Difficulty: Medium
Correct Answer: Input noise voltage (without specifying source impedance and bandwidth)
Explanation:
Introduction / Context:
Noisy front ends degrade weak-signal reception. Engineers therefore compare receivers using normalized noise metrics. This item assesses which metrics are standardized and portable across different systems and which are not.
Given Data / Assumptions:
Concept / Approach:
Noise figure (NF) and noise temperature (Tn) are standardized: both relate output SNR to input SNR independent of absolute signal level, provided the source impedance and temperature are defined. Equivalent noise resistance also references noise back to the input with a known bandwidth and impedance. A bare 'input noise voltage' number, without source impedance and bandwidth, is not portable because thermal noise scales with both.
Step-by-Step Solution:
Verification / Alternative check:
Receiver datasheets always pair noise voltages with the test source impedance and bandwidth. Cross-vendor comparisons typically use NF or Tn.
Why Other Options Are Wrong:
Common Pitfalls:
Final Answer:
Input noise voltage (without specifying source impedance and bandwidth)
Discussion & Comments