1. Attenuation
- Definition: Reduction in signal strength as it travels through a medium.
- Key Causes:
- Distance: Signal weakens over long distances.
- Medium: Different materials absorb signals differently (e.g., copper, fiber).
- Formula: Attenuation (dB)=10⋅log10(Input PowerOutput Power)\text{Attenuation (dB)} = 10 \cdot \log_{10} \left( \frac{\text{Input Power}}{\text{Output Power}} \right)
- Solution: Use repeaters or amplifiers to boost the signal.
2. Noise
- Definition: Unwanted electrical or electromagnetic signals that distort the original signal.
- Types:
- Thermal Noise: Caused by random motion of electrons.
- Intermodulation Noise: Overlapping of signals.
- Crosstalk: Signal leakage from one channel to another.
- Impulse Noise: Sudden, irregular disturbances (e.g., lightning).
- Impact: Reduces the quality and accuracy of communication.
3. Signal-to-Noise Ratio (SNR)
- Definition: Ratio of signal power to noise power. Indicates the quality of a communication link.
- Formula: SNR (dB)=10⋅log10(Signal PowerNoise Power)\text{SNR (dB)} = 10 \cdot \log_{10} \left( \frac{\text{Signal Power}}{\text{Noise Power}} \right)
- High SNR: Indicates better quality (less noise).
- Low SNR: Indicates poor quality (more noise).
Quick Recap Table
| Concept | Definition | Key Solution |
|---|---|---|
| Attenuation | Loss of signal strength over distance. | Amplifiers, repeaters. |
| Noise | Unwanted signals that distort data. | Shielding, filtering. |
| SNR | Measure of signal strength vs. noise level. | Increase signal power or reduce noise. |
4. Tips to Remember
- Attenuation affects signal amplitude; it’s measured in decibels (dB).
- Noise is inevitable but can be minimized with proper shielding or filtering.
- High SNR = Clearer communication.
MCQ
1. What is attenuation in communication systems?
- A. Loss of signal energy during propagation
- B. Amplification of signal strength
- C. Reduction of noise in the signal
- D. Enhancement of signal quality
- Answer: A. Loss of signal energy during propagation
2. Which device is used to decrease the strength of a signal?
- A. Amplifier
- B. Attenuator
- C. Modulator
- D. Demodulator
- Answer: B. Attenuator
3. What is noise in a communication system?
- A. Useful signal information
- B. Undesired signal affecting quality
- C. Frequency of the carrier signal
- D. Signal bandwidth
- Answer: B. Undesired signal affecting quality
4. How is the Signal-to-Noise Ratio (SNR) calculated?
- A. Signal Power ÷ Noise Power
- B. Noise Power ÷ Signal Power
- C. Signal Voltage × Noise Voltage
- D. Signal Voltage ÷ Noise Voltage
- Answer: A. Signal Power ÷ Noise Power
5. If the SNR increases, what happens to the signal quality?
- A. Decreases
- B. Remains the same
- C. Increases
- D. Depends on attenuation
- Answer: C. Increases
6. What is the typical unit of measurement for SNR?
- A. Watts
- B. Decibels (dB)
- C. Hertz
- D. Amperes
- Answer: B. Decibels (dB)
7. What type of noise is caused by thermal agitation of electrons?
- A. White noise
- B. Pink noise
- C. Flicker noise
- D. Shot noise
- Answer: A. White noise
8. In which scenario does attenuation typically occur?
- A. Wireless signal transmission
- B. Optical fiber communication
- C. Copper wire communication
- D. All of the above
- Answer: D. All of the above
9. Which type of noise is dependent on the movement of charged particles in semiconductors?
- A. White noise
- B. Shot noise
- C. Impulse noise
- D. Flicker noise
- Answer: B. Shot noise
10. What is the primary effect of noise on a communication system?
- A. Amplifies the signal
- B. Degrades signal quality
- C. Improves bandwidth
- D. Increases attenuation
- Answer: B. Degrades signal quality
For further details and practice, you can explore resources like Testbook and Sanfoundry, which provide in-depth question banks.