Amakhebula e-SAS ashesha kakhulu: Izixhumi kanye Nokwenza Amasignali Asebenze Kahle

Amakhebula e-SAS ashesha kakhulu: Izixhumi kanye Nokwenza Amasignali Asebenze Kahle

Imininingwane Yobuqotho Besignali

Ezinye zezimiso eziyinhloko zobuqotho besignali zifaka phakathi ukulahlekelwa kokufakwa, ukukhuluma okuseduze nokuphela, ukulahlekelwa kokubuya, ukuphazamiseka kwe-skew ngaphakathi kwama-differential pairs, kanye nokuphakama kusuka kumodi yokwahluka kuya kumodi evamile. Nakuba lezi zici zihlobene futhi zithintana, singacabangela isici ngasinye ngesikhathi ukuze sifunde umthelela waso oyinhloko.
Ukulahlekelwa Kokufakwa
Ukulahlekelwa kokufakwa kuwukuncipha kobukhulu besiginali kusukela ekugcineni kokudlulisa kuya ekugcineni kokwamukela kwekhebula, futhi kuhambelana ngqo nemvamisa. Ukulahlekelwa kokufakwa kuncike kugeyiji yentambo, njengoba kuboniswe kugrafu yokuncipha engezansi. Ezingxenyeni zangaphakathi zebanga elifushane ezisebenzisa izintambo ezingu-30 noma ezingu-28-AWG, izintambo zekhwalithi ephezulu kufanele zibe nokuncipha okungaphansi kuka-2 dB/m ku-1.5 GHz. Ku-6 Gb/s SAS yangaphandle usebenzisa izintambo ezingu-10m, kunconywa ukusebenzisa izintambo ezinesilinganiso sentambo esingu-24, ezinokuncipha okungu-13 dB kuphela ku-3 GHz. Uma ufuna ukufeza imajini yesignali eyengeziwe ngamanani aphezulu okudlulisa idatha, chaza izintambo ezinokuncipha okuphansi kumaza aphezulu ezintambo ezinde, njenge-SFF-8482 enekhebula le-POWER noma i-SlimSAS SFF-8654 8i.

Ukuxoxa nge-Crosstalk
I-Crosstalk ibhekisela enanini lamandla adluliselwa kusuka ku-signal eyodwa noma i-differential pair kuya kwesinye isignali noma i-differential pair. Kumakhebula e-SAS, uma i-crosstalk eseduze (NEXT) incane ngokwanele, izobangela izinkinga eziningi zesixhumanisi. Ukulinganiswa kwe-NEXT kwenziwa kuphela ekugcineni kwekhebula, futhi ubukhulu bamandla adluliselwe kusuka ku-output transmission signal pair kuya ku-input receiving pair. Ukulinganiswa kwe-far-end crosstalk (FEXT) kwenziwa ngokufaka isignali ku-transmission pair ekugcineni kwekhebula nokubheka ukuthi mangakanani amandla asagcinwe ku-transmission signal komunye umkhawulo wekhebula. I-NEXT ezingxenyeni zekhebula kanye nezixhumi ngokuvamile ibangelwa ukuhlukaniswa okungekuhle kwe-signal differential pair, mhlawumbe ngenxa yama-socket nama-plug, i-grounding engaphelele, noma ukuphathwa kabi kwendawo yokuphela kwekhebula. Abaklami besistimu badinga ukuqinisekisa ukuthi abahlanganisi bekhebula babhekane nalezi zinkinga ezintathu, njengasezingxenyeni ezifana ne-MINI SAS HD SFF-8644 noma i-OCuLink SFF-8611 4i.

Ama-24, 26 kanye no-28 ayizikhombo ezijwayelekile zokulahlekelwa kwekhebula ezingama-100Ω.

Kuma-cable assemblies asezingeni eliphezulu, i-NEXT elinganiswe ngokuhambisana ne-“SFF-8410 – Specification for HSS Copper Testing and Performance Requirements” kufanele ibe ngaphansi kuka-3%. Ngokuphathelene ne-S-parameter, i-NEXT kufanele ibe ngaphezu kuka-28 dB.
Ukulahlekelwa yimbuyiselo
Ukulahleka kokubuya kulinganisa ubukhulu bamandla abonakala ohlelweni noma kukhebula lapho kufakwa isignali. La mandla abonakalayo abangela ukwehla kwe-amplitude yesignali ekugcineni kwekhebula futhi kungaholela ezinkingeni zobuqotho besignali ekugcineni kokudlulisa, okungabangela izinkinga zokuphazamiseka kwe-electromagnetic kuhlelo nakubaklami besistimu.
Lokhu kulahlekelwa kokubuya kubangelwa ukungalingani kwe-impedance ezingxenyeni zekhebula. Kuphela ngokuphatha le nkinga ngokucophelela okukhulu lapho i-impedance ingashintshi khona lapho isignali idlula kuma-socket, ama-plug, nama-terminal ekhebula, ukuze kuncishiswe ukuhlukahluka kwe-impedance. Izinga lamanje le-SAS-4 libuyekeza inani le-impedance kusuka ku-±10Ω ku-SAS-2 kuya ku-±3Ω. Izintambo zekhwalithi ephezulu kufanele zigcine isidingo ngaphakathi kokubekezelelana kwe-nominal 85 noma i-100 ± 3Ω, njenge-SFF-8639 ene-SATA 15P noma i-MCIO 74 Pin Cable.

Ukuhlanekezela okugobile
Kumakhebula e-SAS, kunezinhlobo ezimbili zokuphambuka kwe-skew: phakathi kwama-differential pairs kanye nangaphakathi kwama-differential pairs (i-signal integrity theory - i-differential signal). Ngokwethiyori, uma amasignali amaningi efakwa ngesikhathi esisodwa kolunye uhlangothi lwekhebula, kufanele afinyelele kolunye uhlangothi ngesikhathi esisodwa. Uma lezi zimpawu zingafiki ngesikhathi esisodwa, lesi simo sibizwa ngokuthi i-cable skew distortion, noma i-delay-skew distortion. Kuma-differential pairs, i-skew distortion ngaphakathi kwe-differential pair ukulibaziseka phakathi kwabaqhubi ababili be-differential pair, kuyilapho i-skew distortion phakathi kwama-differential pairs ukulibaziseka phakathi kwamasethi amabili ama-differential pairs. I-skew distortion enkulu ngaphakathi kwe-differential pair ingalimaza ibhalansi ye-differential yesignali edlulisiwe, inciphise ubukhulu besignali, yandise i-time jitter, futhi ibangele izinkinga zokuphazamiseka kwe-electromagnetic. Kumakhebula asezingeni eliphezulu, i-skew distortion ngaphakathi kwe-differential pair kufanele ibe ngaphansi kwama-10 ps, ​​njenge-SFF-8654 8i kuya ku-SFF-8643 noma i-Anti-misalignment Insertion cable.
Ukuphazamiseka kwe-electromagnetic
Kunezimbangela eziningi zezinkinga zokuphazamiseka kwe-electromagnetic ezintanjeni: ukuvikela okungekuhle noma ukungabikho kokuvikela, indlela engalungile yokusekela, izimpawu zokuhlukanisa ezingalingani, futhi ngaphezu kwalokho, ukungafani kwe-impedance nakho kuyimbangela. Kuzintambo zangaphandle, ukuvikela kanye nokusekela kungenzeka kube yizinto ezimbili ezibaluleke kakhulu okufanele zixazululwe, njenge-SFF-8087 ene-red mesh noma ikhebula lokusekela le-Cooper mesh.
Ngokuvamile, ukuvikela ukuphazamiseka kwangaphandle noma kwe-electromagnetic kufanele kube ukuvikela okubili okwenziwe nge-foil yensimbi kanye nesendlalelo esilukiwe, okumbozwe okungenani u-85%. Ngesikhathi esifanayo, lokhu kuvikela kufanele kuxhunywe ejazini langaphandle lesixhumi, ngokuxhumeka okuphelele okungu-360°. Ukuvikela amabhangqa ahlukene kufanele kuhlukaniswe nokuvikela kwangaphandle, futhi imigqa yawo yokuhlunga kufanele iphele esignalini yesistimu noma emhlabathini we-DC ukuqinisekisa ukulawulwa kwe-impedance okuhlanganisiwe kwesixhumi nezingxenye zekhebula, njengekhebula lesixhumi le-SFF-8654 8i Full Wrap anti-slash noma i-Scoop-proof.