Cov Cheebtsam Passive hauv RF Circuits
Cov Resistors, capacitors, Antennas. . . . Kawm txog cov khoom siv passive siv hauv RF systems.
Cov txheej txheem RF tsis txawv ntawm lwm hom hluav taws xob. Cov kev cai lij choj ntawm physics siv tau, thiab yog li ntawd cov khoom siv yooj yim siv hauv RF tsim kuj pom muaj nyob rau hauv cov voj voog digital thiab cov voj voog analog tsawg zaus.
Txawm li cas los xij, kev tsim RF muaj cov teeb meem thiab cov hom phiaj tshwj xeeb, thiab yog li ntawd cov yam ntxwv thiab kev siv ntawm cov khoom siv xav tau kev txiav txim siab tshwj xeeb thaum peb ua haujlwm hauv cov ntsiab lus ntawm RF. Tsis tas li ntawd, qee lub voj voog sib xyaw ua haujlwm uas tshwj xeeb rau RF systems - lawv tsis siv rau hauv cov voj voog qis thiab tej zaum yuav tsis nkag siab zoo los ntawm cov neeg uas muaj kev paub me ntsis nrog cov txheej txheem tsim RF.
Peb feem ntau faib cov khoom ua pawg ua cov khoom siv nquag lossis cov khoom siv tsis siv zog, thiab txoj hauv kev no kuj siv tau zoo ib yam hauv thaj chaw ntawm RF. Cov xov xwm tham txog cov khoom siv tsis siv zog tshwj xeeb hauv kev sib raug zoo nrog RF circuits, thiab nplooj ntawv tom ntej no npog cov khoom siv nquag.
Cov Capacitors
Ib lub capacitor zoo tagnrho yuav muab cov haujlwm zoo ib yam rau lub teeb liab 1 Hz thiab lub teeb liab 1 GHz. Tab sis cov khoom tsis zoo tagnrho, thiab qhov tsis zoo ntawm lub capacitor tuaj yeem tseem ceeb heev ntawm cov zaus siab.
"C" sib raug rau lub capacitor zoo tagnrho uas faus rau ntawm ntau cov khoom parasitic. Peb muaj qhov tsis muaj qhov tsis kawg ntawm cov phaj (RD), series resistance (RS), series inductance (LS), thiab parallel capacitance (CP) ntawm PCB pads thiab lub dav hlau hauv av (peb xav tias cov khoom siv surface-mount; ntxiv rau qhov no tom qab).
Qhov tsis zoo tshaj plaws thaum peb ua haujlwm nrog cov teeb liab siab yog qhov inductance. Peb xav tias qhov impedance ntawm lub capacitor yuav txo qis tas li thaum zaus nce, tab sis qhov muaj cov parasitic inductance ua rau qhov impedance poob qis ntawm qhov zaus resonant thiab tom qab ntawd pib nce:
Cov resistors, thiab lwm yam.
Txawm tias cov resistors tuaj yeem ua teeb meem ntawm cov zaus siab, vim tias lawv muaj cov inductance series, parallel capacitance, thiab cov capacitance ib txwm muaj nrog PCB pads.
Thiab qhov no coj ib qho tseem ceeb los: thaum koj ua haujlwm nrog cov zaus siab, cov khoom siv hluav taws xob parasitic nyob txhua qhov chaw. Txawm hais tias cov khoom siv resistive yooj yim lossis zoo tagnrho li cas los xij, nws tseem yuav tsum tau ntim thiab soldered rau PCB, thiab qhov tshwm sim yog parasitics. Tib yam siv rau lwm yam khoom: yog tias nws tau ntim thiab soldered rau lub rooj tsavxwm, cov khoom siv parasitic muaj nyob.
Cov pob zeb ci ntsa iab
Lub ntsiab lus ntawm RF yog kev tswj cov teeb liab siab kom lawv xa cov ntaub ntawv, tab sis ua ntej peb tswj peb yuav tsum tsim. Ib yam li lwm hom circuits, cov siv lead ua yog ib txoj hauv kev tseem ceeb los tsim kom muaj qhov ruaj khov zaus siv.
Txawm li cas los xij, hauv kev tsim cov teeb liab digital thiab sib xyaw, feem ntau nws yog qhov teeb meem uas cov voj voog siv lead ua tsis xav tau qhov tseeb uas siv lead ua tuaj yeem muab tau, thiab yog li ntawd nws yooj yim ua tsis saib xyuas txog kev xaiv siv lead ua. Ib qho RF circuit, qhov sib piv, tej zaum yuav muaj cov kev cai zaus nruj, thiab qhov no tsis yog tsuas yog xav tau qhov tseeb zaus thawj zaug tab sis kuj tseem muaj kev ruaj khov zaus.
Lub zaus oscillation ntawm ib lub siv lead ua ib txwm muaj kev cuam tshuam rau qhov kub thiab txias hloov pauv. Qhov tsis ruaj khov ntawm zaus ua rau muaj teeb meem rau RF systems, tshwj xeeb tshaj yog cov systems uas yuav raug rau qhov kub thiab txias hloov pauv loj. Yog li, ib lub system yuav xav tau TCXO, piv txwv li, lub oscillator siv lead ua uas them nyiaj rau qhov kub thiab txias. Cov khoom siv no suav nrog cov circuitry uas them nyiaj rau qhov zaus hloov pauv ntawm cov siv lead ua:
Cov kav hlau txais xov
Lub kav hlau txais xov yog ib qho khoom siv passive uas siv los hloov lub teeb liab hluav taws xob RF mus rau hauv hluav taws xob electromagnetic (EMR), lossis vice versa. Nrog rau lwm cov khoom thiab cov conductors peb sim txo qhov cuam tshuam ntawm EMR, thiab nrog rau cov kav hlau txais xov peb sim ua kom zoo tshaj plaws ntawm kev tsim lossis kev txais tos ntawm EMR nrog rau qhov xav tau ntawm daim ntawv thov.
Kev tshawb fawb txog antenna tsis yog ib qho yooj yim kiag li. Muaj ntau yam uas cuam tshuam rau txoj kev xaiv lossis tsim lub antenna uas zoo tshaj plaws rau ib daim ntawv thov tshwj xeeb. AAC muaj ob tsab xov xwm (nias ntawm no thiab ntawm no) uas muab kev qhia zoo heev rau cov tswv yim antenna.
Cov zaus siab dua muaj ntau yam teeb meem tsim qauv, txawm hais tias qhov antenna ntawm lub system tuaj yeem ua teeb meem tsawg dua thaum zaus nce ntxiv, vim tias cov zaus siab dua tso cai rau kev siv cov antennas luv dua. Niaj hnub no nws yog ib txwm siv "chip antenna," uas yog soldered rau PCB zoo li cov khoom siv surface-mount, lossis PCB antenna, uas yog tsim los ntawm kev koom ua ke ib qho tshwj xeeb tsim kab rau hauv PCB layout.
Kev Txheeb Xyuas
Qee cov khoom siv tsuas yog siv rau hauv cov ntawv thov RF xwb, thiab lwm tus yuav tsum tau xaiv thiab siv kom zoo dua vim lawv cov cwj pwm tsis zoo ntawm cov zaus siab.
Cov khoom passive qhia txog cov lus teb zaus tsis zoo li qub vim yog parasitic inductance thiab capacitance.
Cov ntawv thov RF yuav xav tau cov siv lead ua uas raug dua thiab / lossis ruaj khov dua li cov siv lead ua feem ntau siv hauv cov voj voog digital.
Antennas yog cov khoom tseem ceeb uas yuav tsum tau xaiv raws li cov yam ntxwv thiab cov kev xav tau ntawm lub kaw lus RF.
Si Chuan Keenlion Microwave muaj ntau hom kev xaiv hauv narrowband thiab broadband configurations, npog cov zaus txij li 0.5 txog 50 GHz. Lawv tau tsim los tswj hwm los ntawm 10 txog 30 watts input zog hauv 50-ohm transmission system. Microstrip lossis stripline designs siv, thiab optimized rau kev ua tau zoo tshaj plaws.
Lub sijhawm tshaj tawm: Kaum Ib Hlis-03-2022
