1. Receiver Sensitivity
Sensitivity describes the weakest signal power level that the receiver is able to detect and decode
Sensitivity is dependent on the lowest signal-to-noise ratio at which the signal can be recovered
Different modulation and coding schemes have different minimum SNRs
Range: <0 dB to 60 dB
Sensitivity is determined by adding the required SNR to the noise present at the receiver
Noise Sources
Thermal noise
Noise introduced by the receiver’s pre-amplifier

2. Thermal Noise Thermal Noise = N = kTB (Watts)
k= x J/K
T = temperature in Kelvin
B=receiver bandwidth
So Thermal Noise can be expressed by following formula
N = -228,6 dBw + 10 log T + 10 log B
Thermal noise is usually very small for reasonable bandwidths
Noise introduced by the receiver pre-amplifier
Noise Factor = Noise Figure = SNRin/SNRout (positive because amplifiers always generate noise)

3. Receiver Sensitivity Calculation
The smaller the sensitivity, the better the receiver
Sensitivity (W) = kTB * NF(linear) * minimum SNR required (linear)
Sensitivity (dBm) = 10log10(kTB*1000) + NF(dB) + minimum SNR required (dB)

4. Sensitivity Example Example parameters
Signal with 200KHz bandwidth at 290K
NF for amplifier is 1.2dB or (linear)
Modulation scheme requires SNR of 15dB or (linear)
Sensitivity = Thermal Noise + NF + Required SNR
Thermal Noise = kTB = ( x J/K) (290K)(200KHz) = x W = -151dBW or -121dBm
Sensitivity (W) = (8.006 x W )(1.318)(31.62) = 3.33 x W
Sensitivity (dBm) = -121dBm + 1.2dB + 15dB = dBm
Sensitivity decreases when:
Bandwidth increases
Temperature increases
Amplifier introduces more noise