Thaum nws los txogkav hlau txais xov, lo lus nug uas tib neeg txhawj xeeb tshaj plaws yog "Yuav ua li cas hluav taws xob ua tau tiav?" Yuav ua li cas cov electromagnetic teb generated los ntawm lub teeb liab qhov chaw propagate los ntawm cov kis tau tus mob kab thiab nyob rau hauv lub kav hlau txais xov, thiab thaum kawg "sib cais" los ntawm tus kav hlau txais xov los tsim ib tug dawb chaw yoj.
1. Ib leeg xaim hluav taws xob
Cia peb xav tias tus nqi ceev, qhia raws li qv (Coulomb / m3), yog uniformly faib nyob rau hauv ib lub voj voog nrog ib tug cross-sectional cheeb tsam ntawm ib tug thiab ib tug ntim ntawm V, raws li qhia nyob rau hauv daim duab 1.
Daim duab 1
Tag nrho cov nqi Q hauv ntim V txav mus rau z kev taw qhia ntawm qhov sib txawv ceev Vz (m / s). Nws tuaj yeem ua pov thawj tias qhov ceev tam sim no Jz ntawm ntu ntu ntawm cov hlau yog:
Jz = qv vz (1)
Yog tias cov hlau yog tsim los ntawm tus neeg xyuas pib zoo, qhov ceev tam sim no Js ntawm cov hlau nto yog:
Js = qs vz (2)
Qhov twg qs yog qhov ntom ntom ntom. Yog tias cov hlau nyias nyias (qhov zoo tshaj plaws, lub vojvoog yog 0), qhov tam sim no hauv cov hlau tuaj yeem qhia tau tias:
Iz = ql vz (3)
Qhov twg ql (coulomb / meter) yog tus nqi ib chav tsev ntev.
Peb tsuas yog txhawj xeeb nrog cov xov hlau nyias, thiab cov lus xaus siv rau saum peb rooj plaub. Yog tias lub sijhawm tam sim no sib txawv, qhov sib txawv ntawm cov qauv (3) nrog rau lub sijhawm yog raws li hauv qab no:
(4)
az yog tus nqi acceleration. Yog hais tias cov hlau ntev yog l, (4) tuaj yeem sau tau raws li hauv qab no:
(5)
Qhov sib npaug (5) yog qhov kev sib raug zoo ntawm cov nqi tam sim no thiab cov nqi hluav taws xob, thiab tseem yog qhov kev sib raug zoo ntawm hluav taws xob hluav taws xob hluav taws xob. Cias muab, los tsim hluav taws xob, yuav tsum muaj lub sijhawm sib txawv tam sim no lossis acceleration (los yog deceleration) ntawm tus nqi. Peb feem ntau hais txog tam sim no hauv kev siv sijhawm-kev sib haum xeeb, thiab kev them nqi feem ntau tau hais hauv cov ntawv thov hloov pauv. Txhawm rau tsim cov nqi nrawm (lossis deceleration), cov hlau yuav tsum tau khoov, folded, thiab tsis txuas ntxiv. Thaum tus nqi oscillates nyob rau hauv lub sij hawm-harmonic tsab ntawv tsa suab, nws tseem yuav ua rau lub sij hawm them nqi acceleration (los yog deceleration) los yog lub sij hawm-varying tam sim no. Yog li ntawd:
1) Yog tias tus nqi tsis txav mus, yuav tsis muaj tam sim no thiab tsis muaj hluav taws xob.
2) Yog hais tias tus nqi txav ntawm qhov ceev tsis tu ncua:
ib. Yog hais tias cov hlau yog ncaj thiab infinite ntev, tsis muaj hluav taws xob.
b. Yog hais tias cov hlau yog khoov, folded, los yog discontinuous, raws li qhia nyob rau hauv daim duab 2, muaj hluav taws xob.
3) Yog hais tias tus nqi oscillates lub sij hawm, tus nqi yuav radiate txawm tias cov hlau ncaj.
Daim duab 2
Kev nkag siab zoo ntawm lub tshuab hluav taws xob tuaj yeem tau txais los ntawm kev saib ntawm lub tshuab hluav taws xob txuas nrog lub xov hlau qhib uas tuaj yeem siv los ntawm kev thauj khoom ntawm nws qhov qhib kawg, raws li qhia hauv daim duab 2(d). Thaum cov hlau pib ua kom muaj zog, cov nqi hluav taws xob (dawb electrons) hauv cov hlau yog teem rau hauv kev txav los ntawm cov kab hluav taws xob uas tsim los ntawm qhov chaw. Raws li cov nqi nrawm nrawm ntawm qhov kawg ntawm cov xaim thiab decelerated (tsis zoo acceleration txheeb ze rau qhov qub txav) thaum xav txog ntawm nws qhov kawg, ib qho hluav taws xob hluav taws xob yog tsim los ntawm nws qhov kawg thiab raws li tus so ntawm cov hlau. Lub acceleration ntawm tsub nqi yog ua tiav los ntawm ib tug sab nraud qhov chaw ntawm lub zog uas teev cov nqi nyob rau hauv cov kev taw qhia thiab ua rau muaj feem xyuam rau cov hluav taws xob teb. Lub deceleration ntawm cov nqi ntawm qhov kawg ntawm cov hlau yog ua tiav los ntawm lub zog sab hauv txuam nrog induced teb, uas yog tshwm sim los ntawm cov tsub zuj zuj ntawm concentrated nqi nyob rau hauv lub kawg ntawm cov hlau. Lub zog sab hauv tau txais lub zog los ntawm kev sib sau ntawm cov nqi raws li nws qhov nrawm txo mus rau xoom ntawm qhov kawg ntawm cov hlau. Yog li ntawd, lub acceleration ntawm tsub nqi vim hluav taws xob teb excitation thiab lub deceleration ntawm cov nqi vim lub discontinuity los yog du nkhaus ntawm cov hlau impedance yog cov mechanisms rau tiam ntawm electromagnetic tawg. Txawm hais tias ob qho tib si tam sim no qhov ntom ntom (Jc) thiab tus nqi them ceev (qv) yog cov ntsiab lus hauv Maxwell qhov sib npaug, tus nqi raug suav tias yog qhov tseem ceeb dua, tshwj xeeb tshaj yog rau cov chaw nyob ib ntus. Txawm hais tias qhov kev piav qhia ntawm cov hluav taws xob no feem ntau yog siv rau cov xeev ntu, nws kuj tuaj yeem siv los piav qhia txog hluav taws xob tsis tu ncua.
Pom zoo ob peb yam zoo heevcov khoom siv kav hlau txais xovtsim los ntawmRFMISO:
RM-TCR406.4 ib
RM-BCA082-4 (0.8-2GHz)
RM-SWA910-22 (9-10GHz)
2. Ob txoj kab hluav taws xob
Txuas lub qhov hluav taws xob mus rau ob-tus neeg xyuas pib kis kab mob txuas nrog lub kav hlau txais xov, raws li pom hauv daim duab 3(a). Kev siv hluav taws xob rau ob txoj kab hluav taws xob tsim hluav taws xob nruab nrab ntawm cov khoom siv hluav taws xob. Cov kab hluav taws xob ua haujlwm ntawm cov hluav taws xob dawb (yooj yim sib cais los ntawm atoms) txuas nrog txhua tus neeg xyuas pib thiab yuam kom lawv txav mus los. Lub zog ntawm tsub generates tam sim no, uas nyob rau hauv lem generates ib magnetic teb.
Daim duab 3
Peb tau lees tias cov kab hluav taws xob hluav taws xob pib nrog cov nqi zoo thiab xaus nrog cov nqi tsis zoo. Tau kawg, lawv tuaj yeem pib nrog cov nqi zoo thiab xaus rau qhov tsis muaj tseeb; los yog pib ntawm infinity thiab xaus nrog cov nqi tsis zoo; los yog daim ntawv kaw lub voj uas tsis pib lossis xaus nrog kev them nqi. Cov kab hlau nplaum ib txwm tsim cov voj voog nyob ib ncig ntawm cov neeg nqa khoom tam sim no vim tias tsis muaj cov nqi sib nqus hauv physics. Hauv qee cov qauv lej, qhov sib npaug sib nqus thiab cov khoom sib nqus tau qhia kom pom qhov sib npaug ntawm cov kev daws teeb meem uas muaj lub zog thiab cov khoom sib nqus.
Cov kab hluav taws xob hluav taws xob tau kos ntawm ob tus neeg xyuas pib pab qhia qhov kev faib tawm ntawm cov nqi. Yog tias peb xav tias qhov hluav taws xob qhov hluav taws xob yog sinusoidal, peb cia siab tias qhov hluav taws xob nruab nrab ntawm cov conductors kuj yog sinusoidal nrog lub sij hawm sib npaug ntawm qhov chaw. Tus txheeb ze qhov loj ntawm lub zog hluav taws xob yog sawv cev los ntawm qhov ntom ntawm cov kab hluav taws xob, thiab cov xub taw qhia qhov txheeb ze (zoo lossis tsis zoo). Lub sijhawm sib txawv ntawm cov hluav taws xob thiab cov hlau nplaum sib nqus ntawm cov neeg siv hluav taws xob tsim hluav taws xob nthwv dej uas nthuav tawm raws cov kab sib kis, raws li pom hauv daim duab 3(a). Lub electromagnetic yoj nkag mus rau lub kav hlau txais xov nrog cov nqi thiab cov khoom siv tam sim no. Yog tias peb tshem tawm ib feem ntawm cov qauv kav hlau txais xov, raws li pom hauv daim duab 3(b), qhov chaw dawb-yoj yoj tuaj yeem tsim los ntawm "txuas" qhib qhov kawg ntawm cov kab hluav taws xob (pom los ntawm cov kab dotted). Lub yoj qhov chaw dawb kuj tseem nyob ib ntus, tab sis qhov ntu ntu ntu P0 txav mus rau sab nraud ntawm qhov ceev ntawm lub teeb thiab taug kev deb ntawm λ/2 (rau P1) ib nrab ntawm lub sijhawm. Nyob ze ntawm lub kav hlau txais xov, qhov tsis tu ncua-theem taw tes P0 txav nrawm dua li qhov ceev ntawm lub teeb thiab mus txog qhov ceev ntawm lub teeb ntawm cov ntsiab lus deb ntawm lub kav hlau txais xov. Daim duab 4 qhia txog qhov chaw dawb ntawm hluav taws xob faib ntawm λ∕2 kav hlau txais xov ntawm t = 0, t/8, t/4, thiab 3T/8.
Daim duab 4 Qhov chaw dawb hluav taws xob faib tawm ntawm λ∕2 kav hlau txais xov ntawm t = 0, t/8, t/4 thiab 3T/8
Nws tsis paub yuav ua li cas cov nthwv dej coj tau sib cais los ntawm tus kav hlau txais xov thiab nws thiaj li tsim los nthuav tawm hauv qhov chaw dawb. Peb tuaj yeem sib piv cov kev taw qhia thiab qhov chaw tsis pub dawb rau cov dej nthwv dej, uas tuaj yeem tshwm sim los ntawm lub pob zeb poob rau hauv lub cev tsis muaj dej lossis lwm yam. Thaum qhov kev cuam tshuam hauv dej pib, cov dej nthwv dej tau tsim tawm thiab pib nthuav tawm sab nraud. Txawm hais tias qhov kev cuam tshuam nres, cov nthwv dej tsis nres tab sis txuas ntxiv mus rau pem hauv ntej. Yog tias muaj kev cuam tshuam tsis tu ncua, cov nthwv dej tshiab tau tsim los tas li, thiab kev nthuav tawm ntawm cov nthwv dej no poob qis dua lwm cov nthwv dej.
Tib yam muaj tseeb rau cov hluav taws xob hluav taws xob uas tsim los ntawm hluav taws xob cuam tshuam. Yog tias qhov pib hluav taws xob cuam tshuam los ntawm qhov chaw yog lub sijhawm luv luv, cov hluav taws xob hluav taws xob tau tsim tawm hauv cov kab sib kis, tom qab ntawd nkag mus rau lub kav hlau txais xov, thiab thaum kawg tawg raws li qhov chaw tsis muaj zog, txawm tias qhov kev zoo siab tsis muaj lawm (xws li cov dej tsis muaj zog. thiab kev ntxhov siab uas lawv tsim). Yog hais tias qhov hluav taws xob cuam tshuam tsis tu ncua, cov hluav taws xob tsis sib xws muaj nyob tsis tu ncua thiab ua raws li nyob rau hauv qab lawv thaum lub sij hawm nthuav tawm, raws li qhia nyob rau hauv lub biconical kav hlau txais xov qhia nyob rau hauv daim duab 5. Thaum electromagnetic nthwv dej nyob rau hauv lub kis tau tus mob kab thiab kav hlau txais xov, lawv lub neej muaj feem xyuam rau lub hav zoov ntawm hluav taws xob. them nyiaj hauv tus neeg xyuas pib. Txawm li cas los xij, thaum cov nthwv dej tau tawg, lawv tsim lub voj kaw thiab tsis muaj nqi los tswj lawv lub neej. Qhov no coj peb mus rau qhov xaus tias:
Excitation ntawm lub teb yuav tsum acceleration thiab deceleration ntawm tus nqi, tab sis kev saib xyuas ntawm lub teb tsis xav tau acceleration thiab deceleration ntawm tus nqi.
Daim duab 5
3. Dipole Radiation
Peb sim piav qhia txog cov txheej txheem uas cov kab hluav taws xob hauv hluav taws xob tawg tawm ntawm lub kav hlau txais xov thiab tsim cov nthwv dej dawb, thiab coj tus kav hlau txais xov dipole ua piv txwv. Txawm hais tias nws yog ib qho kev piav qhia yooj yim, nws kuj ua rau tib neeg tuaj yeem pom cov cim ntawm qhov chaw dawb. Daim duab 6(a) qhia cov kab hluav taws xob uas tsim los ntawm ob sab caj npab ntawm dipole thaum cov kab hluav taws xob tawm mus sab nraud los ntawm λ∕4 hauv thawj peb lub hlis twg ntawm lub voj voog. Piv txwv li no, cia peb xav tias tus naj npawb ntawm cov kab hluav taws xob tau tsim yog 3. Nyob rau lub quarter tom ntej ntawm lub voj voog, thawj peb kab hluav taws xob hluav taws xob txav lwm λ∕4 (tag nrho ntawm λ∕2 los ntawm qhov pib), thiab tus nqi ceev ntawm tus neeg xyuas pib pib txo. Nws tuaj yeem suav tias yog tsim los ntawm kev qhia txog cov nqi sib txawv, uas tshem tawm cov nqi ntawm tus neeg xyuas pib thaum kawg ntawm thawj ib nrab ntawm lub voj voog. Cov kab hluav taws xob hluav taws xob tsim los ntawm cov nqi sib txawv yog 3 thiab txav mus deb ntawm λ∕4, uas yog sawv cev los ntawm cov kab dotted hauv daim duab 6(b).
Qhov kawg tshwm sim yog tias muaj peb txoj kab hluav taws xob qis hauv thawj λ∕4 nrug thiab tib tus lej ntawm cov kab hluav taws xob nce toj hauv qhov thib ob λ∕4 nrug. Txij li thaum tsis muaj kev them nyiaj ntawm tus kav hlau txais xov, cov kab hluav taws xob yuav tsum raug yuam kom sib cais los ntawm tus neeg xyuas pib thiab sib txuas ua ke los tsim lub voj kaw. Qhov no yog qhia hauv daim duab 6(c). Nyob rau hauv ib nrab thib ob, tib lub cev txheej txheem yog ua raws, tab sis nco ntsoov tias qhov kev taw qhia yog qhov txawv. Tom qab ntawd, cov txheej txheem rov ua dua thiab txuas ntxiv mus tsis tu ncua, tsim cov khoom siv hluav taws xob zoo ib yam li daim duab 4.
Daim duab 6
Yog xav paub ntxiv txog antennas, thov mus saib:
Post lub sij hawm: Jun-20-2024
