Application of the spherical wave theory to the calculation of the near-field radiation from an open-ended circular waveguide

In present work the spherical wave expansion technique is used to analyse the general near-field radiation characteristics of an open-ended semi-infinite circular waveguide. The coefficients of the spherical-wave expansion have been obtained by using far-field data calculated by means of application of Wiener-Hopf technique for solving the integral equations for rigorous solution of diffraction problem. The amplitude and phase radiation characteristics for waveguide excited by dominant mode TE₁₁ in near and intermediate zone have been calculated and analysed in a wide frequency band. The calculations of the radiation characteristics in terms of Kirchhoff technique have been also carried out in order to determine the applicability limits of the aperture approximate methods to calculating near-field radiation characteristics