Electromagnetic scattering by perfectly conducting bodies

• Main Author: Gribble, Jeremy
• Published: University of Surrey 1981
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.731014

A number of approaches to the problem of scattering of electromagnetic waves by metallic bodies are examined, in the context of earlier work done at the University of Surrey under a contract from the Royal Aircraft Establishment at Farnborough. A review of this earlier work is given, followed by some fundamental electromagnetic theory and a discussion of solutions of the two dimensional wave equation. This leads naturally to the introduction of the Rayleigh hypothesis for scattering from irregularly shaped cylinders. The analytical continuation method of Wilton and Mittra for overcoming the problem of the invalidity of the Rayleigh hypothesis is given, and its reformulation in matrix notation motivates discussion of the properties of the scattering matrices of bodies which gave a number of symmetries. Because the scattering matrix of a body, depends only on the body and not at all upon the incident field, any symmetries of the scatterer must be reflected in the form of the scattering matrix. These results are used to discuss the boundary condition problem for a perfectly conducting body of rotation. Chapter eight contains an attempt to extend aperture field theory as used for calculating near-axis fields in, for example, reflector antenna systems to more general scattering problems. Some related work by Bach and his associates is discussed. In chapter nine an alternative approach to the calculation of the scattering matrix is given which leads to a reformulation of the method of physical optics. The modified method is used to investigate the validity of the Rayleigh hypothesis for a slightly perturbed circular cylinder and the results compared with those due to Van Den Berg and Fokkema. Finally, in chapter ten another method of overcoming the invalidity of the Rayleigh hypothesis is examined, but is shown to be impractical to implement numerically.