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

Radiation loss depends on many circuit parameters such as operating frequency, circuit substrate thickness, PCB dielectric constant (relative dielectric constant or εr) and design plan. As far as design schemes are concerned, radiation loss often stems from poor impedance transformation in the circuit or electromagnetic waves in the circuit. The difference in transmission. Circuit impedance transformation area usually includes signal feed-in area, step impedance point, stub and matching network. Reasonable circuit design can realize smooth impedance transformation, thereby reducing the radiation loss of the circuit. Of course, it should be realized that there is the possibility of impedance mismatch leading to radiation loss at any interface of the circuit. From the point of view of operating frequency, usually the higher the frequency, the greater the radiation loss of the circuit.

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.

Emva kokungahoywa kwelahleko yemitha engaphantsi kwe-20GHz, ukulahleka kokufakwa kwesekethe yokuhambisa i-microstrip kubandakanya iinxalenye ezimbini: ukulahleka kwe-dielectric kunye nokulahleka komqhubi. Umlinganiselo wezo zimbini ubukhulu becala kuxhomekeke kubukhulu be-substrate yesiphaluka. Kwii-substrates ezincinci, ilahleko ye-conductor iyona nxalenye ephambili. Ngezizathu ezininzi, ngokuqhelekileyo kunzima ukuqikelela ngokuchanekileyo ukulahleka komqhubi. Umzekelo, uburhabaxa bomphezulu bomqhubi unempembelelo enkulu kwiimpawu zothumelo zamaza ombane. Uburhabaxa bomphezulu befoyile yobhedu abuyi kutshintsha kuphela i-electromagnetic wave propagation constant yesekethe ye-microstrip, kodwa ikwanyuse ilahleko yomqhubi wesekethe. Ngenxa yempembelelo yolusu, impembelelo yefoyile yobhedu ekulahlekeni komqhubi nayo ixhomekeke rhoqo. Umzobo we-1 uthelekisa ukulahleka kokufakwa kweesekethe ze-50 ohm microstrip transmission line based on different PCB thicknesses, eziyi-6.6 mils kunye ne-10 mils, ngokulandelanayo.

The simulation results are obtained using Rogers Corporation’s MWI-2010 microwave impedance calculation software. The MWI-2010 software quotes the analytical equations in the classic papers in the field of microstrip line modeling. The test data in Figure 1 is obtained by the differential length measurement method of a vector network analyzer. It can be seen from Fig. 1 that the simulation results of the total loss curve are basically consistent with the measured results. It can be seen from the figure that the conductor loss of the thinner circuit (the curve on the left corresponds to a thickness of 6.6 mil) is the main component of the total insertion loss. As the circuit thickness increases (the thickness corresponding to the curve on the right is 10mil), the dielectric loss and the conductor loss tend to approach, and the two together constitute the total insertion loss.

The circuit material parameters used in the simulation model and the actual circuit are: dielectric constant 3.66, loss factor 0.0037, and copper conductor surface roughness 2.8 um RMS. When the surface roughness of the copper foil under the same circuit material is reduced, the conductor loss of the 6.6 mil and 10 mil circuits in Figure 1 will be significantly reduced; however, the effect is not obvious for the 20 mil circuit. Figure 2 shows the test results of two circuit materials with different roughness, namely Rogers RO4350B™ standard circuit material with high roughness and Rogers RO4350B LoPro™ circuit material with low roughness.

For thinner substrates, the use of smooth copper foil can significantly reduce the insertion loss. For the 6.6mil substrate, the insertion loss is reduced by 0.3 dB due to the use of smooth copper foil at 20GHz; the 10mil substrate is reduced by 0.22 dB at 20GHz; and the 20mil substrate, the insertion loss is only reduced by 0.11 dB.

This means that when the circuit is fed with a certain amount of RF microwave power, the thinner the circuit will generate more heat. When comprehensively weighing the issue of circuit heating, on the one hand, a thinner circuit generates more heat than a thick circuit at high power levels, but on the other hand, a thinner circuit can obtain more effective heat flow through the heat sink. Keep the temperature relatively low.

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.