Xov Xwm - Kev Tshuaj Xyuas Txog Cov Antennas ntawm Kab Xa Xov Tooj Metamaterial

I. Kev Taw Qhia
Cov khoom siv metamaterials tuaj yeem piav qhia zoo tshaj plaws tias yog cov qauv tsim los ntawm kev dag ntxias los tsim cov khoom siv hluav taws xob uas tsis muaj nyob hauv ntuj. Cov khoom siv metamaterials uas muaj kev tso cai tsis zoo thiab kev nkag mus tsis zoo hu ua cov khoom siv sab laug tes (LHMs). LHMs tau raug kawm ntau hauv cov zej zog kev tshawb fawb thiab kev tsim kho. Xyoo 2003, LHMs tau raug xaiv los ua ib qho ntawm kaum qhov kev tshawb fawb zoo tshaj plaws ntawm lub sijhawm niaj hnub no los ntawm Science magazine. Cov ntawv thov tshiab, cov tswv yim, thiab cov khoom siv tau tsim los ntawm kev siv cov khoom tshwj xeeb ntawm LHMs. Txoj hauv kev xa xov (TL) yog ib txoj hauv kev tsim qauv zoo uas tuaj yeem tshuaj xyuas cov ntsiab cai ntawm LHMs. Piv nrog cov TLs ib txwm muaj, qhov tseem ceeb tshaj plaws ntawm cov khoom siv metamaterial TLs yog kev tswj hwm ntawm cov kev cai TL (kev sib kis tas li) thiab cov yam ntxwv impedance. Kev tswj hwm ntawm cov kev cai TL metamaterial muab cov tswv yim tshiab rau kev tsim cov qauv antenna nrog qhov loj me me dua, kev ua haujlwm siab dua, thiab cov haujlwm tshiab. Daim Duab 1 (a), (b), thiab (c) qhia cov qauv circuit tsis poob ntawm cov kab xa xov sab xis (PRH), kab xa xov sab laug (PLH), thiab kab xa xov sab laug-sab xis (CRLH) sib xyaw. Raws li pom hauv Daim Duab 1 (a), tus qauv circuit sib npaug PRH TL feem ntau yog kev sib xyaw ua ke ntawm series inductance thiab shunt capacitance. Raws li pom hauv Daim Duab 1 (b), tus qauv circuit PLH TL yog kev sib xyaw ua ke ntawm shunt inductance thiab series capacitance. Hauv kev siv tiag tiag, nws tsis yooj yim sua kom siv PLH circuit. Qhov no yog vim muaj cov teebmeem parasitic series inductance thiab shunt capacitance uas tsis zam tau. Yog li ntawd, cov yam ntxwv ntawm kab xa xov sab laug uas tuaj yeem ua tiav tam sim no yog txhua yam sib xyaw ua ke sab laug-sab xis thiab sab xis, raws li pom hauv Daim Duab 1 (c).

Daim Duab 1 Cov qauv sib txawv ntawm cov kab hluav taws xob sib kis

Qhov kev sib kis tas mus li (γ) ntawm txoj kab xa xov (TL) yog suav ua: γ=α+jβ=Sqrt(ZY), qhov twg Y thiab Z sawv cev rau kev nkag mus thiab impedance feem. Xav txog CRLH-TL, Z thiab Y tuaj yeem qhia ua:

Ib qho CRLH TL sib xws yuav muaj cov kev sib raug zoo hauv qab no:

Tus lej theem tas mus li β tuaj yeem yog tus lej tiag tiag lossis tus lej xav xwb. Yog tias β yog tus lej tiag tiag hauv qhov ntau zaus, muaj ib qho passband hauv qhov ntau zaus vim yog qhov xwm txheej γ = jβ. Ntawm qhov tod tes, yog tias β yog tus lej xav xwb hauv qhov ntau zaus, muaj ib qho stopband hauv qhov ntau zaus vim yog qhov xwm txheej γ = α. Qhov stopband no yog tshwj xeeb rau CRLH-TL thiab tsis muaj nyob hauv PRH-TL lossis PLH-TL. Cov duab 2 (a), (b), thiab (c) qhia cov kab dispersion (piv txwv li, qhov kev sib raug zoo ω - β) ntawm PRH-TL, PLH-TL, thiab CRLH-TL, raws li. Raws li cov kab dispersion, qhov ceev ntawm pawg (vg = ∂ω / ∂β) thiab qhov ceev ntawm theem (vp = ω / β) ntawm txoj kab xa tuaj yeem tau txais thiab kwv yees. Rau PRH-TL, nws kuj tuaj yeem xav tau los ntawm cov kab uas vg thiab vp yog sib luag (piv txwv li, vpvg> 0). Rau PLH-TL, daim kab qhia tias vg thiab vp tsis sib luag (piv txwv li, vpvg < 0). Daim kab dispersion ntawm CRLH-TL kuj qhia txog qhov muaj nyob ntawm thaj tsam LH (piv txwv li, vpvg < 0) thiab thaj tsam RH (piv txwv li, vpvg > 0). Raws li pom los ntawm Daim Duab 2(c), rau CRLH-TL, yog tias γ yog tus lej tiag tiag, muaj ib txoj kab nres.

Daim Duab 2 Cov kab sib kis ntawm cov kab sib kis sib txawv

Feem ntau, cov resonances series thiab parallel ntawm CRLH-TL yog txawv, uas hu ua lub xeev tsis sib npaug. Txawm li cas los xij, thaum cov zaus resonance series thiab parallel yog tib yam, nws hu ua lub xeev sib npaug, thiab cov qauv sib npaug ntawm lub voj voog tau pom hauv Daim Duab 3 (a).

Daim Duab 3 Tus qauv Circuit thiab cov kab sib kis ntawm cov kab sib txuas sab laug

Thaum lub zaus nce ntxiv, cov yam ntxwv ntawm kev sib kis ntawm CRLH-TL maj mam nce ntxiv. Qhov no yog vim tias qhov ceev ntawm theem (piv txwv li, vp = ω / β) yuav nce ntxiv nyob ntawm qhov zaus. Ntawm cov zaus qis, CRLH-TL yog tus thawj coj los ntawm LH, thaum ntawm cov zaus siab, CRLH-TL yog tus thawj coj los ntawm RH. Qhov no qhia txog qhov xwm txheej ob npaug ntawm CRLH-TL. Daim duab sib npaug ntawm CRLH-TL tau qhia hauv Daim Duab 3 (b). Raws li tau qhia hauv Daim Duab 3 (b), kev hloov pauv ntawm LH mus rau RH tshwm sim ntawm:

Qhov twg ω0 yog qhov zaus hloov pauv. Yog li ntawd, nyob rau hauv qhov xwm txheej sib npaug, kev hloov pauv du tshwm sim los ntawm LH mus rau RH vim γ yog tus lej xav xwb. Yog li ntawd, tsis muaj qhov nres rau qhov sib npaug CRLH-TL dispersion. Txawm hais tias β yog xoom ntawm ω0 (infinite piv rau qhov wavelength coj, piv txwv li, λg = 2π / | β |), nthwv dej tseem nthuav dav vim vg ntawm ω0 tsis yog xoom. Ib yam li ntawd, ntawm ω0, qhov hloov pauv theem yog xoom rau TL ntawm qhov ntev d (piv txwv li, φ = - βd = 0). Qhov kev nce qib theem (piv txwv li, φ> 0) tshwm sim hauv LH zaus ntau yam (piv txwv li, ω < ω 0), thiab qhov kev qeeb theem (piv txwv li, φ < 0) tshwm sim hauv RH zaus ntau yam (piv txwv li, ω > ω 0). Rau CRLH TL, tus yam ntxwv impedance tau piav qhia raws li hauv qab no:

Qhov twg ZL thiab ZR yog cov PLH thiab PRH impedances, raws li. Rau qhov xwm txheej tsis sib npaug, tus yam ntxwv impedance nyob ntawm qhov zaus. Cov kab zauv saum toj no qhia tau hais tias qhov xwm txheej sib npaug yog ywj pheej ntawm zaus, yog li nws tuaj yeem muaj qhov sib phim bandwidth dav. Cov kab zauv TL tau los saum toj no zoo ib yam li cov kev teeb tsa uas txhais cov khoom siv CRLH. Qhov kev sib kis tas mus li ntawm TL yog γ = jβ = Sqrt (ZY). Muab qhov kev sib kis tas mus li ntawm cov khoom siv (β = ω x Sqrt (εμ)), cov kab zauv hauv qab no tuaj yeem tau txais:

Ib yam li ntawd, tus yam ntxwv impedance ntawm TL, piv txwv li, Z0 = Sqrt (ZY), zoo ib yam li tus yam ntxwv impedance ntawm cov khoom siv, piv txwv li, η = Sqrt (μ / ε), uas yog qhia ua:

Tus refractive index ntawm balanced thiab unbalanced CRLH-TL (piv txwv li, n = cβ/ω) tau qhia nyob rau hauv Daim Duab 4. Hauv Daim Duab 4, tus refractive index ntawm CRLH-TL hauv nws qhov LH yog negative thiab tus refractive index hauv nws qhov RH yog positive.

Daim Duab 4 Cov ntsuas refractive ib txwm muaj ntawm cov CRLH TLs sib npaug thiab tsis sib npaug.

1. LC network
Los ntawm kev sib sau ua ke cov bandpass LC cells uas pom hauv Daim Duab 5(a), ib qho CRLH-TL ib txwm muaj nrog kev sib npaug zoo ntawm qhov ntev d tuaj yeem tsim tau ib ntus lossis tsis ib ntus. Feem ntau, txhawm rau kom ntseeg tau tias yooj yim ntawm kev xam thiab kev tsim khoom ntawm CRLH-TL, lub voj voog yuav tsum yog ib ntus. Piv nrog rau tus qauv ntawm Daim Duab 1(c), lub voj voog cell ntawm Daim Duab 5(a) tsis muaj qhov loj me thiab qhov ntev ntawm lub cev yog me me heev (piv txwv li, Δz hauv meters). Xav txog nws qhov ntev hluav taws xob θ=Δφ (rad), theem ntawm LC cell tuaj yeem qhia tau. Txawm li cas los xij, txhawm rau kom paub tseeb tias siv inductance thiab capacitance, qhov ntev ntawm lub cev p yuav tsum tau tsim. Kev xaiv cov thev naus laus zis siv (xws li microstrip, coplanar waveguide, surface mount components, thiab lwm yam) yuav cuam tshuam rau qhov loj ntawm lub cev ntawm LC cell. Lub LC cell ntawm Daim Duab 5(a) zoo ib yam li tus qauv incremental ntawm Daim Duab 1(c), thiab nws qhov txwv p=Δz→0. Raws li qhov xwm txheej sib xws p → 0 hauv Daim Duab 5 (b), TL tuaj yeem tsim tau (los ntawm cov hlwb LC cascading) uas sib npaug rau CRLH-TL zoo tagnrho nrog qhov ntev d, yog li TL zoo li sib xws rau cov nthwv dej electromagnetic.

Daim Duab 5 CRLH TL raws li LC network.

Rau lub LC cell, xav txog cov xwm txheej ciam teb (PBCs) zoo ib yam li Bloch-Floquet theorem, qhov kev sib raug zoo ntawm kev tawg ntawm lub LC cell tau ua pov thawj thiab qhia raws li hauv qab no:

Qhov kev sib txuas ntawm cov koob (Z) thiab kev nkag mus rau hauv lub hlwb (Y) ntawm LC cell yog txiav txim siab los ntawm cov qauv hauv qab no:

Vim tias qhov ntev ntawm lub voj voog LC ntawm chav tsev me heev, Taylor qhov kev kwv yees siv tau los tau txais:

2. Kev Siv Lub Cev
Hauv seem dhau los, lub network LC los tsim CRLH-TL tau tham txog lawm. Cov network LC no tsuas yog ua tau los ntawm kev siv cov khoom siv lub cev uas tuaj yeem tsim cov peev xwm xav tau (CR thiab CL) thiab inductance (LR thiab LL). Nyob rau xyoo tas los no, kev siv cov khoom siv nto (SMT) chip lossis cov khoom faib tau nyiam heev. Microstrip, stripline, coplanar waveguide lossis lwm yam thev naus laus zis zoo sib xws tuaj yeem siv los ua kom cov khoom faib. Muaj ntau yam yuav tsum xav txog thaum xaiv cov chips SMT lossis cov khoom faib. Cov qauv CRLH raws li SMT yog qhov tshwm sim ntau dua thiab yooj yim dua rau kev siv hauv kev tshuaj xyuas thiab tsim. Qhov no yog vim muaj cov khoom siv SMT chip uas tsis tas yuav kho dua tshiab thiab tsim piv rau cov khoom faib. Txawm li cas los xij, qhov muaj cov khoom siv SMT yog tawg, thiab lawv feem ntau tsuas yog ua haujlwm ntawm cov zaus qis (piv txwv li, 3-6GHz). Yog li ntawd, cov qauv CRLH raws li SMT muaj cov zaus ua haujlwm tsawg thiab cov yam ntxwv theem tshwj xeeb. Piv txwv li, hauv kev siv hluav taws xob, cov khoom siv SMT chip yuav tsis ua tau. Daim Duab 6 qhia txog cov qauv faib tawm raws li CRLH-TL. Cov qauv no tau ua tiav los ntawm cov kab sib txuas ntawm cov lej thiab cov kab luv luv, tsim cov kab sib txuas ntawm cov lej CL thiab cov kab sib txuas ntawm cov lej LL ntawm LH. Lub peev xwm ntawm cov kab thiab GND yog xav tias yog lub peev xwm RH CR, thiab qhov inductance tsim los ntawm cov hluav taws xob sib nqus uas tsim los ntawm cov dej ntws tam sim no hauv cov qauv sib txuas ntawm cov lej yog xav tias yog RH inductance LR.