Derivation of the SAR Noise Equivalent Sigma Nought

This paper shows a derivation for the Noise Equivalent Sigma Nought .The starting point is the physical meaning of this parameter thus, the equations are derived on the basis of energetic consideration. We analyze both the Distributed Target and the Point Target scenarios aiming at highlight their differences and commonalities as well as corroborate the approach adopted. We will demonstrate the different equations yield to significant difference in the computation of the Noise Equivalent Sigma Nought, such variation in sensitivity can be used to optimize other SAR figure of merit, or to pose different requirements concerning the SAR sensitivity. In the paper is also reported a method to perform the in-flight measurement.