Power From Target Reflected

Equation:  Pr    =    ( Pp x G x δ) / (4 x pi x r2)
P =   reflected power (Watt)
G   =   antenna gain (figure not dB)
Pp  =   RF peak power (Watt)
δ =  target Radar Cross Section (RCS m2)
r  =  target range (m)
    
 Example:   Pp    = 1000 Watt
G      = 1000 (30 dB)
δ     = 1 m2
r        = 100 000 m (100km)
   Pp          G        δ                   pi           r
 P   = (1000 x 1000 x 1)   /   (4 x pi x 1000002) =
 (1000 x 1000 x 1) / (12.57 x 10 000 000) = 

0.00795775 Watt  or - 20.99 dBW