1. Ua haujlwm tsawg - Txij li thaum lub zog muaj txiaj ntsig uas nyob hauv cov kab me me yog qhov me me, yog li qhov ua tau zoo ntawm AM system yog qis.

2. Kev ua haujlwm tsawg -Qhov ntau ntawm kev ua haujlwm yog me me vim qhov ua haujlwm qis. Yog li, kev sib kis ntawm cov teeb liab yog qhov nyuaj.

3. Suab nrov hauv txais tos - Raws li tus neeg txais xov tooj cua pom tias nws nyuaj rau qhov txawv ntawm qhov sib txawv ntawm qhov sib txawv uas sawv cev rau lub suab nrov thiab cov teeb liab, cov suab nrov hnyav yuav tshwm sim hauv nws qhov kev txais tos.

4. Suab zoo - Txhawm rau kom tau txais kev ncaj ncees siab, txhua lub suab zaus txog 15 KiloHertz yuav tsum tau ua dua tshiab thiab qhov no yuav tsum muaj qhov bandwidth ntawm 10 KiloHertz kom txo qis kev cuam tshuam los ntawm cov chaw tshaj tawm xov xwm uas nyob ib sab. Yog li ntawd nyob rau hauv AM broadcasting stations lub suab tsis zoo yog paub tias tsis zoo.

1. Xov tooj cua tshaj tawm

2. Kev tshaj tawm hauv TV

3. Lub qhov rooj ntawm qhov chaw nres tsheb qhib cov chaw taws teeb tseem ceeb

4. Xa cov teeb liab TV

5. Cov xov tooj cua luv luv

6. Ob txoj kev xov tooj cua sib txuas lus

VSB-SC

1. Lus txhais - Ib tug vestigial sideband (hauv xov tooj cua kev sib txuas lus) yog ib tug sideband uas tsuas yog ib feem txiav tawm los yog suppressed.

2. Daim ntawv thov - Kev tshaj tawm TV & xov tooj cua tshaj tawm

3. siv - Tshaj tawm TV teeb liab

SWB-SC

1. Lus txhais - Ib leeg-sidebandmodulation (SSB) yog kev kho kom zoo ntawm amplitude modulation uas muaj txiaj ntsig zoo siv hluav taws xob thiab bandwidth

2. Daim ntawv thov - TV tshaj tawm & Shortwave Xov tooj cua tshaj tawm

3. siv -Shortwave xov tooj cua sib txuas lus

DSB-SC

1. Lus txhais - Hauv kev sib txuas lus hauv xov tooj cua, ib sab band yog ib pawg ntawm cov zaus nws siab dua lossis qis dua tus neeg nqa khoom zaus, muaj lub zog raws li cov txheej txheem hloov kho.

2. Daim ntawv thov - Kev tshaj tawm TV & xov tooj cua tshaj tawm

3. siv - 2-txoj kev xov tooj cua sib txuas lus

Amplitude Modulation (AM) yog dab tsi?

-"Modulation yog txheej txheem ntawm superimposing ib tug tsawg zaus teeb liab ntawm ib tug high zaus cov teeb liab."

-"Cov txheej txheem ntawm kev hloov kho tuaj yeem txhais tau tias yog qhov sib txawv ntawm RF cov cab kuj yoj raws li nrog rau kev txawj ntse los yog cov ntaub ntawv nyob rau hauv ib tug tsawg zaus teeb liab."

-"Modulation txhais tau tias yog qhov ua ntej uas qee tus yam ntxwv, feem ntau amplitude, zaus lossis theem, ntawm tus cab kuj sib txawv raws li tus nqi tam sim ntawm qee qhov hluav taws xob, hu ua modulating voltage."

Vim li cas Modulation thiaj xav tau?

1. Yog tias ob lub suab paj nruag tau ua si tib lub sijhawm nyob deb, nws yuav nyuaj rau leej twg los mloog ib lub hauv paus thiab tsis hnov ​​​​qhov thib ob. Txij li thaum tag nrho cov suab paj nruag muaj kwv yees li qhov ntau zaus, tsim txog 50 Hz txog 10KHz. Yog tias qhov kev pabcuam xav tau raug hloov mus rau ib pawg ntawm ntau zaus ntawm 100KHz thiab 110KHz, thiab qhov kev pabcuam thib ob tau hloov mus rau cov qhab ntawm 120KHz thiab 130KHz, Ces ob qho kev pabcuam tseem muab 10KHz bandwidth thiab tus mloog tuaj yeem (los ntawm kev xaiv band) rov qab tau qhov kev pab cuam ntawm nws tus kheej xaiv. Lub receiver yuav down hloov tsuas yog xaiv band frequencies mus rau ib tug haum ntau yam ntawm 50Hz mus rau 10KHz.

2. Qhov thib ob yog vim li cas rau kev hloov cov lus teeb liab mus rau ntau zaus yog cuam tshuam nrog cov kav hlau txais xov loj. Nws yuav tsum tau muab sau tseg tias tus kav hlau txais xov loj yog inversely proportional rau zaus yuav tsum radiated. Qhov no yog 75 meters ntawm 1 MHz tab sis ntawm 15KHz nws tau nce mus rau 5000 meters (los yog tsuas yog tshaj 16,000 ko taw) ib tug ntsug kav hlau txais xov ntawm qhov loj no yog tsis yooj yim sua.

3. Qhov thib peb yog vim li cas rau modulating ib tug high zaus cov cab kuj yog hais tias RF (xov tooj cua zaus) lub zog yuav mus deb heev tshaj li qub npaum li cas ntawm lub zog kis mus rau lub suab zog.

Hom Kev Qhia Txog

Lub teeb liab tus cab kuj yog ib qho sine yoj ntawm tus cab kuj zaus. Hauv qab kab zauv qhia tau hais tias sine yoj muaj peb yam ntxwv uas tuaj yeem hloov pauv.

Instantaneous voltage (E) = Ec(max)Sin(2πfct + θ)

Lub sij hawm uas tej zaum yuav txawv yog cov cab kuj voltage Ec, cov cab kuj zaus fc, thiab cov cab kuj theem kaum θ. Yog li peb hom kev hloov pauv tau ua tau.

1. Amplitude Modulation

Amplitude modulation yog qhov nce lossis txo qis ntawm cov cab kuj voltage (Ec), yuav tag nrho lwm yam tseem ceeb tas li.

2. Zaus Modulation

Kev hloov pauv zaus yog qhov hloov pauv ntawm tus neeg nqa khoom zaus (fc) nrog rau tag nrho lwm yam tseem ceeb uas nyob tas li.

3. Phase Modulation

Phase modulation yog ib qho kev hloov ntawm cov cab kuj theem kaum (θ). Lub kaum sab xis tsis tuaj yeem hloov pauv yam tsis muaj kev cuam tshuam rau kev hloov pauv zaus. Yog li ntawd, theem modulation yog nyob rau hauv qhov tseeb ib daim ntawv thib ob ntawm zaus modulation.

Kev piav qhia ntawm AM

Cov txheej txheem ntawm kev sib txawv ntawm qhov sib txawv ntawm cov neeg nqa khoom siv nthwv dej ntau zaus raws li cov ntaub ntawv xa mus, ua kom qhov zaus thiab theem ntawm cov cab kuj tsis hloov pauv yog hu ua Amplitude Modulation. Cov ntaub ntawv yog suav tias yog lub teeb liab modulating thiab nws yog superimposed ntawm tus cab kuj yoj los ntawm kev siv ob qho tib si rau lub modulator. Daim duab qhia ntxaws qhia txog cov txheej txheem amplitude modulation yog muab hauv qab no.

Raws li qhia saum toj no, cov cab kuj yoj muaj qhov zoo thiab tsis zoo ib nrab voj voog. Ob lub voj voog no tau sib txawv raws li cov ntaub ntawv xa mus. Tus cab kuj muaj sine nthwv dej uas nws amplitudes ua raws li amplitude variations ntawm modulating nthwv dej. Cov cab kuj tau khaws cia rau hauv ib lub hnab ntawv uas tsim los ntawm kev hloov pauv yoj. Los ntawm daim duab, koj tuaj yeem pom tias qhov kev hloov pauv ntawm qhov sib txawv ntawm cov neeg nqa khoom siab yog nyob ntawm lub teeb liab zaus thiab qhov zaus ntawm cov cab kuj yog tib yam li qhov zaus ntawm qhov tshwm sim yoj.

Kev tsom xam ntawm Amplitude Modulation Carrier Wave

Cia vc = Vc Sin wct

vm = Vm Sin wmt

vc - Instantaneous tus nqi ntawm cov cab kuj

Vc - Peak tus nqi ntawm cov cab kuj

Wc - Angular tshaj tawm ntawm cov cab kuj

vm - Instantaneous tus nqi ntawm lub teeb liab modulating

Vm - Tus nqi siab tshaj ntawm cov teeb liab modulating

wm – Angular tshaj tawm ntawm lub teeb liab modulating

fm - Modulating teeb liab zaus

Nws yuav tsum raug sau tseg tias lub kaum sab xis ntawm theem tseem nyob tas li hauv cov txheej txheem no. Yog li nws tuaj yeem tsis quav ntsej.

Nws yuav tsum raug sau tseg tias lub kaum sab xis ntawm theem tseem nyob tas li hauv cov txheej txheem no. Yog li nws tuaj yeem tsis quav ntsej.

Lub amplitude ntawm tus cab kuj yoj txawv ntawm fm.Qhov amplitude modulated yoj yog muab los ntawm kab zauv A = Vc + vm = Vc + Vm Sin wmt

= Vc [1+ (Vm/Vc Sin wmt)]

= Vc(1 + mSin wmt)

m – Modulation Index. Qhov ratio ntawm Vm/Vc.

Instantaneous tus nqi ntawm amplitude modulated yoj yog muab los ntawm kab zauv v = A Sin wct = Vc (1 + m Sin wmt) Sin wct

= Vc Sin wct + mVc (Sin wmt Sin wct)

v = Vc Sin wct + [mVc/2 Cos (wc-wm)t – mVc/2 Cos (wc + wm)t]

Qhov kev sib npaug saum toj no sawv cev rau cov lej ntawm peb sine waves. Ib qho nrog amplitude ntawm Vc thiab zaus ntawm wc / 2, qhov thib ob nrog qhov amplitude ntawm mVc / 2 thiab zaus ntawm (wc - wm) / 2 thiab qhov thib peb nrog qhov amplitude ntawm mVc / 2 thiab zaus ntawm (wc + wm)/2.

Nyob rau hauv kev xyaum lub angular tshaj tawm ntawm tus cab kuj paub tias yuav ntau dua lub angular tshaj tawm ntawm lub modulating teeb liab (wc >> wm). Yog li, qhov sib npaug thib ob thiab thib peb cosine yog ze rau cov neeg nqa khoom zaus. Qhov sib npaug yog sawv cev graphically raws li qhia hauv qab no.

Zaus Spectrum ntawm AM Wave

Tsawg sab zaus – (wc – wm)/2

Upper side zaus – (wc + wm)/2

Cov khoom siv zaus tam sim no nyob rau hauv AM nthwv dej yog sawv cev los ntawm kab ntsug kwv yees li nyob ntawm qhov zaus axis. Qhov siab ntawm txhua kab ntsug yog kos nyob rau hauv kev faib ua feem rau nws amplitude. Txij li thaum lub angular tshaj tawm ntawm tus cab kuj yog ntau dua li lub angular tshaj tawm ntawm lub modulating teeb liab, lub amplitude ntawm sab band frequencies yuav tsis tau tshaj ib nrab ntawm cov cab kuj amplitude.

Yog li yuav tsis muaj qhov hloov pauv hauv qhov qub zaus, tab sis sab band zaus (wc – wm)/2 thiab (wc + wm)/2 yuav raug hloov. Tus qub yog hu ua Upper side band (USB) zaus thiab tom qab ntawd hu ua low side band (LSB) zaus.

Txij li thaum lub teeb liab zaus wm/2 tam sim no nyob rau hauv sab bands, nws yog tseeb hais tias cov cab kuj voltage tivthaiv tsis xa tej ntaub ntawv.

Ob sab banded zaus yuav raug tsim thaum tus cab kuj yog amplitude modulated los ntawm ib zaus. Ntawd yog, AM nthwv dej muaj qhov dav dav ntawm (wc - wm) / 2 rau (wc + wm) / 2, uas yog, 2wm / 2 lossis ob zaug lub teeb liab zaus raug tsim. Thaum lub teeb liab modulating muaj ntau tshaj ib zaus, ob sab band zaus yog tsim los ntawm txhua zaus. Ib yam li ntawd rau ob zaus ntawm cov teeb liab modulating 2 LSB's thiab 2 USB zaus yuav raug tsim.

Sab bands ntawm frequencies tam sim no saum tus cab kuj zaus yuav zoo ib yam li cov nyob hauv qab no. Sab band frequencies tam sim no saum cov cab kuj zaus paub tias yog sab qaum band thiab tag nrho cov hauv qab cov cab kuj yog nyob rau sab qis. USB zaus sawv cev rau qee qhov ntawm tus neeg hloov pauv zaus thiab LSB zaus sawv cev qhov sib txawv ntawm qhov hloov pauv zaus thiab cov khoom siv zaus. Tag nrho bandwidth yog sawv cev nyob rau hauv cov nqe lus ntawm ntau dua modulating zaus thiab yog sib npaug rau ob zaug no zaus.

Modulation Index (m)

Qhov piv ntawm qhov amplitude hloov ntawm cov cab kuj yoj mus rau qhov amplitude ntawm lub cev muaj zog nthwv dej yog hu ua modulation index. Nws yog sawv cev los ntawm tsab ntawv 'm'.

Nws kuj tseem tuaj yeem txhais tau tias yog qhov ntau ntawm qhov amplitude ntawm cov cab kuj sib txawv los ntawm cov teeb liab modulating. m = Vm/Vc.

Kev hloov pauv feem pua, %m = m * 100 = Vm / Vc * 100

Qhov feem pua ​​​​ntawm kev hloov pauv nyob nruab nrab ntawm 0 thiab 80%.

Lwm txoj hauv kev ntawm kev nthuav qhia qhov ntsuas ntsuas ntsuas yog nyob rau hauv cov nqe lus ntawm qhov siab tshaj plaws thiab qhov tsawg kawg nkaus qhov tseem ceeb ntawm qhov amplitude ntawm modulated carrier yoj. Qhov no yog qhia nyob rau hauv daim duab hauv qab no.

2 Vin = Vmax – Vmin

Vin = (Vmax – Vmin)/2

Vc = Vmax – Vin

= Vmax – (Vmax-Vmin)/2 = (Vmax + Vmin)/2

Hloov cov txiaj ntsig ntawm Vm thiab Vc hauv kab zauv m = Vm / Vc, peb tau txais

M = Vmax – Vmin/Vmax + Vmin

Raws li tau hais ua ntej, tus nqi ntawm 'm' nyob nruab nrab ntawm 0 thiab 0.8. Tus nqi ntawm m txiav txim siab lub zog thiab qhov zoo ntawm cov teeb liab kis. Hauv AM nthwv dej, lub teeb liab muaj nyob rau hauv qhov kev hloov pauv ntawm tus cab kuj amplitude. Lub teeb liab kis tau tus mob yuav tsis muaj zog yog tias tus neeg nqa khoom nthwv dej tsuas yog hloov kho mus rau qhov tsawg heev. Tab sis yog tias tus nqi ntawm m tshaj kev sib koom ua ke, lub transmitter tso zis ua rau muaj kev cuam tshuam tsis zoo.

Lub zog sib raug zoo hauv AM nthwv dej

Lub modulated nthwv dej muaj zog ntau dua li muaj los ntawm cov neeg nqa khoom nthwv dej ua ntej modulating. Tag nrho cov khoom siv fais fab hauv amplitude modulation tuaj yeem sau tau raws li:

Ptotal = Pcarrier + PLSB + PUSB

Xav txog kev tiv thaiv ntxiv xws li kav hlau txais xov kuj R.

Pcarrier = [(Vc/√2)/R]2 = V2C/2R

Txhua sab band muaj tus nqi ntawm m / 2 Vc thiab rms tus nqi ntawm mVc / 2√2. Li no lub hwj chim hauv LSB thiab USB tuaj yeem sau ua

PLSB = PUSB = (mVc/2√2) 2/R = m2/4 * V2C/2R = m2/4 Pcarrier

Ptotal = V2C/2R + [m2/4*V2C/2R] + [m2/4*V2C/2R] = V2C/2R (1 + m2/2) = Pcarrier (1 + m2/2)

Hauv qee qhov kev siv, tus cab kuj yog ib txhij hloov kho los ntawm ntau lub sinusoidal modulating signals. Nyob rau hauv xws li ib tug teeb meem, tag nrho modulation index yog muab raws li

Mt = √(m12 + m22 + m32 + m42 + ......

Yog tias Ic thiab Nws yog rms qhov tseem ceeb ntawm qhov tsis hloov pauv tam sim no thiab tag nrho cov hloov pauv tam sim no thiab R yog qhov kev tawm tsam los ntawm cov dej ntws tam sim no, tom qab ntawd

Ptotal/Pcarrier = (Ib.R/Ic.R)2 = (It/Ic)2

Ptotal/Pcarrier = (1 + m2/2)

IB = 1 + m2/2

1. Txhais kev hloov kho?

Modulation yog ib qho txheej txheem uas qee tus yam ntxwv ntawm cov teeb liab muaj peev xwm ua tau zoo sib txawv raws li tus nqi tam sim ntawm cov teeb liab modulating.

2. Dab tsi yog hom kev hloov pauv analog?

Amplitude modulation.

Lub Ntsej Muag Tes Haujlwm

Zaus modulation

Phase modulation.

3. Txhais qhov tob ntawm kev hloov kho.

Nws yog txhais raws li qhov piv ntawm cov lus amplitude rau ntawm cov cab kuj amplitude. m=Em/Ec

4. Dab tsi yog qib ntawm kev hloov kho?

Hauv qab modulation. m <1

Critical modulation m=1

Hla kev hloov pauv m> 1

5. Dab tsi yog qhov xav tau rau kev hloov kho?

- Kev xav tau rau kev hloov kho:

- Yooj yim ntawm kev sib kis

- Multiplexing

- Txo suab nrov

- Nqaim bandwidth

- Kev ua haujlwm zaus

- Txo cov kev txwv cov khoom siv

6. Hom AM modulators yog dab tsi?

Muaj ob hom AM modulators. Lawv yog

- Linear modulators

- Tsis-linear modulators

Linear modulators raug cais raws li hauv qab no

- Transistor modulator

Muaj peb hom transistor modulator.

- Cov khoom siv modulator

- Emitter modulator

- Base modulator

- Hloov cov modulators

Non-linear modulators raug faib raws li hauv qab no

- Square txoj cai modulator

- Khoom modulator

- Tshuav cov ntsuas

7. Dab tsi yog qhov txawv ntawm qib siab thiab qib qis kev hloov kho?

Nyob rau hauv qib siab modulation, lub modulator amplifier ua haujlwm nyob rau theem siab zog thiab xa lub zog ncaj qha mus rau lub kav hlau txais xov. Hauv qib qis modulation, lub modulator amplifier ua kev hloov kho ntawm qib qis zog. Lub teeb liab modulated ces amplified mus rau qib siab zog los ntawm chav kawm B fais fab amplifier. Lub amplifier pub lub zog rau kav hlau txais xov.

8. Txhais Kev Ntsuas (lossis) Demodulation.

Kev kuaj xyuas yog cov txheej txheem ntawm kev rho tawm cov teeb liab modulating los ntawm cov cab kuj modulated. Ntau hom kev ntes tau siv rau ntau hom kev hloov pauv.

9. Txhais Amplitude Modulation.

Nyob rau hauv amplitude modulation, lub amplitude ntawm ib tug carrier teeb liab yog txawv raws li variations nyob rau hauv amplitude ntawm modulating teeb liab.

Lub teeb liab AM tuaj yeem sawv cev rau lej raws li, eAM = (Ec + Em sinωmt ) sinωct thiab qhov ntsuas ntsuas ntsuas tau muab raws li, m = Em / EC (lossis) Vm / Vc

10. Super Heterodyne Receiver yog dab tsi?

Tus super heterodyne receiver hloov tag nrho cov khoom RF zaus mus rau qhov qis qis, hu ua intermediate zaus (IF). Qhov no IF yog ces amplitude thiab kuaj tau tus thawj teeb liab.

11. Ib lub suab nrov thiab ntau lub suab hloov pauv yog dab tsi?

- Yog hais tias kev hloov kho tau ua rau cov lus teeb liab nrog ntau dua ib qho kev sib txuas, ces qhov kev hloov kho hu ua multitone modulation.

- Yog hais tias kev hloov kho tau ua rau cov lus ceeb toom nrog ib qho kev sib txuas zaus ces qhov kev hloov kho hu ua ib lub suab hloov.

12. Sib piv AM nrog DSB-SC thiab SSB-SC.

13. Qhov zoo ntawm VSB-AM yog dab tsi?

- Nws muaj bandwidth ntau dua SSB tab sis tsawg dua DSB system.

- Kev xa hluav taws xob ntau dua DSB tab sis tsawg dua SSB system.

- Tsis muaj tsawg zaus feem poob. Li no nws zam theem distortion.

14. Koj yuav tsim DSBSC-AM li cas?

Muaj ob txoj hauv kev tsim DSBSC-AM xws li

- Sib npaug modulator

- Ntiv nplhaib modulators.

15. Qhov zoo ntawm lub nplhaib modulator yog dab tsi?

- Nws cov zis yog ruaj khov.

- Nws yuav tsum tsis muaj hluav taws xob sab nraud los qhib lub diodes. c) Virtually tsis tu.

- Lub neej ntev.

16. Txhais Demodulation.

Demodulation los yog nrhiav kom tau yog cov txheej txheem uas modulating voltage yog zoo los ntawm cov teeb liab modulated. Nws yog tus txheej txheem thim rov qab ntawm kev hloov pauv. Cov cuab yeej siv rau kev demodulation lossis kev kuaj xyuas yog hu ua demodulators lossis detectors. Rau amplitude modulation, detectors los yog demodulators yog categorized li: 

- Square-txoj cai detectors

- Lub hnab ntawv ntes

17. Txhais Multiplexing.

Multiplexing yog txhais raws li tus txheej txheem ntawm kev xa ob peb cov lus qhia ib txhij dhau ib channel.

18. Txhais ntau zaus Division Multiplexing.

Kev faib ntau zaus ntau zaus txhais tau tias muaj ntau lub teeb liab raug xa mus ib txhij nrog txhua lub teeb liab nyob ntawm qhov sib txawv zaus hauv ib qho bandwidth.

19. Txhais Guard Band.

Guard Bands tau qhia nyob rau hauv spectrum ntawm FDM kom tsis txhob muaj kev cuam tshuam ntawm cov channel uas nyob ib sab. Dav dav ntawm cov hlua tiv thaiv, Me me qhov cuam tshuam.

20. Txhais SSB-SC.

- SSB-SC sawv cev rau Ib Leeg Ib Sab Band Txhaum Cai

- Thaum tsuas yog ib qho sideband kis tau tus mob, qhov kev hloov pauv yog hu ua Single sideband modulation. Nws tseem hu ua SSB lossis SSB-SC.

21. Txhais DSB-SC.

Tom qab hloov kho, cov txheej txheem ntawm kev xa cov sidebands (USB, LSB) ib leeg thiab suppressing tus cab kuj hu ua Ob Sab Band-Suppressed Carrier.

22. Dab tsi yog qhov tsis zoo ntawm DSB-FC?

- Lub zog khib nyiab yuav tshwm sim hauv DSB-FC

- DSB-FC yog bandwidth inefficient system.

23. Txhais Kev Tshawb Nrhiav Kev Coherent.

Thaum lub sij hawm Demodulation cab kuj yog raws nraim coherent los yog synchronized nyob rau hauv ob qho tib si zaus thiab theem, nrog thawj cov cab kuj siv los tsim DSB-SC yoj.

Txoj kev tshawb nrhiav no hu ua coherent detection lossis synchronous detection.

24. Vestigial Side Band Modulation yog dab tsi?

Vestigial Sideband Modulation yog txhais tau tias yog ib qho kev hloov kho uas ib feem ntawm lub sideband raug tshem tawm thiab cov vestige ntawm lwm tus sideband raug xa mus los them rau qhov kev tawm tsam ntawd.

25. Dab tsi yog qhov zoo ntawm cov teeb liab sideband kis tau tus mob?

- Kev siv zog

- Kev txuag bandwidth

- Txo suab nrov

26. Dab tsi yog qhov tsis zoo ntawm ib sab band kis tau tus mob?

- Complex receivers: Ib sab band systems xav tau ntau dua thiab kim receivers thn conventiaonal AM kis tau tus mob.

- Tuning nyuaj: Ib sab band receivers xav tau ntau qhov nyuaj thiab meej tunig dua li cov neeg txais AM.

27. Sib piv linear thiab non-linear modulators?

Linear Modulators

- Kev lim dej hnyav tsis tas yuav tsum tau ua.

- Cov modulators no yog siv nyob rau hauv qib siab modulation.

- Cov cab kuj voltage yog ntau dua li modulating teeb liab voltage.

Tsis yog Linear Modulators

- Kev lim dej hnyav yuav tsum tau ua.

- Cov modulators no yog siv nyob rau hauv qib qis modulation.

- Lub teeb liab modulating voltage yog ntau dua li cov teeb liab teeb liab voltage.

28. Dab tsi yog kev txhais lus zaus?

Piv txwv tias lub teeb liab yog band txwv rau qhov ntau zaus txuas ntawm ib zaus f1 mus rau zaus f2. Cov txheej txheem ntawm kev txhais lus zaus yog ib qho uas thawj lub teeb liab hloov nrog lub teeb liab tshiab uas nws cov spectral ntau txuas ntxiv los ntawm f1' thiab f2' thiab cov teeb liab tshiab twg, hauv daim ntawv zoo tib yam cov ntaub ntawv uas tau yug los ntawm thawj lub teeb liab.

29. Ob qhov xwm txheej twg raug txheeb xyuas hauv kev txhais lus ntau zaus?

- Up Hloov: Nyob rau hauv cov ntaub ntawv no tus txhais cov cab kuj zaus yog ntau dua li cov khoom xa tuaj

- Kev hloov dua siab tshiab: Nyob rau hauv cov ntaub ntawv no tus txhais cov cab kuj zaus yog tsawg tshaj li qhov nce tus cab kuj zaus.

Yog li, lub teeb liab nqaim FM yuav tsum muaj tib qhov kev sib kis bandwidth raws li AM teeb liab.

30. BW rau AM yoj yog dab tsi?

 Qhov sib txawv ntawm ob qhov ntau zaus yog sib npaug ntawm bandwidth ntawm AM nthwv dej.

 Yog li ntawd, Bandwidth, B = (fc + fm) - (fc - fm) B = 2fm

31. BW ntawm DSB-SC teeb liab yog dab tsi?

Bandwidth, B = (fc + fm) - (fc - fm) B = 2f

Nws yog qhov pom tseeb tias qhov bandwidth ntawm DSB-SC kev hloov pauv yog tib yam li ntawm cov AM nthwv dej dav dav.

32. Dab tsi yog cov txheej txheem demodulation rau DSB-SC cov cim?

DSB-SC teeb liab yuav raug txiav tawm los ntawm ob txoj hauv qab no:

- Synchronous nrhiav kom tau txoj kev.

- Siv lub hnab ntawv ntes tom qab muab cov khoom thauj rov qab.

33. Sau cov ntawv thov Hilbert hloov pauv?

- Rau tiam ntawm SSB cov cim,

- Rau kev tsim cov theem yam tsawg kawg nkaus lim,

- Rau kev sawv cev ntawm band pass signals.

34. Dab tsi yog txoj hauv kev tsim cov teeb liab SSB-SC?

SSB-SC cov teeb liab yuav raug tsim los ntawm ob txoj hauv kev raws li hauv qab no:

-Frequency discrimination method lossis filter method.

- Phase discrimination method lossis phase-shift method.

GLOSSARY TERMS

1. Amplitude modulation: Kev hloov pauv ntawm nthwv dej los ntawm qhov sib txawv ntawm nws qhov amplitude, siv tshwj xeeb tshaj yog siv los ntawm kev tshaj tawm cov suab paj nruag los ntawm kev sib txuas nrog lub xov tooj cua yoj.

2. Qhov ntsuas ntsuas ntsuas: (modulation qhov tob) ntawm cov qauv kev hloov pauv piav qhia los ntawm ntau npaum li cas qhov hloov pauv hloov pauv ntawm cov teeb liab nqa khoom sib txawv nyob ib puag ncig nws qib unmodulated.

3. Narrowband FM: Yog tias qhov ntsuas ntsuas ntawm FM khaws cia qis dua 1, ces FM tsim tau suav tias yog FM nqaim.

4. Kev hloov pauv zaus (FM): tus encoding ntawm cov ntaub ntawv nyob rau hauv ib tug cab kuj yoj los ntawm txawv qhov instantaneous zaus ntawm yoj.

5. Amplication: Cov qib tau ua tib zoo xaiv kom nws tsis txhob overload lub tov khoom thaum muaj teeb meem muaj zog tam sim no, tab sis ua kom cov teeb liab tau nthuav dav kom txaus los xyuas kom meej lub teeb liab zoo rau lub suab nrov ua tiav.

6. Modulation: Cov txheej txheem los ntawm qee yam ntawm cov yam ntxwv ntawm tus neeg nqa khoom nthwv dej sib txawv raws li cov lus qhia.

Shortwave (SW)

Lub xov tooj cua Shortwave muaj ntau yam loj - nws tuaj yeem tau txais ntau txhiab mais ntawm lub tshuab xa tawm, thiab kev sib kis tuaj yeem hla dej hiav txwv thiab roob. Qhov no ua rau nws zoo tagnrho rau kev mus txog cov tebchaws uas tsis muaj xov tooj cua lossis qhov chaw tshaj tawm cov ntseeg Vajtswv raug txwv. Muab tso tseg, xov tooj cua shortwave overcomes ciam teb, txawm thaj chaw los yog nom tswv. SW kis tau yooj yim tau txais, ib yam nkaus: txawm tias pheej yig, xov tooj cua yooj yim tuaj yeem khaws lub teeb liab.

Lub zog ntawm lub xov tooj cua shortwave ua rau nws zoo haum rau Feba qhov chaw tseem ceeb ntawm lub Lub Koom Txoos raug tsim txom. Piv txwv li, nyob rau thaj tsam ntawm North East Africa qhov chaw tshaj tawm kev ntseeg raug txwv hauv lub tebchaws, peb cov neeg koom tes hauv zos tuaj yeem tsim cov ntsiab lus suab, xa tawm hauv lub tebchaws thiab kom nws rov qab los ntawm SW kis tsis muaj kev pheej hmoo ntawm kev foob.  

Tam sim no Yemen tab tom muaj kev kub ntxhov hnyav thiab muaj kev kub ntxhov nrog rau kev tsis sib haum xeeb ua rau muaj kev kub ntxhov loj heev rau tib neeg. Ntxiv nrog rau kev txhawb nqa ntawm sab ntsuj plig, peb cov neeg koom tes tshaj tawm cov khoom siv hais txog cov teeb meem kev noj qab haus huv, kev noj qab haus huv thiab kev noj qab haus huv tam sim no los ntawm kev xav ntawm Christian.  

Hauv ib lub tebchaws uas cov ntseeg tsuas yog 0.08% ntawm cov pejxeem thiab ntsib kev tsim txom vim lawv txoj kev ntseeg, Lub Koom Txoos Kav Tos Liv yog ib lub lim tiam 30 feeb xov tooj cua luv luv uas txhawb nqa cov neeg ntseeg Yemeni hauv cov lus hauv zos. Cov neeg mloog tuaj yeem nkag mus rau kev txhawb nqa xov tooj cua hauv kev ntiag tug thiab tsis qhia npe.  

Ib txoj hauv kev muaj zog kom ncav cuag cov zej zog uas tsis muaj kev cuam tshuam thoob plaws ciam teb, qhov luv luv yog qhov ua tau zoo ntawm kev ncav cuag cov neeg tuaj yeem nyob deb nrog Txoj Moo Zoo thiab, nyob rau thaj chaw uas cov ntseeg raug tsim txom, tso cov neeg mloog thiab cov tshaj tawm kom tsis txhob ntshai kev ua pauj. 

Nruab nrab-yoj (MW)

Cov xov tooj cua nruab nrab feem ntau yog siv rau kev tshaj tawm hauv zos thiab zoo meej rau cov zej zog nyob deb nroog. Nrog rau qhov nruab nrab kis tau tus mob, nws tuaj yeem ncav cuag thaj chaw sib cais nrog lub teeb liab muaj zog, txhim khu kev qha. Kev xa xov nruab nrab-yoj tuaj yeem tshaj tawm los ntawm cov xov tooj cua tsim tawm - qhov twg cov tes hauj lwm no muaj nyob.  

In sab qaum teb India, kev ntseeg hauv zos ua rau cov poj niam marginalized thiab ntau nyob hauv lawv lub tsev. Rau cov poj niam hauv txoj haujlwm no, kev xa tawm los ntawm Feba North Is Nrias teb (siv lub xov tooj cua tsim tawm) yog qhov tseem ceeb txuas nrog lub ntiaj teb sab nraud. Nws cov txiaj ntsig-raws li kev pab cuam muab kev kawm, kev qhia txog kev noj qab haus huv thiab kev nkag siab txog poj niam txoj cai, ua rau muaj kev sib tham ntawm sab ntsuj plig nrog cov poj niam uas hu rau lub chaw nres tsheb. Nyob rau hauv cov ntsiab lus no, xov tooj cua yog nqa cov lus ntawm kev cia siab thiab kev txhawb nqa rau cov poj niam mloog hauv tsev.   

Zaus Modulation (FM)

Rau qhov chaw xov tooj cua hauv zej zog, FM yog huab tais! 

Xov tooj cua Umoja FM nyob rau hauv DRC nyuam qhuav pib, aiming muab lub suab rau cov zej zog. FM muab lub teeb liab luv luv - feem ntau mus rau txhua qhov chaw hauv qhov pom ntawm lub tshuab xa tawm, nrog lub suab zoo heev. Nws feem ntau tuaj yeem npog thaj tsam ntawm ib lub nroog me lossis lub nroog loj - ua rau nws zoo meej rau lub chaw nres tsheb xov tooj cua tsom mus rau thaj chaw txwv tsis pub hais lus rau cov teeb meem hauv zos. Txawm hais tias qhov chaw nres tsheb luv luv thiab nruab nrab nthwv dej tuaj yeem ua haujlwm kim, daim ntawv tso cai rau lub zej zog FM chaw nres tsheb yog pheej yig dua. 

Afno FM, Feba tus khub hauv Nepal, muab cov lus qhia txog kev noj qab haus huv tseem ceeb rau cov zej zog hauv zos hauv Okhaldhunga thiab Dadeldhura. Siv FM tso cai rau lawv tso hla cov ntaub ntawv tseem ceeb, kom meej meej, rau thaj chaw tsom. Hauv Nepal nyob deb nroog, muaj qhov tsis txaus ntseeg ntawm cov tsev kho mob thiab qee qhov kev mob tshwm sim tau pom tias yog kev txwv. Muaj qhov xav tau tiag tiag rau cov lus qhia zoo, tsis yog kev txiav txim siab txog kev noj qab haus huv thiab Afno FM pab ua kom tau raws li qhov xav tau no. Pab neeg ua haujlwm koom tes nrog cov tsev kho mob hauv zos los tiv thaiv thiab kho cov teeb meem kev noj qab haus huv (tshwj xeeb yog cov neeg muaj kev qias neeg nrog rau lawv) thiab los daws cov neeg hauv zos kev ntshai ntawm cov kws kho mob, txhawb cov neeg mloog mus nrhiav kev kho mob hauv tsev kho mob thaum lawv xav tau. FM kuj tseem siv hauv xov tooj cua rau teb thaum muaj xwm ceev - nrog rau 20kg FM transmitter yog lub teeb txaus los nqa mus rau cov zej zog muaj kev puas tsuaj uas yog ib feem ntawm qhov yooj yim rau kev thauj mus los hauv studio. 

Internet Xov Tooj Cua

Txoj kev loj hlob sai ntawm lub vev xaib thev naus laus zis muaj lub sijhawm zoo rau kev tshaj tawm xov tooj cua. Internet-based chaw nres tsheb yog ceev thiab yooj yim rau kev teeb tsa (qee zaum siv tsawg li ib lub lim tiam kom sawv thiab khiav! Nws tuaj yeem raug nqi ntau dua li kev sib kis.

Thiab vim tias internet tsis muaj ciam teb, lub vev xaib xov tooj cua tuaj yeem ncav cuag thoob ntiaj teb. Ib qho teeb meem yog tias Internet xov tooj cua yog tso siab rau kev pab cuam hauv Is Taws Nem thiab cov neeg mloog nkag mus rau lub computer lossis smartphone.  

Hauv ib lub ntiaj teb cov pej xeem ntawm 7.2 billion, peb feem tsib, lossis 4.2 billion tus neeg, tseem tsis tau muaj kev nkag mus rau Internet li niaj zaus. Hauv Internet raws li cov xov tooj cua hauv zej zog yog li tam sim no tsis haum rau qee qhov chaw txom nyem thiab tsis tuaj yeem nkag mus rau hauv ntiaj teb.

Amplitude modulation (AM) yog nyob deb ntawm daim ntawv qub tshaj plaws ntawm kev hloov kho paub. Thawj qhov chaw tshaj tawm xov xwm yog AM, tab sis txawm tias ua ntej, CW lossis txuas ntxiv-yoj lub cim nrog Morse code yog daim ntawv AM. Lawv yog qhov peb hu ua on-off keying (OOK) lossis amplitude-shift keying (ASK) hnub no.

Txawm hais tias AM yog thawj zaug thiab laus tshaj plaws, nws tseem nyob ib puag ncig hauv ntau hom ntau dua li koj xav. AM yog qhov yooj yim, tus nqi qis, thiab ua haujlwm zoo heev. Txawm hais tias qhov kev thov rau cov ntaub ntawv ceev ceev tau tsav peb mus rau orthogonal zaus-division multiplexing (OFDM) raws li qhov feem ntau spectrally npaum modulation scheme, AM tseem koom nrog hauv daim ntawv ntawm quadrature amplitude modulation (QAM).

Dab tsi ua rau kuv xav txog AM? Thaum lub caij ntuj no cua daj cua dub loj ob lub hlis dhau los, kuv tau txais feem ntau ntawm kuv cov huab cua thiab cov ntaub ntawv xwm txheej ceev los ntawm cov chaw nres tsheb AM hauv zos. Feem ntau los ntawm WOAI, qhov chaw nres tsheb 50-kW uas tau nyob ib puag ncig rau hnub nyoog. Kuv tsis ntseeg tias lawv tseem cranking tawm 50 kW thaum lub zog hluav taws xob, tab sis lawv tau nyob saum huab cua thaum lub caij huab cua tag nrho. Ntau yog tias tsis yog feem ntau AM chaw nres tsheb tau nce thiab khiav ntawm lub zog thaub qab. Kev ntseeg siab thiab kev nplij siab.

Muaj ntau tshaj 6,000 AM chaw nres tsheb hauv Asmeskas hnub no. Thiab lawv tseem muaj cov neeg mloog coob heev, feem ntau yog cov neeg hauv zos uas nrhiav cov huab cua tshiab, tsheb khiav, thiab xov xwm. Feem ntau tseem mloog hauv lawv lub tsheb lossis tsheb thauj khoom. Muaj ntau yam kev sib tham hauv xov tooj cua thiab koj tseem tuaj yeem hnov ​​​​cov ntaus pob ntaus pob lossis ncaws pob ntawm AM. Cov kev xaiv suab paj nruag tau poob qis, vim lawv feem ntau tau tsiv mus rau FM. Txawm li cas los xij, muaj qee lub tebchaws thiab Tejano suab paj nruag chaw nres tsheb ntawm AM. Nws tag nrho yog nyob ntawm cov neeg tuaj saib hauv zos, uas yog qhov sib txawv heev.

AM xov tooj cua tshaj tawm hauv 10-kHz wide channels ntawm 530 thiab 1710 kHz. Txhua qhov chaw nres tsheb siv yees, yog li polarization yog ntsug. Thaum nruab hnub, propagation yog feem ntau hauv av nthwv dej nrog thaj tsam li 100 mais. Rau feem ntau, nws nyob ntawm theem fais fab, feem ntau 5 kW lossis 1 kW. Tsis muaj ntau qhov chaw 50-kW muaj nyob, tab sis lawv qhov ntau yog pom tseeb nyob deb.

Thaum tsaus ntuj, tau kawg, qhov kev nthuav tawm hloov pauv raws li cov txheej txheem ionized hloov thiab ua kom cov teeb liab mus deb dua ua tsaug rau lawv lub peev xwm los ntawm cov txheej txheem ion sab saud los tsim ntau lub teeb liab hops ntawm qhov deb mus rau ib txhiab mais lossis ntau dua. Yog tias koj muaj xov tooj cua AM zoo thiab kav hlau txais xov ntev koj tuaj yeem mloog cov chaw nres tsheb thoob plaws lub tebchaws thaum hmo ntuj.

AM tseem yog lub ntsiab lus hloov kho ntawm lub xov tooj cua luv luv, uas koj tuaj yeem hnov ​​​​txog thoob ntiaj teb los ntawm 5 txog 30 MHz. Nws tseem yog ib qho ntawm cov ntaub ntawv tseem ceeb rau ntau lub teb chaws thib peb. Kev mloog luv luv kuj tseem yog qhov nyiam nyiam.

Dhau li ntawm kev tshaj tawm, AM tseem siv qhov twg? Ham xov tooj cua tseem siv AM; tsis yog nyob rau hauv thawj theem siab, tab sis raws li ib leeg sideband (SSB). SSB yog AM nrog cov neeg nqa khoom txwv tsis pub thiab ib lub sideband lim tawm, tawm hauv qhov nqaim 2,800-Hz channel ntawm lub suab. Nws yog dav siv thiab zoo heev, tshwj xeeb tshaj yog nyob rau hauv cov nqaij npua bands ntawm 3 mus rau 30 MHz. Cov tub rog thiab qee lub xov tooj cua hauv hiav txwv txuas ntxiv siv qee hom SSB, ib yam nkaus.

Tab sis tos, tsis yog tag nrho. AM tseem tuaj yeem pom hauv Citizen's Band xov tooj cua. Plain-laus AM tseem nyob hauv qhov sib xyaw, zoo li SSB. Ntxiv mus, AM yog qhov kev hloov pauv tseem ceeb ntawm cov xov tooj cua dav hlau siv nruab nrab ntawm cov dav hlau thiab cov pej thuam. Cov xov tooj cua no ua haujlwm hauv 118- rau 135-MHz band. Vim li cas AM? Kuv tsis tau paub qhov ntawd, tab sis nws ua haujlwm zoo.

Thaum kawg, AM tseem nrog peb nyob hauv QAM daim ntawv, kev sib xyaw ua ke ntawm theem thiab amplitude modulation. Feem ntau OFDM channel siv ib daim ntawv ntawm QAM kom tau txais cov ntaub ntawv ntau dua lawv tuaj yeem xa.

Txawm li cas los xij, AM tseem tsis tau tuag, thiab qhov tseeb nws zoo li Aging Majestically.

AM Transmitter yog dab tsi?

Transmitters uas xa AM signals yog hu ua AM transmitters, nws tseem hu ua AM xov tooj cua transmitter los yog AM tshaj tawm xov tooj cua transmitter, rau lawv tau siv los xa xov tooj cua signals ntawm ib sab mus rau lwm yam.

Cov transmitters yog siv nyob rau hauv nruab nrab yoj (MW) thiab luv yoj (SW) zaus bands rau AM tshaj tawm.

MW band muaj zaus ntawm 550 KHz thiab 1650 KHz, thiab SW band muaj ntau zaus ntawm 3 MHz txog 30 MHz. Ob hom AM transmitters uas tau siv raws li lawv lub zog xa tawm yog:

• Qib Siab
• Theem Qis

Cov qib siab transmitters siv qib siab hloov kho, thiab cov qib qis transmitters siv cov qib qis qis. Qhov kev xaiv ntawm ob qhov kev hloov pauv yog nyob ntawm lub zog xa tawm ntawm AM transmitter.

Hauv kev tshaj tawm xov xwm, qhov twg lub zog xa tawm tuaj yeem yog qhov kev txiav txim ntawm kilowatts, qib siab hloov kho yog ua haujlwm. Hauv cov hluav taws xob tsis tshua muaj hluav taws xob, qhov twg tsuas yog ob peb watts ntawm lub zog xa hluav taws xob yuav tsum tau siv, kev hloov kho qis yog siv..

High-Level Thiab Low-Level Transmitters

Daim duab hauv qab no qhia txog daim duab thaiv ntawm qib siab thiab qib qis transmitters. Qhov yooj yim sib txawv ntawm ob lub transmitters yog lub zog amplification ntawm cov cab kuj thiab modulating signals.

Daim duab (a) qhia daim duab thaiv ntawm qib siab AM transmitter.

Daim duab (a) yog kos rau kev xa suab. Nyob rau hauv high-theem kis tau tus mob, lub hwj chim ntawm cov cab kuj thiab modulating signals yog amplified ua ntej siv lawv mus rau lub modulator theem, raws li qhia nyob rau hauv daim duab (a). Nyob rau hauv qis-theem modulation, lub hwj chim ntawm ob input signals ntawm lub modulator theem tsis amplified. Lub zog xa hluav taws xob yuav tsum tau txais los ntawm theem kawg ntawm lub tshuab xa hluav taws xob, chav kawm C lub zog amplifier.

Feem ntau ntawm daim duab (a) yog:

• Carrier oscillator
• Tsis muaj amplifier
• Zaus muaj khoo
• Lub zog amplifier
• Audio chain
• Modulated chav kawm C lub zog amplifier

Carrier Oscillator

Cov cab kuj oscillator tsim cov teeb liab cab kuj, uas nyob hauv RF ntau. Qhov zaus ntawm tus cab kuj yog ib txwm siab heev. Vim tias nws yog ib qho nyuaj heev los tsim cov zaus siab nrog kev ruaj ntseg zoo, cov cab kuj oscillator generates ib sub ntau nrog cov cab kuj yuav tsum tau.

Qhov no sub ntau zaus yog muab faib los ntawm ntau zaus ntau zaus kom tau txais cov cab kuj yuav tsum tau.

Tsis tas li ntawd, siv lead ua oscillator tuaj yeem siv nyob rau theem no los tsim cov khoom siv zaus tsawg nrog qhov zoo tshaj plaws kev ruaj ntseg. Cov theem ntau zaus ces nce qhov zaus ntawm tus cab kuj mus rau nws tus nqi xav tau.

Tsis Siv Neeg Amplifier

Lub hom phiaj ntawm qhov tsis muaj amplifier yog ob npaug. Nws thawj zaug sib tw cov zis impedance ntawm tus cab kuj oscillator nrog cov input impedance ntawm tus zaus multiplier, theem tom ntej ntawm cov cab kuj oscillator. Nws ces cais cov cab kuj oscillator thiab zaus multiplier.

Qhov no yog yuav tsum tau kom tus multiplier tsis kos ib tug loj tam sim no los ntawm cov cab kuj oscillator. Yog tias qhov no tshwm sim, qhov zaus ntawm tus cab kuj oscillator yuav tsis nyob ruaj khov.

Ntau zaus

Lub sub-ntau zaus ntawm cov teeb liab cab kuj, tsim los ntawm cov cab kuj oscillator , yog tam sim no siv rau cov zaus multiplier los ntawm tsis amplifier. Cov theem no tseem hu ua harmonic generator. Qhov ntau zaus ua kom muaj kev sib haum xeeb ntau dua ntawm cov cab kuj oscillator zaus. Cov zaus ntau zaus yog ib lub voj voog tuned uas tuaj yeem hloov mus rau qhov yuav tsum tau muaj cov cab kuj zaus uas yuav tsum tau xa mus.

Fais Amplifier

Lub zog ntawm lub teeb liab xaim hluav taws xob yog ces amplified nyob rau hauv lub hwj chim amplifier theem. Qhov no yog qhov yuav tsum tau ua ntawm high-level transmitter. Chav kawm C lub hwj chim amplifier muab lub zog siab tam sim no pulses ntawm cov teeb liab ntawm nws cov zis.

Audio Chain

Lub suab teeb liab yuav kis tau los ntawm lub microphone, raws li qhia hauv daim duab (a). Lub suab tsav amplifier amplifies qhov voltage ntawm lub teeb liab no. Qhov no amplification yog tsim nyog los tsav lub hwj chim amplifier. Tom ntej no, chav kawm A lossis chav kawm B lub zog amplifier ua kom lub zog ntawm lub teeb liab.

Modulated Class C Amplifier

Qhov no yog theem tso zis ntawm lub transmitter. Lub modulating suab teeb liab thiab lub teeb liab cov cab kuj, tom qab lub hwj chim amplification, yog siv rau no modulating theem. Qhov kev hloov kho yuav tshwm sim nyob rau theem no. Chav kawm C amplifier kuj ua kom lub zog ntawm AM teeb liab mus rau lub zog xa rov qab. Qhov teeb liab no thaum kawg dhau mus rau lub kav hlau txais xov., uas radiates lub teeb liab mus rau qhov chaw ntawm kev sib kis.

Lub low-level AM transmitter qhia nyob rau hauv daim duab (b) zoo ib yam li high-theem transmitter, tshwj tsis yog tias lub hwj chim ntawm cov cab kuj thiab lub suab teeb liab tsis yog amplified. Ob lub teeb liab no tau siv ncaj qha rau hauv chav kawm C lub zog hluav taws xob hloov pauv.

Modulation tshwm sim nyob rau theem, thiab lub zog ntawm cov teeb liab modulated yog amplified mus rau qhov yuav tsum tau transmitting zog theem. Tus kav hlau txais xov kis tau tus kab mob ces xa cov teeb liab.

Coupling ntawm Output theem thiab kav hlau txais xov

Cov theem tso zis ntawm cov chav kawm C lub zog hloov pauv hloov pauv cov teeb liab mus rau lub kav hlau txais xov xa xov.

Txhawm rau hloov lub zog siab tshaj plaws los ntawm theem tso tawm mus rau lub kav hlau txais xov nws yog qhov tsim nyog kom lub impedance ntawm ob ntu sib phim. Rau qhov no, yuav tsum muaj qhov sib txuam network.

Qhov sib piv ntawm ob yuav tsum zoo tag nrho ntawm txhua qhov kev sib kis ntau zaus. Raws li qhov sib txuam yuav tsum tau nyob ntawm ntau zaus, inductors thiab capacitors muab cov impedance sib txawv ntawm cov zaus sib txawv yog siv hauv kev sib koom tes.

Lub network sib txuam yuav tsum tau tsim los siv cov khoom siv passive no. Qhov no yog qhia hauv qab daim duab (c).

Qhov sib txuam network siv rau coupling cov zis theem ntawm lub transmitter thiab tus kav hlau txais xov yog hu ua ob chav π-network.

Lub network no tau qhia hauv daim duab (c). Nws muaj ob lub inductors, L1 thiab L2 thiab ob lub capacitor, C1 thiab C2. Qhov tseem ceeb ntawm cov khoom no raug xaiv xws li cov input impedance ntawm lub network ntawm 1 thiab 1'. Qhia hauv daim duab (c) yog txuam nrog cov zis impedance ntawm cov zis theem ntawm lub transmitter.

Tsis tas li ntawd, cov zis impedance ntawm lub network yog txuam nrog lub impedance ntawm lub kav hlau txais xov.

Ob chav π txuam network kuj lim cov khoom siv zaus tsis xav tau tshwm sim ntawm cov zis ntawm theem kawg ntawm lub tshuab xa tawm.

Qhov tso zis ntawm cov chav kawm C lub hwj chim amplifier yuav muaj ntau dua harmonics, xws li ob thiab peb harmonics, uas yog heev undesirable.

Cov lus teb zaus ntawm qhov sib txuam network tau teeb tsa xws li qhov tsis xav tau siab dua cov kev sib haum xeeb no tau raug tshem tawm tag nrho, thiab tsuas yog qhov xav tau teeb liab txuas nrog rau lub kav hlau txais xov..

Lub kav hlau txais xov tam sim no kawg ntawm kev xa khoom ntu, sib kis yoj mus yoj. Hauv tshooj no, peb tham txog AM thiab FM transmitters.

AM Transmitter

AM transmitter yuav siv lub suab ua lub suab tawm suab thiab ua kom muaj qhov cuam tshuam suab yoj mus rau lub kav hlau txais xov raws li kev tsim tawm kom kis tau. Daim duab thaiv ntawm AM transmitter yog qhia hauv daim duab hauv qab no.

Kev ua haujlwm ntawm AM transmitter tuaj yeem piav qhia raws li hauv qab no: 

• Lub suab teeb liab los ntawm cov zis ntawm lub microphone raug xa mus rau lub tshuab ntsuas ua ntej, uas ua rau muaj qib ntawm lub teeb liab modulating.
• Lub RF oscillator tsim kom muaj cov teeb liab cab kuj.
• Ob qho tag nrho cov txheej txheem thiab cov teeb meem cov cab kuj tau xa mus rau AM modulator.
• Lub zog txuas ntxiv yog siv los ua kom lub zog ntawm AM nthwv dej. Cov nthwv dej no thaum kawg kis rau tus kav hlau txais xov kom kis tau.

FM Transmitter

FM transmitter yog tag nrho cov khoom siv, uas siv lub teeb liab audio li cov kev tawm tswv yim thiab muab FM ຄື້ນ rau lub kav hlau txais xov raws li cov khoom tso tawm kom kis tau. Daim duab thaiv ntawm FM transmitter yog qhia hauv daim duab hauv qab no.

Kev ua haujlwm ntawm FM transmitter tuaj yeem piav qhia raws li hauv qab no:

• Lub suab teeb liab los ntawm cov zis ntawm lub microphone raug xa mus rau lub tshuab ntsuas ua ntej, uas ua rau muaj qib ntawm lub teeb liab modulating.
• Cov paib no tom qab tau dhau los dhau high pass lim, uas ua raws li kev sib txuas ua ntej network los lim tawm cov suab nrov thiab txhim kho cov teeb liab rau cov suab nrov.
• Cov paib no txuas ntxiv mus rau FM modulator Circuit Court.
• Lub voj voos oscillator ua rau muaj cov neeg siab loj, uas xa mus rau qhov ntsuas hluav taws xob txuas nrog cov teeb liab ntsuas.
• Ntau theem ntawm cov zaus sib xyaw ua ke tau siv los ua kom qhov kev ua haujlwm tsawg zaus. Txawm tias tom qab ntawd los, lub zog ntawm lub teeb liab tsis txaus rau kis. Li no, RF zog txuas ntxiv tau siv nyob rau thaum xaus kom nce lub zog ntawm lub teeb liab modulated. No FM cov qauv tsim tawm thaum kawg xa mus rau tus kav hlau txais xov kom kis tau.

Kev sib piv ntawm AM thiab FM Signals

Ob lub AM thiab FM yog siv hauv kev lag luam thiab tsis yog lag luam. Xws li kev tshaj tawm xov tooj cua thiab kev xa xov tooj cua. Txhua qhov system muaj nws tus kheej zoo thiab demerits. Hauv daim ntawv thov tshwj xeeb, AM system tuaj yeem tsim nyog tshaj li FM. Yog li ob qho tib si tseem ceeb los ntawm kev siv lub ntsiab lus ntawm kev pom.

Qhov zoo ntawm FM tshuab tshaj AM Systems

Lub amplitude ntawm FM nthwv dej tseem nyob tas li. Qhov no muab lub sijhawm rau cov neeg tsim qauv kom tshem tawm lub suab nrov ntawm lub teeb liab tau txais. Qhov no yog ua nyob rau hauv FM receivers los ntawm kev siv lub amplitude limiter Circuit Court kom lub suab nrov saum lub limiting amplitude yog suppressed. Yog li, FM system yog suav tias yog lub suab nrov tiv thaiv kab mob. Qhov no tsis tuaj yeem ua tau nyob rau hauv AM systems vim hais tias lub teeb liab baseband yog nqa los ntawm lub amplitude variations nws tus kheej thiab lub hnab ntawv ntawm AM teeb liab tsis tuaj yeem hloov.

- Feem ntau ntawm lub hwj chim hauv lub teeb liab FM yog nqa los ntawm sab bands. Rau cov nqi siab dua ntawm qhov ntsuas ntsuas ntsuas, mc, qhov loj ntawm tag nrho lub zog muaj nyob yog sab bands, thiab cov teeb liab cab kuj muaj tsawg zog. Nyob rau hauv sib piv, nyob rau hauv ib tug AM system, tsuas yog ib feem peb ntawm tag nrho cov hwj chim yog nqa los ntawm sab bands thiab ob feem peb ntawm tag nrho cov hwj chim yog poob nyob rau hauv daim ntawv ntawm cov cab kuj.

- Hauv FM systems, lub zog ntawm cov teeb liab kis tau tus mob nyob ntawm qhov amplitude ntawm lub teeb liab tsis hloov pauv, thiab yog li nws tsis tas li. Nyob rau hauv sib piv, nyob rau hauv AM systems, lub hwj chim nyob ntawm lub modulation index ma. Lub zog siab tshaj plaws hauv AM systems yog 100 feem pua ​​thaum ma yog kev sib sau. Cov kev txwv no tsis muaj feem xyuam rau hauv cov txheej txheem FM. Qhov no yog vim tias tag nrho lub zog hauv FM system yog ywj pheej ntawm qhov ntsuas ntsuas, mf thiab zaus sib txawv fd. Yog li, kev siv hluav taws xob zoo tshaj plaws hauv FM.

Nyob rau hauv ib qho system AM, tib txoj kev ntawm kev txo suab nrov yog ua kom lub zog xa hluav taws xob ntawm lub teeb liab. Qhov kev ua haujlwm no nce tus nqi ntawm AM system. Hauv FM kaw lus, koj tuaj yeem ua kom qhov sib txawv ntawm qhov sib txawv hauv lub teeb liab los txo cov suab nrov. Yog tias qhov sib txawv ntawm qhov sib txawv siab, ces qhov sib txawv ntawm qhov sib txawv ntawm qhov amplitude ntawm lub teeb liab baseband tuaj yeem muab tau yooj yim. Yog hais tias qhov sib txawv zaus me me, lub suab nrov tuaj yeem cuam tshuam qhov kev hloov pauv no thiab qhov sib txawv zaus tsis tuaj yeem muab txhais ua nws qhov sib txawv ntawm qhov sib txawv. Yog li, los ntawm kev sib txawv ntau zaus hauv FM teeb liab, lub suab nrov tuaj yeem txo nws. Tsis muaj kev qhia hauv AM system los txo cov suab nrov los ntawm txhua txoj kev, dua li ua kom nws lub zog xa mus.

Nyob rau hauv ib lub teeb liab FM, cov xov tooj cua FM uas nyob ib sab yog sib cais los ntawm pawg neeg saib xyuas. Hauv FM kaw lus tsis muaj teeb liab kis tau los ntawm qhov chaw spectrum lossis pawg neeg saib xyuas. Yog li ntawd, tsis muaj kev cuam tshuam ntawm FM channels uas nyob ib sab. Txawm li cas los xij, hauv ib qho AM system, tsis muaj kev tiv thaiv band muab nruab nrab ntawm ob txoj kab uas nyob ib sab. Yog li ntawd, ib txwm muaj kev cuam tshuam ntawm AM xov tooj cua chaw nres tsheb tshwj tsis yog tias qhov tau txais signalis muaj zog txaus los cuam tshuam cov teeb liab ntawm cov channel uas nyob ib sab.

Qhov tsis zoo ntawm FM tshuab tshaj AM systems

Muaj ntau tus lej ntawm sab bands nyob rau hauv lub teeb liab FM thiab yog li qhov theoretical bandwidth ntawm FM system tsis muaj qhov kawg. Lub bandwidth ntawm FM system yog txwv los ntawm Carson txoj cai, tab sis tseem ntau dua, tshwj xeeb tshaj yog nyob rau hauv WBFM. Hauv AM systems, bandwidth tsuas yog ob zaug ntawm qhov hloov pauv zaus, uas tsawg dua li ntawm WBFN. Qhov no ua rau FM systems costlier dua AM systems.

Cov khoom siv ntawm FM system yog qhov nyuaj tshaj li AM systems vim hais tias ntawm lub complex circuitry ntawm FM systems; Qhov no yog lwm qhov laj thawj uas FM systems yog cov nqi qis dua AM systems.

Qhov chaw txais xov tooj ntawm FM yog me dua li AM system yog li FM channel txwv tsis pub rau cov nroog loj thaum AM xov tooj cua tuaj yeem tau txais txhua qhov chaw hauv ntiaj teb. FM system xa cov teeb liab los ntawm txoj kab ntawm kev pom kev nthuav dav, nyob rau hauv qhov kev ncua deb ntawm kev xa xov thiab txais kav hlau txais xov yuav tsum tsis txhob ntau. nyob rau hauv ib qho AM system cov cim qhia ntawm cov chaw nres tsheb luv nthwv dej raug xa mus los ntawm cov txheej txheem huab cua uas cuam tshuam cov xov tooj cua nthwv dej thoob plaws cheeb tsam.

Vim muaj kev siv sib txawv, AM Transmitter tau muab faib ua pej xeem AM Transmitter (DIY thiab qis zog AM transmitters) thiab kev lag luam AM Transmitter (rau tub rog xov tooj cua lossis lub teb chaws AM xov tooj cua chaw nres tsheb).

Kev lag luam AM Transmitter yog ib qho ntawm cov khoom sawv cev tshaj plaws hauv RF teb. 

Hom xov tooj cua xov tooj cua no tuaj yeem siv nws cov AM tshaj tawm xov tooj cua loj (guyed mast, thiab lwm yam) los tshaj tawm cov teeb liab thoob ntiaj teb. 

Vim tias AM tsis tuaj yeem thaiv tau yooj yim, kev lag luam AM transmitter feem ntau yog siv rau kev tshaj tawm nom tswv lossis tub rog kev tshaj tawm ntawm lub tebchaws.

Zoo ib yam li FM tshaj tawm hauv xov tooj cua, AM tshaj tawm xov tooj cua transmitter kuj tau tsim nrog lub zog sib txawv. 

Noj FMUSER ua piv txwv, lawv cov lag luam AM transmitter series suav nrog 1KW AM transmitter, 5KW AM transmitter, 10kW AM transmitter, 25kW AM transmitter, 50kW AM transmitter, 100kW AM transmitter, thiab 200kW AM transmitter. 

Cov AM transmitters no yog tsim los ntawm lub gilt-ua khoom lub xeev txee, thiab muaj AUI tej thaj chaw deb tswj systems thiab modular Cheebtsam tsim, uas txhawb tas mus li high-zoo AM teeb liab tso zis.

Txawm li cas los xij, tsis zoo li kev tsim lub xov tooj cua FM, tsim lub chaw nres tsheb AM transmitter yog tus nqi siab dua. 

Rau cov neeg tshaj tawm xov xwm, pib qhov chaw nres tsheb AM tshiab yog kim, suav nrog:

- Tus nqi yuav khoom thiab kev thauj mus los ntawm AM cov khoom siv xov tooj cua. 

- Tus nqi rau kev ntiav neeg ua haujlwm thiab cov khoom siv.

- Tus nqi rau kev thov daim ntawv tso cai tshaj tawm AM.

- Lwm yam. 

Yog li ntawd, rau lub teb chaws los yog tub rog xov tooj cua chaw nres tsheb ib tug txhim khu kev qha tsum nrog ib-nres kev daws teeb meem yog urgently xav tau rau cov nram qab no AM tshaj tawm cov khoom:

Lub zog siab AM Transmitter (ntau pua txhiab lub zog tso zis xws li 100KW lossis 200KW)

AM tshaj tawm cov kav hlau txais xov (AM kav hlau txais xov thiab xov tooj cua ntauwd, kav hlau txais xov accessories, cov kab sib kis tsis zoo, thiab lwm yam)

AM test loads thiab cov cuab yeej pabcuam. 

Etc.

Raws li rau lwm cov tshaj tawm xov xwm, qhov kev daws teeb meem qis dua yog qhov txaus nyiam, piv txwv li:

- Yuav AM Transmitter nrog lub zog qis (xws li 1kW AM Transmitter)

- Yuav siv AM Broadcast transmitter

- Xauj ib lub xov tooj cua AM uas twb muaj lawm

- Lwm yam.

Raws li cov chaw tsim khoom nrog ua tiav AM xov tooj cua chaw nres tsheb cov khoom siv saw, FMUSER yuav pab tsim cov kev daws teeb meem zoo tshaj plaws los ntawm lub taub hau mus rau ntiv taw raws li koj cov peev nyiaj, koj tuaj yeem tau txais cov khoom siv xov tooj cua AM tiav los ntawm lub xeev siab zog AM transmitter rau AM test load thiab lwm yam khoom siv. , nyem qhov no kom paub ntau ntxiv txog FMUSER AM xov tooj cua daws teeb meem.

Cov neeg pej xeem AM Transmitter muaj ntau dua li kev lag luam AM transmitter vim lawv nrog tus nqi qis.

Lawv tuaj yeem muab faib ua DIY AM transmitter thiab qis zog AM transmitter. 

Rau DIY AM transmitters, qee tus neeg nyiam xov tooj cua feem ntau siv lub rooj tsav xwm yooj yim los txuas cov khoom xws li suab hauv, kav hlau txais xov, transformer, oscillator, fais fab kab thiab hauv av kab.

Vim nws txoj haujlwm yooj yim, DIY AM transmitter yuav tsuas muaj qhov loj ntawm ib nrab xibtes. 

Tias yog vim li cas qhov no hom AM transmitter raug nqi tsuas yog kaum ob lub hlis xwb, lossis tuaj yeem ua dawb. Koj tuaj yeem ua raws li online tutorial video rau DIY ib qho.

Tsawg zog AM transmitters muag rau $ 100. Lawv feem ntau yog hom khib nyiab lossis tshwm nyob rau hauv ib lub thawv me me me me. Cov transmitters no nyuaj tshaj li DIY AM transmitters thiab muaj ntau tus neeg xa khoom me me.