Polarization yog ib qho ntawm cov yam ntxwv ntawm cov kav hlau txais xov. Peb thawj zaug yuav tsum to taub qhov polarization ntawm dav hlau nthwv dej. Tom qab ntawd peb tuaj yeem sib tham txog hom tseem ceeb ntawm kav hlau txais xov polarization.
linear polarization
Peb yuav pib nkag siab txog polarization ntawm lub dav hlau electromagnetic yoj.
Planar electromagnetic (EM) yoj muaj ob peb yam ntxwv. Thawj yog tias lub zog mus rau hauv ib qho kev taw qhia (tsis muaj kev hloov pauv hauv ob qho kev qhia orthogonal). Qhov thib ob, lub teb hluav taws xob thiab cov hlau nplaum sib nqus yog perpendicular rau ib leeg thiab orthogonal rau ib leeg. Hluav taws xob thiab magnetic teb yog perpendicular rau cov kev taw qhia ntawm dav hlau nthwv dej propagation. Ua piv txwv, xav txog ib qho hluav taws xob ib zaug (E field) muab los ntawm kab zauv (1). Electromagnetic teb yog nyob rau hauv lub + z kev taw qhia. Lub teb hluav taws xob yog qhia nyob rau hauv cov kev taw qhia + x. Lub magnetic teb yog nyob rau hauv lub + y kev taw qhia.
Hauv kev sib npaug (1), saib cov cim: . Qhov no yog ib chav vector (ib vector ntawm qhov ntev), uas hais tias qhov hluav taws xob teb taw tes yog nyob rau hauv x kev taw qhia. Lub dav hlau nthwv dej tau piav qhia hauv daim duab 1.
daim duab 1. Graphical sawv cev ntawm cov hluav taws xob teb mus rau hauv lub +z kev taw qhia.
Polarization yog cov kab thiab nthuav tawm cov duab (contour) ntawm lub teb hluav taws xob. Ua piv txwv, xav txog lub dav hlau yoj hluav taws xob sib npaug (1). Peb yuav soj ntsuam txoj hauj lwm qhov chaw hluav taws xob yog (X, Y, Z) = (0,0,0) raws li lub sijhawm ua haujlwm. Lub amplitude ntawm daim teb no yog npaj rau hauv daim duab 2, ntawm ob peb lub sijhawm. Lub teb yog oscillating ntawm zaus "F".
Daim duab 2. Saib xyuas qhov hluav taws xob (X, Y, Z) = (0,0,0) ntawm lub sijhawm sib txawv.
Lub teb hluav taws xob tau pom ntawm lub hauv paus chiv keeb, oscillating rov qab thiab tawm hauv amplitude. Lub teb hluav taws xob yog ib txwm nyob ntawm x-axis qhia. Txij li thaum lub teb hluav taws xob tau khaws cia raws ib kab, daim teb no tuaj yeem hais tias yog linearly polarized. Tsis tas li ntawd, yog tias X-axis sib npaug rau hauv av, daim teb no kuj tau piav qhia raws li kab rov tav polarized. Yog hais tias lub teb yog taw qhia raws Y-axis, lub nthwv dej tuaj yeem hais tau vertically polarized.
Linearly polarized nthwv dej tsis tas yuav tsum tau coj raws li kab rov tav lossis ntsug axis. Piv txwv li, ib qho hluav taws xob nthwv dej nrog ib qho kev txwv nyob rau hauv ib txoj kab raws li qhia hauv daim duab 3 kuj yuav yog linearly polarized.
duab 3. Lub teb hluav taws xob amplitude ntawm ib tug linearly polarized nthwv dej uas nws trajectory yog lub kaum sab xis.
Cov hluav taws xob hauv daim duab 3 tuaj yeem piav qhia los ntawm kev sib npaug (2). Tam sim no muaj ib qho x thiab y tivthaiv ntawm lub tshuab hluav taws xob. Ob qho tib si sib npaug ntawm qhov loj.
Ib yam uas yuav tsum nco ntsoov txog kev sib npaug (2) yog qhov xy-cov khoom thiab cov khoom siv hluav taws xob hauv theem ob. Qhov no txhais tau hais tias ob qho tib si muaj qhov amplitude tib lub sijhawm.
ncig polarization
Tam sim no xav tias qhov hluav taws xob ntawm lub dav hlau nthwv dej tau muab los ntawm kev sib npaug (3):
Hauv qhov no, X- thiab Y-cov ntsiab lus yog 90 degrees tawm ntawm theem. Yog tias daim teb tau pom zoo li (X, Y, Z) = (0,0,0) dua li ua ntej, qhov hluav taws xob teb 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).
Cov hluav taws xob hauv daim duab 4 tig hauv ib lub voj voog. Hom teb no tau piav raws li lub voj voog polarized. Rau kev sib tw polarization, cov hauv qab no yuav tsum tau ua raws li:
- Txheem rau ncig polarization
- Lub teb hluav taws xob yuav tsum muaj ob lub orthogonal (perpendicular) Cheebtsam.
- Lub orthogonal Cheebtsam ntawm hluav taws xob teb yuav tsum muaj sib npaug amplitudes.
- Lub quadrature Cheebtsam yuav tsum yog 90 degrees tawm ntawm theem.
Yog tias taug kev ntawm Wave Figure 4 screen, qhov kev sib hloov teb tau hais tias yuav tsum yog counterclockwise thiab sab xis-txias ncig polarized (RHCP). Yog hais tias lub teb yog tig nyob rau hauv ib tug clockwise kev taw qhia, lub teb yuav yog sab laug-tes ncig polarization (LHCP).
Elliptical polarization
Yog hais tias lub teb hluav taws xob muaj ob qhov sib txuas, 90 degrees tawm ntawm theem tab sis ntawm qhov sib npaug, daim teb yuav raug elliptical polarized. Xav txog qhov hluav taws xob hluav taws xob ntawm lub dav hlau nthwv dej taug kev hauv + z, piav qhia los ntawm Equation (4):
Qhov chaw ntawm qhov taw tes ntawm qhov kawg ntawm qhov hluav taws xob teb vector yuav xav tias yog muab rau hauv daim duab 5
Daim duab 5. Prompt elliptical polarization yoj hluav taws xob teb. (4).
Daim teb nyob rau hauv daim duab 5, taug kev nyob rau hauv ib tug counterclockwise kev taw qhia, yuav yog sab tes xis elliptical yog hais tias tawm ntawm qhov screen. Yog hais tias qhov hluav taws xob teb vector rotates nyob rau hauv lub opposite kev taw qhia, lub teb yuav yog sab laug-tes elliptical polarized.
Tsis tas li ntawd, elliptical polarization hais txog nws eccentricity. Qhov piv ntawm eccentricity rau lub amplitude ntawm cov loj thiab me axes. Piv txwv li, yoj eccentricity ntawm kab zauv (4) yog 1/0.3 = 3.33. Elliptically polarized nthwv dej tau piav qhia ntxiv los ntawm kev taw qhia ntawm cov axis loj. Qhov sib npaug yoj (4) muaj ib qho axis feem ntau suav nrog x-axis. Nco ntsoov tias lub axis loj tuaj yeem nyob ntawm txhua lub kaum sab xis. Lub kaum sab xis tsis tas yuav haum rau X, Y lossis Z axis. Thaum kawg, nws yog ib qho tseem ceeb kom nco ntsoov tias ob qho tib si ncig thiab kab polarization yog tshwj xeeb ntawm elliptical polarization. 1.0 eccentric elliptical polarized nthwv dej yog ib ncig polarized nthwv dej. Elliptically polarized nthwv dej nrog infinite eccentricity. Linearly polarized nthwv dej.
Kav hlau txais xov polarization
Tam sim no peb paub txog polarized dav hlau yoj electromagnetic teb, lub polarization ntawm tus kav hlau txais xov yog txhais tau yooj yim.
Kav hlau txais xov Polarization Tus kav hlau txais xov nyob deb ntawm kev soj ntsuam, lub polarization ntawm qhov tshwm sim radiated teb. Yog li ntawd, cov kav hlau txais xov feem ntau tau teev tseg raws li "linearly polarized" los yog "txoj cai-tes ncig polarized antennas".
Lub tswv yim yooj yim no yog qhov tseem ceeb rau kev sib txuas lus kav hlau txais xov. Ua ntej, lub kav hlau txais xov kab rov tav polarized yuav tsis sib txuas lus nrog tus kav hlau txais xov polarized vertically. Vim lub theorem reciprocity, tus kav hlau txais xov xa thiab tau txais raws nraim tib txoj kev. Yog li ntawd, vertically polarized kav hlau txais xov xa thiab tau txais vertically polarized teb. Yog li ntawd, yog tias koj sim xa ib lub vertically polarized horizontally polarized kav hlau txais xov, yuav tsis muaj kev txais tos.
Hauv cov ntaub ntawv dav dav, rau ob lub kav hlau txais xov polarized tig txheeb ze rau ib leeg los ntawm lub kaum sab xis ( ), lub zog poob vim qhov tsis sib xws ntawm qhov polarization no yuav piav qhia los ntawm polarization poob yam (PLF):
Yog li ntawd, yog tias ob lub kav hlau txais xov muaj tib lub polarization, lub kaum sab xis ntawm lawv cov hluav taws xob hluav taws xob yog xoom thiab tsis muaj hluav taws xob poob vim polarization mismatch. Yog tias ib lub kav hlau txais xov yog vertically polarized thiab lwm qhov yog kab rov tav polarized, lub kaum sab xis yog 90 degrees, thiab tsis muaj lub zog yuav raug xa mus.
CEEB TOOM: Tsiv lub xov tooj hla koj lub taub hau mus rau ntau lub ces kaum piav qhia tias vim li cas kev txais tos qee zaum tuaj yeem nce ntxiv. Lub xov tooj ntawm tes kav hlau txais xov feem ntau yog linearly polarized, yog li tig lub xov tooj tuaj yeem sib phim lub polarization ntawm lub xov tooj, yog li txhim kho kev txais tos.
Lub voj voog polarization yog qhov xav tau ntawm ntau lub kav hlau txais xov. Ob lub kav hlau txais xov yog ncig polarized thiab tsis raug kev txom nyem los ntawm cov teeb liab poob vim polarization mismatch. Kav hlau txais xov siv nyob rau hauv GPS systems yog txoj cai-tes ncig polarized.
Tam sim no xav tias tus kav hlau txais xov linearly polarized tau txais lub voj voog polarized. Sib npaug, xav tias lub kav hlau txais xov polarized ncig ua kom tau txais cov kab hluav taws xob polarized. Dab tsi yog qhov tshwm sim polarization poob?
Nco qab tias lub voj voog polarization tiag tiag yog ob lub orthogonal linearly polarized tsis, 90 degrees tawm ntawm theem. Yog li ntawd, ib tug linearly polarized (LP) kav hlau txais xov yuav tsuas tau txais lub voj voog polarized (CP) yoj theem tivthaiv. Yog li, LP kav hlau txais xov yuav muaj qhov polarization tsis sib haum ntawm 0.5 (-3dB). Qhov no muaj tseeb txawm tias lub kaum sab xis ntawm LP kav hlau txais xov tig. yog li ntawd:
Polarization poob qhov tseem ceeb yog qee zaum hu ua polarization efficiency, kav hlau txais xov tsis sib haum, lossis tus kav hlau txais xov txais tos. Tag nrho cov npe no hais txog tib lub tswv yim.
Post lub sij hawm: Dec-22-2023
