Communication Signals and Gain Chapter

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Questions and Answers

What is the primary role of the modulator in analog communication?

To transform the message signal into the transmitted signal (correct)

To act as the pathway for the signals

To convert the received signal back to its original form

To provide redundancy for error recovery

In digital communication, what is the function of the channel encoder?

To convert the message signal into a sequence of bits

To estimate the original message from received signals

To add redundancy that aids in error recovery (correct)

To process the signal for transmission

What is considered a baseband signal?

A high-frequency sine-wave signal

A signal used for recovery from transmission errors

The original information or intelligence before modulation (correct)

A signal that has been modulated for transmission

Which component in the digital communication system processes the imperfect bit estimates?

Channel decoder Signup and view all the answers

What is the function of the demodulator in analog communication?

To convert the transmitted signal into a message signal Signup and view all the answers

Which of the following components maps coded bits to be sent to the channel in digital communication?

Modulator Signup and view all the answers

What is an information bit in the context of digital communications?

A basic unit of data/message Signup and view all the answers

What is the primary purpose of modulation in communication systems?

To convert a low-frequency signal to high-frequency for transmission Signup and view all the answers

What system allows for simultaneous two-way communication?

Full Duplex Signup and view all the answers

Which of the following inventions occurred first in the history of communication?

Invention of the telephone Signup and view all the answers

What is the function of a receiver in communication systems?

Accepts and converts transmitted signals back to understandable form Signup and view all the answers

Which of the following describes the term 'Noise' in electronic communication?

Undesired current or voltages occurring in a circuit Signup and view all the answers

What does the bandwidth (BW) of a medium determine?

The maximum speed of data pulses the medium can handle Signup and view all the answers

Which of the following formulas correctly expresses total gain (AT) in cascaded circuits?

AT = A1 × A2 × A3 × ... × An Signup and view all the answers

Which milestone in electronic communication happened in the year 1982?

TCP/IP protocol adopted Signup and view all the answers

What unit is used to express gain or attenuation?

Decibels (dB) Signup and view all the answers

What distinguishes Half Duplex communication from Full Duplex communication?

Half Duplex alternates the direction of communication Signup and view all the answers

What is the correct mathematical expression for converting voltage gain to decibels?

dB = 20 log(Vout / Vin) Signup and view all the answers

In communication systems, what is the primary role of a transmitter?

Convert electrical signals to suitable signals for transmission Signup and view all the answers

When was the first deployment of the Global Positioning System (GPS)?

1995 Signup and view all the answers

What is attenuation referring to in signal processing?

The loss of power of a signal Signup and view all the answers

Which prefix corresponds to a multiplier of $10^{-9}$?

Nano (n) Signup and view all the answers

If the output power (Pout) is greater than the input power (Pin), what can be said about the gain?

Gain is positive Signup and view all the answers

What is the formula for calculating power gain in decibels?

dB = 10 log(Pout / Pin) Signup and view all the answers

What frequency range is classified as Extremely Low Frequencies (ELFs)?

30-300 Hz Signup and view all the answers

Which frequency range is primarily used for AM radio broadcasting?

300 kHz–3 MHz Signup and view all the answers

What is the use of Very Low Frequencies (VLFs)?

Government and military communications Signup and view all the answers

What is the bandwidth (BW) in relation to electromagnetic signals?

The portion of the electromagnetic spectrum occupied by a signal Signup and view all the answers

Which frequency range corresponds to Low Frequencies (LFs)?

30–300 kHz Signup and view all the answers

What is a primary usage of Ultrahigh Frequencies (UHFs)?

UHF TV channels and land mobile communication Signup and view all the answers

At what frequency range do Extremely High Frequencies (EHFs) operate?

30 GHz – 300 GHz Signup and view all the answers

Which range is NOT part of high frequencies (HFs)?

3 GHz – 30 GHz Signup and view all the answers

What role does the modulator play in the communication system?

It converts the intelligence signal into a modulated carrier. Signup and view all the answers

How is wavelength ($oldsymbol{ au}$) calculated in relation to frequency ($oldsymbol{f}$)?

$oldsymbol{ au} = rac{c}{f}$ Signup and view all the answers

What is the frequency unit equivalent to cycles per second (cps)?

Hertz (Hz) Signup and view all the answers

What is the primary purpose of the International Telecommunications Union (ITU) in relation to the electromagnetic spectrum?

To allocate frequency bands to different services. Signup and view all the answers

What is the relationship between frequency ($oldsymbol{f}$) and period ($oldsymbol{T}$)?

$f = rac{1}{T}$ Signup and view all the answers

Which of the following correctly describes the electromagnetic spectrum?

A range of wavelengths and frequencies used in communication. Signup and view all the answers

What is the speed of light used in the wavelength calculation?

3 x $10^8$ m/s Signup and view all the answers

Why is avoiding interference in communication important?

To enable simultaneous broadcasting on different frequencies. Signup and view all the answers

Study Notes

Data Communication Fundamentals

Maximum speed of data pulses handled by a medium is determined by its bandwidth.
Bandwidth is expressed in Hertz (Hz) and calculated as BW = fU - fL.
fU represents the upper limit frequency, while fL is the lower limit frequency.

Gain, Attenuation, and Decibels

Gain (A) measures the amplification of a signal, while attenuation refers to its power loss.
Both gain and attenuation are ratios comparing output to input.
For cascaded circuits, total gain or attenuation (AT) is the product of individual gain/attenuation factors.
Gain and attenuation can be expressed in Decibels (dB).
Decibels are defined by specific formulas:
- Voltage: dB = 20 log(Vout/Vin)
- Current: dB = 20 log(Iout/Iin)
- Power: dB = 10 log(Pout/Pin)

Metric Unit Guide

Tera (T) = 10²¹, Giga (G) = 10⁹, Mega (M) = 10⁶, Kilo (k) = 10³
Milli (m) = 10⁻³, Micro (μ) = 10⁻⁶, Nano (n) = 10⁻⁹, Pico (p) = 10⁻¹²

Analog Communication

Information source generates the intelligence or data to be sent.
Message signal represents the original information in electrical form.
Modulator transforms the message signal into a transmitted signal.
Demodulator converts the transmitted signal back into a human-understandable format.
Channels or mediums serve as pathways for signal transmission.

Digital Communication

Source encoder converts message signals into a binary bit sequence.
Information bit functions as the fundamental data unit for digital communications.
Channel encoder adds redundancy to support error recovery.
Modulator maps coded bits for transmission.
Demodulator and channel decoder process and restore the transmitted data.

Modulation Concepts

Modulation modifies the intelligence signal using a carrier signal.
Carrier signals are high-frequency sine waves produced by oscillators.
Baseband signals represent original information transmitted directly into a medium.

Frequency and Wavelength

Frequency (f) is the number of cycles per second, measured in Hz.
Calculated using f = 1/T, where T is the period in seconds.
Wavelength (λ) indicates the distance of one cycle of a wave, calculated by λ = c/f, where c is the speed of light (3 x 10⁸ m/s).

Electromagnetic Spectrum

Encompasses a range of frequencies and wavelengths essential for communication.
Various frequency bands are allocated by the International Telecommunications Union (ITU) to prevent interference.
Frequency bands include Extremely Low Frequencies (30-300 Hz) to Extremely High Frequencies (30-300 GHz) catering to different applications.

Bandwidth

Represents the portion of the electromagnetic spectrum that a signal occupies.

Historical Milestones in Communication

1876: Alexander Bell invented the telephone.
1887: Heinrich Hertz discovered radio waves.
1948: BELL Laboratories invented the transistor.
1973-1976: Development of Ethernet and first LANs by Metcalfe.
1977: Introduction of the first fiber-optic cables in the U.S.
1982: Adoption of TCP/IP protocol in the U.S.
1995: Deployment of the Global Positioning System.
1997: Introduction of the first Wireless LANs.
2009: Launch of the first 100 Gb/s fiber optical networks globally.

Block Diagram of Communication Systems

Transmitter converts electrical signals for transmission over a medium.
Channel or medium refers to the material transmitting the electronic signal.
Receiver converts the received signal back into a comprehensible form.
Noise represents unwanted currents/voltages in circuits.
Transceivers can both transmit and receive signals.

Types of Electronic Communication

Simplex: One-way communication allowing data transmission in one direction.
Full Duplex: Two-way communication allowing simultaneous transmission and reception.
Half Duplex: Two-way communication alternating transmission direction.

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Description

Explore the concepts of maximum data pulse speed, gain, and attenuation in communication signals. This quiz covers essential equations and definitions like bandwidth and decibels, helping you understand the technical aspects of signal processing. Test your knowledge on this critical chapter in telecommunications.