Communication Modulation Types

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Questions and Answers

What is the primary reason AM is commonly used in broadcasting?

It has a wider frequency range than FM.

It is less sensitive to electromagnetic interference.

It is easier and cheaper to demodulate. (correct)

It allows for higher quality audio transmission.

In an AM transmission, where is the information primarily located?

In the modulating signal amplitude.

In the frequency of the carrier wave.

In the sidebands. (correct)

In the carrier frequency.

What is the relationship between the bandwidth of an AM signal and the maximum frequency of the modulating signal?

The bandwidth is three times the modulating frequency.

The bandwidth is twice the modulating frequency. (correct)

The bandwidth is equal to the modulating frequency.

The bandwidth is half of the modulating frequency.

What does the modulating index, $ u$, represent in amplitude modulation?

The modulation depth between the carrier amplitude and modulating amplitude. Signup and view all the answers

What type of modulation system does the term Double Sideband Full Carrier (DSBFC) refer to?

A system that transmits all components of the AM signal. Signup and view all the answers

What factors contribute to the total power transmitted in an AM signal?

Carrier power, upper sideband power, and lower sideband power. Signup and view all the answers

In what situations is AM particularly vulnerable to noise?

In environments with significant electromagnetic interference. Signup and view all the answers

What is the role of the crystal oscillator in an AM radio transmitter?

It generates the high frequency carrier wave. Signup and view all the answers

How does the Fourier transform relate to amplitude modulation?

It provides a visual representation of the modulated signal's components. Signup and view all the answers

Which component is responsible for mixing the carrier wave and the audio frequency signal in an AM radio transmitter?

AM modulator Signup and view all the answers

What role does the AF amplifier play in the AM radio transmission process?

It increases the magnitude of energy of the signal. Signup and view all the answers

Which section of an AM radio transmitter is responsible for signal processing before transmission?

Radio Frequency (RF) section Signup and view all the answers

What is the function of the receiving antenna in an AM radio receiver?

To convert the received signal into electrical form. Signup and view all the answers

Which of the following components is NOT part of the AM radio transmitter?

Receiver Signup and view all the answers

What is the primary purpose of the power amplifier in an AM radio transmitter?

To increase the power of the modulated signal before transmission. Signup and view all the answers

Which frequency range does the bandwidth of the modulating signal typically cover?

0 to fm Signup and view all the answers

What is a primary characteristic of VSB modulation?

It simplifies the design process due to relaxed filter requirements. Signup and view all the answers

What is the primary purpose of suppressing the carrier in DSB-SC modulation?

To save power Signup and view all the answers

Which modulation technique is noted for better management of the frequency spectrum?

SSB-SC Signup and view all the answers

What is a key challenge associated with coherent detection in DSB-SC modulation?

Ensuring local oscillator synchronization Signup and view all the answers

What is the advantage of using DSB-SC modulation?

Lower power consumption. Signup and view all the answers

Which type of modulation transmits only a single sideband?

Single Sideband Modulation Signup and view all the answers

What is a significant disadvantage of VSB-SC?

The demodulation system is still complex. Signup and view all the answers

What is the role of an envelope detector in amplitude modulation?

Capturing the envelope of the AM signal Signup and view all the answers

Which application is most suitable for VSB modulation?

Analog TV broadcasting Signup and view all the answers

What is a notable challenge in DSB-SC demodulation?

Maintaining carrier phase synchronisation. Signup and view all the answers

Why is the value of the RC circuit in an envelope detector critical?

It determines the efficiency of demodulation Signup and view all the answers

Which of the following statements about SSB-SC is true?

It has a lower power requirement than VSB-SC. Signup and view all the answers

What advantage does Vestigial Sideband Modulation (VSB) offer?

It allows transmission of a vestige part of a signal Signup and view all the answers

What percentage of bandwidth does VSB-SC typically have compared to SSB-SC?

25% greater Signup and view all the answers

How does single sideband modulation differ from traditional amplitude modulation?

It is more power and bandwidth efficient Signup and view all the answers

What is one of the main drawbacks of using coherent detection in DSB-SC modulation?

Higher complexity and cost for receivers Signup and view all the answers

What is the primary characteristic that changes in amplitude modulation?

Amplitude of the carrier wave Signup and view all the answers

Which modulation technique uses changes in amplitude to transmit information?

Amplitude Modulation Signup and view all the answers

Which type of communication includes methods like Ethernet and twisted-pair?

Baseband Communication Signup and view all the answers

What is one reason for using different carrier frequencies in communication systems?

To facilitate multiplexing Signup and view all the answers

Which modulation technique is an example of digital modulation?

Amplitude Shift Keying Signup and view all the answers

How does increased frequency affect bandwidth?

Increases bandwidth Signup and view all the answers

Which of the following is not a type of modulation mentioned?

Digital Amplitude Modulation Signup and view all the answers

What factor significantly affects the height of an antenna for signal transmission?

Carrier frequency Signup and view all the answers

Which modulation technique is characterized by the use of varying pulse widths?

Pulse Width Modulation Signup and view all the answers

Which type of modulation is not classified under analog modulation?

Pulse Code Modulation Signup and view all the answers

Study Notes

Modulation Types and Amplitude Modulation

Unit 7 covers modulation types and amplitude modulation.
The instructor is Professor Thushara Weerawardane.

Outcomes

Define different communication types.
Differentiate modulation techniques.
Discuss amplitude modulation and its applications.
Study transmitter and receiver techniques.
Analyze various amplitude modulation schemes and their usage.

Types of Communication

Baseband Communication: Direct transmission of the message signal. Examples include Ethernet, coaxial cable, twisted-pair, and fiber-optic (broadband) transmission.
Carrier Communication: Transmission of a message signal by modulating a carrier wave. This is used for high power transmission.

Baseband Communication Details

Baseband signals are transmitted directly.
Examples of P2P transmission include Ethernet, coaxial cable, twisted-pair, and fiber-optic (broadband).

Carrier Communication Details

Information is sent by changing the characteristics of the carrier wave (amplitude, frequency, phase).
A carrier wave is modulated by a message signal to create an amplitude modulated signal.
High power transmission is frequently associated with carrier communication.

Modulation

Modulation is the process of adjusting a carrier signal's characteristics in relation to the message signal.
The carrier wave's amplitude, frequency, or phase can be changed to carry information.
The faster the carrier wave can be changed, the more information it can transmit.

Modulation Types

Analog Modulation: Continuous variations in the carrier signal's amplitude, frequency, and phase. Included are Amplitude Modulation (AM), Frequency Modulation (FM), and Phase Modulation (PM).
Digital Modulation: Discrete, distinct changes in the carrier signal's amplitude, frequency, and phase. Examples include Amplitude Shift Keying (ASK), Frequency Shift Keying (FSK), and Phase Shift Keying (PSK).

Example Modulations Explained

Amplitude Modulation (AM): The amplitude of a carrier wave is adjusted in proportion to the message signal.
Frequency Modulation (FM): The frequency of a carrier wave is adjusted in proportion to the message signal.
Phase Modulation (PM): The phase of a carrier wave is adjusted in proportion to the message signal.
Pulse Amplitude Modulation (PAM): The amplitude of a carrier signal is adjusted in proportion to specific pulses, or amplitude, of the message signal.

Why Modulation is Needed

To increase antenna height (for different signal frequencies)
To reduce interference
To use overlapping frequency bands for multiplexing
To enhance bandwidth by using high frequencies.

Types of Pulse Modulations

PAM: Pulse Amplitude Modulation
PWM: Pulse Width Modulation
PPM: Pulse Position Modulation
PCM: Pulse Code Modulation (including delta modulation and adaptive delta modulation)

Digital Modulation Schemes

ASK: Amplitude Shift Keying
FSK: Frequency Shift Keying
PSK: Phase Shift Keying

Amplitude Modulation Further Details

Amplitude Modulation (AM) is used in radio and television broadcasting.
AM is easy to demodulate, therefore radio receivers for AM are easier and cheaper to manufacture.
However, AM is sensitive to noise and electromagnetic interference

Types of Amplitude Modulation

Double sideband with full carrier (DSB-FC),
Double sideband-suppressed carrier (DSB-SC)
Single sideband (SSB)
Vestigial sideband (VSB)

Double Sideband Suppressed Carrier (DSB-SC)

A technique where carrier signal is removed for power saving.
Coherent detection is used. The greatest challenge is maintaining correct synchronization of the local oscillator

Single Sideband (SSB)

Uses fewer transmitters
High bandwidth efficiency

Vestigial Sideband (VSB)

Is employed in television transmissions, due to the need for low frequency components.

AM Radio Transmitter (Simplified)

Consists of two main sections: AF (Audio Frequency) and RF (Radio Frequency).
Key components include a microphone, preamplifier, RF oscillator, AM modulator, and power amplifier.

AM Radio Receiver

Antenna receives the signal, which is amplified, frequency translated (IF), and detected.
An envelope detector is used to capture variations in the received amplitude (EMF)
Finally, amplification of the signal and output

Trigonometric Identities

Various trigonometric identities, including sin(α + β), sin(α - β), cos(α + β), cos(α - β), tan(α + β), and tan(α - β), have been defined in the lecture.

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Description

This quiz focuses on Unit 7, which covers different modulation types, including amplitude modulation. Students will learn to define communication types and differentiate between various modulation techniques, as well as explore transmitter and receiver techniques along with their applications. Gain insights into baseband and carrier communication methods through this assessment.

Communication Modulation Types - Unit 7