Improved analysis of the conical horn to free space junction

Previously in the analysis of feedhorns with the modal-matching technique (MMT), a further method such as the aperture field method or spherical wave expansion was needed in order to describe the radiated fields. In the theory presented by the authors, the MMT is used to evaluate all fields. The application of the MMT to infinite extended areas permits the inclusion of the transition from feedhorn to free space in the analysis. Furthermore, a coordinate transformation with the help of a Zwischenmedium intermediate medium is discussed, which is needed, if the fields inside the feedhorn are analysed with the MMT in cylindrical coordinates