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Angle Modulation for Engineering Students

This document discusses angle modulation techniques used in communication systems. It describes that angle modulation varies the phase or frequency of the carrier signal according to the message signal. Angle modulation includes frequency modulation and phase modulation. Frequency modulation varies the frequency of the carrier linearly with the message signal, keeping the amplitude and phase constant. Phase modulation varies the phase of the carrier linearly with the message signal. Narrowband and wideband frequency modulation are also discussed. Examples and equations are provided.

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rahman
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109 views17 pages

Angle Modulation for Engineering Students

This document discusses angle modulation techniques used in communication systems. It describes that angle modulation varies the phase or frequency of the carrier signal according to the message signal. Angle modulation includes frequency modulation and phase modulation. Frequency modulation varies the frequency of the carrier linearly with the message signal, keeping the amplitude and phase constant. Phase modulation varies the phase of the carrier linearly with the message signal. Narrowband and wideband frequency modulation are also discussed. Examples and equations are provided.

Uploaded by

rahman
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as PDF, TXT or read online on Scribd
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Communication Systems

Instructor: Dr. Muhammad Arif


muhammad.arif@ee.uol.edu.pk

Lecture 11

The University of Lahore – Islamabad Campus

Communication Systems - Dr. Arif Wahla


Angle Modulation
▪ Angle Modulation is the process in which the frequency or the
phase of the carrier signal varies according to the message signal.
▪ The standard equation of the angle modulated wave is

Where,
▪ AC is the amplitude of the modulated wave, which is the same as the
amplitude of the carrier signal.
▪ 𝜃𝑖 𝑡 is the angle of the modulated wave

2 Communication Systems - Dr. Arif Wahla


Angle Modulation
Angle modulation is further divided into frequency modulation and
phase modulation.

▪ Frequency Modulation is the process of varying the frequency of


the carrier signal linearly with the message signal.

▪ Phase Modulation is the process of varying the phase of the carrier


signal linearly with the message signal.

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Angle Modulation
Frequency Modulation
▪ In frequency modulation, the amplitude and the phase of the carrier
signal remains constant. This can be better understood by observing
the following figures.

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Frequency Modulation
▪ Mathematical Representation The equation for instantaneous
frequency in FM is

where

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Frequency Modulation
Substituting the value of fi

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Angle Modulation

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Frequency Modulation
Narrowband FM
Following are the features of Narrowband FM.
•This frequency modulation has a small bandwidth when compared to
wideband FM.
•The modulation index β is small, i.e., less than 1.
•Its spectrum consists of the carrier, the upper sideband and the lower
sideband.
•This is used in mobile communications such as police wireless,
ambulances, taxicabs, etc.
Wideband FM
Following are the features of Wideband FM.
•This frequency modulation has infinite bandwidth.
•The modulation index β is large, i.e., higher than 1.
•Its spectrum consists of a carrier and infinite number of sidebands,
which are located around it.
•This is used in entertainment, broadcasting applications such as FM
radio, TV, etc.

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Phase Modulation
In Phase Modulation (PM), the phase of the carrier signal varies in
accordance with the instantaneous amplitude of the modulating signal.
This can be better
understood by observing the following figures.

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Phase Modulation

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Angle Modulation

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Angle Modulation
Problem 1
▪ A sinusoidal modulating waveform of amplitude 5 V and a
frequency of 2 KHz is applied to FM generator, which has a
frequency sensitivity of 40 Hz/volt. Calculate the frequency
deviation, modulation index, and bandwidth.

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Angle Modulation
Solution

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Angle Modulation

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Angle Modulation

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Angle Modulation

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Angle Modulation

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