An improved raised-cosine feed model for reflector antenna applications

The raised-cosine feed model is widely used, both in the literature and in practical simulations, to represent the electromagnetic field radiated by tapered spherical-wave sources (e.g., corrugated horns). This model is convenient mostly for three reasons: it is simple, fully characterized by a single parameter, and has perfect pattern reproducibility. These reasons yield a common source that can be employed by different authors to characterize their antennas. However, the model has the shortcoming of representing a true electromagnetic field only in its far-zone, causing it to suffer from accuracy problems in many instances. The other available source model, the gaussian beam, although accurate at both near- and far-zone observation points, is based on paraxial approximations that can create inaccuracies. In the present work these limitations are removed with the introduction of a new improved raised-cosine feed model. This new model is accurate in the near- and far-zone regions, and accounts for pattern dependence on the observation point distance, polarization effects, and the presence of radial field components. Herein the improved raised-cosine feed model is presented and discussed. Its near-zone accuracy is confirmed by comparisons with exact (in a numerical sense) results obtained using the spherical wave expansion technique (SWE) and by demonstrations using an infinite plane reflector. The usefulness and improvement of the model over that of the original far-zone raised-cosine feed model is demonstrated by computing scattering results of a typical reflector antenna geometry employing an axially symmetric hyperboloidal subreflector.<>