Xa isignali yefrikhwensi ephezulu/irediyo ye-microwave ifakwe kwi PCB isiphaluka, ilahleko ebangelwa yisekethe ngokwayo kunye nezinto zesiphaluka ngokuqinisekileyo ziya kuvelisa umlinganiselo othile wobushushu. Okukhona ilahleko inkulu, kokukhona amandla aphezulu adlula kwizinto zePCB, kwaye kokukhona ubushushu obuveliswayo. Xa ubushushu bokusebenza besiphaluka budlula ixabiso elilinganisiweyo, isiphaluka sinokubangela iingxaki ezithile. Ngokomzekelo, i-parameter yokusebenza eqhelekileyo ye-MOT, eyaziwayo kwii-PCBs, lolona bushushu buphezulu bokusebenza. Xa ubushushu bokusebenza budlula i-MOT, ukusebenza kunye nokuthembeka kwesekethe yePCB kuya kusongelwa. Ngokudityaniswa kwemodeli ye-electromagnetic kunye nemilinganiselo yovavanyo, ukuqonda iimpawu zobushushu zeRF microwave PCBs kunokuncedisa ukunqanda ukuthotywa kokusebenza kwesekethe kunye nokuthotywa kokuthembeka okubangelwa ngamaqondo obushushu aphezulu.

Ukuqonda indlela ilahleko yokufakela eyenzekayo ngayo kwizinto zesekethe kunceda ukuchaza kakuhle izinto ezibalulekileyo ezinxulumene nokusebenza kwe-thermal ye-high-frequency PCB circuits. Eli nqaku liza kuthatha i-microstrip transmission line circuit njengomzekelo wokuxoxa nge-trade-offs ehambelana nokusebenza kwe-thermal yesekethe. Kwisekethe ye-microstrip ene-PCB enamacala amabini, ilahleko ibandakanya ukulahleka kwe-dielectric, ukulahleka komqhubi, ukulahleka kwemitha, kunye nokulahleka kokuvuza. Umahluko phakathi kwamacandelo elahleko ahlukeneyo mkhulu. Ngaphandle kwezinto ezimbalwa, ilahleko yokuvuza kweesekethe ze-PCB ezisebenza rhoqo ziphantsi kakhulu. Kweli nqaku, ekubeni ixabiso lelahleko yokuvuza liphantsi kakhulu, liya kuhoywa okwangoku.

Ilahleko yemitha

Ukulahleka kwemitha kuxhomekeke kwiiparamitha ezininzi zesekethe ezifana nokusebenza rhoqo, ubukhulu be-substrate yesiphaluka, i-PCB ye-dielectric engaguqukiyo (i-dielectric constant constant or εr) kunye nesicwangciso soyilo. Ngokubhekiselele kwizikimu zoyilo, ilahleko yemitha ihlala isuka kutshintsho olwenzekayo lwe-impedance kwisekethe okanye umahluko kukuhanjiswa kwamaza ombane kwisekethe. Indawo yoguqulo lwesekethe ihlala ibandakanya indawo yokutyala umqondiso, indawo yokuthintela inyathelo, i-stub kunye nenethiwekhi ehambelanayo. Uyilo lwesekethe olufanelekileyo lunokuqonda utshintsho olugudileyo lwe-impedance, ngaloo ndlela lunciphisa ilahleko yemitha yesekethe. Ewe kunjalo, kufanele kuqondwe ukuba kukho ithuba lokungahambelani kwe-impedance ekhokelela ekulahlekeni kwemitha nakweyiphi na imbonakalo yesekethe. Ukusuka kwindawo yokujonga i-frequency yokusebenza, ngokuqhelekileyo iphezulu i-frequency, inkulu ilahleko ye-radiation yesekethe.

Iiparamitha zemathiriyeli yesekethe enxulumene nokulahleka kwemitha ubukhulu becala yi-dielectric engaguqukiyo kunye nobukhulu bezinto zePCB. Okukhona ingqindilili ye-substrate yesekethe, kokukhona kunokwenzeka ukuba kubangele ilahleko yemitha; Okukhona isezantsi i-εr yesixhobo se-PCB, kokukhona ilahleko yemitha yemitha yesekethe. Ukulinganisa ngokubanzi iimpawu zezinto eziphathekayo, ukusetyenziswa kwee-substrates zesekethe ezibhityileyo zingasetyenziswa njengendlela yokuphelisa ilahleko yemitha ebangelwa yimathiriyeli yesekethe ephantsi. Impembelelo yobukhulu be-substrate yesekethe kunye ne-εr kwilahleko yemitha yesekethe kungenxa yokuba ngumsebenzi oxhomekeke kumaza. Xa ubukhulu be-substrate yesiphaluka bungadluli i-20mil kunye ne-frequency yokusebenza ingaphantsi kwe-20GHz, ilahleko ye-radiation yesiphaluka iphantsi kakhulu. Kuba uninzi lweemodeli zesekethe kunye nee-frequency zokulinganisa kweli nqaku zingaphantsi kwe-20GHz, ingxoxo kweli nqaku ayiyi kuyihoya impembelelo yokulahleka kwemitha ekufudumezeni kwesekethe.

After ignoring the radiation loss below 20GHz, the insertion loss of a microstrip transmission line circuit mainly includes two parts: dielectric loss and conductor loss. The proportion of the two mainly depends on the thickness of the circuit substrate. For thinner substrates, conductor loss is the main component. For many reasons, it is generally difficult to accurately predict conductor loss. For example, the surface roughness of a conductor has a huge influence on the transmission characteristics of electromagnetic waves. The surface roughness of copper foil will not only change the electromagnetic wave propagation constant of the microstrip circuit, but also increase the conductor loss of the circuit. Due to the skin effect, the influence of copper foil roughness on conductor loss is also frequency-dependent. Figure 1 compares the insertion loss of 50 ohm microstrip transmission line circuits based on different PCB thicknesses, which are 6.6 mils and 10 mils, respectively

Iziphumo ezilinganisiweyo nezilinganisiweyo

Ijika kwi-Figure 1 iqulethe iziphumo ezilinganisiweyo kunye neziphumo zokulinganisa. Iziphumo zokulinganisa zifunyanwa ngokusebenzisa i-MWI-2010 microwave impedance software ye-Rogers Corporation. Isoftware ye-MWI-2010 icaphula i-equations yohlalutyo kumaphepha eklasiki kwintsimi ye-microstrip line modeling. Idatha yokuvavanya kwi-Figure 1 ifunyenwe yindlela yokulinganisa ubude obuhlukeneyo bomhlalutyi womnatha we-vector. Ingabonwa kwi-Fig. 1 ukuba iziphumo zokulinganisa i-curve yelahleko iyonke ihambelana ngokusisiseko neziphumo ezilinganisiweyo. Ingabonwa kumzobo wokuba umqhubi wokulahlekelwa kwesiphaluka esincinci (i-curve ngakwesobunxele ihambelana nobukhulu be-6.6 mil) iyona nto iphambili yokulahlekelwa kokufakwa ngokupheleleyo. Njengoko ubukhulu besiphaluka bukhula (ubukhulu obuhambelana negophe ngasekunene yi-10mil), ilahleko ye-dielectric kunye nokulahleka kwe-conductor kuthanda ukusondela, kwaye zombini kunye zenza ilahleko yokufaka iyonke.

Imodeli yokulinganisa kwi-Figure 1 kunye neeparitha zezinto zesekethe ezisetyenziswe kwisekethe yangempela yile: i-dielectric constant 3.66, i-loss factor 0.0037, kunye ne-copper conductor surface roughness 2.8 um RMS. Xa ubunzima bomphezulu we-foil yethusi phantsi kwesixhobo sesiphaluka esifanayo sincitshisiwe, ukulahleka komqhubi we-6.6 mil kunye ne-10 mil circuits kuMfanekiso 1 kuya kuncitshiswa kakhulu; nangona kunjalo, umphumo awubonakali kwisekethe ye-20 mil. Umzobo 2 ubonisa iziphumo zeemathiriyeli zesekethe ezimbini ezinoburhabaxa obahlukeneyo, ezizezi, iRogers RO4350B™ imathiriyeli yesekethe eqhelekileyo enoburhabaxa obuphezulu kunye nemathiriyeli yesekethe yeRogers RO4350B LoPro™ enoburhabaxa obuphantsi.

Njengoko kuboniswe kwi-Figure 1 kunye ne-Figure 2, i-substrate yesiphaluka incinci, iphakamisa ukulahleka kokufakwa kwesekethe. Oku kuthetha ukuba xa isekethe isondliwa ngesixa esithile samandla e-RF microwave, isekethe ebhityileyo iya kuvelisa ubushushu obuninzi. Xa ulinganisa ngokubanzi umba wokufudumeza kwesekethe, kwelinye icala, isekethe encinci ivelisa ubushushu obuninzi kunesekethe eshinyeneyo kumanqanaba aphezulu ombane, kodwa kwelinye icala, isekethe ebhityileyo inokufumana ukuhamba kobushushu okusebenzayo ngakumbi kwi-sink yobushushu. Gcina ubushushu buphantsi.

Ukuze ucombulule ingxaki yokufudumala kwesekethe, isiphaluka esincinci esifanelekileyo kufuneka sibe nezi mpawu zilandelayo: ilahleko ephantsi yezinto eziphathekayo, i-copper epholileyo ebusweni, i-ether ephantsi kunye ne-conductivity ephezulu ye-thermal. Xa kuthelekiswa nezinto ezijikelezayo ze-high εr, ububanzi bomqhubi we-impedance efanayo efunyenwe phantsi kweemeko eziphantsi εr ingaba mkhulu, enenzuzo ekunciphiseni ukulahleka komqhubi wesiphaluka. Ukusuka kwimbono yokutshatyalaliswa kobushushu besiphaluka, nangona uninzi lwee-substrates zesekethe ze-PCB ezikwi-high-frequency zine-conductivity ephantsi kakhulu ye-thermal xa kuthelekiswa nabaqhubi, ukuqhutyelwa kwe-thermal yezinto zesekethe kuseyipharamitha ebaluleke kakhulu.

Uninzi lweengxoxo malunga ne-thermal conductivity yee-substrates zesiphaluka ziye zachazwa kumanqaku angaphambili, kwaye eli nqaku liza kucaphula ezinye iziphumo kunye nolwazi oluvela kumanqaku angaphambili. Ngokomzekelo, i-equation elandelayo kunye ne-Figure 3 iluncedo ekuqondeni izinto ezinxulumene nokusebenza kwe-thermal yezinto zesekethe ze-PCB. Kwi-equation, k yi-thermal conductivity (W / m / K), A yindawo, i-TH yiqondo lokushisa lomthombo wobushushu, i-TC yiqondo lokushisa lomthombo obandayo, kwaye L ngumgama phakathi komthombo wobushushu kunye umthombo obandayo.