Lect-4_Part1_07 - Lecture - 4 AMPLITUDE MODULATION...

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Lecture - 4 AMPLITUDE MODULATION
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Modulation Analog Digital AM (Amplitude Modulation) FM (Frequency Modulation) Angle PM (Phase Modulation ) (Shift keying) ASK FSK -BFSK -MSK (FFSK) -GMSK PSK -BPSK -QPSK -MPSK -QAM
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NEED FOR MODULATION: 1. Efficient Electro-magnetic radiation 2. Multiplexing 3. To overcome equipment limitations 4. Frequency assignment for different services like Radio, TV etc. 5. Reduction of Noise and interference.
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Amplitude Modulation: The Carrier signal A c cosω c t (where A c is the amplitude of the Carrier and f c its frequency) is varied in accordance with the message signal m(t). Standard AM wave may be expressed as x AM (t) = A c [1+k a m(t)]cosω c t Where k a is called the amplitude sensitivity of the modulator. The envelope of the modulated wave is given as A c [1+k a m(t)].
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Let m(t) be a single frequency message signal in the baseband given by m(t) = A m cosω m t where Am is its amplitude and fm its frequency. Modulating the carrier by single frequency is also referred to as single-tone modulation x AM (t) = A c [1+k a A m cosω m t]cosω c t = A c [1+μcosω m t]cosω c t where μ = k a A m is called the modulation index
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Lect-4_Part1_07 - Lecture - 4 AMPLITUDE MODULATION...

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