How do I calculate the sensitivity of a receiver in dBm given the noise figure and bandwidth?
Calculating Receiver Sensitivity
Sensitivity defines the minimum input signal level that produces acceptable output quality. The calculation starts from the thermal noise floor and adds the receiver's noise contribution and the minimum signal-to-noise ratio needed by the demodulator or detector.
| Parameter | Superheterodyne | Direct Conversion | Digital IF |
|---|---|---|---|
| Image Rejection | 60-90 dB (filter) | 30-50 dB (mismatch) | N/A (digital) |
| DC Offset | No issue | Major issue | No issue |
| LO Leakage | Low | High | Low |
| Integration | Difficult | Easy (single chip) | Moderate |
| Dynamic Range | 80-120 dB | 60-90 dB | 70-100 dB |
- Performance verification: confirm specifications against the application requirements before finalizing the design
- Environmental factors: temperature range, humidity, and vibration affect long-term reliability and parameter drift
- Cost vs. performance: evaluate whether the application demands premium components or standard commercial grades
Frequently Asked Questions
Does antenna gain affect sensitivity?
Antenna gain increases received signal power but does not change the receiver sensitivity specification. However, it improves the system sensitivity (minimum detectable signal at the antenna input) by the antenna gain in dB.
What SNR is needed for BER = 10⁻⁶?
For BPSK: about 10.5 dB. For QPSK: about 10.5 dB. For 16-QAM: about 14.5 dB. For 64-QAM: about 18.5 dB. These are theoretical values; practical implementations require 1 to 3 dB additional margin.
How does coding gain improve sensitivity?
Forward error correction (FEC) provides coding gain that effectively reduces the required SNR. A rate-1/2 convolutional code provides approximately 5 dB coding gain, improving sensitivity by 5 dB without changing the receiver hardware.