Amacala amaningi wokufaka isicelo wemikhiqizo yezimboni, yesayensi, kanye neyezokwelapha (ISM-RF) akhombisa ukuthi ibhodi yesifunda ephrintiwe ukwakheka kwale mikhiqizo kuthanda ukukhubazeka okuhlukahlukene.Abantu bavame ukuthola ukuthi i-IC efanayo ifakiwe kumabhodi wesekethe ahlukene, izinkomba zokusebenza zizohluka kakhulu. Ukwehluka kwezimo zokusebenza, imisebe ye-harmonic, ikhono lokulwa nokuphazamiseka, nesikhathi sokuqala kungachaza ukubaluleka kokuhlelwa kwebhodi lesifunda kumklamo ophumelelayo.

Lo mbhalo ubala ukushiywa okuhlukahlukene kokuklama, uxoxa ngezimbangela zokwehluleka ngakunye, futhi unikeze neziphakamiso zokuthi ungakugwema kanjani lokhu kungaphumeleli kokuklanywa. Kuleli phepha, fr-4 dielectric, 0.0625in ukujiya ungqimba oluphindwe kabili i-PCB njengesibonelo, isisekelo sebhodi lesifunda. Isebenza kumabhendi ehlukene wemvamisa phakathi kuka-315MHz no-915MHz, amandla we-Tx ne-Rx phakathi kuka -120dbm no + 13dBm.

Inductance isiqondiso

Lapho ama-inductors amabili (noma imigqa emibili ye-PCB) eseduze komunye nomunye, ukungenelela kokunye kuzokwenzeka. Amandla kazibuthe akhiqizwe njengamanje kumjikelezo wokuqala ajabulisa amanje kusekethe yesibili (Umdwebo 1). Le nqubo ifana nokuxhumana phakathi kwamakhoyili aphambili nawesibili we-transformer. Lapho imisinga emibili ihlangana ngamandla kazibuthe, amandla kagesi akhiqizwa anqunywa ngokungenisa ngaphakathi i-LM:

Lapho, i-YB amandla wephutha afakwe kusifunda B, i-IA yi-1 yamanje esebenza kusekethe A. I-LM izwela kakhulu ekuhlukaneni kwesifunda, indawo ye-inductance loop (isb., Magnetic flux), kanye ne-loop direction. Ngakho-ke, ibhalansi enhle kunazo zonke phakathi kokuhlelwa kwesekethe okuhlanganisiwe nokuhlanganiswa okuncishisiwe ukuqondanisa okulungile kwabo bonke abasebenza ngaphakathi.

ISITHOMBE. 1. Kungabonakala kumigqa yamagnetic field ukuthi i-inductance yomunye nomunye ihlobene nokuqondiswa kokuqondiswa kwe-inductance

Ukuqondiswa kwesifunda B kulungiswa ukuze iluphu yayo yamanje ifane nolayini kazibuthe wesekethe A. Ngale njongo, njengokuqondakalayo ngangokunokwenzeka komunye nomunye, sicela ubheke ukwakheka kwesifunda kwebhodi yamandla ephansi ye-FSK superheterodyne Receiver Evaluation (EV) (MAX7042EVKIT) (Umdwebo 2). Abangenisi abathathu ebhodini (i-L3, i-L1 ne-L2) basondelene kakhulu, futhi ukuma kwabo ku-0 °, 45 ° no-90 ° kusiza ukunciphisa ukungahambisani.

Umdwebo 2. Izakhiwo ezimbili ezihlukene ze-PCB zikhonjisiwe, enye yazo enezakhi ezihlelwe ngendlela engafanele (i-L1 ne-L3), kanti enye ifaneleka kakhulu.

Ukufingqa, kufanele kulandelwe imigomo elandelayo:

Isikhala se-inductance kufanele sibe ngangokunokwenzeka.

Ama-inductors ahlelwe ngama-engeli afanele ukunciphisa i-crosstalk phakathi kwabangenisi.

Hola ukuhlangana

Njengoba ukuma kwe-inductors kuthinta ukuhlangana kukazibuthe, kanjalo nokuhlangana uma imikhondo isondelene kakhulu. Lolu hlobo lwenkinga yokuhleleka luphinde lukhiqize lokho okubizwa ngokuthi ukujwayelana. Enye yezinkinga ezikhathaza kakhulu isekethe le-RF wiring yezingxenye ezizwelayo zohlelo, njenge-network efanayo yokufaka, isiteshi se-resonant sesamukeli, inethiwekhi efanayo ye-antenna yesidlulisi, njll.

Indlela yamanje yokubuyisa kufanele isondele kakhulu endleleni yamanje yamanje ukunciphisa amandla kazibuthe wemisebe. Leli lungiselelo lisiza ukunciphisa indawo yamanje yeluphu. Indlela ekahle yokumelana nesikhathi samanje sokubuya imvamisa isifunda esingaphansi komthofu – sinciphisa ngempumelelo indawo yeluphu esifundeni lapho ubukhulu be-dielectric bandiswa ngobude bokuhola. Kodwa-ke, uma indawo yomhlabathi ihlukanisiwe, indawo yeluphu iyanda (Umdwebo 3). Ngemikhombandlela edlula esifundeni esihlukanisiwe, i-current Return izophoqeleka ngomgwaqo omkhulu wokumelana, ikhulise kakhulu indawo yamanje yeluphu. Leli lungiselelo liphinde lenze ukuhola kwesekethe kube sethubeni lokuthinteka kokunye.

Umfanekiso 3. Ukuqedela indawo enkulu kusiza ukuthuthukisa ukusebenza kohlelo

Ukuze uthole i-inductor yangempela, ukuqondiswa kokuhola nakho kunomthelela omkhulu ekuhlanganisweni kwensimu kazibuthe. Uma ukuhola kwesekethe elizwelayo kufanele kusondelane, kungcono ukuqondanisa izinkomba zibheke phezulu ukunciphisa ukuhlangana (Umdwebo 4). Uma ukuqondanisa okumile kungenzeki, cabanga ukusebenzisa ulayini wokuqapha. Ngokuklanywa kwentambo yokuvikela, sicela ubheke isigaba sokwelashwa nokugcwalisa ngezansi.

Umdwebo 4. Ngokufana noMdwebo 1, kukhombisa ukuhlangana okungenzeka kwemigqa yamagnetic field.

Ukufingqa, lezi zimiso ezilandelayo kufanele zilandelwe lapho kusatshalaliswa ipuleti:

Ukuqedwa ngokuphelele kufanele kuqinisekiswe ngaphansi kokuhola.

Ukuhola okubucayi kufanele kuhlelwe kubheke phezulu.

Uma umkhondo kufanele uhlelwe ngokufana, qiniseka ukuthi kunesikhala esanele noma usebenzise izintambo zonogada.

Ukwenza isisekelo nge

Inkinga enkulu ngokuhlelwa kwesekethe ye-RF imvamisa ukungabi namandla kwesici sesifunda, kufaka phakathi izinto zesekethe nokuxhuma kwazo. Ukuhola okunengubo yethusi elincanyana kulingana nentambo ye-inductance futhi kwakha amandla asatshalaliswa neminye imikhondo eseduze. Ukuhola kubuye kuveze nezimpawu zokuthwebula kanye nezamandla njengoba kudlula emgodini.

I-through-hole capacitance ikakhulu ivela ekuthini capacitance eyakhiwe phakathi kokumbozwa kwethusi ohlangothini lwe-pad-hole pad kanye ne-cladding yethusi phansi, ehlukaniswe yiringi encane impela. Elinye ithonya livela kwisilinda se-perforation yensimbi uqobo. Umphumela we-capacitance ye-parasitic uvame ukuba mncane futhi imvamisa kubangela ukwehluka konqenqema kwizimpawu zedijithali ezinejubane eliphezulu (okungakhulunywa ngalo kuleli phepha).

Umphumela omkhulu we-hole-hole yi-inductance yesinambuzane ebangelwa yimodi yokuxhuma ehambisanayo. Ngoba ukwenziwa kwensimbi okuningi emiklamweni ye-RF PCB kusayizi ofanayo wezinto ezikhanyisiwe, umphumela wamapayipi kagesi angalinganiselwa kusetshenziswa ifomula elula (ISITHOMBE 5):

Lapho, i-LVIA ifakwa ngaphakathi ngembobo; H ukuphakama kwe -holehole, ngamasentimitha; D ububanzi be-throughhole, ngamasentimitha 2.

Ungakugwema kanjani ukukhubazeka okuhlukahlukene kusakhiwo se-PCB samabhodi aphrintiwe

ISITHOMBE. 5. Isigaba esiphambanweni se-PCB esisetshenziselwa ukulinganisa imiphumela yezinambuzane ezakhiweni eziyimbobo

I-inductance ye-parasitic ivame ukuba nomthelela omkhulu ekuxhumekeni kwama-capacitors okudlula. Ama-capacitors wokudlula afanele anikezela ngemijikelezo emifushane ephezulu kakhulu phakathi kwendawo yokuhlinzeka nokwakheka, kepha izimbobo ezingezona ezikahle ezingathinta indlela yokuzwela okuphansi phakathi kokwakheka nendawo yokunikezela. I-PCB ejwayelekile ngembobo (d = 10 mil, h = 62.5 mil) icishe ilingane ne-1.34nH inductor. Njengoba kunikezwe imvamisa yokusebenza ethile yomkhiqizo we-ISM-RF, izimbobo ezihamba phakathi kwazo zingathinta kabi amasekethe abucayi njengamasekhethi wesiteshi anama-resonant, izihlungi namanethiwekhi afanayo.

Ezinye izinkinga zivela uma amasekethe abucayi abelana ngezimbobo, njengezingalo ezimbili zenethiwekhi yohlobo lwe-π. Isibonelo, ngokubeka imbobo ekahle elingana ne-lumped inductance, uhlelo olulinganayo luhluke kakhulu kumklamo wesekethe wokuqala (ISITHOMBE. 6). Njengakwi-crosstalk yendlela ejwayelekile yamanje 3, okuholela ekwandeni kokunciphisana kokubambisana, ukwanda kwe-crosstalk nokuphakelayo.

Ungazivikela kanjani izinkinga zokuklanywa kwe-PCB

Umdwebo 6. I-Ideal vs. izakhiwo ezingafanelekile, kukhona “izindlela zesiginali” ezingaba khona esifundeni.

Ukufingqa, ukwakheka kwesifunda kufanele kulandele lezi zimiso ezilandelayo:

Ensure modeling of through-hole inductance in sensitive areas.

Isihlungi noma inethiwekhi efanayo isebenzisa izimbobo ezizimele.

Note that a thinner PCB copper-clad will reduce the effect of parasitic inductance through the hole.

Ubude bokuhola

Idatha yomkhiqizo weMaxim ISM-RF ivame ukuncoma ukusebenzisa okokufaka okufushane kakhulu okuvama kakhulu nokukhipha kuholela ekunciphiseni ukulahleka nemisebe. Ngakolunye uhlangothi, ukulahleka okunjalo kuvame ukubangelwa yimingcele yezinambuzane engeyona ekahle, ngakho-ke kokubili ukufakwa kwesidlakudla namandla okuthinta ukwakheka kwesifunda, futhi ukusebenzisa ukuhola okufushane kakhulu kusiza ukunciphisa imingcele yezinambuzane. Imvamisa, i-10 mil ebanzi ye-PCB ehola ngebanga le-0.0625in… ​​Kusuka ebhodini le-FR4 kuveza ukungeniswa cishe kwe-19nH / in kanye ne-capacitance esatshalalisiwe ecishe ibe yi-1pF / in. Okwesekethe ye-LAN / mixer ene-inductor engu-20nH kanye ne-3pF capacitor, inani lengxenye elisebenzayo lizothinteka kakhulu lapho ukwakheka kwesifunda nokwakheka kwezinto kuhlangana kakhulu.

I-Ipc-d-317a4 ku-‘Institute for Printed Circuits ‘inikeza i-equation ejwayelekile embonini yokulinganisa imingcele ehlukahlukene ye-impedance ye-microstrip PCB. Lo mbhalo washintshwa ngo-2003 yi-IPC-2251 5, enikeza indlela yokubala enembe kakhudlwana yemikhombandlela eyahlukahlukene ye-PCB. Ama-calculator akwi-inthanethi ayatholakala emithonjeni ehlukahlukene, iningi lawo lincike kwizibalo ezinikezwe yi-IPC-2251. I-Electromagnetic Compatibility Lab eMissouri Institute of Technology inikeza indlela esebenzayo yokubala i-PCB lead impedance 6.

Izindlela ezamukelekayo zokubala impedance yolayini be-microstrip yilezi:

Kwifomula, i-εr ingukuguquguquka kwe-dielectric okungaguquki, h ukuphakama komthofu kusuka ku-stratum, W ububanzi bokuhola, kanti i-T ubukhulu bomthofu (ISITHOMBE 7). Lapho i-w / h iphakathi kuka-0.1 no-2.0 no-εr iphakathi kuka-1 no-15, imiphumela yokubalwa kwale fomula inembile impela.

Umdwebo 7. Lesi sibalo isigaba se-PCB esiphambanweni (esifana noMdwebo 5) futhi simele isakhiwo esisetshenziselwe ukubala i-impedance yomugqa we-microstrip.

Ukuze uhlole umphumela wobude bokuhola, kusebenza kakhulu ukuthola umphumela wokunqanda wesifunda esifanele ngamapharamitha wokuhola. Kulesi sibonelo, sixoxa ngokuduka kwamandla nokuzikhandla. I-equation ejwayelekile ye-capacitance yesici yolayini be-microstrip yile:

Ngokufanayo, ukungeniswa kwesici kungabalwa kusuka ku-equation ngokusebenzisa i-equation engenhla:

Isibonelo, cabanga ukushuba kwe-PCB engu-0.0625in. (h = 62.5 mil), i-ounce eholini elilodwa elenziwe ngethusi (t = 1 mil), 1.35in. (w = 0.01 mil), nebhodi le-FR-10. Qaphela ukuthi i-ε R ka-FR-4 imvamisa ingu-4.35 farad / m (F / m), kepha ingaba phakathi kuka-4.0F / m iye ku-4.7F / m. Ama-eigenvalue abalwe kulesi sibonelo angama-Z0 = 134 ω, C0 = 1.04pF / in, L0 = 18.7nH / in.

Ngokuklanywa kwe-AN ISM-RF, ubude besakhiwo semidwebo engu-12.7mm (0.5in) ebhodini bungakhiqiza amapharamitha angama-0.5pF no-9.3nH (Umfanekiso 8). Umphumela wamapharamitha we-parasitic kuleli zinga esiteshini se-resonant somamukeli (ukwahluka komkhiqizo we-LC) kungahle kuholele ekushintsheni kwe-315MHz ± 2% noma 433.92mhz ± 3.5%. Ngenxa ye-capacitance eyengeziwe kanye ne-inductance ebangelwe ngumphumela wesinambuzane sokuhola, ukuphakama kwemvamisa ye-oscillation ye-315MHz kufinyelela ku-312.17mhz, futhi ukuphakama kwemvamisa ye-oscillation ye-433.92mhz kufinyelela ku-426.6mhz.

Esinye isibonelo ishaneli enesigqi sesamukeli seMaxim’s superheterodyne (MAX7042). Izinto ezinconyiwe yi-1.2pF ne-30nH ku-315MHz; At 433.92MHz, it is 0pF and 16nH. Bala imvamisa ye-oscillation yesekethe eguquguqukayo ngokusebenzisa isibalo:

Ukuhlolwa kwesekethe elizwakalayo lepuleti kufanele kufake phakathi imiphumela yezinambuzane zephakeji nokuhleleka, nemingcele yezinambuzane ingu-7.3PF no-7.5PF ngokulandelana lapho kubalwa imvamisa ye-resonant engu-315MHz. Qaphela ukuthi umkhiqizo we-LC umele amandla we-lumped.

Ukufingqa, le migomo elandelayo kufanele ilandelwe:

Gcina ukuhola kufushane ngangokunokwenzeka.

Beka amasekethe ayisihluthulelo asondele edivayisini ngangokunokwenzeka.

Izakhi ezisemqoka zinxeshezelwa ngokuya ngokwezibalo zangempela zesakhiwo.

Ukwelashwa okuyisisekelo nokugcwalisa

Isisekelo noma isendlalelo samandla sichaza i-voltage evamile yesethenjwa enikezela amandla kuzo zonke izingxenye zohlelo ngendlela ephansi yokumelana. Ukulinganisa zonke izinkambu zikagesi ngale ndlela kukhiqiza indlela enhle yokuvikela.

I-Direct yamanje ivame ukugeleza ngendlela ephansi yokumelana. Ngendlela efanayo, imvamisa ephezulu yamanje ikhetha ukugeleza ngendlela enokumelana okuphansi kakhulu. Ngakho-ke, ngentambo ejwayelekile ye-PCB microstrip ngenhla kokwakheka, okwamanje okubuyayo kuzama ukugeleza kungene esifundeni somhlaba ngqo ngaphansi komholi. As described in the lead coupling section above, the cut ground area introduces various noises that increase crosstalk either through magnetic field coupling or by converging currents (Figure 9).

Ungakugwema kanjani ukukhubazeka okuhlukahlukene kusakhiwo se-PCB samabhodi aphrintiwe

ISITHOMBE. 9. Gcina ukwakheka kuqinile ngangokunokwenzeka, ngaphandle kwalokho i-current Return izobangela i-crosstalk.

Umhlabathi ogcwalisiwe, owaziwa nangokuthi imigqa yokuqapha, uvame ukusetshenziswa kumasekethe lapho kunzima khona ukubeka phansi okuqhubekayo noma lapho kudingeka khona ukuvikela amasekethe abucayi (ISITHOMBE. 10). Umphumela wokuvikela ungakhuphuka ngokubeka izimbobo zokubeka phansi (okungukuthi ukuhleleka kwemigodi) kuzo zombili izinhlangothi zokuhola noma phambili. 8. Ungahlanganisi ucingo lokuqapha nomthofu owenzelwe ukunikeza indlela yamanje yokubuyela. Leli lungiselelo lingaletha i-crosstalk.

Ungakugwema kanjani ukukhubazeka okuhlukahlukene kusakhiwo se-PCB samabhodi aphrintiwe

ISITHOMBE. 10. Umklamo wohlelo lwe-RF kufanele ugweme izintambo ezigqokiwe zethusi ezintantayo, ikakhulukazi uma kudingeka ukugudluza ithusi.

Indawo egqokiwe ngethusi ayibekiwe phansi (intanta) noma ibekelwe eceleni kuphela, evimbela ukusebenza kwayo kahle. Kwezinye izimo, kungadala imiphumela engadingeki ngokwakha amandla wezinambuzane aguqula impedance yezintambo ezizungezile noma idale indlela “efihlekile” phakathi kwamasekethe. Ngamafuphi, uma ucezu lwentambo yethusi (i-wiring yesiginali engeyona yesekethe) lubekwa ebhodini lesifunda ukuqinisekisa ukujiya okungaguquguquki. Izindawo ezigqoke zethusi kufanele zigwenywe ngoba zithinta ukwakheka kwesifunda.

Ekugcineni, qiniseka ukuthi ucabanga ngemiphumela yanoma iyiphi indawo esemhlabathini eseduze ne-antenna. Noma yiluphi uthi lwe-monopole luzoba nesifunda esingaphansi, izintambo nezimbobo njengengxenye yohlelo lokulingana, futhi izintambo zokulinganisa ezingezona ezikahle zizothinta ukusebenza kahle kwemisebe kanye nokuqondiswa kwe-antenna (i-radiation template). Ngakho-ke, indawo engaphansi akufanele ibekwe ngqo ngaphansi kwe-monopole PCB lead antenna.

Ukufingqa, kufanele kulandelwe imigomo elandelayo:

Nikeza izindawo eziqhubekayo zokumelana nokuphansi ngangokunokwenzeka.

Zombili iziphetho zomugqa wokugcwalisa zisuselwe phansi, futhi kusetshenziswa i-hole-hole array ngangokunokwenzeka.

Musa ukuntanta izintambo ezigqokiwe zethusi eduze kwesifunda se-RF, ungabeki ithusi ezungeze isifunda se-RF.

Uma ibhodi lesifunda liqukethe izingqimba eziningi, kungcono ukubeka umhlabathi ngomgodi lapho ikhebula lesiginali lidlula lisuka kolunye uhlangothi luye kolunye.

Ukweqisa kwe-crystal capacitance

Amandla we-parasitic azobangela ukuthi imvamisa ye-crystal iphambuke kunani elihlosiwe 9. Ngakho-ke, eminye imihlahlandlela ejwayelekile kufanele ilandelwe ukunciphisa amandla wokuphambuka kwezikhonkwane ze-crystal, amapayipi, izintambo, noma ukuxhumana kumadivayisi we-RF.

Izimiso ezilandelayo kufanele zilandelwe:

Ukuxhumana phakathi kwekristalu ne-RF kufanele kube kufushane ngangokunokwenzeka.

Gcina izintambo zomunye nomunye ngangokunokwenzeka.

Uma i-shunt parasitic capacitance inkulu kakhulu, susa isizinda sokumisa ngaphansi kwekristalu.

Ukuhlelwa kwentambo kwe-Planar

Izintambo zeplanethi noma i-PCB spiral inductors azinconyiwe. Izinqubo zokukhiqiza ezijwayelekile ze-PCB zinokungalungi okuthile okuthile, njengokubekezelelana kwesikhala nobubanzi, okuthinta kakhulu ukunemba kwamanani ento ethile. Ngakho-ke, inductors elawulwa kakhulu futhi ephezulu ye-Q uhlobo lwenxeba. Okwesibili, ungakhetha i-multilayer ceramic inductor, abakhiqizi be-multilayer chip capacitor nabo banikela ngalo mkhiqizo. Noma kunjalo, abanye abaklami bakhetha abafaka umoya lapho kufanele. Ifomula ejwayelekile yokubala i-planar spiral inductance imvamisa ifomula le-Wheeler 10:

Lapho, i-radius ejwayelekile yekhoyili, ngamasentimitha; N yinombolo yokujika; C ububanzi be-coil core (i-router-rinner), ngamasentimitha. Lapho ikhoyili c “0.2a 11, ukunemba kwendlela yokubala kungaphakathi kuka-5%.

Kungasetshenziswa ama-inductors ongqimba olulodwa wesikwele, i-hexagonal, noma obunye ubujamo. Ukulinganisa okuhle kakhulu kungatholakala ukumodela i-planar inductance kuma-wafers wesekethe ahlanganisiwe. Ukuze kuzuzwe le njongo, ifomula ejwayelekile ye Wheeler iyashintshwa ukuthola indlela yokulinganisa inductance efanelekayo ngosayizi omncane nosayizi wesikwele 12.

Kuphi, ρ isilinganiso sokugcwalisa :; N yinombolo yokujika, futhi i-dAVG ububanzi obumaphakathi:. Okwezinhlamvu zesikwele, K1 = 2.36, K2 = 2.75.

Kunezizathu eziningi zokugwema ukusebenzisa lolu hlobo lwe-inductor, okuvame ukuholela ekunciphiseni amanani we-inductance ngenxa yokulinganiselwa kwesikhala. Izizathu eziyinhloko zokugwema ama-indarter inductors ama-geometry alinganiselwe nokulawulwa okungafanele kobukhulu obubucayi, okwenza kube nzima ukubikezela amanani we-inductor. Ngaphezu kwalokho, amanani we-inductance wangempela kunzima ukuwalawula ngesikhathi sokukhiqizwa kwe-PCB, futhi ukwehliswa kwemali kuvame ukubanga umsindo kwezinye izingxenye zesifunda.