Hello,
We do have so many distributive functions related to estimation of noise or to find signal occurance in RADARS ,how to choose appropriate distribution function.

 

Am i not clear about my question? If no please try to answer it quickly.

 

Well, actually you aren't too clear. This is kind of one of the first things to be learned in the technical study of Radar, I would expect anybody thinking of this to already have seen it.

However, just to get you going (admittedly I am primarily self taught on this topic, so perhaps thats what you're doing)...Usually the noise at the RX antenna, or generated by any thermal process is considered to be Gaussian. After detection (absolute magnitude function, rectifying, or calculating its magnitude, take your pick) a Gaussian distribution has a Rayliegh distribution.
this link http://www.acfr.usyd.edu.au/pdfs/training/sensorSystems/10 Detection of Signals in Noise.pdf
will get you started.

 

It is not a matter of choosing. You don't get to pick the statistical properties of the thing you are studying!! You study the natural phenomena and you see if a particular distribution function allows you to predict or explain the phenomena in question.

 

The question is complicated and yet not cleared. What you are asking about the radar or some distribution of its functions.