Pamene ma frequency apamwamba / mawayilesi a mawayilesi a microwave amadyetsedwa mu PCB dera, kutayika komwe kumachitika chifukwa cha dera lokha komanso zinthu zozungulira zidzatulutsa kutentha kwina. Kutayika kwakukulu, kumapangitsanso mphamvu yodutsa muzinthu za PCB, komanso kutentha kwakukulu komwe kumapangidwa. Pamene kutentha kwa ntchito ya dera kumaposa mtengo wovotera, dera lingayambitse mavuto. Mwachitsanzo, mmene ntchito chizindikiro MOT, amene amadziwika PCBs, ndi pazipita ntchito kutentha. Pamene kutentha ntchito kuposa MOT, ntchito ndi kudalirika kwa dera PCB adzakhala pangozi. Kupyolera mu kuphatikizika kwa ma electromagnetic modelling ndi kuyeza koyesera, kumvetsetsa mawonekedwe amafuta a RF microwave PCBs kungathandize kupewa kuwonongeka kwa magwiridwe antchito komanso kudalirika komwe kumachitika chifukwa cha kutentha kwambiri.

Kumvetsetsa momwe kutayika kwa kuyika kumachitika m’magawo ozungulira kumathandiza kufotokozera bwino zinthu zofunika zokhudzana ndi kutentha kwa ma frequency apamwamba a PCB. Nkhaniyi idzatenga gawo la microstrip transmission line circuit monga chitsanzo kuti tikambirane za malonda okhudzana ndi kutentha kwa dera. M’dera la microstrip lomwe lili ndi mbali ziwiri za PCB, zotayika zimaphatikizapo kutayika kwa dielectric, kutayika kwa conductor, kutayika kwa ma radiation, ndi kutaya kutayikira. Kusiyana pakati pa zigawo zosiyana zotayika ndi zazikulu. Kupatulapo pang’ono, kutayikira kwa ma frequency apamwamba a PCB nthawi zambiri kumakhala kotsika kwambiri. M’nkhaniyi, popeza mtengo wotayika wotayika ndi wotsika kwambiri, udzanyalanyazidwa panthawiyi.

Kutaya kwa radiation

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.

Magawo azinthu zamagawo okhudzana ndi kutayika kwa ma radiation nthawi zambiri amakhala dielectric osasintha komanso makulidwe azinthu za PCB. Kukhuthala kwa gawo lapansi, kumapangitsanso mwayi wopangitsa kuti ma radiation awonongeke; kutsika kwa εr kwa zinthu za PCB, kumapangitsa kuti ma radiation awonongeke kwambiri. Kuyeza mozama zakuthupi, kugwiritsa ntchito magawo ocheperako atha kugwiritsidwa ntchito ngati njira yothanirana ndi kutayika kwa ma radiation komwe kumayambitsidwa ndi zida zotsika za εr. Mphamvu ya makulidwe a gawo lapansi ndi εr pakutayika kwa ma radiation ndi chifukwa ndi ntchito yodalira pafupipafupi. Pamene makulidwe a gawo lapansi lozungulira sadutsa 20mil ndipo ma frequency ogwiritsira ntchito ndi otsika kuposa 20GHz, kutayika kwa ma radiation kumachepa kwambiri. Popeza kuti ma frequency ambiri oyendera mayendedwe ndi kuyeza m’nkhaniyi ndi otsika kuposa 20GHz, zokambirana zomwe zili m’nkhaniyi sizinyalanyaza chikoka cha kutayika kwa ma radiation pa kutentha kwa dera.

Pambuyo ponyalanyaza kutayika kwa ma radiation pansi pa 20GHz, kutayika kwa kuyika kwa microstrip transmission line circuit makamaka kumaphatikizapo magawo awiri: dielectric loss and conductor loss. Gawo la ziwirizi makamaka zimadalira makulidwe a gawo lapansi. Kwa magawo ocheperako, kutayika kwa conductor ndiye gawo lalikulu. Pazifukwa zambiri, nthawi zambiri zimakhala zovuta kulosera molondola kutayika kwa conductor. Mwachitsanzo, kuuma kwa kondakitala kumakhudza kwambiri mawonekedwe a mafunde a electromagnetic mafunde. Kukula kwapamtunda kwa zojambula zamkuwa sikungosintha kufalikira kwa ma electromagnetic wave pagawo la microstrip, komanso kumawonjezera kutayika kwa kondakitala kwa dera. Chifukwa cha zotsatira za khungu, chikoka cha zojambulazo zamkuwa pakutayika kwa conductor kumadaliranso pafupipafupi. Chithunzi 1 chikufanizira kutayika kwa ma 50 ohm microstrip transmission line circuits kutengera makulidwe osiyanasiyana a PCB, omwe ndi 6.6 mils ndi 10 mils, motsatana.

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.

Pofuna kuthetsa vuto la kutentha kwa dera, dera lochepetsetsa loyenera liyenera kukhala ndi makhalidwe awa: kutayika kochepa kwa zinthu zozungulira, mkuwa wosalala wonyezimira, otsika εr ndi matenthedwe apamwamba. Poyerekeza ndi zinthu zadera za mkulu εr, kondakitala m’lifupi wa impedance yemweyo wopezedwa pansi chikhalidwe otsika εr akhoza kukhala lalikulu, amene n’kopindulitsa kuchepetsa wochititsa imfa ya dera. Kuchokera pamalingaliro a kutentha kwa dera, ngakhale kuti zigawo zambiri za PCB zapafupipafupi zimakhala ndi matenthedwe otsika kwambiri okhudzana ndi ma conductor, matenthedwe azinthu zamagetsi akadali chinthu chofunikira kwambiri.

Zokambirana zambiri zokhuza kutentha kwa magawo ozungulira zidafotokozedwa m’nkhani zam’mbuyomu, ndipo nkhaniyi ifotokoza zotsatira ndi zidziwitso kuchokera m’nkhani zam’mbuyomu. Mwachitsanzo, equation yotsatirayi ndi Chithunzi 3 ndizothandiza kumvetsetsa zinthu zokhudzana ndi kutentha kwa zipangizo zamagetsi za PCB. Mu equation, k ndi kutentha kwa matenthedwe (W / m / K), A ndi malo, TH ndi kutentha kwa gwero la kutentha, TC ndi kutentha kwa gwero lozizira, ndi L ndi mtunda pakati pa gwero la kutentha ndi gwero lozizira.