A GTD analysis of the radiation from slots in planar and cylindrical perfectly-conducting structures with a surface impedance patch

A theoretical approach based on the geometrical theory of diffraction (GTD) is employed to analyze the fields radiated by thin slots in perfectly-conducting infinite planar, and electrically large circular cylindrical structures which are covered with an impedance surface patch. The solution to these antenna problems is built up from the solutions to several, appropriate canonical problems. The total field radiated by the slot is composed of the fields of rays which emanate from the slot to the observation point via points of diffraction on the surface, in addition to the direct ray path. The type of impedance surface chosen is such that the slot excites a bound surface wave mode on the flat impedance surface patch for the planar case, whereas it excites an Elliot type mode on the curved impedance patch for the circular cylinder case. The GTD solution not only imparts a physical insight into the radiation mechanisms involved, but it is also efficient for numerical calculations. Some numerical results based on this initial GTD analysis are presented, and are seen to agree well with the results obtained by other approaches.