Tshooj no qhia txog cov yam ntxwv tseem ceeb ntawm kev sib txuas lus wireless, lub hom phiaj yog kom nkag siab zoo dua txog lub luag haujlwm ntawm antennas hauv cov kab ke sib txuas lus. Kev sib txuas lus wireless yog ua tiav hauv daim ntawv ntawm cov nthwv dej electromagnetic, ua rau nws tseem ceeb heev kom nkag siab txog cov yam ntxwv ntawm cov nthwv dej.
Hauv tshooj no, peb yuav tham txog cov kev teeb tsa hauv qab no:
• Zaus
•Qhov ntev ntawm lub zog
• Kev Sib Tw Impedance
•VSWR & Lub zog cuam tshuam
•Qhov dav
• Feem pua ntawm Bandwidth
• Kev Siv Hluav Taws Xob
Tam sim no, cia peb saib lawv kom meej.
Zaus:
Raws li tus qauv txhais, zaus yog tus naj npawb ntawm kev rov ua dua ntawm nthwv dej ib lub sijhawm. Hauv cov lus yooj yim, zaus piav qhia txog qhov xwm txheej tshwm sim ntau npaum li cas. Ib nthwv dej tsis tu ncua rov ua dua txhua T vib nas this (ib lub sijhawm), thiab nws qhov zaus yog qhov sib pauv ntawm lub sijhawm T.
Mathematically, nws zoo li nram no:
$$f = \frac{1}{T}$$
•F sawv cev rau zaus ntawm nthwv dej ib txwm muaj, thaum
•T yog lub sijhawm uas yuav tsum tau ua kom tiav ib lub voj voog tag nrho.
Zaus ntsuas hauv hertz, luv ua Hz.
Daim duab saum toj no qhia txog nthwv dej sine, kos lub zog (hauv mV) ua lub luag haujlwm ntawm lub sijhawm (hauv ms). Cov nthwv dej no rov ua dua txhua 2t milliseconds; yog li ntawd, nws lub sijhawm T = 2t ms, thiab nws qhov zaus f = 1/(2t) kHz.
Qhov ntev ntawm lub zog:
Raws li tus qauv txhais, qhov deb ntawm ob lub ncov sib law liag lossis ob lub qhov dej sib law liag hu ua qhov wavelength.
Hais yooj yim xwb, qhov wavelength yog qhov deb ntawm ob lub ncov zoo uas nyob ib sab lossis ob lub ncov tsis zoo uas nyob ib sab. Daim duab hauv qab no qhia txog ib qho waveform periodic, nrog rau qhov wavelength (λ) thiab amplitude cim. Qhov zaus siab dua, qhov wavelength luv dua, thiab vice versa.
Cov mis rau wavelength yog:
$$\lambda = \frac{c}{f}$$
•λ sawv cev rau qhov wavelength
•C yog qhov ceev ntawm lub teeb ($3 \times 10^8 $ meters ib ob)
•F yog zaus
Tus wavelength λ yog qhia ua units ntawm qhov ntev, xws li meters, feet, lossis inches. Lub unit feem ntau siv yog lub 'meter'.
Kev Sib Tw Impedance:
Raws li tus qauv txhais, kev sib phim impedance tshwm sim thaum lub impedance ntawm lub transmitter yog kwv yees li sib npaug rau lub impedance ntawm lub receiver.
Yuav tsum muaj kev sib phim impedance ntawm lub antenna thiab lub circuit. Cov impedances ntawm lub antenna, kab kis, thiab lub circuit yuav tsum tau sib phim kom ua tiav qhov kev hloov pauv fais fab siab tshaj plaws ntawm lub antenna thiab lub receiver lossis transmitter.
Qhov yuav tsum tau sib phim
Cov khoom siv resonant muaj peev xwm xa cov zis zoo tshaj plaws hauv qee qhov zaus nqaim. Ua ib lub cuab yeej resonant, lub antenna tuaj yeem ua tiav qhov ua tau zoo dua thaum nws cov impedance raug phim kom raug.
•Thaum lub impedance ntawm lub antenna phim lub impedance ntawm qhov chaw dawb, lub zog uas lub antenna tawm yuav raug xa mus zoo
•Rau lub kav hlau txais xov tooj, nws cov zis impedance yuav tsum phim cov input impedance ntawm lub voj voog amplifier txais
•Rau lub kav hlau txais xov xa xov, nws qhov input impedance yuav tsum phim qhov output impedance ntawm lub amplifier xa xov nrog rau qhov impedance ntawm kab xa xov.
Impedance ntsuas hauv ohms, qhia los ntawm lub cim Z.
VSWR & Lub zog rov qab los:
Raws li tus qauv txhais, qhov piv ntawm qhov hluav taws xob siab tshaj plaws rau qhov hluav taws xob tsawg kawg nkaus hauv nthwv dej sawv ntsug hu ua qhov sib piv ntawm qhov hluav taws xob sawv ntsug (VSWR).
Thaum cov impedances ntawm lub antenna, kab kis, thiab lub circuit tsis sib xws, lub zog tsis tuaj yeem tawm mus tau zoo; hloov chaw, ib feem ntawm lub zog raug cuam tshuam rov qab.
Cov yam ntxwv tseem ceeb yog -
• Tus parameter uas qhia txog qib ntawm impedance mismatch hu ua Voltage Standing Wave Ratio (VSWR)
VSWR sawv cev rau Voltage Standing Wave Ratio thiab kuj tseem hu ua SWR
• Qhov ntau dua qhov impedance mismatch, qhov siab dua VSWR tus nqi
•Yuav kom ua tiav qhov hluav taws xob zoo, tus nqi VSWR zoo tagnrho yog 1: 1
• Lub zog cuam tshuam yog hais txog qhov feem ntawm lub zog pem hauv ntej uas raug pov tseg. Lub zog cuam tshuam thiab VSWR piav qhia txog tib qho xwm txheej ntawm lub cev los ntawm ntau qhov kev xav sib txawv.
Bandwidth:
Raws li tus qauv txhais, qhov zaus band hauv qhov ntau thiab tsawg wavelength tshwj xeeb uas tau muab faib rau kev sib txuas lus tshwj xeeb hu ua bandwidth.
Thaum ib lub teeb liab raug xa lossis tau txais, nws ua haujlwm hauv ib qho zaus. Qhov zaus tshwj xeeb no tau muab rau ib lub teeb liab tshwj xeeb kom tiv thaiv kev cuam tshuam los ntawm lwm lub teeb liab thaum lub sijhawm xa.
•Bandwidth txhais tau hais tias qhov ntau zaus ntawm qhov siab thiab qis zaus txwv ntawm kev xa xov tooj cua
•Thaum twg bandwidth raug muab faib lawm, lwm tus yuav siv tsis tau.
• Tag nrho cov spectrum raug muab faib ua cov ntu bandwidth, txhua tus muab faib rau cov transmitters sib txawv
Qhov bandwidth uas peb nyuam qhuav tham txog kuj tseem tuaj yeem raug xa mus rau qhov bandwidth tsis muaj kev txwv.
Feem pua ntawm Bandwidth:
Raws li tus qauv txhais, qhov piv ntawm qhov bandwidth kiag li rau nws qhov chaw nruab nrab hu ua feem pua bandwidth.
Qhov zaus hauv ib pawg uas lub zog teeb liab ncav cuag nws qhov siab tshaj plaws hu ua qhov zaus resonant, tseem hu ua qhov zaus nruab nrab ntawm pawg, uas yog fC.
•Cov zaus siab dua thiab qis dua ntawm cov band yog cim ua fH thiab fL, raws li
•Qhov bandwidth kiag li yog muab los ntawm fH − fL
•Txhawm rau ntsuas qhov dav ntawm qhov zaus band, nws yog qhov tsim nyog los xam nws cov fractional bandwidth lossis feem pua bandwidth
Qhov feem pua ntawm bandwidth yog suav los nkag siab txog qhov ntau ntawm cov zaus hloov pauv uas ib qho khoom lossis lub kaw lus tuaj yeem ua haujlwm.
•fH qhia txog qhov zaus siab dua
•fL qhia txog qhov zaus qis dua
•fc qhia txog qhov zaus nruab nrab
Qhov loj dua qhov feem pua bandwidth, qhov dav dua ntawm cov channel bandwidth.
Kev Siv Hluav Taws Xob:
Lub zog ntawm cov hluav taws xob yog txhais tias yog lub zog uas tau tawg ib lub kaum sab xis.
Ib lub kav hlau txais xov hluav taws xob muaj zog dua nyob rau hauv qee qhov kev taw qhia, uas sib raug rau nws qhov muaj zog tshaj plaws ntawm cov hluav taws xob. Qhov ntau ntawm cov hluav taws xob uas ua tau yog tus cwj pwm los ntawm qhov muaj zog ntawm cov hluav taws xob.
Kev Qhia Txog lej
Lub zog hluav taws xob tau los ntawm kev sib npaug ntawm lub zog hluav taws xob los ntawm lub plaub fab ntawm qhov deb radial:
Qhov twg U yog qhov muaj zog ntawm lub teeb ci, r yog qhov deb ntawm lub teeb ci, thiab (Wrad) yog qhov ceev ntawm lub zog uas tau tawg.
•U sawv cev rau qhov muaj zog ntawm cov hluav taws xob
•r sawv cev rau qhov deb ntawm radial
•Wrad sawv cev rau qhov ceev ntawm lub zog hluav taws xob
Cov kab zauv saum toj no qhia txog qhov muaj zog ntawm lub kav hlau txais xov. Qhov deb radial qee zaum yog cim los ntawm lub cim Φ.
Lub chav ntsuas ntawm qhov muaj zog ntawm hluav taws xob yog watts ib steradian (W/sr), lossis watts ib square radian (W/rad²).
Yog xav paub ntxiv txog antennas, thov mus saib:
Lub sijhawm tshaj tawm: Lub Peb Hlis-26-2026
