Analyze noise power across RF and test bandwidths. Adjust temperature, figures, losses, and filter factors. Export clear results for design reviews and calculations fast.
Thermal noise density at 290 K is -174 dBm/Hz.
Temperature correction = 10 × log10(T / 290).
Equivalent noise bandwidth = input bandwidth × ENBW factor.
Thermal noise over bandwidth = -174 + 10 × log10(ENBW) + temperature correction.
Total receiver noise floor = thermal noise + noise figure + implementation loss.
SNR = signal level - total noise floor.
SNR margin = available SNR - required SNR.
Noise voltage RMS = √(4kTRB).
Required bandwidth for target noise is solved by rearranging the total noise equation.
| Scenario | Bandwidth | Temperature | Noise Figure | ENBW Factor | Total Noise Floor | SNR Margin |
|---|---|---|---|---|---|---|
| Narrow IF Receiver | 10 kHz | 290 K | 3.00 dB | 1.0000 | -130.0000 dBm | 25.0000 dB |
| Wideband SDR | 1 MHz | 300 K | 6.00 dB | 1.0600 | -106.0997 dBm | 11.0997 dB |
| Audio Measurement Chain | 20 kHz | 295 K | 2.00 dB | 1.1100 | -127.9622 dBm | 37.9622 dB |
A noise floor bandwidth calculator estimates receiver noise over a chosen passband. It helps engineers size filters, compare front ends, and review sensitivity limits. The page combines thermal noise, filter spread, noise figure, and implementation loss. It also checks SNR margin for real signal levels.
Noise power rises with bandwidth. A wider channel collects more random energy. A narrow channel rejects more of it. This is why a spectrum analyzer shows a lower floor at smaller resolution bandwidth. The same rule guides radios, sensors, audio chains, and test instruments.
Real filters are not perfectly rectangular. Their skirts pass slightly more energy than an ideal brick-wall response. Equivalent noise bandwidth captures that difference. A Butterworth or Gaussian stage can increase total noise compared with the same nominal bandwidth. That adjustment matters when margins are tight.
Thermal noise depends on absolute temperature. The common reference is 290 K. Hotter systems generate more noise. Colder systems generate less. Noise figure then adds receiver degradation above the thermal limit. Implementation loss covers mixers, digital shaping, cable loss, and practical nonideal behavior.
Use the density result when comparing devices across different bandwidths. Use total noise floor when checking minimum detectable signal. Use noise voltage for resistor and instrumentation work. Use required bandwidth when you must meet a target floor. Use SNR margin to see whether demodulation or measurement goals are realistic.
This tool fits RF link budgets, low-noise amplifier studies, SDR chains, radar IF paths, lab receivers, and acoustic measurement systems. It supports fast design reviews and clearer documentation. Small bandwidth changes can shift sensitivity, false alarm rate, and detection confidence. Good noise estimates improve every stage.
Noise floor is the total unwanted noise level seen by a receiver or measurement system over a stated bandwidth. It sets the practical lower limit for detectable signals and influences sensitivity, dynamic range, and measurement confidence.
Wider bandwidth admits more random thermal energy. Because noise is spread across frequency, collecting more hertz increases integrated noise power. The growth follows the 10 × log10(B) relationship when temperature and other factors stay fixed.
ENBW means equivalent noise bandwidth. It adjusts a real filter to an ideal rectangular filter that would pass the same total noise power. It is useful whenever filter shape changes the integrated noise result.
-174 dBm/Hz is the approximate thermal noise density at 290 K in a 1 Hz bandwidth. Engineers use it as a standard reference before adding temperature correction, noise figure, bandwidth, and implementation loss.
Noise figure raises the theoretical thermal floor to reflect real receiver degradation. Lower noise figure improves sensitivity. Higher noise figure means the receiver adds more internal noise and reduces available SNR for the same signal level.
Noise voltage matters in instrumentation, sensor interfaces, resistor studies, and audio paths. It translates thermal noise into RMS voltage across a specified resistance, which helps with amplifier and ADC front-end design.
Yes. The same thermal noise principles apply to RF, IF, baseband, and audio systems. You only need consistent bandwidth, temperature, resistance, and receiver assumptions for the calculated values to stay meaningful.
Required input bandwidth is the approximate bandwidth needed to reach a chosen target noise floor after accounting for ENBW, temperature, noise figure, and implementation loss. It helps when setting filters or defining measurement resolution.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.