Thermal Noise Calculator
Calculate system noise floor, kTB power, and cascaded noise figure analysis using Friis formula.
Density @ 290K: -174 dBm/Hz
Standard: kTB + NF
System Noise Parameters
Define bandwidth, temperature, and receiver noise characteristics
bandwidth configuration
environment & noise
Additional noise added by the receiver stages
Analysis Output
Awaiting Logic
Input system parameters to calculate noise floor results
Technical Reference & Formulas
-174 dBm/Hz @ 290 Kelvin
Where B is Bandwidth in Hz
System Noise Floor including Receiver loss
Cascaded Analysis (Friis Formula)
Analyze noise contributions across multiple receiver stages
Standard Noise Floor Values
Reference values at 290 Kelvin (17°C) for typical channel bandwidths
| bandwidth | thermal power (ktb) | with 3 db nf | with 5 db nf |
|---|---|---|---|
| 1 kHz | -144 dBm | -141 dBm | -139 dBm |
| 10 kHz | -134 dBm | -131 dBm | -129 dBm |
| 100 kHz | -124 dBm | -121 dBm | -119 dBm |
| 1 MHz | -114 dBm | -111 dBm | -109 dBm |
| 5 MHz | -107 dBm | -104 dBm | -102 dBm |
| 10 MHz | -104 dBm | -101 dBm | -99 dBm |
| 20 MHz | -101 dBm | -98 dBm | -96 dBm |
| 40 MHz | -98 dBm | -95 dBm | -93 dBm |
| 100 MHz | -94 dBm | -91 dBm | -89 dBm |
Understanding Thermal Noise
What is Thermal Noise?
Thermal noise (Johnson-Nyquist noise) is generated by the thermal agitation of charge carriers. It is ubiquitous in all electronic systems above absolute zero.
The -174 dBm/Hz Constant
At standard room temperature (290K), the noise density is calculated as kT ≈ 4×10⁻²¹ W/Hz, which equals -174 dBm/Hz.
Doubling the bandwidth (+3dB) doubles the noise floor.
Practical Applications
Link Budgeting
Knowing the noise floor is critical for calculating SNR and link margins. It defines the "floor" across which your signal must climb.
Optimization Tips
- Use cryogenic cooling for high sensitivity
- Front-end LNA selection is mission-critical
- Minimize RF filter insertion loss
- Avoid cable loss before the first LNA