Subelement F: Receivers— Topic 41: Receiver Theory
Question 3-41F4
Element 3 (GROL)What is meant by the term noise figure of a communications receiver?
Explanation
Noise figure measures how much a receiver degrades the signal-to-noise ratio (SNR) by adding its own internal noise. It quantifies the excess noise generated within the receiver's front-end and subsequent stages, beyond the inherent thermal noise present at the input. A lower noise figure indicates better performance for weak signals, as the receiver contributes less unwanted internal noise. Therefore, option C accurately describes the level of noise generated internally by the receiver.
Option A refers to external noise entering from the antenna, not the receiver's internal contribution. Option B describes aspects of selectivity or filter characteristics, unrelated to noise figure. Option D describes receiver selectivity, which is its ability to reject adjacent interfering signals, distinct from its internal noise performance.
Related Questions
3-41F2 What is the definition of the term “receiver desensitizing”?3-41F3 What is the term used to refer to a reduction in receiver sensitivity caused by unwanted high-level adjacent channel signals?3-41F5 Which stage of a receiver primarily establishes its noise figure?3-41F6 What is the term for the ratio between the largest tolerable receiver input signal and the minimum discernible signal?3-42F1 How can selectivity be achieved in the front-end circuitry of a communications receiver?