Uma isignali yefrikhwensi ephezulu/microwave radio frequency ifakwa ku PCB isifunda, ukulahlekelwa okubangelwa i-circuit ngokwayo kanye ne-circuit material nakanjani kuzokhiqiza inani elithile lokushisa. Ukulahlekelwa okukhulu, amandla adlula ezintweni ze-PCB aphezulu, kanye nokushisa okukhiqizwa kakhulu. Lapho izinga lokushisa lokusebenza lesifunda lidlula inani elilinganiselwe, isifunda singabangela izinkinga ezithile. Isibonelo, ipharamitha yokusebenza ejwayelekile ye-MOT, eyaziwa kakhulu kuma-PCB, izinga lokushisa eliphakeme lokusebenza. Uma izinga lokushisa lokusebenza lidlula i-MOT, ukusebenza nokuthembeka kwesekethe ye-PCB kuzosongelwa. Ngenhlanganisela yemodeli kazibuthe kagesi kanye nezilinganiso zokuhlola, ukuqonda izici ezishisayo zama-RF microwave PCB kungasiza ukugwema ukuwohloka kokusebenza kwesekethe kanye nokuwohloka kokwethembeka okubangelwa amazinga okushisa aphezulu.

Ukuqonda ukuthi kwenzeka kanjani ukulahlekelwa kokufaka ezintweni zesekethe kusiza ukuchaza kangcono izici ezibalulekile ezihlobene nokusebenza okushisayo kwamasekhethi e-PCB anemvamisa ephezulu. Lesi sihloko sizothatha isekethe yomugqa wokudlulisa we-microstrip njengesibonelo sokuxoxa ngokuhwebelana okuhlobene nokusebenza okushisayo kwesekhethi. Kumjikelezo we-microstrip onesakhiwo se-PCB esinezinhlangothi ezimbili, ukulahlekelwa kufaka phakathi ukulahlekelwa kwe-dielectric, ukulahlekelwa kwe-conductor, ukulahlekelwa kwemisebe, nokulahlekelwa kokuvuza. Umehluko phakathi kwezingxenye ezihlukene zokulahlekelwa mkhulu. Ngaphandle kokumbalwa, ukulahleka kokuvuza kwamasekhethi e-PCB anemvamisa ephezulu ngokuvamile kuphansi kakhulu. Kulesi sihloko, njengoba inani lokulahlekelwa kokuvuza liphansi kakhulu, lizozitshwa okwamanje.

Ukulahleka kwemisebe

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.

Imingcele yezinto zesekethe ezihlobene nokulahlekelwa kwemisebe ngokuyinhloko i-dielectric constant kanye nogqinsi lwempahla ye-PCB. Ukuqina kwe-substrate yesifunda, amathuba amakhulu okubangela ukulahleka kwemisebe; lapho i-εr yezinto ze-PCB ephansi, ukulahleka okukhulu kwemisebe yesekethe. Ukulinganisa izici ezibonakalayo, ukusetshenziswa kwama-substrate wesifunda esincane kungasetshenziswa njengendlela yokuqeda ukulahlekelwa kwemisebe okubangelwa izinto eziphansi zesekethe ze-εr. Umthelela wokujiya kwe-substrate yesekethe kanye no-εr ekulahlekeni kwemisebe yesekethe kungenxa yokuthi kuwumsebenzi oncike emazingeni. Uma ubukhulu be-substrate yesifunda bungadluli ku-20mil futhi imvamisa yokusebenza ingaphansi kuka-20GHz, ukulahlekelwa kwemisebe yesekethe kuphansi kakhulu. Njengoba iningi lamamodeli wesekethe namaza okulinganisa kulesi sihloko angaphansi kuka-20GHz, ingxoxo kulesi sihloko izoziba umthelela wokulahleka kwemisebe ekushisiseni kwesekethe.

Ngemva kokuziba ukulahlekelwa kwemisebe engaphansi kuka-20GHz, ukulahlekelwa kokufaka kwesekethe yomugqa wokudlulisa we-microstrip ikakhulukazi kufaka izingxenye ezimbili: ukulahlekelwa kwe-dielectric nokulahlekelwa kwe-conductor. Ingxenye yalokhu okubili ngokuyinhloko incike ebukhulu be-substrate yesifunda. Kuma-substrates azacile, ukulahleka kwe-conductor kuyisici esiyinhloko. Ngenxa yezizathu eziningi, ngokuvamile kunzima ukubikezela ngokunembile ukulahleka komqhubi. Isibonelo, ubulukhuni obungaphezulu be-conductor bunomthelela omkhulu ezicini zokudlulisela zamagagasi kagesi. Ubukhulu obungaphezulu be-foil yethusi ngeke buguqule nje kuphela i-electromagnetic wave propagation constant yesekethe ye-microstrip, kodwa futhi kwandise ukulahleka komqhubi wesekethe. Ngenxa yomphumela wesikhumba, umthelela we-foil yethusi ekulahlekeni kwe-conductor nakho kuncike emazingeni. Umfanekiso 1 uqhathanisa ukulahleka kokufakwa kwamasekethe olayini wokudlulisa we-microstrip angu-50 ohm ngokusekelwe kogqinsi obuhlukene be-PCB, okuyi-6.6 mils kanye ne-10 mils, ngokulandelana.

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 uxazulule inkinga yokushisa yesifunda, isifunda esincane esifanelekile kufanele sibe nezici ezilandelayo: isici esiphansi sokulahlekelwa kwezinto zesifunda, ithusi elibushelelezi elibushelelezi eliphansi, i-εr ephansi kanye ne-conductivity ephezulu yokushisa. Uma kuqhathaniswa nempahla yesifunda ye-high εr, ububanzi bomqhubi we-impedance efanayo etholakala ngaphansi kwesimo se-εr ephansi ingaba mkhulu, okuzuzisa ukunciphisa ukulahlekelwa komqhubi wesifunda. Ngokombono wokuchithwa kokushisa kwesifunda, nakuba ama-substrates amaningi e-PCB aphakeme kakhulu ane-conductivity ephansi kakhulu ye-thermal ehlobene nama-conductor, ukuqhutshwa kokushisa kwezinto zokujikeleza kuseyipharamitha ebaluleke kakhulu.

Izingxoxo eziningi mayelana ne-thermal conductivity ye-circuit substrates ziye zachazwa ezihlokweni zangaphambili, futhi lesi sihloko sizocaphuna eminye imiphumela nolwazi oluvela ezihlokweni zangaphambili. Isibonelo, i-equation elandelayo kanye nomfanekiso wesi-3 kuyasiza ukuqonda izici ezihlobene nokusebenza okushisayo kwezinto zokujikeleza ze-PCB. Esilinganisweni, k i-thermal conductivity (W/m/K), A indawo, TH izinga lokushisa lomthombo wokushisa, i-TC izinga lokushisa lomthombo obandayo, futhi L ibanga phakathi komthombo wokushisa kanye umthombo obandayo.