HIGHER-ORDER IMPEDANCE BOUNDARY-CONDITIONS APPLIED TO SCATTERING BY COATED BODIES OF REVOLUTION

In this paper higher order impedance boundary conditions will be emplo yed in the solution of scattering by coated conducting bodies of revol ution. The higher order impedance solution reduces the total number of unknowns relative to the exact solution, and produces a system matrix which is less dense than that of the exact solution, The construction of the solution involves two distinct steps, In the first step the bo dy of revolution is replaced by an equivalent set of electric and magn etic currents on its exterior surface which generate the true fields o utside the body, An integral equation relating these currents through the free space Green's function is derived, Step two employs the highe r order impedance boundary condition to relate the electric and magnet ic currents on the surface of the body, This replaces the rigorous sol ution of the interior problem, The higher order impedance boundary con ditions are derived by obtaining an exact impedance boundary condition in the spectral domain for the coated ground plane, approximating the impedances as ratios of polynomials in the transform variables, and e mploying the Fourier transform, The resulting spatial domain different ial equations are solved in conjunction with the integral equation usi ng the method of moments, Several examples of bistatic and monostatic radar cross section for coated bodies of revolution are used to illust rate the accuracy of the higher order impedance boundary condition sol ution relative to the standard impedance boundary condition solution a nd the exact solution, The effects of coating thickness, loss, and cur vature on the accuracy of the solution are discussed.