Analysis of circular waveguide arrays on cylinders

An analysis is given of the mutual coupling effects in a finite-array antenna of circular waveguide elements on a conducting cylinder. The array is described in terms of a scattering matrix, and the multimode aperture fields of the elements are solved for by moment methods. Mutual coupling through wave propagation along the surface is treated according to the geometrical theory of diffraction, since for most cases of interest the surface curvature is small in terms of wavelength. Appropriate asymptotic expansions for the magnetic-field Green's function are derived for the two basic cases of an axial and a circumferential magnetic current element on the cylinder. The method, which allows the array elements to be nonuniformly spaced, applies to cylinders with radii greater than two wavelengths and thus also includes planar arrays. Illustrative numerical examples and comparisons with infinite cylindrical and planar arrays are included.