A passive matched attenuator at the reference temperature adds loss before amplification. Under those assumptions, its noise figure equals its attenuation in dB.
How it works in practice
Pre-receiver loss reduces available signal and affects system noise performance. The full cascade depends on component temperatures and the receiver's own noise figure. Attenuation can still be necessary for overload protection; calculate the sensitivity consequence rather than assuming it is free.
Example and interpretation
A 3 dB pad before a receiver generally adds about 3 dB to cascaded noise figure under standard matched-temperature assumptions.
Checks before use
- Determine required protection
- Calculate pre-receiver loss
- Check temperature assumptions
- Evaluate system sensitivity
Important limit
Do not apply this simple result to arbitrary temperatures or mismatched networks without analysis.
Related Centron RF product
SMA 2 W 6 GHz fixed attenuator. Use calculated levels to define a requirement, then compare it with the exact product’s current bandwidth, input power, impedance and available attenuation options. Calculations assume stated conditions and do not replace a component datasheet.
Further reading
Keysight: Fundamentals of RF and Microwave Power Measurements. This background reference explains general principles; the selected Centron RF model’s datasheet governs its own ratings.
Related guides
- How to Calculate Required Receiver Protection Attenuation
- Adding Two RF Powers: Why dBm Cannot Be Added Directly
Educational guide. Numerical examples use the stated assumptions and are not test results for a supplied unit.