Question
What is the noise figure of a receiver?
Answer Options
- A) The ratio of atmospheric noise to phase noise
- B) The ratio of the noise bandwidth in hertz to the theoretical bandwidth of a resistive network
- C) The ratio in dB of the noise generated in the receiver to atmospheric noise
- D) The ratio in dB of the noise generated by the receiver to the theoretical minimum noise
Correct Answer: D
Explanation
The noise figure is a fundamental figure of merit used to characterize the quality of a radio receiver or amplifier, particularly in the VHF/UHF/Microwave frequency ranges. It quantifies how much the device itself degrades the overall signal-to-noise ratio (SNR) as the signal passes through it.
The noise figure is defined as the ratio in dB of the noise generated by the receiver to the theoretical minimum noise (thermal noise) that a perfect receiver operating at room temperature would generate. A perfect, noiseless device would have a noise figure of 0 \text{ dB}. The lower the noise figure, the better the receiver’s ability to detect weak signals.
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