On the concept of near field radar cross section

The notion of far field radar cross section (RCS) is intuitively pleasing in that it provides a measure of the scattering characteristics of an object independent of antenna orientation or range to the object. When the transmitting or receiving antenna of a radar move into the near field, the assumptions made to calculate far field RCS are no longer valid. This paper presents two definitions of near field RCS developed by Lee, Wang, and Labarre (1991), based on variations of the radar range equation: RCS1 and RCS2. Results of numerical simulations of a sphere and a square flat plate within the near field showed that these definitions failed to achieve the antenna orientation and range independence observed in far field RCS. The final conclusion drawn from this work is that the only physically meaningful quantity measured in a near field radar scenario is the ratio of the power received to the power transmitted called the power return ratio.