C. Cao

Current antenna research at K. U. Leuven

Four antenna research projects at the Katholieke Universiteit Leuven are described. In the first project, four different methods for the transformation of plane-polar near-field data to far-field antenna characteristics have been compared, and the method with the best performance (accuracy versus computer time) has been implemented on an HP 1000 and on a VAX under VMS. In the second project, a test method has been developed to detect faulty columns in three-dimensional array antennas. The method is based on a reconstruction technique, and has been implemented in an air-surveillance secondary radar system. In the third project, the transmission-line model developed for rectangular microstrip antennas has been implemented and verified for linear and planar arrays. The software package runs on a PC, as well as on VAX workstations. In the fourth project, a software package, running on a VAX under VMS, has been developed based on a moment-method approach for the analysis of multiprobe, multipatch configurations in stratified-dielectric media. The procedure developed contains features to improve the convergence, accuracy and efficiency of the moment method.<<ETX>>

A fast interpolation procedure for plane-polar near-field to far-field transforms

A technique involving the use of a 2-D fast Fourier transform has been developed to evaluate the plane-polar near-field-to-far-field transformation. Because of the efficiency of the interpolation, which makes it possible to compute the field in any plane comprising the origin of the polar grid, a software package including probe correction has been written to perform both plane-polar and plane-rectangular near-field-to-far-field transformations. A highly directive antenna with rapidly varying near fields has been used to test the proposed method.<<ETX>>

A plane-polar near-field to far-field transformation with the fast Hankel transform method

It is known that a direct radial integration, used to compute the far-field from uniformly spaced plane-polar near-field measurements requires the evaluation of a large amount of Bessel functions and hence CPU time. Up to 1985 only unequally spaced fast Hankel algorithms were available. Hansen [3] developed an algorithm that was usable for equally spaced measurements points, but only for order zero. His theory is generalised in this paper and applied to a plane-polar near-field to far-field transformation.RésuméIl a été établi que les transformations de champs proches plans-polaires requièrent l’évaluation de maintes fonctions de Bessel et donc un temps de calcul considérable. Jusqu’en 1985 les algorithmes rapides de Hankel se limitaient à des points espacés de manière inégale. Hansen [3] a développé un algorithme qui se prêtait à des points de mesures uniformément espacés. mais pour l’ordre zéro seulement. Sa théorie est généralisée dans cet article et appliquée à une transformation de champs plans-polaires proches en champs lointains.