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Amplitude modulators

Amplitude modulator can be classified as
1.Linear modulators
a)collector modulator
b)base modulator
2.square law modulators
a)Square law diode modulator
b)square law balanced modulator or simply balanced modulator

1.Linear modulators
a)collector modulator


collector modulator is a modulator in which the AF signal is applied at the collector of the BJT &RF signal is applied at the base .(high frequency BJT).


b) base modulators


In base modulator the RF & AF signal is applied at the base of the BJT .


2.square law modulators
a)square law diode modulators


In sauare law diode modulators the modulated current follows the square law
Ip=a1es+a2es2........
es=em+ec
where Ip is the current through the diode
es the sum of the modulating and carrier voltages
b)balanced modulator


In balanced modulator the product of the input frequencies is produced along with other frequency components .Simply a balanced modulator is a combination of 2 mixers

  • DIFFERENT MODULATION TECHNIQUES

    • DSB-LC-AM
    There are three components to any DSB-LC waveform, the upper and lower sidebands and the carrier frequency. If the powers in all three of these are added up, the total power in the modulated signal will be
    P = Pc + Pusb + Plsb
    the o/p contains product of the signals + carrier
    DSB SC AM
    The sceme is same as above with suppression of the carrier.The o/p contains product of the signals
    SSB
    Only a sideband is transmitted along with carrier. The o/p contains sum or difference frequencies of base band signal and carrier along with the carrier frequency.
    SSB-SC-AM
    A sideband along with suppressed carrier is transmitted,only sum or diff: freq
    Pilot carrier
    A sideband or 2 is transmitted with carrier power reduced or carrier attenuated to a reasonable extent.
    It is used as a ref: for the generation of carrier at the receiver.
    The suppressed carrier balanced modulator
    It producess carrier suppression along with the multiplication
    In general almost all the amplitude modulators are mixers.
    "In general modulation is the process of obtaining a product of the signals ,of both carrier and base band signal."
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    Comments

    rUhI said…
    valuable post :)
    thnkssss
    September 14, 2011 at 10:30 AM
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