modulation by sanjay
TRANSCRIPT
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MODULATION
BY- SANJAY KUMAR0900321088
EN-2(A)
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introduction
Modulation is the process by which some characteristics of a carrier is varied in accordance with a modulation wave .
Modulation is the process of putting information onto a high frequency carrier for transmission (frequency translation).
such a modification is achieved by mean of a process called modulation .
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In the modulation process, the baseband signle is called “modulating signal” and anther higher frequency signal is called as the “carrier”. The carrier signal will carry the modulating signal to the destination.
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Different of Modulation Method
Analog modulation - The modulating signal and
carrier both are analogue signal.
TYPES : Amplitude modulation (AM), Frequency modulation (FM),
Phase modulation (PM)
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Figure Types of analog- modulation
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Digital modulation - The modulating signal is
a digital signal , but the carrier is an analogue
signal.
TYPES :
Amplitude Shift Keying (ASK),
Frequency Shift keying (FSK),
Phase Shift Keying (PSK)
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Amplitude Modulation
Amplitude Modulation is a process of changing the amplitude of a high frequency carrier signal in proportion with the instantaneous value of modulating signal (information).
Amplitude Modulation is the simplest and earliest form of transmitters.
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Figure : Amplitude modulation
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AM Characteristics
AM is a nonlinear process
Sum and difference frequencies are created that carry the information
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modulation index
The ratio between the amplitudes between the amplitudes of the modulating signal and carrier, expressed by the equation:
c
m
E
Em =
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Measurement of Modulation Index
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Overmodulation When the modulation index is greater than 1,
overmodulation is present
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Modulation Index for Multiple Modulating Frequencies
Two or more sine waves of different, uncorrelated frequencies modulating a single carrier is calculated by the equation:
m m12 m2
2
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Full-Carrier AM: Frequency Domain
Time domain information can be obtained using an oscilloscope
Frequency domain information can be calculated using Fourier methods, but trigonometric methods are simpler and valid
Sidebands are calculated using the formulas at the right
fusb fc fmf lsb fc fm
E lsb Eusb mEc2
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Bandwidth
• Signal bandwidth is an important characteristic of any modulation scheme
• In general, a narrow bandwidth is desirable• Bandwidth is calculated by:
mFB 2
fC fc+fmfc-fm
2fm
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applications Amplitude Modulation
AM applications include broadcasting in medium- and high-frequency applications,
CB radio , and
aircraft communications
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THANK YOU