Wave propagation through curved shells and the validity of the plane-slab approximation

A variety of results is presented for the transmission of microwaves through curved shells. Cylindrical shells with line sources and spherical shells with dipole sources, located in the shell cavity, are considered, and ray theory is applied in systematic computation following G.H. Deschamps´ procedure (1972). The ray tracing procedure implemented in the program includes the contribution of multiple reflections between the shell dielectric and free-space medium interface. These results are compared with the local plane-slab approximation described by G. Tricoles (1964). Errors <1% in magnitude are found for radii of curvature >10 λ₀, and thickness <1% λ₀. For the extreme case of shells with radii <5 λ₀ and thickness greater than 1 λ₀, the plane-slab approximation appears to have significant error. Typically, for a shell of radius 5 λ₀ and thickness of 1 λ₀, the error in the normalized far field is less than 4%. The procedure of P.D. Einziger and L.B. Felsen (1983) is extended to provide a basis for the plane-slab approximation