Kev sib cais yog ib qho ntawm cov yam ntxwv tseem ceeb ntawm cov antennas. Peb yuav tsum xub nkag siab txog kev sib cais ntawm cov nthwv dej dav hlau. Tom qab ntawd peb tuaj yeem tham txog cov hom kev sib cais tseem ceeb ntawm antenna.
kev sib hloov pauv ntawm cov kab ncaj
Peb yuav pib nkag siab txog qhov polarization ntawm lub dav hlau electromagnetic nthwv dej.
Ib nthwv dej electromagnetic planar (EM) muaj ntau yam ntxwv. Thawj qhov yog tias lub zog mus rau hauv ib qho kev taw qhia (tsis muaj kev hloov pauv hauv ob qho kev taw qhia orthogonal). Qhov thib ob, lub teb hluav taws xob thiab lub teb sib nqus yog perpendicular rau ib leeg thiab orthogonal rau ib leeg. Lub teb hluav taws xob thiab sib nqus yog perpendicular rau qhov kev taw qhia ntawm lub dav hlau nthwv dej propagation. Ua piv txwv, xav txog ib lub teb hluav taws xob ib zaug (E teb) muab los ntawm kab zauv (1). Lub teb electromagnetic taug kev hauv +z kev taw qhia. Lub teb hluav taws xob yog qhia hauv +x kev taw qhia. Lub teb sib nqus yog nyob rau hauv +y kev taw qhia.
Hauv kab zauv (1), ua raws li cov cim qhia: . Qhov no yog ib lub vector unit (ib lub vector ntawm qhov ntev), uas hais tias lub ntsiab lus ntawm lub teb hluav taws xob nyob hauv x kev taw qhia. Lub dav hlau nthwv dej tau piav qhia hauv Daim Duab 1.
daim duab 1. Duab kos ntawm lub zog hluav taws xob uas mus ncig hauv qhov kev taw qhia +z.
Polarization yog qhov kab thiab cov duab nthuav dav (contour) ntawm lub teb hluav taws xob. Ua piv txwv, xav txog qhov sib npaug ntawm lub dav hlau nthwv dej hluav taws xob (1). Peb yuav saib qhov chaw uas lub teb hluav taws xob yog (X, Y, Z) = (0,0,0) ua lub luag haujlwm ntawm lub sijhawm. Qhov loj ntawm lub teb no tau plotted hauv Daim Duab 2, ntawm ntau qhov xwm txheej hauv lub sijhawm. Lub teb yog oscillating ntawm zaus "F".
daim duab 2. Saib seb lub teb hluav taws xob (X, Y, Z) = (0,0,0) nyob rau ntau lub sijhawm sib txawv.
Lub teb hluav taws xob raug pom ntawm qhov pib, oscillating rov qab thiab tawm hauv amplitude. Lub teb hluav taws xob yeej ib txwm nyob ntawm x-axis qhia. Txij li thaum lub teb hluav taws xob raug tswj hwm raws ib kab, lub teb no tuaj yeem hais tias yog linearly polarized. Tsis tas li ntawd, yog tias X-axis yog sib luag rau hauv av, lub teb no kuj raug piav qhia tias yog horizontally polarized. Yog tias lub teb raug taw qhia raws Y-axis, lub nthwv dej tuaj yeem hais tias yog vertically polarized.
Cov nthwv dej uas muaj polarized linearly tsis tas yuav tsum tau taw qhia raws txoj kab kab rov tav lossis ntsug. Piv txwv li, ib lub nthwv dej hluav taws xob uas muaj kev txwv nyob raws txoj kab raws li pom hauv Daim Duab 3 kuj yuav raug polarized linearly.
daim duab 3. Qhov amplitude ntawm lub zog hluav taws xob ntawm ib nthwv dej linearly polarized uas nws txoj kev mus los yog lub kaum sab xis.
Lub teb hluav taws xob hauv Daim Duab 3 tuaj yeem piav qhia los ntawm kab zauv (2). Tam sim no muaj ib feem x thiab y ntawm lub teb hluav taws xob. Ob qho tib si muaj qhov loj sib npaug.
Ib qho uas yuav tsum nco ntsoov txog kab zauv (2) yog cov xy-component thiab cov teb hluav taws xob hauv theem thib ob. Qhov no txhais tau tias ob qho tib si muaj tib lub amplitude txhua lub sijhawm.
kev sib hloov ntawm lub voj voog
Tam sim no xav tias lub zog hluav taws xob ntawm lub dav hlau nthwv dej yog muab los ntawm kab zauv (3):
Hauv qhov no, cov X- thiab Y-elements yog 90 degrees tawm ntawm theem. Yog tias lub teb raug pom raws li (X, Y, Z) = (0,0,0) dua li ua ntej, lub teb hluav taws xob piv rau lub sijhawm nkhaus yuav tshwm sim raws li qhia hauv qab no hauv Daim Duab 4.
Daim Duab 4. Lub zog hluav taws xob (X, Y, Z) = (0,0,0) EQ domain. (3).
Lub teb hluav taws xob hauv Daim Duab 4 tig ua ib lub voj voog. Hom teb no piav qhia tias yog nthwv dej polarized ncig. Rau kev polarization ncig, yuav tsum ua raws li cov qauv hauv qab no:
- Tus qauv rau kev sib hloov polarization
- Lub zog hluav taws xob yuav tsum muaj ob lub orthogonal (perpendicular) Cheebtsam.
- Cov khoom orthogonal ntawm lub teb hluav taws xob yuav tsum muaj cov amplitudes sib npaug.
- Cov khoom sib txuas ntawm cov quadrature yuav tsum yog 90 degrees tawm ntawm theem.
Yog tias mus ncig ntawm Wave Figure 4 screen, qhov kev tig ntawm lub teb raug hais tias yog counterclockwise thiab right-handed circularly polarized (RHCP). Yog tias lub teb raug tig mus rau hauv clockwise, lub teb yuav yog left-handed circular polarization (LHCP).
Kev sib hloov ntawm elliptical
Yog tias lub teb hluav taws xob muaj ob lub Cheebtsam perpendicular, 90 degrees tawm ntawm theem tab sis ntawm qhov sib npaug zos, lub teb yuav yog elliptically polarized. Xav txog lub teb hluav taws xob ntawm lub dav hlau nthwv dej mus ncig hauv qhov kev taw qhia + z, piav qhia los ntawm Equation (4):
Qhov chaw ntawm qhov chaw uas lub taub hau ntawm lub vector hluav taws xob yuav xav tias yog muab rau hauv Daim Duab 5
Daim Duab 5. Lub zog hluav taws xob ntawm lub zog elliptical polarization wave. (4).
Lub teb hauv Daim Duab 5, uas mus ncig hauv qhov kev taw qhia counterclockwise, yuav yog sab tes xis elliptical yog tias mus ncig tawm ntawm lub vijtsam. Yog tias lub teb hluav taws xob vector tig mus rau qhov kev taw qhia rov qab, lub teb yuav yog sab tes laug elliptically polarized.
Ntxiv mus, elliptical polarization hais txog nws qhov eccentricity. Qhov piv ntawm eccentricity rau qhov loj ntawm cov axes loj thiab me. Piv txwv li, qhov nthwv dej eccentricity los ntawm kab zauv (4) yog 1 / 0.3 = 3.33. Cov nthwv dej elliptically polarized tau piav qhia ntxiv los ntawm kev coj ntawm lub axis loj. Cov kab zauv nthwv dej (4) muaj ib txoj kab uas feem ntau muaj x-axis. Nco ntsoov tias lub axis loj tuaj yeem nyob ntawm txhua lub kaum sab xis. Lub kaum sab xis tsis tas yuav tsum haum rau X, Y lossis Z axis. Thaum kawg, nws yog ib qho tseem ceeb uas yuav tsum nco ntsoov tias ob qho tib si voj voog thiab linear polarization yog cov xwm txheej tshwj xeeb ntawm elliptical polarization. 1.0 eccentric elliptically polarized nthwv dej yog nthwv dej voj voog polarized. Elliptically polarized nthwv dej nrog infinite eccentricity. Linearly polarized nthwv dej.
Kev sib hloov ntawm lub kav hlau txais xov
Tam sim no peb paub txog cov teb hluav taws xob polarized dav hlau, lub polarization ntawm lub antenna yooj yim txhais.
Kev Ntsuas Polarization ntawm Antenna Ib qho kev ntsuam xyuas deb ntawm antenna, qhov kev ntsuas polarization ntawm qhov tshwm sim ntawm lub tshav pob tawg. Yog li ntawd, antennas feem ntau raug teev tias yog "linearly polarized" lossis "right-handed circularly polarized antennas".
Lub tswv yim yooj yim no tseem ceeb rau kev sib txuas lus ntawm lub kav hlau txais xov. Ua ntej, lub kav hlau txais xov uas muaj kab rov tav yuav tsis sib txuas lus nrog lub kav hlau txais xov uas muaj kab ntsug. Vim yog qhov kev sib pauv sib pab, lub kav hlau txais xov xa thiab tau txais tib yam nkaus. Yog li ntawd, cov kav hlau txais xov uas muaj kab ntsug xa thiab tau txais cov teb uas muaj kab ntsug. Yog li ntawd, yog tias koj sim xa lub kav hlau txais xov uas muaj kab ntsug, yuav tsis muaj kev txais tos.
Feem ntau, rau ob lub antennas linearly polarized tig sib piv rau ib leeg los ntawm lub kaum sab xis ( ), qhov poob hluav taws xob vim qhov kev sib txawv polarization no yuav piav qhia los ntawm qhov polarization loss factor (PLF):
Yog li ntawd, yog tias ob lub antennas muaj tib lub polarization, lub kaum sab xis ntawm lawv cov teb hluav taws xob radiating yog xoom thiab tsis muaj kev poob hluav taws xob vim yog polarization mismatch. Yog tias ib lub antenna yog polarized ntsug thiab lwm qhov yog polarized kab rov tav, lub kaum sab xis yog 90 degrees, thiab tsis muaj hluav taws xob yuav raug hloov pauv.
LUS CEEV: Kev txav lub xov tooj hla koj lub taub hau mus rau ntau lub kaum sib txawv piav qhia vim li cas qee zaum kev txais tau tuaj yeem nce ntxiv. Cov kav hlau txais xov tooj ntawm tes feem ntau yog linearly polarized, yog li tig lub xov tooj feem ntau tuaj yeem phim lub polarization ntawm lub xov tooj, yog li txhim kho kev txais tau.
Kev sib hloov polarization yog ib qho yam ntxwv zoo ntawm ntau lub antennas. Ob lub antennas yog circularly polarized thiab tsis raug kev poob ntawm lub teeb liab vim yog polarization mismatch. Antennas siv hauv GPS systems yog sab tes xis circularly polarized.
Tam sim no xav tias lub kav hlau txais xov linearly polarized tau txais cov nthwv dej circularly polarized. Sib npaug, xav tias lub kav hlau txais xov circularly polarized sim txais cov nthwv dej linearly polarized. Dab tsi yog qhov tshwm sim polarization poob factor?
Nco ntsoov tias qhov kev sib hloov ntawm lub voj voog yog ob lub nthwv dej orthogonal linearly polarized, 90 degrees tawm ntawm theem. Yog li ntawd, lub kav hlau txais xov linearly polarized (LP) tsuas yog yuav tau txais cov khoom sib hloov ntawm lub voj voog polarized (CP) nthwv dej. Yog li ntawd, lub kav hlau txais xov LP yuav muaj qhov poob tsis sib xws ntawm 0.5 (-3dB). Qhov no muaj tseeb txawm tias lub kav hlau txais xov LP tig lub kaum sab xis twg los xij. yog li ntawd:
Qee zaum qhov polarization loss factor hu ua polarization efficiency, antenna mismatch factor, lossis antenna reception factor. Tag nrho cov npe no hais txog tib lub tswv yim.
Lub sijhawm tshaj tawm: Lub Kaum Ob Hlis-22-2023
