Xa kufikwa kuii-eriyali, umbuzo abantu abaxhalabele kakhulu ngawo ngulo "Ifumaneka njani imitha ngokwenene?" Intsimi ye-electromagnetic eveliswa ngumthombo wesignali isasazeka njani ngomgca wothumelo nangaphakathi kwi-antenna, kwaye ekugqibeleni "yahlukane" ne-antenna ukuze yenze i-free space wave.
1. Imitha yentsimbi enye
Masithi uxinano lwetshaja, oluchazwa njenge-qv (Coulomb/m3), lusasazwe ngokulinganayo kwintambo ejikelezayo enommandla onqamlezileyo we-a kunye nomthamo we-V, njengoko kubonisiwe kuMfanekiso 1.
Umfanekiso 1
Ixabiso elipheleleyo le-Q kwivolumu V lihamba kwicala le-z ngesantya esifanayo se-Vz (m/s). Kungangqinwa ukuba i-current density Jz kwicandelo elinqamlezileyo lentambo yile:
Jz = qv vz （1）
Ukuba ucingo lwenziwe ngomqhubi ofanelekileyo, uxinano lwangoku lwe-Js kumphezulu wocingo lulandelayo:
Js = qs vz (2)
Apho i-qs ibubuninzi betshaja yomphezulu. Ukuba intambo incinci kakhulu (ngokufanelekileyo, i-radius yi-0), umbane kwintambo ungachazwa ngolu hlobo:
Iz = ql vz (3)
Apho i-ql (coulomb/meter) ingumrhumo ngobude beyunithi nganye.
Sixhalabele kakhulu iintambo ezincinci, kwaye izigqibo zisebenza kwezi meko zintathu zingasentla. Ukuba i-current iyatshintsha-tshintsha, i-derivative yefomula (3) malunga nexesha yile ilandelayo:
(4)
i-az kukukhawuleziswa kwetshaja. Ukuba ubude bentambo buyi-l, (4) bungabhalwa ngolu hlobo lulandelayo:
(5)
I-equation (5) lulwalamano olusisiseko phakathi kombane kunye netshaja, kunye nolwalamano olusisiseko lwemitha ye-electromagnetic. Ngamafutshane, ukuvelisa imitha, kufuneka kubekho umsinga otshintsha-tshintsha ngexesha okanye ukukhawulezisa (okanye ukuhla kwesantya) kwetshaja. Sihlala sikhankanya umsinga kwizicelo ze-time-harmonic, kwaye itshaja idla ngokukhankanywa kwizicelo zexesha elifutshane. Ukuze kuveliswe ukukhawuleziswa kwetshaja (okanye ukuhla kwesantya), ucingo kufuneka lugotywe, lugotywe, kwaye lungaqhubeki. Xa itshaja ijikeleza kwintshukumo ye-time-harmonic, iya kuvelisa ukukhawuleziswa kwetshaja rhoqo (okanye ukuhla kwesantya) okanye umsinga otshintsha-tshintsha ixesha. Ke ngoko:
1) Ukuba itshaja ayishukumi, akuyi kubakho msinga kwaye akuyi kubakho mitha.
2) Ukuba itshaja ihamba ngesantya esingaguqukiyo:
a. Ukuba ucingo luthe tye kwaye alunasiphelo ngobude, akukho mitha.
b. Ukuba ucingo lugobile, lugobile, okanye aluqhubeki, njengoko kubonisiwe kuMfanekiso 2, kukho imitha.
3) Ukuba itshaja iyajika ngokuhamba kwexesha, itshaja iya kukhazimla nokuba intambo ithe tye.
Umfanekiso 2
Ukuqonda okusemgangathweni kwendlela yokukhanya kwemitha kungafunyanwa ngokujonga umthombo oshukumayo oqhagamshelwe kwintambo evulekileyo enokusekelwa phantsi komthwalo kwicala layo elivulekileyo, njengoko kubonisiwe kuMfanekiso 2(d). Xa ucingo lunikwa amandla ekuqaleni, iitshaja (ii-electron zasimahla) kwintambo ziqaliswa yimigca yentsimi yombane eveliswa ngumthombo. Njengoko iitshaja zikhawuleziswa kwicala lomthombo wentambo kwaye zincitshiswa (ukukhawuleziswa okungalunganga xa kuthelekiswa nentshukumo yokuqala) xa kubonakaliswa ekupheleni kwayo, intsimi yemitha iveliswa eziphelweni zayo nakwenye intambo eseleyo. Ukukhawuleziswa kweetshaja kwenziwa ngumthombo wamandla wangaphandle obeka iitshaja kwintshukumo kwaye uvelise intsimi yemitha ehambelanayo. Ukuncitshiswa kweetshaja eziphelweni zentambo kwenziwa ngamandla angaphakathi anxulumene nentsimi ebangelwayo, okubangelwa kukuqokelelwa kweetshaja ezixineneyo eziphelweni zentambo. Amandla angaphakathi afumana amandla ekuqokeleleni kwetshaja njengoko isantya sayo sincipha ukuya kwi-zero eziphelweni zentambo. Ngoko ke, ukukhawuleziswa kweetshaja ngenxa yokuvuselelwa kwentsimi yombane kunye nokucotha kweetshaja ngenxa yokungaqhubeki okanye ukugoba okubushelelezi kwe-wire impedance ziindlela zokwenza imitha ye-electromagnetic. Nangona zombini i-current density (Jc) kunye ne-charge density (qv) zizinto ezisetyenziswa kwi-equations kaMaxwell, i-charge ithathwa njengeyona nto ibalulekileyo, ngakumbi kwiintsimi ze-transient. Nangona le ngcaciso ye-radiation isetyenziswa kakhulu kwii-transient states, ingasetyenziselwa ukuchaza i-steady-state radiation.
Ndicebisa ezininzi ezibalaseleyoiimveliso ze-antennayenziwe nguI-RFMISO:
RM-TCR406.4
RM-BCA082-4 （0.8-2GHz)
RM-SWA910-22(9-10GHz)
2. Imitha yeengcingo ezimbini
Qhagamshela umthombo wevolthi kumgca wokudlulisela we-conductor ezimbini oqhagamshelwe kwi-antenna, njengoko kubonisiwe kuMfanekiso 3(a). Ukusebenzisa i-voltage kumgca weengcingo ezimbini kuvelisa intsimi yombane phakathi kwe-conductors. Imigca yentsimi yombane isebenza kwii-elektroni ezikhululekileyo (ezahlulwe ngokulula kwiiathom) eziqhagamshelwe kumqhubi ngamnye kwaye ziwanyanzele ukuba ahambe. Ukuhamba kweetshaja kuvelisa umbane, nto leyo evelisa intsimi yemagnethi.
Umfanekiso 3
Sivumile ukuba imigca yentsimi yombane iqala ngeetshaji ezilungileyo kwaye iphele ngeetshaji ezilungileyo. Kakade ke, ingaqala ngeetshaji ezilungileyo kwaye iphele kwi-infinity; okanye iqale kwi-infinity kwaye iphele ngeetshaji ezilungileyo; okanye yenze ii-loops ezivaliweyo ezingaqali kwaye zingapheli nangaziphi na iitshaji. Imigca yentsimi yemagnethi ihlala yenza ii-loops ezivaliweyo ezijikeleze ii-conductors ezithwala umbane kuba akukho zindleko zemagnethi kwifiziksi. Kwezinye iifomyula zezibalo, iitshaji zemagnethi ezifanayo kunye ne-magnetic currents ziyaziswa ukubonisa ubumbano phakathi kwezisombululo ezibandakanya amandla kunye nemithombo yemagnethi.
Imigca yentsimi yombane edwetshwe phakathi kwabaqhubi ababini inceda ukubonisa ukusasazwa kwetshaja. Ukuba sicinga ukuba umthombo we-voltage yi-sinusoidal, silindele ukuba intsimi yombane phakathi kwabaqhubi nayo ibe yi-sinusoidal enexesha elilingana nelomthombo. Ubukhulu bamandla entsimi yombane bumelwa bubuninzi bemigca yentsimi yombane, kwaye iintolo zibonisa icala elihambelanayo (elihle okanye elibi). Ukuveliswa kwamacandelo ombane kunye nemagnethi atshintsha-tshintshayo phakathi kwabaqhubi kwenza i-electromagnetic wave esasazeka kumgca wothumelo, njengoko kubonisiwe kuMfanekiso 3(a). I-electromagnetic wave ingena kwi-antenna kunye netshaja kunye nomsinga ohambelanayo. Ukuba sisusa inxalenye yesakhiwo se-antenna, njengoko kubonisiwe kuMfanekiso 3(b), i-free-space wave inokwenziwa "ngokudibanisa" iziphelo ezivulekileyo zemigca yentsimi yombane (eboniswe yimigca enamachaphaza). I-free-space wave nayo iphindaphindeka, kodwa i-constant-phase point P0 iya ngaphandle ngesantya sokukhanya kwaye ihambe umgama we-λ/2 (ukuya kwi-P1) kwisiqingatha sexesha. Kufuphi ne-antenna, i-constant-phase point P0 ihamba ngokukhawuleza kunesantya sokukhanya kwaye isondela kwisantya sokukhanya kwiindawo ezikude ne-antenna. Umfanekiso 4 ubonisa ukusasazwa kwentsimi yombane ye-free-space ye-antenna ye-λ∕2 kwi-t = 0, t/8, t/4, kunye ne-3T/8.
Umfanekiso 4 Ukusasazwa kwentsimi yombane yesithuba esikhululekileyo se-antenna ye-λ∕2 kwi-t = 0, t/8, t/4 kunye ne-3T/8
Akwaziwa ukuba amaza akhokelwayo ahlukaniswa njani kwi-antenna aze ekugqibeleni enziwe ukuze asasazeke kwindawo ekhululekileyo. Singathelekisa amaza esithuba akhokelwayo nakhululekileyo namaza amanzi, anokubangelwa lilitye eliwiswe emanzini azolileyo okanye ngezinye iindlela. Nje ukuba ukuphazamiseka emanzini kuqale, amaza amanzi aveliswa aze aqale ukusasazeka ngaphandle. Nokuba ukuphazamiseka kuyeka, amaza awayeki kodwa ayaqhubeka nokusasazeka phambili. Ukuba ukuphazamiseka kuyaqhubeka, amaza amatsha ahlala eveliswa, kwaye ukusasazeka kwala maza kushiyeka emva kwamanye amaza.
Kunjalo ke nangamaza e-electromagnetic aveliswa kukuphazamiseka kombane. Ukuba ukuphazamiseka kokuqala kombane okuvela kumthombo kuthathe ixesha elifutshane, amaza e-electromagnetic aveliswayo asasazeka ngaphakathi komgca wokudlulisela, aze angene kwi-antenna, aze ekugqibeleni akhanye njengamaza esithuba esikhululekileyo, nangona uvuselelo lungasekho (njengamaza amanzi kunye nokuphazamiseka akwenzileyo). Ukuba ukuphazamiseka kombane kuyaqhubeka, amaza e-electromagnetic ahlala ekho kwaye alandela ngasemva kwawo ngexesha lokusasazwa, njengoko kubonisiwe kwi-antenna ye-biconical eboniswe kuMfanekiso 5. Xa amaza e-electromagnetic engaphakathi kwimigca yokudlulisela kunye nee-antenna, ubukho bawo bunxulumene nobukho bombane ngaphakathi komqhubi. Nangona kunjalo, xa amaza esasazwa, enza iluphu evaliweyo kwaye akukho mrhumo wokugcina ubukho bawo. Oku kusikhokelela kwisigqibo sokuba:
Ukuvuthuza kwentsimi kufuna ukukhawuleziswa kunye nokuncitshiswa kwetshaja, kodwa ukugcinwa kwentsimi akufuneki ukukhawuleziswa kunye nokuncitshiswa kwetshaja.
Umfanekiso 5
3. Imitha yeDipole
Sizama ukuchaza indlela imigca yentsimi yombane ephuma ngayo kwi-antenna ize yenze amaza esithuba esikhululekileyo, size sithathe i-antenna ye-dipole njengomzekelo. Nangona iyinkcazo elula, ikwavumela abantu ukuba babone ngokuzenzekelayo ukuveliswa kwamaza esithuba esikhululekileyo. Umfanekiso 6(a) ubonisa imigca yentsimi yombane eyenziwe phakathi kweengalo ezimbini ze-dipole xa imigca yentsimi yombane isiya ngaphandle nge-λ∕4 kwikota yokuqala yomjikelo. Kulo mzekelo, masicinge ukuba inani lemigca yentsimi yombane eyenziweyo yi-3. Kwikota elandelayo yomjikelo, imigca emithathu yokuqala yentsimi yombane ihambisa enye i-λ∕4 (inani lilonke le-λ∕2 ukusuka kwindawo yokuqala), kwaye uxinano lwetshaja kumqhubi luqala ukwehla. Ingathathwa njengeyenziwe ngokungeniswa kweetshaja ezichaseneyo, ezicima iitshaja kumqhubi ekupheleni kwesiqingatha sokuqala somjikelo. Imigca yentsimi yombane eyenziwe ziitshaja ezichaseneyo yi-3 kwaye ihambisa umgama we-λ∕4, omelwa yimigca enamachaphaza kuMfanekiso 6(b).
Isiphumo sokugqibela kukuba kukho imigca emithathu yentsimi yombane esezantsi kumgama wokuqala we-λ∕4 kunye nenani elifanayo lemigca yentsimi yombane ephezulu kumgama wesibini we-λ∕4. Ekubeni kungekho tshaja ipheleleyo kwi-antenna, imigca yentsimi yombane kufuneka inyanzelwe ukuba yahlukane nomqhubi kwaye idibane kunye ukuze yenze iluphu evaliweyo. Oku kuboniswe kuMfanekiso 6(c). Kwisiqingatha sesibini, kulandelwa inkqubo efanayo yomzimba, kodwa qaphela ukuba icala lichasene. Emva koko, inkqubo iyaphindwa kwaye iyaqhubeka ngokungenasiphelo, yenza usasazo lwentsimi yombane olufana noMfanekiso 4.
Umfanekiso 6
Ukuze ufunde okungakumbi ngee-antenna, nceda undwendwele:
Ixesha lokuthumela: Juni-20-2024
