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What is the receiver sensitivity requirement for LoRa at SF12 spreading factor?

What is the receiver sensitivity requirement for LoRa at SF12 spreading factor? LoRa at SF12 with 125 kHz bandwidth achieves a receiver sensitivity of approximately -137 dBm, one of the most sensitive values for any non-satellite wireless technology: (1) How -137 dBm is achieved: the thermal noise power in 125 kHz bandwidth: N = kTB = -174 dBm/Hz + 10 log(125000) = -174 + 51 = -123 dBm. With receiver noise figure NF = 6 dB: noise floor = -123 + 6 = -117 dBm. At SF12: the chirp spreading provides a processing gain of approximately 20 dB. The required SNR for demodulation at SF12 is approximately -20 dB (the signal can be 20 dB below the noise floor). Sensitivity = noise floor + required SNR = -117 + (-20) = -137 dBm. This means the receiver can successfully demodulate a signal that is 100× weaker than the thermal noise. (2) Comparison across spreading factors: SF7 (125 kHz): processing gain ≈ 7 dB, required SNR ≈ -7.5 dB, sensitivity ≈ -123 dBm. SF8: required SNR ≈ -10 dB, sensitivity ≈ -126 dBm. SF9: SNR ≈ -12.5 dB, sensitivity ≈ -129 dBm. SF10: SNR ≈ -15 dB, sensitivity ≈ -132 dBm. SF11: SNR ≈ -17.5 dB, sensitivity ≈ -134.5 dBm. SF12: SNR ≈ -20 dB, sensitivity ≈ -137 dBm. Each SF step adds approximately 2.5 dB of sensitivity improvement. (3) Transceiver specification: Semtech SX1261/SX1262: guaranteed -137 dBm at SF12, 125 kHz. Practical devices typically achieve -134 to -137 dBm depending on: PCB layout quality, LNA noise figure, antenna matching, and crystal reference accuracy. (4) What limits sensitivity further: crystal reference accuracy: the LoRa receiver must search for the chirp within a frequency uncertainty window. A ±10 ppm crystal at 868 MHz introduces ±8.7 kHz uncertainty. This does not directly affect sensitivity but increases the search time (and power consumption during RX). Interference: in the ISM band, other devices may generate energy in the LoRa channel. Even broadband noise from nearby switching regulators can raise the effective noise floor. Phase noise: the local oscillator phase noise contributes to the noise floor. At SF12: the integration bandwidth is very narrow (the chirp coherence time is long), making phase noise a less critical factor than in wideband systems.
Category: Wireless Standards and Protocols
Updated: April 2026
Product Tie-In: IoT Modules, Filters, Antennas

LoRa SF12 Sensitivity

LoRa at SF12 operates in a regime where the signal is well below the noise floor, similar to GPS or deep-space communication, using spread-spectrum processing gain to extract the information.

  1. Performance verification: confirm specifications against the application requirements before finalizing the design
  2. Environmental factors: temperature range, humidity, and vibration affect long-term reliability and parameter drift
  3. Cost vs. performance: evaluate whether the application demands premium components or standard commercial grades
  4. Interface compatibility: verify impedance, connector type, and mechanical form factor match the system architecture
  5. Margin allocation: include sufficient design margin to account for manufacturing tolerances and aging effects
Common Questions

Frequently Asked Questions

Can I achieve better than -137 dBm?

With standard LoRa (Semtech SX126x): -137 dBm is the practical limit at SF12/125 kHz. To improve further: reduce the bandwidth (62.5 kHz → -140 dBm theoretical, but rarely used due to crystal tolerance requirements). Use a lower-NF LNA (external GaAs LNA with NF < 1 dB → potential 4-5 dB improvement). Use a higher SF (SF12 is the maximum defined in LoRa). In practice: improving the antenna efficiency by 2-3 dB (better antenna design) is more impactful and cheaper than pushing the receiver sensitivity.

How does the -137 dBm compare to other technologies?

LoRa SF12: -137 dBm. Sigfox UNB (base station): -142 dBm (narrower BW = 100 Hz). NB-IoT: -141 dBm (with 2048 repetitions). BLE 5 (coded PHY, 125 kbps): -103 dBm. Wi-Fi 6 (MCS0, 20 MHz): -82 dBm. GPS: -130 to -165 dBm (with long integration). LoRa sensitivity is remarkable for a simple, low-cost transceiver and rivals cellular IoT technologies that use significantly more complex receiver architectures.

Why not always use SF12?

SF12 has significant drawbacks: data rate: 250 bps (22× slower than SF7). Airtime: a 20-byte packet at SF12 takes 1.5 seconds (vs 0.07 seconds at SF7). Duty cycle: at 1% (EU 868 MHz), SF12 allows only 24 packets/hour vs 514 at SF7. Battery: longer airtime = more energy per packet. Gateway capacity: SF12 occupies the channel 22× longer, reducing the number of devices a gateway can serve. Use SF12 only for devices at the extreme range edge. Use SF7-SF9 for close-to-medium range with better throughput and battery life.

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Glossary

Related Terms

Noise Figure → LNA → Noise Floor → S-Parameters → Insertion Loss → Return Loss →
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