This presentation will explain about the need for modulation in communication system. We made this presentation as our group assignment in Analog and Digital Communication System course in MIIT.

1. Need For Modulation
Pyae Sone Hein(2015-MIIT-ECE-042)
Myat Myint Zu Thin(2015-MIIT-ECE-03)

2. Objectives
➢To understand the meaning of Modulation
➢To know the important of Modulation
➢To learn the need for Modulation
➢To introduce various kinds of Modulation
techniques
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3. What is Modulation?
➢ Modulate = Regulate
➢ The process of regulating is modulation
➢ One physical quantity is changing in
accordance with another physical quantity.
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➢Carrier signal is changing
with message signal in
electrical communication.

4. The role of Modulation
➢ How can we communicate with people
from distant places?
➢ We need something which will carry our
message to desire place(carrier signal).
➢ Modulation can only do the process to
take carrier signal with our message
signal.
➢ Without modulation, our message signal
will not be received by destination.
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5. Need for modulation
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➢ The main reason is the disturbance of
noise.
➢ After transmitting, our message signal can
be attacked by unwanted signals in the
channel.
➢ Message signal can be modified into
unwanted signal by noise.
➢ Because of noise, modulation must be
done before transmitting.

6. Need for modulation Cont…
Factors that suggest need of modulation
1. Practicable Size of Antenna
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➢ Speech and music signal(20Hz – 20kHz) can only travel for
a few distance.
➢ To receive the transmitted signal, the length of antenna
should be a quarter-wavelength of the frequency used.
➢ If frequency is 20kHz,
wavelength will be 15km and
the height of antenna will
become 3.75km which is
impossible to install.

7. Need for modulation Cont…
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➢ When we add high frequency signal(10MHz) with our
message signal, frequency becomes high(10.02MHz).
➢ Then the wavelength will low(30m) and the height of
antenna will become practicable(7.5m).

8. Need for modulation Cont…
2. Power Radiation
➢ Radiated power ∝ (
1
𝜆
)2
➢ Without modulation, the frequency of signal is
low, wavelength will large and Power will low
➢ If Power is very low, it will not reach destination
and noise can also be added in the channel
➢ If we used modulation, the frequency of
modulating signal is high and radiated power will
become high.
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9. Need for modulation Cont…
3. Narrow banding
➢ Narrow banding does not mean that
reducing the bandwidth.
➢ Bandwidth will remain same
➢ It means that making wavelength same
➢ Example: We calculated the height of
antenna based on wavelength. Without
modulation, each frequency will need
antenna to communicate.
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10. Need for modulation Cont…
➢ If we use modulation, the wavelengths of
many signals will be the same(not exactly)
➢ By using modulation, antenna size
requirement becomes same
4. Common Processing
➢ How if we have only one transmitter to
control or use various signal transmitting
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11. Need for modulation Cont…
5. Multiplexing
➢ Multiplexing is the process of sending
several signals through a common channel.
➢ Most of the television channels use the same
frequency range(bandwidth).
➢ How multiple signals go without overlapping
each other?
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12. Different types of modulation
techniques
➢ analog and digital modulations.
➢ In analog modulation, carrier is analog
signal(continuous signal)
➢ Base on the instantaneous value of message
signal, amplitude, frequency and phase of carrier
signal will change.
1. Amplitude modulation(AM)
2. Frequency modulation(FM)
3. Phase modulation(PM)
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13. Different types of modulation
techniques
➢ In digital modulation, the carrier signal is
digital signal(train of pulses)
➢ Base on the instantaneous value of
message signal, amplitude, frequency
and phase of carrier signal will change.
1. Amplitude shift keying(ASK)
2. Frequency shift keying(FSK)
3. Phase shift keying(PSK)
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14. Learning Outcome
➢ During the lecture, our professor(Dr.Gr Sinha)
explained about the modulation without
presentation.
➢ We had to watch videos and listen carefully to the
professor. So, we understood clearly about
modulation.
➢ While preparing the presentation, we have to refer
our text book and search on the internet. So, we got
many experiences in reading text book and
understanding the topic.
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15. ECE-3050-02 15
Pyae Sone Hein(2015-MIIT-ECE-042)
Myat Myint Zu Thin(2015-MIIT-ECE-03)