RF Engineering
What Is the Noise Floor? Thermal Noise, SNR and Receiver Sensitivity Explained
The noise floor is the faint thermal noise present in every receiver, the level a wanted signal has to rise above to be decoded. At room temperature it starts at −174 dBm per hertz, then climbs with bandwidth and the receiver noise figure. Add the signal to noise ratio your modulation needs and you have the receiver sensitivity. Here is where −174 dBm/Hz comes from, the noise floor formula with a reference table, how noise figure and SNR fit in, and a worked example that turns into a sensitivity figure.