Moment method analysis of circular cylindrical array of waveguide elements covered with a multilayer radome

An analysis of an array of rectangular waveguide openings in a circular cylindrical groundplane covered with a radome is presented. The analysis method is based on the modal solution, i.e. on the superposition of one-dimensional spectral solutions, and on the method of moments. The modal approach requires the summation of a large number of terms in the Fourier series for structures with large radii. Furthermore, highly oscillating integrals occur when the waveguide openings are axially separated. Both problems are treated with special care: asymptotic formulas are used for calculating the Green´s functions, and the integration contour for calculating the inverse Fourier transformation is carefully selected. Measurements on an 18×3 waveguide array on a circular cylindrical structure covered with a radome have been used for verification of the theoretical results. The effect of an airgap between the waveguide openings and the radome is discussed. The agreement between calculated and measured values of mutual coupling, input admittance and radiation patterns is very good.