grounding cable.
Ngokwesiqhelo, isikhuselo sokuphazamiseka kwangaphandle okanye kwe-electromagnetic kufuneka sibe sisikhuselo esiphindwe kabini esenziwe ngefoyile yesinyithi kunye nomaleko oboyiweyo, kunye nesigqubuthelo sisonke se-85%. Kwangaxeshanye, esi sikhuselo kufuneka siqhagamshelwe kwijakethi yangaphandle yesixhumi, kunye noqhagamshelo olupheleleyo lwe-360°. Isikhuselo seepawundi ezahlukeneyo kufuneka sahlulwe kwisikhuselo sangaphandle, kwaye imigca yazo yokucoca kufuneka iphele kwisignali yenkqubo okanye umhlaba we-DC ukuqinisekisa ulawulo oludibeneyo lwe-impedance kwisixhobo sokudibanisa kunye nezixhobo zekhebula, ezifana ne-SFF-8654 8i Full Wrap anti-slash okanye intambo yesixhumi esingena-Scoop.