Noise in Communication Systems

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Questions and Answers

What does a higher Signal-to-Noise Ratio (SNR) indicate about the signal and noise?

The signal is weak and the noise is strong.

The signal and noise are equal in strength.

The signal is strong and the noise is weaker. (correct)

The noise is stronger and the signal is stronger.

Which formula correctly represents the quantity for Signal-to-Noise Ratio in terms of voltage?

$S/V_s = N/V_n$ (correct)

$S = V_s / N_v$

$S/V_s = N/P_n$

$S/V_n = N/V_s$

If the signal voltage is 4.2 $ ext{μV}$ and the noise voltage is 0.3 $ ext{μV}$, what is the calculated S/N ratio?

14 (correct)

1.4

Why is the S/N ratio typically expressed in terms of power rather than voltage?

Power provides a more accurate representation of signal strength. Signup and view all the answers

What is indicated if the S/N ratio is low?

The signal is weak and the noise is strong. Signup and view all the answers

What is thermal noise also known as?

Johnson noise Signup and view all the answers

Which type of noise is associated with semiconductor components like diodes and transistors?

Shot noise Signup and view all the answers

What phenomenon occurs due to the random movement of current carriers in a semiconductor?

Shot noise Signup and view all the answers

What does flicker noise refer to in semiconductor materials?

Minute random variations of resistance Signup and view all the answers

What is transit-time noise related to?

Time taken for a current carrier to move through a circuit Signup and view all the answers

What type of noise is described as filtered or band-limited noise?

Pink noise Signup and view all the answers

What does intermodulation distortion result from?

Generating new signals from circuit nonlinearities Signup and view all the answers

How does noise affect communication systems?

It is problematic with low amplitude received signals Signup and view all the answers

What type of external noise is caused by manufacturing equipment?

Industrial noise Signup and view all the answers

Which form of atmospheric noise is commonly associated with lightning?

Static Signup and view all the answers

What is the primary cause of solar noise?

Signals from the sun Signup and view all the answers

What typically causes internal noise in a receiver?

Electronic components Signup and view all the answers

What is noise in terms of electronic signals?

An electronic signal with random frequencies and amplitudes. Signup and view all the answers

How does noise affect digital signals compared to analog signals?

Digital signals require a higher amount of noise to be confused. Signup and view all the answers

Which type of noise is affected by a noise cycle from the sun?

Solar noise Signup and view all the answers

What is a characteristic of cosmic noise?

It is generated by stars outside the solar system Signup and view all the answers

What common household example demonstrates noise during radio tuning?

Hiss or static between radio stations. Signup and view all the answers

Which of the following is a common type of internal noise?

Thermal noise Signup and view all the answers

What visual phenomenon identifies noise on a television screen?

Snow on black-and-white screens. Signup and view all the answers

What happens when noise overshadows the original signal?

The original signal may be completely lost. Signup and view all the answers

Which type of noise shows the greatest impact on signals with frequencies below 30 𝑀𝐻𝑧?

Atmospheric noise Signup and view all the answers

What defines the difference between noise and interference?

Noise consists of random frequencies, while interference involves specific conflicting signals. Signup and view all the answers

What can high levels of noise lead to in electronic communication?

Unpredictable and possibly damaging results. Signup and view all the answers

What does the term 'signal noise' refer to?

Unwanted interference that degrades communication signals. Signup and view all the answers

What is the calculated S/N ratio if the signal power is 6 𝜇𝑊 and the noise power is 120 𝑛𝑊?

50 Signup and view all the answers

What is the correct formula for converting S/N ratio to decibels (dB) for power?

$dB = 10 log(S/N)$ Signup and view all the answers

What is the result of $10 log(50)$?

16.99 dB Signup and view all the answers

Which calculation method is used to express the noise quality of a receiver?

Noise Factor and Noise Figure Signup and view all the answers

What is the decibel value for the S/N voltage calculated as $20 log(14)$?

22.92 dB Signup and view all the answers

Which of the following values represents noise power in the example?

120 𝑛𝑊 Signup and view all the answers

When calculating the S/N ratio, what is the standard notation for signal power?

$S$ Signup and view all the answers

Which of the following correctly represents the S/N ratio formula using example values?

$6 imes 10^{-6} / 120 imes 10^{-9}$ Signup and view all the answers

What does the noise factor (NR) represent?

The ratio of signal power at the input to noise power at the output Signup and view all the answers

When expressed in decibels, what is the noise factor called?

Noise figure Signup and view all the answers

Which of the following is NOT a factor that causes distortion?

Signal amplification levels Signup and view all the answers

What is a characteristic of distortion in audio transmission?

It can result in harsh and unnatural sounds. Signup and view all the answers

How is distortion used in a Dolby system?

To distort audio signals for enhancing certain aspects. Signup and view all the answers

How does distortion differ from noise?

Distortion affects the waveform, while noise affects only the amplitude. Signup and view all the answers

Which instrument commonly uses distortion as an effect?

Electric guitar Signup and view all the answers

What is one potential outcome of distortion in audio signal processing?

Garbled sound quality. Signup and view all the answers

Study Notes

Noise

Noise is an electronic signal with random frequencies and amplitudes, added to a signal during transmission or processing.
It appears as a random AC voltage on an oscilloscope, regardless of the source.
Noise differs from interference, which disrupts a signal by adding unwanted signals.
Signal noise degrades analog and digital signals.
More noise is needed to affect digital signals than analog signals, as digital signals use binary pulses.

Signal-to-Noise Ratio (SNR)

SNR represents the relative strengths of signal and noise in communication systems.
High SNR means a strong signal and weak noise; low SNR vice versa.
Reception is unreliable with low SNR.
SNR can be expressed in voltage or power using formulas.
SNR is often expressed in decibels (dB).

Types of Noise

External Noise: Uncontrollable noise sources like industrial, atmospheric, or extraterrestrial.
- Industrial Noise: From manufacturing equipment (e.g., generators, motors).
- Atmospheric Noise: Electrical disturbances, often from lightning (static).
- Extraterrestrial Noise: From the sun (solar noise), with an 11-year cycle of increased intensity.

Internal Noise

Noise from components within a receiver (resistors, diodes, transistors).
- Thermal Noise (White Noise): Random motion of electrons due to heat.
- Semiconductor Noise: From diodes and transistors, including shot noise, transit-time noise, and flicker noise.
- Intermodulation Distortion: From generating new signals and harmonics due to circuit nonlinearities.

Distortion

Distortion is an unwanted change in an information signal (audio/video).
Distortion affects signal waveform in electronic devices and communication channels.
Causes include environmental factors, channel properties, and transmission distance.
Some distortions are desirable, like in noise reduction systems or musical effects (e.g., electric guitar).

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Description

This quiz explores the concept of noise in electronic communication systems, detailing its random nature and impact on signal quality. It covers the Signal-to-Noise Ratio (SNR) and various types of noise, emphasizing the differences between external and internal noise sources. Test your understanding of how noise affects both analog and digital signals.