Communication Systems Overview

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Questions and Answers

What distinguishes an analog signal from a digital signal?

Analog signals have continuous variations over time. (correct)

Digital signals have infinite values.

Digital signals change smoothly over time.

Analog signals are measured in decibels.

Which modulation technique alters the amplitude of a carrier wave?

Code Division Multiplexing (CDM)

Frequency Modulation (FM)

Phase Modulation (PM)

Amplitude Modulation (AM) (correct)

What type of noise measurement expresses the signal-to-noise ratio in decibels?

Logarithmic scale (correct)

Voltage

Signal strength

Thermal noise

Which of the following is NOT a component of a communication system?

Decoder Signup and view all the answers

Which agency is primarily responsible for managing the electromagnetic spectrum in the U.S.?

Federal Communications Commission (FCC) Signup and view all the answers

What is the general term for the phenomenon that degrades transmitted information?

Noise Signup and view all the answers

Which of the following is a basic type of multiplexing?

Time Division Multiplexing (TDM) Signup and view all the answers

Which of the following does NOT represent a long-distance communication method used by early humans?

Television Signup and view all the answers

Which organization is known for maintaining communication system standards?

ITU Signup and view all the answers

What is a transceiver?

A device that acts as both transmitter and receiver Signup and view all the answers

What frequency range is allocated for FM radio broadcasting?

88 MHz to 108 MHz Signup and view all the answers

What is the primary difference between baseband and broadband transmission?

Baseband is single channel and short-distance; broadband is multiple channels and long-distance. Signup and view all the answers

Which of the following describes multiplexing?

A process that allows multiple signals to share the same medium. Signup and view all the answers

What is the upper-frequency limit of a television signal occupying a 6 MHz bandwidth starting at 54 MHz?

60 MHz Signup and view all the answers

What frequency does an electromagnetic wave have if the distance between peaks is 8 inches?

1.5 GHz Signup and view all the answers

Which term describes the compatibility of equipment across manufacturers?

Interoperability Signup and view all the answers

Study Notes

Analog vs. Digital Signals

Analog signals are continuous and change smoothly over time.
Digital signals are discrete and change in steps or intervals, typically represented as binary (0s and 1s).

Signal Degradation and Noise

Free-space path loss is signal degradation proportional to the square of the distance.
Noise power is measured in decibels (dB).
Signal-to-noise ratio (SNR) is expressed as 10 * log(signal power/noise power).

Modulation Techniques

Amplitude Modulation (AM): The amplitude of the carrier wave is varied based on the baseband signal.
Frequency Modulation (FM): The frequency of the carrier wave is varied based on the baseband signal.
Phase Modulation (PM): The phase of the carrier wave is varied based on the baseband signal.

Communication System Components

A communication system includes a transmitter, a medium/channel, and a receiver.

Baseband and Broadband Signals

Baseband signals transmit one signal over a channel, often over short distances.
Broadband signals transmit multiple signals simultaneously over long distances.

Multiplexing Techniques

Time Division Multiplexing (TDM): Divides time segments into slots, each allocated to a different signal.
Frequency Division Multiplexing (FDM): Each signal is assigned a specific frequency band within the channel.
Code Division Multiplexing (CDM): Each signal is assigned a unique code that allows the receiver to separate it from other signals.

Standards and Organizations

The IEEE, ITU, and ISO maintain communication system standards, ensuring interoperability and compatibility.

Government Agencies

The Federal Communications Commission (FCC), National Telecommunications Commission (NTC), and International Telecommunication Union (ITU) are responsible for managing the electromagnetic spectrum.

Communication Media and Channels

Examples of communication channels include fiber optic cables, radio waves, coaxial cables, satellite links, and twisted pair wires.

Digital Data Transmission

ASCII (American Standard Code for Information Interchange) is the most commonly used digital code in communications.
Examples of transmitting digital data by modulation include ASK (Amplitude Shift Keying) and FSK (Frequency Shift Keying).

Electromagnetic Spectrum

The electromagnetic spectrum encompasses all frequencies, including radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays.
Bandwidth refers to the portion of the electromagnetic spectrum occupied by a signal.

Communication System Model

The general model of a communication system consists of an information source, a transmitter, a channel, a receiver, and a destination.

Early Communication Methods

Early Humans used smoke signals, fire beacons, drums, flags, and carrier pigeons for long-distance communication

Key Terms

Transmitter: A collection of electronic components designed for transmission
Receiver: A collection of components accepting and converting transmitted messages
Transceiver: combines transmitter and receiver functions in a single device.
Communication: The process of exchanging information
Information Age: A period marked by a shift in focus from manufacturing to information exchange.
Interoperability: Equipment compatibility across manufacturers
Frequency: The number of times a phenomenon occurs in a given period.
Half-duplex: A two-way communication system where only one party transmits at any given time.
Laser: A light signal with a narrow beam that can be modulated.
Wireless Communication: Communication using free space as the medium.
Standards: Specifications and guidelines for compatibility between equipment.

Additional Examples and Information

FM radio broadcasts occupy the frequency range of 88 MHz to 108 MHz.
The upper-frequency limit of a 6 MHz bandwidth television signal in Channel 2 (lower limit 54 MHz) is 60 MHz.
An electromagnetic wave with an 8-inch separation between peaks has a frequency of approximately 1.5 GHz.
The common AC power line frequency range is 50 Hz to 60 Hz.

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Description

Explore the fundamentals of communication systems in this quiz. Delve into the differences between analog and digital signals, modulation techniques, and components of a communication system. Test your knowledge on key concepts like signal degradation and noise as well.