GENERATION OF PLANE-WAVES

A method of finding the parameters of spherical horn waveguide capable of generation of plane wave at its open end, is presented. The field functions in this case are expressed in terms of associated Legendre and Spherical Hankel function of non-integer parameter. The order of Spherical Hankel function for a particular combination of flare angles of horn, is determined from the solution of transcendental equation expressed in terms of associated Legendre function of non-integral parameters. The radial dimension, for which the wave impedance approaches that of free space, thereby satisfying plane wave condition at the mouth of horn, is then determined. The generation of numerical data involves the computation of Spherical Hankel and Legendre, since these are not available in standard tables.