Ponena zatinyanga, funso lomwe anthu amadandaula nalo kwambiri ndi lakuti "Kodi kuwala kwa dzuwa kumachitika bwanji?" Kodi mphamvu yamagetsi yopangidwa ndi gwero la chizindikiro imafalikira bwanji kudzera mu chingwe chotumizira ndi mkati mwa antenna, ndipo pamapeto pake "imasiyana" ndi antenna kuti ipange mafunde a mlengalenga.
1. Kuwala kwa waya umodzi
Tiyeni tiyerekeze kuti kuchuluka kwa ma charge, komwe kumafotokozedwa ngati qv (Coulomb/m3), kumagawidwa mofanana mu waya wozungulira wokhala ndi dera lopingasa la a ndi voliyumu ya V, monga momwe zasonyezedwera pa Chithunzi 1.
Chithunzi 1
Chiwerengero chonse cha Q mu voliyumu V chimayenda molunjika ku z pa liwiro lofanana Vz (m/s). Zingatsimikizidwe kuti kuchuluka kwa Jz komwe kuli pa waya ndi:
Jz = qv vz (1)
Ngati waya wapangidwa ndi kondakitala woyenera, kuchuluka kwa mphamvu yamagetsi Js pamwamba pa waya ndi:
Js = qs vz (2)
Kumene qs ndi kuchuluka kwa mphamvu ya pamwamba. Ngati waya ndi woonda kwambiri (bwino kwambiri, utali wa radius ndi 0), mphamvu yamagetsi mu waya ikhoza kufotokozedwa motere:
Iz = ql vz (3)
Kumene ql (coulomb/meter) ndi mtengo pa unit level.
Tikukhudzidwa kwambiri ndi mawaya owonda, ndipo mfundo zake zikugwira ntchito pazochitika zitatu zomwe zili pamwambapa. Ngati mphamvu yamagetsi ikusintha nthawi, zotsatira za fomula (3) zokhudzana ndi nthawi ndi izi:
(4)
az ndiye kufulumizitsa kwa chaji. Ngati kutalika kwa waya ndi l, (4) kungalembedwe motere:
(5)
Equation (5) ndi ubale woyambira pakati pa mphamvu yamagetsi ndi mphamvu, komanso ubale woyambira wa mphamvu yamagetsi. Mwachidule, kuti tipange mphamvu yamagetsi, payenera kukhala mphamvu yamagetsi yosinthasintha nthawi kapena kufulumira (kapena kuchepetsa mphamvu yamagetsi). Nthawi zambiri timatchula mphamvu yamagetsi mu ntchito za nthawi yamagetsi, ndipo mphamvu yamagetsi nthawi zambiri imatchulidwa mu ntchito zosakhalitsa. Kuti tipange mphamvu yamagetsi yamagetsi (kapena kuchepetsa mphamvu yamagetsi), waya uyenera kupindika, kupindika, ndi kuleka kupitirira. Mphamvu yamagetsi ikasinthasintha mu kayendedwe ka nthawi yamagetsi yamagetsi, imapanganso mphamvu yamagetsi ...
1) Ngati mphamvu siisuntha, sipadzakhala mphamvu yamagetsi komanso kuwala kwa dzuwa.
2) Ngati mphamvu ikuyenda pa liwiro losasintha:
a. Ngati waya uli wowongoka komanso wautali wopanda malire, palibe kuwala kwa dzuwa.
b. Ngati waya wapindika, wapindika, kapena wosapitirira, monga momwe zasonyezedwera pa Chithunzi 2, pali kuwala kwa dzuwa.
3) Ngati mphamvu ya magetsi isinthasintha pakapita nthawi, mphamvu ya magetsi idzawala ngakhale wayayo ili yowongoka.
Chithunzi 2
Kumvetsetsa bwino momwe ma radiation imagwirira ntchito kungapezeke poyang'ana gwero lolumikizidwa ndi waya wotseguka lomwe lingathe kukhazikika kudzera mu katundu kumapeto kwake kotseguka, monga momwe zasonyezedwera pa Chithunzi 2(d). Pamene waya wapatsidwa mphamvu poyamba, ma charge (ma electron aulere) mu waya amayendetsedwa ndi mizere yamagetsi yopangidwa ndi gwero. Pamene ma charge amafulumizitsidwa kumapeto kwa waya woyambira ndikuchepetsedwa mphamvu (kuthamanga koyipa poyerekeza ndi kayendedwe koyambirira) akawonetsedwa kumapeto kwake, gawo la ma radiation limapangidwa kumapeto kwake komanso m'mbali mwa waya wotsala. Kuthamanga kwa ma charge kumachitika ndi gwero lakunja la mphamvu lomwe limayendetsa ma charge ndikupanga gawo logwirizana la ma radiation. Kutsika kwa ma charge kumapeto kwa waya kumachitika ndi mphamvu zamkati zogwirizana ndi gawo loyambitsidwa, zomwe zimachitika chifukwa cha kuchuluka kwa ma charge okhazikika kumapeto kwa waya. Mphamvu zamkati zimapeza mphamvu kuchokera ku kuchuluka kwa ma charge pamene liwiro lake limachepa kufika pa zero kumapeto kwa waya. Chifukwa chake, kufulumizitsa kwa ma charge chifukwa cha kusonkhezera kwa magetsi komanso kuchepa kwa ma charge chifukwa cha kulephera kapena kupindika kosalala kwa waya ndi njira zopangira ma electromagnetic radiation. Ngakhale kuti current density (Jc) ndi charge density (qv) ndi ma source terms mu ma equation a Maxwell, charge imaonedwa kuti ndi source quantity, makamaka pa transient fields. Ngakhale kuti kufotokozera kumeneku kwa radiation kumagwiritsidwa ntchito makamaka pa transient states, kungagwiritsidwenso ntchito kufotokoza steady-state radiation.
Ndibwino kwambiri zingapozinthu za antennazopangidwa ndiRFMISO:
RM-TCR406.4
RM-BCA082-4 (0.8-2GHz)
RM-SWA910-22(9-10GHz)
2. Kuwala kwa mawaya awiri
Lumikizani gwero la magetsi ku chingwe chotumizira magetsi chokhala ndi ma conductor awiri cholumikizidwa ku antenna, monga momwe zasonyezedwera pa Chithunzi 3(a). Kugwiritsa ntchito magetsi ku chingwe chokhala ndi mawaya awiri kumapanga mphamvu yamagetsi pakati pa ma conductor. Mizere ya magetsi imagwira ntchito pa ma elekitironi aulere (olekanitsidwa mosavuta ndi maatomu) olumikizidwa ku kondakitala aliyense ndikuwakakamiza kuti asunthe. Kusuntha kwa ma charges kumapanga mphamvu yamagetsi, yomwe imapanga mphamvu ya maginito.
Chithunzi 3
Tavomereza kuti mizere yamagetsi imayamba ndi ma positive charges ndipo imatha ndi ma negative charges. Zachidziwikire, imathanso kuyamba ndi ma positive charges ndikutha pa infinity; kapena kuyamba pa infinity ndikutha ndi ma negative charges; kapena kupanga ma closed loops omwe sayamba kapena kutha ndi ma charges aliwonse. Mizere yamagetsi nthawi zonse imapanga ma closed loops kuzungulira ma current-carrier conductors chifukwa palibe ma magnetic charges mu physics. Mu ma formula ena a masamu, ma magnetic charges ofanana ndi ma magnetic currents amayambitsidwa kuti awonetse duality pakati pa mayankho okhudzana ndi mphamvu ndi magwero amagetsi.
Mizere yamagetsi yojambulidwa pakati pa ma conductor awiri imathandiza kuwonetsa kugawa kwa mphamvu. Ngati tikuganiza kuti gwero la magetsi ndi sinusoidal, tikuyembekeza kuti mphamvu yamagetsi pakati pa ma conductors ikhalenso sinusoidal yokhala ndi nthawi yofanana ndi ya gwero. Kukula kwa mphamvu yamagetsi kumayimiridwa ndi kuchuluka kwa mizere yamagetsi, ndipo mivi ikuwonetsa njira yoyerekeza (yabwino kapena yoipa). Kupanga kwa magetsi ndi maginito osiyanasiyana pakati pa ma conductors kumapanga mafunde amagetsi omwe amafalikira pamzere wotumizira, monga momwe zasonyezedwera pa Chithunzi 3(a). Mafunde amagetsi amalowa mu antenna ndi mphamvu ndi mphamvu yofanana. Ngati tichotsa gawo la kapangidwe ka antenna, monga momwe zasonyezedwera pa Chithunzi 3(b), mafunde a free-space angapangidwe mwa "kulumikiza" malekezero otseguka a mizere yamagetsi (yomwe yasonyezedwa ndi mizere yokhala ndi madontho). Mafunde a free-space nawonso ndi okhazikika, koma mfundo ya gawo lokhazikika P0 imapita kunja pa liwiro la kuwala ndikuyenda mtunda wa λ/2 (mpaka P1) mkati mwa theka la nthawi. Pafupi ndi antenna, mfundo yokhazikika ya gawo P0 imayenda mofulumira kuposa liwiro la kuwala ndipo imayandikira liwiro la kuwala pamalo omwe ali kutali ndi antenna. Chithunzi 4 chikuwonetsa kufalikira kwa mphamvu zamagetsi za antenna ya λ∕2 pa t = 0, t/8, t/4, ndi 3T/8.
Chithunzi 4 Kugawa kwa malo amagetsi a λ∕2 pa t = 0, t/8, t/4 ndi 3T/8
Sizikudziwika momwe mafunde otsogozedwa amalekanitsidwira ndi antenna kenako n’kupangidwa kuti afalikire m’malo omasuka. Tikhoza kufananiza mafunde otsogozedwa ndi a m’malo omasuka ndi mafunde a m’madzi, omwe angayambitsidwe ndi mwala wogwetsedwa m’madzi odekha kapena m’njira zina. Kusokonezeka m’madzi kukayamba, mafunde a m’madzi amapangidwa ndikuyamba kufalikira kunja. Ngakhale kusokonezekako kutayike, mafundewo sasiya koma amapitirira kufalikira patsogolo. Ngati kusokonezekako kukupitirira, mafunde atsopano amapangidwa nthawi zonse, ndipo kufalikira kwa mafunde amenewa kumatsalira kumbuyo kwa mafunde ena.
N’chimodzimodzinso ndi mafunde amagetsi opangidwa ndi kusokonezeka kwa magetsi. Ngati kusokonezeka koyamba kwa magetsi kuchokera ku gwero kuli kwa kanthawi kochepa, mafunde amagetsi opangidwa amafalikira mkati mwa chingwe chotumizira, kenako amalowa mu antenna, ndipo pamapeto pake amatuluka ngati mafunde a malo omasuka, ngakhale kuti kusokonezeka sikuliponso (monga mafunde amadzi ndi kusokonezeka komwe adapanga). Ngati kusokonezeka kwa magetsi kukupitirira, mafunde amagetsi amakhalapo mosalekeza ndipo amawatsatira pafupi kwambiri panthawi yofalikira, monga momwe zasonyezedwera mu antenna ya biconical yomwe yawonetsedwa pa Chithunzi 5. Mafunde amagetsi akakhala mkati mwa mizere yotumizira ndi ma antenna, kukhalapo kwawo kumakhudzana ndi kukhalapo kwa mphamvu yamagetsi mkati mwa kondakitala. Komabe, mafunde akamatulutsidwa, amapanga kuzungulira kotsekedwa ndipo palibe mphamvu yoti apitirize kukhalapo. Izi zikutitsogolera ku lingaliro lakuti:
Kutulutsa mphamvu kwa munda kumafuna kufulumizitsa ndi kuchepetsa mphamvu ya mphamvu, koma kusamalira munda sikufuna kufulumizitsa ndi kuchepetsa mphamvu ya mphamvu.
Chithunzi 5
3. Kutulutsa kwa Dipole
Timayesetsa kufotokoza njira yomwe mizere yamagetsi imapatukana ndi antenna ndikupanga mafunde a free-space, ndikutenga antenna ya dipole ngati chitsanzo. Ngakhale ndi kufotokozera kosavuta, kumathandizanso anthu kuwona mwachidwi kupanga mafunde a free-space. Chithunzi 6(a) chikuwonetsa mizere yamagetsi yomwe imapangidwa pakati pa mikono iwiri ya dipole pamene mizere yamagetsi imapita kunja ndi λ∕4 mu kotala yoyamba ya kuzungulira. Mwachitsanzo, tiyeni tiyerekeze kuti chiwerengero cha mizere yamagetsi yomwe imapangidwa ndi 3. Mu kotala lotsatira la kuzungulira, mizere itatu yoyambirira yamagetsi imasuntha ina λ∕4 (yonse ya λ∕2 kuchokera pomwe idayambira), ndipo kuchuluka kwa mphamvu pa kondakitala kumayamba kuchepa. Itha kuonedwa kuti imapangidwa poyambitsa ma charge otsutsana, omwe amachotsa ma charge pa kondakitala kumapeto kwa theka loyamba la kuzungulira. Mizere yamagetsi yomwe imapangidwa ndi ma charge otsutsana ndi 3 ndikuyenda mtunda wa λ∕4, womwe ukuimiridwa ndi mizere yokhala ndi madontho mu Chithunzi 6(b).
Zotsatira zake n’zakuti pali mizere itatu yamagetsi yotsika pansi pa mtunda woyamba wa λ∕4 ndi nambala yofanana ya mizere yamagetsi yokwera mmwamba pa mtunda wachiwiri wa λ∕4. Popeza palibe mphamvu yokwanira pa antenna, mizere yamagetsi iyenera kukakamizika kupatukana ndi kondakitala ndikusakanikirana kuti ipange kuzungulira kotsekedwa. Izi zikuwonetsedwa mu Chithunzi 6(c). Mu theka lachiwiri, njira yofananayo ya thupi ikutsatiridwa, koma dziwani kuti njirayo ndi yosiyana. Pambuyo pake, njirayi imabwerezedwa ndipo imapitilira kwamuyaya, ndikupanga kugawa kwamagetsi kofanana ndi Chithunzi 4.
Chithunzi 6
Kuti mudziwe zambiri zokhudza ma antenna, chonde pitani ku:
Nthawi yotumizira: Juni-20-2024
