Kufalitsa Kuchedwa ndi Kuchedwa Skew

Kwa akatswiri angapo aukadaulo, malingaliro monga 'kuchedwa kufalitsa' ndi 'kuchedwa skew' amakumbutsa zowawa zamakalasi asukulu yasekondale.Zoona zake, zotsatira za kuchedwa ndi kuchedwa skew pa kutumiza zizindikiro zimafotokozedwa mosavuta ndikumveka.

Kuchedwa ndi katundu yemwe amadziwika kuti alipo pamitundu yonse yapa media.Kuchedwa kwa kufalitsa kumafanana ndi kuchuluka kwa nthawi yomwe imadutsa pakati pomwe siginecha imatumizidwa komanso ikalandiridwa kumbali ina ya kanjira.Zotsatira zake zimafanana ndi kuchedwa kwa nthawi pakati pa kugunda kwa mphezi ndi kumveka kwa bingu - kupatula kuti ma siginecha amagetsi amayenda mwachangu kwambiri kuposa mawu.Kuchedwetsa kwenikweni kwa ma cabling opotoka ndi ntchito ya velocity of propagation (NVP), kutalika ndi ma frequency.

NVP imasiyanasiyana malinga ndi zida za dielectric zomwe zimagwiritsidwa ntchito mu chingwe ndipo zimawonetsedwa ngati kuchuluka kwa liwiro la kuwala.Mwachitsanzo, zomanga zambiri za gulu 5 la polyethylene (FRPE) zimakhala ndi milingo ya NVP kuchokera ku0.65cto0.70c (pomwe "c" imayimira liwiro la kuwala ~ 3 x108 m/s) ikayezedwa pa chingwe chomalizidwa.Kupanga chingwe cha Teflon (FEP) kumachokera ku0.69cto0.73c, pomwe zingwe zopangidwa ndi PVC zili mu 0.60cto0.64crange.

Makhalidwe otsika a NVP adzathandizira kuchedwetsa kwina kwa utali woperekedwa, monga momwe kuchulukira kwa utali wa chingwe chakumapeto-ku-kumapeto kudzachititsa kuti kuchedwetsedwe komaliza mpaka kumapeto.Monga momwe zimakhalira ndi zina zambiri zotumizira, kuchedwetsa kumadalira pafupipafupi.

Pamene awiriawiri angapo mu chingwe chimodzi akuwonetsa kuchedwa kosiyana, zotsatira zake ndi kuchedwa skew.Kuchedwa skew kumatsimikiziridwa poyesa kusiyana pakati pa awiriwo ndi kuchedwa pang'ono ndi awiriwo ndi kuchedwa kwambiri.Zomwe zimakhudza kuchedwa kwa skew ndi kusankha kwa zinthu, monga kutsekereza kondakitala, ndi kapangidwe ka thupi, monga kusiyana kwa mitengo yopindika kuchokera pawiri kupita pawiri.

Kuchedwa Kufalitsa Chingwe

Ngakhale zingwe zonse zopotoka zimawonetsa kuchedwa kwapang'onopang'ono, zingwe zomwe zidapangidwa mosamala kuti zilole kusiyana kwa NVP ndi kusiyana kwautali wa awiri-ndi-awiri adzakhala ndi kuchedwetsa kovomerezeka kwa masinthidwe opingasa okhazikika.Zina mwazinthu zomwe zitha kusokoneza magwiridwe antchito a skew ndi monga zingwe zokhala ndi ma dielectric opangidwa molakwika komanso omwe ali ndi kusiyana kwakukulu pamitengo yopindika.

Kuchedwetsa kufalitsa ndi kuchedwa kwa skew ntchito kumatchulidwa ndi miyezo ina yapadera lanu (LAN) pakusintha koyipa kwambiri kwa100 mchannel kuti zitsimikizire kufalikira koyenera.Mavuto opatsirana okhudzana ndi kuchedwa kwambiri ndi kuchedwa skew amaphatikizapo kuchuluka kwa jitter ndi zolakwika pang'ono.Kutengera mafotokozedwe a IEEE 802-mndandanda wa LAN, kuchedwetsa kokulirapo kwa 570 ns/100mat 1 MHz komanso kuchedwa kwapakati kwa 45ns/100mup mpaka 100 MHz akuganiziridwa ndi TIA pagulu la 3, 4 ndi 5, zingwe ziwiri.TIA Working Group TR41.8.1 ikulingaliranso za chitukuko cha zofunikira kuti ziwone kuchedwa kwa kufalitsa ndi kuchedwa skew kwa 100 ohm yopingasa maulalo ndi ma tchanelo omwe amamangidwa motsatira ANSI/TIA/EIA-568-A.Chifukwa cha komiti ya TIA ya "Letter Ballot" TR-41:94-4 (PN-3772) idasankhidwa pamsonkhano wa Seputembala 1996 kuti ipereke "Industry Ballot" pamakonzedwe osinthidwa asanatulutsidwe.Zomwe sizinathetsedwe ndi nkhani yoti magulu asintha kapena ayi (mwachitsanzo, gulu 5.1), kuti awonetse kusiyana pakati pa zingwe zomwe zimayesedwa kuti ziwonjezere kuchedwa / kuchedwa kwa skew, ndi zomwe sizili.

Ngakhale kuchedwa kwa kufalitsa ndi kuchedwetsa skew kukuyang'aniridwa kwambiri, ndikofunikira kuzindikira kuti vuto lalikulu kwambiri la ma cabling pamapulogalamu ambiri a LAN ikhala yochepetsetsa ku crosstalk ratio (ACR).Pomwe ma ACR maginito amawongolera ma siginecha kukhala phokoso ndipo potero amachepetsa kuchuluka kwa zolakwika pang'ono, machitidwe amachitidwe samakhudzidwa mwachindunji ndi mayendedwe a ma cabling okhala ndi kuchedwa kwakukulu kwa skew margins.Mwachitsanzo, 15 ns kuchedwa skew kwa tchanelo cha cabling sikungapangitse kuti maukonde agwire bwino ntchito kuposa ma 45 ns, pamakina opangidwa kuti athe kulolera mpaka 50 ns ya kuchedwa skew.

Pachifukwa ichi, kugwiritsa ntchito zingwe zochedwa kwambiri skew margins ndizofunika kwambiri pa inshuwaransi yomwe amapereka motsutsana ndi machitidwe oyikapo kapena zinthu zina zomwe zingakankhire kuchedwa kupitirira malire, m'malo molonjeza kugwira ntchito kwabwinoko poyerekeza ndi njira yomwe zimangokumana ndi dongosolo lochedwa skew malire ndi nanoseconds angapo.

Chifukwa zingwe zomwe zimagwiritsa ntchito zipangizo zosiyanasiyana za dielectric kwa awiriawiri osiyanasiyana zapezeka kuti zimayambitsa mavuto ndi kuchedwa skew, pakhala mkangano waposachedwa pakugwiritsa ntchito zida zosakanikirana za dielectric pomanga chingwe.Mawu ngati "2 ndi 2" (chingwe chokhala ndi mapeyala awiri okhala ndi dielectric "A" ndi awiri awiri okhala ndi "B") kapena "4 ndi 0" (chingwe chokhala ndi mapeyala onse anayi opangidwa kuchokera kuzinthu A, kapena B ) zomwe zimakonda matabwa kuposa chingwe, nthawi zina zimagwiritsidwa ntchito pofotokoza kapangidwe ka dielectric.

Ngakhale kukopa kwamalonda komwe kungasokeretse munthu kukhulupirira kuti zomanga zomwe zili ndi mtundu umodzi wa zida zamagetsi zikuwonetsa kuchedwa kovomerezeka, chowonadi ndichakuti zingwe zopangidwa bwino zokhala ndi zida imodzi ya dielectric, kapena zida zingapo zama dielectric zimatha kukhutiritsa ngakhale Zofunikira zochedwetsa kwambiri za njira zotsatiridwa ndi miyezo ya kagwiritsidwe ntchito ndi zomwe TIA ikuganiziridwa.

Nthawi zina, ma dielectric osakanikirana amatha kugwiritsidwa ntchito kuthetsa kuchedwa kwa skew kusiyana komwe kumabwera chifukwa cha mitengo yopindika.Zithunzi 1 ndi 2 zikuwonetsa kuchedwa kwa oyimira ndi ma skew values ​​omwe atengedwa kuchokera pachitsanzo cha chingwe cha mita 100 chosankhidwa mwachisawawa chokhala ndi "2 by 2" (FRPE/FEP).Zindikirani kuti kuchedwa kwakukulu kwa kufalitsa ndi kuchedwa skew kwa chitsanzo ichi ndi 511 ns / 100mand 34 ns, motsatira mafupipafupi kuchokera ku 1 MHz mpaka 100 MHz.