Sensitivity of a receiver?

What defines the sensitivity of the receiver? What can be done to make a receiver as sensitive as possible?

Hi, sensitivity defines differently for different applications.
Such as for telecom, the sensitivity normally is the receiver's threshhold when BER is 1e-6.
For radar, the sensitivity is minimum detected signal, the signal is about 3dB higher than noise floor.
Sensitivity is the minimum signal power and maximum signal power for receiver detecting.
For lower sensitivity, from theory, is -174+NF(dB)+10log(BW)(Hz)+SNR(dB), the unit is dBm. So make a receiver as sensitive as possible, you should make NF as low as possible, and select modulation plan to make SNR as low as possible. If possible, make BW as narrow as possible.

The most contributors for good sensitivity are low Noise Figure, narrow bandwidth and low SNR requirements.
The problem is, generally Bandwidth and SNR are given by the system requirements, and is not too much room to change them.

about the problemo of sensitivity ,many books give it