Enqubweni yokuklama i-PCB, ngaphambi kokuthatha umzila, ngokuvamile sipakisha izinto esifuna ukuziklama, futhi sibale ukuvinjelwa ngokusekelwe kubukhulu, i-substrate, inani lezendlalelo nolunye ulwazi. Ngemva kokubala, okuqukethwe okulandelayo kungatholakala ngokuvamile.

Njengoba kubonakala kumfanekiso ongenhla, umklamo wenethiwekhi onesiphetho esisodwa ngenhla ngokuvamile ulawulwa ngama-ohms angu-50, ngakho-ke abantu abaningi bazobuza ukuthi kungani kudingekile ukulawula ngokuvumelana nama-ohms angu-50 esikhundleni sama-25 ohms noma ama-80 ohms?
Okokuqala, i-50 ohms ikhethwa ngokuzenzakalelayo, futhi wonke umuntu embonini uyalamukela leli nani. Ngokuvamile, izinga elithile kufanele lakhiwe inhlangano eyaziwayo, futhi wonke umuntu uklama ngokwezinga.
Ingxenye enkulu yobuchwepheshe be-elekthronikhi ivela kwezempi. Okokuqala nje, ubuchwepheshe busetshenziswa kwezempi, futhi kancane kancane bususwa kwezempi buyiswe kubantu. Ezinsukwini zakuqala zezicelo ze-microwave, phakathi neMpi Yezwe Yesibili, ukukhethwa kwe-impedance kwakuncike ngokuphelele ezidingweni zokusetshenziswa, futhi kwakungekho xabiso elijwayelekile. Ngokuthuthuka kobuchwepheshe, izindinganiso ze-impedance zidinga ukunikezwa ukuze kutholakale ukulingana phakathi komnotho kanye nokwenza lula.

E-United States, amapayipi asetshenziswa kakhulu axhunywe izinduku namapayipi amanzi akhona. I-51.5 ohms ivame kakhulu, kodwa ama-adapter neziguquli ezibonwayo futhi ezisetshenzisiwe ziyi-50-51.5 ohms; lokhu kuxazululwa embuthweni wamasosha ahlangene kanye nasolwandle. Inkinga, inhlangano ebizwa ngokuthi i-JAN yasungulwa (kamuva inhlangano ye-DESC), yathuthukiswa ngokukhethekile yi-MIL, futhi ekugcineni yakhetha ama-ohm angu-50 ngemva kokucatshangelwa okuphelele, futhi ama-catheter ahlobene akhiqizwa futhi aguqulwa abe izintambo ezihlukahlukene. Amazinga.

Ngalesi sikhathi, izinga laseYurophu lalingama-ohms angama-60. Ngokushesha ngemva kwalokho, ngaphansi kwethonya lezinkampani ezivelele njenge-Hewlett-Packard, abantu baseYurophu nabo baphoqeleka ukuba bashintshe, ngakho-ke ama-ohms angu-50 agcina eseyindinganiso embonini. Sekuyingqungquthela, futhi i-PCB exhunywe ezintanjeni ezihlukahlukene ekugcineni iyadingeka ukuze ihambisane nendinganiso ye-impedance engu-50 ohm yokufanisa i-impedance.

Okwesibili, ukwakhiwa kwamazinga ajwayelekile kuzosekelwe ekucatshangelweni okuphelele kwenqubo yokukhiqiza ye-PCB nokusebenza kokuklama nokuba nokwenzeka.

Ngokombono wokukhiqizwa kwe-PCB nobuchwepheshe bokucubungula, futhi uma kucutshungulwa izisetshenziswa zabakhiqizi abaningi be-PCB abakhona, kulula ukukhiqiza ama-PCB ane-50 ohm impedance. Kusukela kunqubo yokubala ye-impedance, kungabonakala ukuthi i-impedance ephansi kakhulu idinga ububanzi bomugqa obanzi kanye ne-medium mncane noma i-dielectric constant constant, okunzima kakhulu ukuhlangabezana nebhodi lamanje elisezingeni eliphezulu emkhathini; i-impedance ephezulu kakhulu idinga umugqa omncane omncane Imidiya ebanzi futhi ewugqinsi noma ama-constants amancane e-dielectric awahambisani nokucindezelwa kwe-EMI kanye ne-crosstalk. Ngesikhathi esifanayo, ukuthembeka kokucutshungulwa kwamabhodi anezingqimba eziningi kanye nombono wokukhiqiza ngobuningi kuzoba mpofu kakhulu. Lawula i-impedance engu-50 ohm. Ngaphansi kwemvelo yokusebenzisa amabhodi avamile (FR4, njll.) kanye namabhodi ayisisekelo avamile, khiqiza imikhiqizo yobukhulu bebhodi evamile (efana no-1mm, 1.2mm, njll.). Ububanzi bomugqa obujwayelekile (4~10mil) bungaklanywa. Ifektri ilungele kakhulu ukucubungula, futhi izidingo zemishini yokucubungula kwayo aziphezulu kakhulu.

Ngokombono we-PCB design, ama-ohms angu-50 nawo akhethiwe ngemva kokucatshangelwa okuphelele. Kusukela ekusebenzeni kokulandelelwa kwe-PCB, i-impedance ephansi ngokuvamile ingcono. Ngolayini wokudlulisela onobubanzi bomugqa onikeziwe, lapho ibanga elisondela endizeni liseduze, i-EMI ehambisanayo izoncishiswa, futhi i-crosstalk nayo izoncishiswa. Nokho, ngokombono wendlela yesignali egcwele, enye yezinto ezibaluleke kakhulu idinga ukucatshangelwa, okungukuthi, ikhono lokushayela le-chip. Ezinsukwini zakuqala, ama-chips amaningi awakwazanga ukushayela imigqa yokudlulisela ene-impedance engaphansi kwama-ohms angu-50, futhi imigqa yokudlulisela ene-impedance ephakeme yayingelula ukuyisebenzisa. Ngakho-ke i-50 ohm impedance isetshenziswa njenge-compromise.

Umthombo: Lesi sihloko sidluliswa sisuka ku-inthanethi, futhi i-copyright ingeyombhali wokuqala.