Consider the following statements regarding white noise : 1. The white noise contains all the frequency components in equal proportion. 2. Johnson noise is an example of white noise. 3. The white noise has a Gaussian distribution. Which of the above statements are correct?
Analyzing White Noise Statements
We need to evaluate the correctness of the three statements provided regarding white noise.
Statement 1: Frequency Components
Statement: The white noise contains all the frequency components in equal proportion.
Analysis: This is the fundamental definition of white noise. It implies that the power spectral density (PSD) of white noise is constant across all frequencies.
Conclusion: Statement 1 is correct.
Statement 2: Johnson Noise Example
Statement: Johnson noise is an example of white noise.
Analysis: Johnson noise, also known as thermal noise, is generated by the thermal agitation of charge carriers in conductive materials. It is a significant source of noise in electronic circuits and exhibits a flat power spectral density over a wide frequency range, making it a practical approximation of white noise.
Conclusion: Statement 2 is correct.
Statement 3: Gaussian Distribution
Statement: The white noise has a Gaussian distribution.
Analysis: While the defining characteristic of white noise relates to its frequency spectrum (flat PSD), the amplitude distribution of many physical noise sources that approximate white noise, including Johnson noise, is typically Gaussian. This is often due to the noise resulting from the superposition of numerous independent random events.
Conclusion: Statement 3 is correct.
Final Conclusion
Since all three statements (1, 2, and 3) are correct descriptions or common characteristics associated with white noise, the option including all three is the right choice.
- Statement 1: Correct (Definition)
- Statement 2: Correct (Example)
- Statement 3: Correct (Common characteristic, especially for Johnson noise)
Therefore, the correct option includes statements 1, 2, and 3.
Important Questions from Noise in Analog Communication System
A 1 mW signal having a bandwidth of 100 MHz is transmitted to a receiver through cable that has 40 dB loss. If the effective one side noise spectral density at the receiver is 10-20 Watt/Hz, then the signal to noise ratio at the receiver is
Johnson noise is
Consider the following statements regarding noise :
1. The shot noise has a uniform spectral density like thermal noise.
2. For the amplifying devices, the shot noise is inversely proportional to the output current.
3. The partition noise in a diode will be higher than that in a transistor.
Which of the above statements is/are not correct?
