In PCB wiring, kwenzeka kaningi ukuthi umugqa omncane kufanele usetshenziselwe ukudlula endaweni lapho kunesikhala esilinganiselwe sezintambo, bese ulayini ubuyiselwa kububanzi bayo bokuqala. Ushintsho kububanzi bomugqa luzodala ushintsho ku-impedance, okuzoholela ekubonisweni futhi kuthinte isignali. Ngakho-ke singawuziba nini lo mphumela, futhi kufanele siwucabangele nini umphumela wawo?

Izici ezintathu zihlobene nalomphumela: ubukhulu boshintsho lwe-impedance, isikhathi sokuvuka kwesiginali, nokulibaziseka kwesiginali kulayini omncane.

Okokuqala, kukhulunywa ngobukhulu boshintsho lwe-impedance. Ukwakheka kwamasekethe amaningi kudinga ukuthi umsindo obonisiwe ube ngaphansi kuka-5% we-voltage swing (ehlobene nesabelomali somsindo kusiginali), ngokusho kwefomula yokulinganisa ekhombisa:

Izinga lokushintshwa le-impedance elilinganisiwe lingabalwa njenge- △ Z / Z1 ≤ 10%. Njengoba kungenzeka uyazi, inkomba ejwayelekile ye-impedance ebhodini ngu- +/- 10%, futhi leyo imbangela.

Uma ushintsho lwe-impedance lwenzeka kanye kuphela, njengokuthi lapho ububanzi bomugqa buguquka kusuka ku-8mil kuye ku-6mil futhi buhlala bu-6mil, ushintsho lwe-impedance kufanele lube ngaphansi kuka-10% ukuze kufinyelelwe imfuneko yesabelomali somsindo ukuthi isinali likhombise umsindo ekushintsheni okungazelelwe kwenzeka engeqi ku-5% we-voltage jika. Lokhu kwesinye isikhathi kunzima ukukwenza. Thatha isibonelo semigqa ye-microstrip emapuletini e-FR4 njengesibonelo. Ake sibale. Uma ububanzi bomugqa bungu-8mil, ubukhulu obuphakathi kolayini nendiza eyinkomba bungu-4mil futhi impedance yesici ingu-46.5 ohms. Lapho ububanzi bomugqa buguqukela ku-6mil, i-impedance yesici iba ngu-54.2 ohm, futhi izinga lokushintshwa kwe-impedance lifinyelela kuma-20%. Ukuphakama kwesiginali ekhonjisiwe kufanele kudlule okujwayelekile. Ngokuphathelene nokuthi ungakanani umthelela kusiginali, kodwa futhi nangesikhathi sokuvuka kwesiginali kanye nokubambezeleka kwesikhathi kusuka kumshayeli kuya kusignali yephuzu lokukhombisa. Kepha okungenani indawo engaba nenkinga. Ngenhlanhla, ungaxazulula inkinga ngamatheminali afanayo we-impedance.

Uma ushintsho lwe-impedance lwenzeka kabili, ngokwesibonelo, ububanzi bomugqa buguquka busuka ku-8mil buye ku-6mil, bese buyela emuva ku-8mil ngemuva kokukhipha u-2cm. Bese kuthi ku-2cm ubude obude obungu-6mil emaphethelweni womabili wokubonisa, eyodwa i-impedance iba nkulu, iveze okuhle, bese kuthi i-impedance ibe ncane, ibe nombono omubi. Uma isikhathi esiphakathi kokuboniswa sincane ngokwanele, ukucabanga okubili kungakhanselana, kunciphise umphumela. Uma ucabanga ukuthi isignali yokudlulisa i-1V, i-0.2V ibonakala ekubonisweni kokuqala okuhle, i-1.2V idluliselwa phambili, futhi -0.2 * 1.2 = 0.24V ibonakala emuva ekubonisweni kwesibili. Uma ucabanga ukuthi ubude bomugqa we-6mil bufushane ngokwedlulele futhi ukubonakaliswa okubili kwenzeka cishe ngasikhathi sinye, inani eliphelele lamandla kagesi lingu-0.04V kuphela, ngaphansi kwesidingo sesabelomali somsindo esingu-5%. Ngakho-ke, ukuthi lokhu kukhonjiswa kuthinta isignali nokuthi kungakanani okuthinta isinali kuncike ekubambezelweni kwesikhathi kushintsho lwe-impedance nesikhathi sokuvuka kwesiginali. Izifundo nokuhlolwa kukhombisa ukuthi inqobo nje uma ukubambezeleka kokushintshwa kwe-impedance kungaphansi kwama-20% wesikhathi sokuvuka kwesiginali, isinali elibonisiwe ngeke lidale inkinga. Uma isikhathi sokuvuka kwesiginali kungu-1ns, ukubambezeleka kokushintshwa kwe-impedance kungaphansi kwama-0.2ns ahambelana namasentimitha ayi-1.2, futhi ukubonakaliswa akuyona inkinga. Ngamanye amagama, kuleli cala, ubude bocingo obungu-6mil obungaphansi kuka-3cm akufanele kube yinkinga.

Lapho ububanzi bentambo ye-PCB buguquka, kufanele buhlaziywe ngokucophelela ngokuya ngesimo sangempela ukubona ukuthi kukhona yini umthelela. Kunemingcele emithathu okufanele ukhathazeke ngayo: ukuthi i-impedance iyashintsha kangakanani, isikhathi sokukhuphuka kwesiginali, nokuthi ingxenye yengxenye yentambo yobubanzi bolayini iyashintsha kangakanani. Yenza isilinganiso esinzima ngokususelwa kule ndlela engenhla bese ushiya imajini ethile njengoba kufanele. Uma kungenzeka, zama ukunciphisa ubude bentamo.

Kufanele kuvezwe ukuthi ekusetshenzisweni kwangempela kwe-PCB, amapharamitha awakwazi ukunemba njengalawo embonweni. Ithiyori ingahlinzeka ngokuholwa kokuklanywa kwethu, kepha ayikwazi ukukopishwa noma ukuqiniselwa. Ngemuva kwakho konke, lokhu kuyisayensi esebenzayo. Inani elilinganisiwe kufanele libuyekezwe ngokuya ngesimo sangempela, bese lisetshenziswa ekwakhiweni. Uma uzizwa ungenakho okuhlangenwe nakho, gcina imvelo futhi uzivumelanise nezindleko zokwenza.