Receiver Noise Floor

NF_floor = −174 + NF + 10×log10(BW)

Quick answer

This calculator solves Noise Floor (dBm) = −174 + NF + 10 × log₁₀(BW) for Noise Floor. With Noise Figure 44 dB, Bandwidth 1 kHz, the result is -100 dB.

Calculator

Result
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Formula

Noise Floor (dBm) = −174 + NF + 10 × log₁₀(BW)

Description

The noise floor of a receiver is the minimum detectable signal level, determined by thermal noise, the receiver noise figure, and the bandwidth. The −174 dBm/Hz is the thermal noise power spectral density at room temperature (290 K): kTB in dBm with B = 1 Hz. The noise figure NF adds the receiver internal noise contribution. Wider bandwidth captures more noise power. This formula is fundamental to receiver sensitivity analysis, link budget calculations, and dynamic range assessment in RF, radar, and communication systems.

Variables

  • Noise Floor — Minimum noise power in the receiver (dBm)
  • NF — Receiver noise figure (dB)
  • BW — Receiver bandwidth (Hz)

Practical Notes

Example: An LNA with NF = 2 dB and 200 kHz bandwidth has a noise floor of −174 + 2 + 10×log₁₀(200000) = −174 + 2 + 53 = −119 dBm. The receiver sensitivity is the noise floor plus the minimum required SNR for demodulation. For narrowband systems (LoRa, CW), the narrow bandwidth lowers the noise floor significantly, enabling long-range communication.

Symbols and units

Symbol Meaning Default unit Accepted units
floor Noise Floor dB dB
NF Noise Figure dB dB
BW Bandwidth Hz Hz, kHz, MHz, GHz

Step by step

  1. 1. What you know: Noise Figure 44 dB, Bandwidth 1 kHz
  2. 2. The relation: Noise Floor (dBm) = −174 + NF + 10 × log₁₀(BW)
  3. 3. Substitute: NF = 44 dB, BW = 1 kHz
  4. 4. Result: Noise Floor = -100 dB

Worked examples

Minimum range

Given: Noise Figure 0.66 dB, Bandwidth 5 Hz

Result: Noise Floor = -166.4 dB

Low range

Given: Noise Figure 6.6 dB, Bandwidth 50 Hz

Result: Noise Floor = -150.4 dB

Typical

Given: Noise Figure 44 dB, Bandwidth 1 kHz

Result: Noise Floor = -100 dB

High range

Given: Noise Figure 132 dB, Bandwidth 20 kHz

Result: Noise Floor = 1.01 dB

Maximum range

Given: Noise Figure 1320 dB, Bandwidth 0.2 MHz

Result: Noise Floor = 1199 dB

How Noise Floor changes with Noise Figure

Noise Figure (input) Noise Floor (result)
4.4 dB -139.6 dB
11 dB -133 dB
22 dB -122 dB
33 dB -111 dB
44 dB -100 dB
66 dB -78 dB
88 dB -56 dB
176 dB 32 dB
308 dB 164 dB
440 dB 296 dB

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Frequently asked questions

How do you calculate Receiver Noise Floor?

Use Noise Floor (dBm) = −174 + NF + 10 × log₁₀(BW). With Noise Figure 44 dB, Bandwidth 1 kHz, Noise Floor works out to -100 dB.

What is the formula for Receiver Noise Floor?

The formula is Noise Floor (dBm) = −174 + NF + 10 × log₁₀(BW). The noise floor of a receiver is the minimum detectable signal level, determined by thermal noise, the receiver noise figure, and the bandwidth.

Related Concepts

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