Application of the radar cross section RCS for objects on the ground — example of wind turbines

Wind turbines WT are often to be located in some distance to ground based navigation, landing and radar systems. Unacceptable distortions which harm the mission of the systems have to be avoided. The minimum actual permissible distance to the system has to be determined in some way - often done by the RCS scheme for radar systems. It is recalled and shown again by theoretical as well as for numerical results that the RCS is not defined for objects on the ground if the ground is relevantly illuminated by the radar in a practically realistic finite distance. The ground as well as the near-field effect and the highly statistical behavior of the RCS in space and time for realistic distances prevent a reasonable determination and application of the RCS. Theoretical aspects as well as numerical results for wind turbines are discussed in this paper.