Understanding Noise in Signals

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Questions and Answers

What does a higher S/N ratio indicate in communication systems?

There is no signal present

The signal is strong and noise is weak (correct)

The signal is weak and noise is strong

Both signal and noise are similar in strength

Using the S/N ratio formula, which variable represents signal power?

Ps (correct)

What characterizes noise in a signal?

It is a structured sequence of frequencies.

It enhances the clarity of the transmitted signal.

It only affects digital signals.

It involves random frequencies at various amplitudes. (correct)

If the signal voltage is 4.2 μV and the noise voltage is 0.3 μV, what is the S/N ratio?

14 Signup and view all the answers

Most S/N ratios are expressed in which form?

Power Signup and view all the answers

How does noise differ from interference?

Interference disrupts a signal while noise degrades it. Signup and view all the answers

What happens to digital signals under high noise conditions?

They need a higher noise level to confuse binary pulses. Signup and view all the answers

Which scenario would likely result in a low S/N ratio?

Weak signal and strong noise Signup and view all the answers

Which example illustrates noise in an analog signal?

Hiss or static heard when tuning an AM radio. Signup and view all the answers

What can occur if noise levels are too high in a signal?

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

What is an example of noise observed on a television screen?

Snow on a black-and-white TV screen. Signup and view all the answers

What is the primary source of industrial noise?

Manufacturing equipment Signup and view all the answers

In communication signals, noise can lead to which of the following outcomes?

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

Which type of noise is primarily caused by lightning?

Atmospheric noise Signup and view all the answers

What factors contribute to extraterrestrial noise?

Solar and cosmic signals Signup and view all the answers

How is noise represented visually on an oscilloscope?

As a random AC voltage. Signup and view all the answers

At what frequency range does atmospheric noise have the greatest impact?

Below 30 MHz Signup and view all the answers

What causes thermal noise in electronic components?

Random motion of free electrons due to heat Signup and view all the answers

Which of the following is NOT a type of internal noise?

Cosmic noise Signup and view all the answers

How often does the sun's noise cycle repeat?

Every 11 years Signup and view all the answers

Which source produces lower levels of noise that can still interfere with signals?

Electronic components in a receiver Signup and view all the answers

What phenomenon is referred to as thermal noise?

Johnson noise Signup and view all the answers

What does white noise represent in terms of frequencies?

All frequencies randomly at random amplitudes Signup and view all the answers

What produces shot noise in semiconductor devices?

Random paths taken by current carriers Signup and view all the answers

What type of noise is produced due to variations in resistance in semiconductor materials?

Flicker noise Signup and view all the answers

What condition creates transit-time noise?

Same transit time of current carrier and signal frequency Signup and view all the answers

What issue arises from intermodulation distortion?

Generation of new signals and harmonics Signup and view all the answers

What is composite noise from a semiconductor composed of?

Shot noise, transit-time noise, and flicker noise Signup and view all the answers

When is noise typically an issue in communication systems?

Whenever received signals are low in amplitude Signup and view all the answers

What does the noise factor (NR) represent?

The ratio between input and output signal-to-noise power Signup and view all the answers

How is the noise figure (NF) calculated?

By applying the formula NF = 10 log NR Signup and view all the answers

What primarily distinguishes distortion from noise?

Distortion alters the waveform while noise simply adds to it Signup and view all the answers

In what context can distortion be seen as desirable?

In the use of Dolby noise reduction systems Signup and view all the answers

Which of the following is not a cause of distortion?

Excessive signal amplification Signup and view all the answers

What is the result of distortion in voice transmission?

Garbled, harsh, and unnatural sounds Signup and view all the answers

How does distortion serve a purpose in musical instruments like electric guitars?

It adds character to the instrument's sound Signup and view all the answers

Which factor makes noise harder to remove from a signal compared to distortion?

Noise is less predictable and often more widespread Signup and view all the answers

What is the signal power if it is given as 6 𝜇𝑊?

6 µW Signup and view all the answers

What is the noise power given in this example?

120 nW Signup and view all the answers

What is the formula used to calculate the S/N ratio?

S/N = SPs / NPs Signup and view all the answers

How is the S/N ratio expressed?

In decibels (dB) Signup and view all the answers

What is the S/N power in dB when calculated as 10 log(50)?

16.99 dB Signup and view all the answers

What additional concepts are associated with the quality of noise in a receiver?

Noise figure and noise factor Signup and view all the answers

If the signal power is 6 µW and noise power is 120 nW, what is the S/N ratio?

50 Signup and view all the answers

Study Notes

Noise

Noise is an electronic signal made up of random frequencies at various amplitudes.
It's added to a radio or information signal during transmission or processing, appearing as random AC voltage.
Noise differs from interference, which disrupts a signal by adding unwanted signals.
Signal noise degrades communication signals, affecting both analog and digital signals.
Digital signals are more resistant to noise because of the binary pulses.
Noise affects signals by adding or subtracting from expected values, making results unpredictable.
Noise can obscure the original signal, especially at high levels or with weak signals.

Types of Noise

External Noise: Uncontrollable sources (industrial, atmospheric, extraterrestrial).
- Industrial Noise: Produced by manufacturing equipment (motors, generators).
- Atmospheric Noise: Electrical disturbances due to lightning. Most impactful below 30 MHz.
- Extraterrestrial Noise: From the sun (repeating 11-year cycle), stars, and space. Significant interference in the 10 MHz to 1.5 GHz range.

Internal Noise

Thermal Noise: Arises from random electron movement (thermal agitation) in conductors.
Semiconductor Noise: In diodes and transistors; includes shot noise, transit-time noise, and flicker noise. Shot noise arises from random electron movement. Transit time noise is when transit time equals the signal frequency. Flicker noise is random variations in resistance.
Intermodulation Distortion: Arises from non-linear circuit behaviors when multiple signals are present.

Signal-to-Noise Ratio (SNR)

Measures the relative strengths of signal and noise.
Higher SNR indicates stronger signaling and weaker noise.
Measured in voltage or power using a formula (V_signal / V_noise or P_signal/P_noise).
Conversion to decibels (dB) is common for expressing SNR values.

Distortion

Distortion is unwanted signal alteration.
Factors causing distortion include environmental factors, communication channel properties, and transmission distance.
Distortion can result in garbled, harsh, or unnatural sounds.
Distortion can be desirable (e.g., in noise reduction systems or musical effects).

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Description

This quiz explores the concept of noise in electronic signals, including its types and effects on communication. You will learn about external noise sources, differences between noise and interference, and the impact on both analog and digital signals. Test your knowledge on how noise degrades signal transmission!