am modulation
DESCRIPTION
analog communicationTRANSCRIPT
PRESENTATION ON AM PRESENTATION ON AM MODULATION & POWER AND MODULATION & POWER AND
CURRENT CALCULATIONCURRENT CALCULATION
Amit GuptaECE’066220406501
Amplitude Amplitude modulationmodulation
Amplitude modulationAmplitude modulation
Amplitude Amplitude modulationmodulation
1.1. The frequency of sinusoidal carrier The frequency of sinusoidal carrier is much higher than the modulating is much higher than the modulating signal.signal.
2.2. In AM instantaneous amplitude of In AM instantaneous amplitude of the sinusoidal high frequency the sinusoidal high frequency carrier is change in proportion to carrier is change in proportion to the instantaneous amplitude of the instantaneous amplitude of modulating signal modulating signal
3.3. The information in the AM signal is The information in the AM signal is contain in the amplitude variations contain in the amplitude variations of the carrier of the envelope of the carrier of the envelope
4.4. Note the frequency and phase of Note the frequency and phase of the carrier remain constantthe carrier remain constant
5.5. AM is used in the application such AM is used in the application such as radio transmission, TV as radio transmission, TV transmission etc.transmission etc.
Mathematical representation of Mathematical representation of AM wave AM wave
signalAMtherepresentsthis
tftfmEe
indexulationE
Emlet
tftfE
EEe
tftfEEtfAe
bygiveniswaveAMHence
tfEEeEA
envelopevaleofeoustheinsrepersentAwhere
tfAe
signalcarrieroffrequency
signalcarrierofamplitudepeakE
tEe
asdrepresentebesignalcarrierthelet
signalulatingoffrequency
signalulatingofamplitudeeousinse
tEe
asdrepresentebesignalulatingthelet
cmcAM
c
m
cmc
mcAM
cmmccAM
mmcmc
cc
c
c
ccc
m
m
mmm
)2cos()2cos(1
mod
)2cos()2cos(1
)2cos()2cos()2cos(
)2cos(
tantan
)3........()2cos(
)2........(cos
mod
modtantan
)1........(cos
mod
Modulation IndexModulation IndexIn am wave the Modulation
Index (m) is defined as the ratio of amplitudes of the modulating and carrier waves as follows:
c
m
E
Em
Calculation of Modulation Calculation of Modulation IndexIndex
ressionrequiredisThis
EE
EEEE
EE
m
eqnandeqnfromvaluesngsubstituti
E
EmBut
EEE
EEEE
eqnineqnngsubstituti
EEE
EEE
E
Emindexulationletcalculatetoorderin
c
m
c
c
mc
m
c
m
exp
)4......(
2
2
)2()1(
)3.......(2
2
)2()1(
)2........(
)1........(2
mod
minmax
minmax
minmax
minmax
minmax
minmaxmax
max
minmax
Power relations in AMPower relations in AM
21
44
:
)5.........(4
2.
2.
4
)4.........(8
22
2
:
)3.....(2
2
:
tan
,
)2........(
)1..(
,
2
22
2
2
22
222
2
222
222
mPP
Pm
Pm
PP
PPPP
powerTotal
Pm
PP
PR
Eeqnabovein
R
EmPP
R
Em
R
mEPP
mEsidebandeachofamplitudepeakknowwe
R
EPP
sidebandsinpower
amplitudecarrierpeakER
E
R
E
R
EP
powerCarrier
antennaofceresissticscharacteriR
amplitudessideband
andcarrierofvaluermsareEandEEwhereR
E
R
E
R
EP
LSBinpowerUSBinpowerpowercarrierP
bygiveniswaveAManinpowertotalthe
ct
ccct
LSBUSBct
cLSBUSB
c
c
c
LSBUSB
ccLSBUSB
c
SB
LSBUSB
c
cccarr
c
LSBUSBcarr
LSBUSBcarr
t
t
AM power in terms of AM power in terms of CurrentCurrent
)13.....(12
21),12(
:mod
)13.(..........2
1
)12.(..........2
1
21
)11..(..........
mod
,
212
22
212
22
2
2
2
2
2
22
c
t
c
t
ct
c
t
c
t
c
t
c
t
c
t
ttcc
t
c
I
Im
I
Imeqnfrom
currentsofterminindexulation
mII
m
I
I
m
P
Pbut
I
I
RI
RI
P
P
RIPandRIP
waveAMforcurrent
rmsthebetoIandcarrierulatedun
toingcorrespondcurrentrmsthebetoIassume
currentofinpowerAM
