engleski

Multi-Shell Radially Symmetrical Lens Antennas

In this chapter we review several aspects of the analysis and the design of multi-shell spherical and circular cylindrical lens antennas. Such lens antennas are attractive for implementation in communication and radar systems, in particular in the millimetre-wave frequency band, due to their broadband behaviour, excellent focusing properties, possibility of beam scanning, and the ability to form multiple beams. In order to develop an efficient analysis tool, needed for successful design of multi-shell lens antennas, we first demonstrate the principles of the analysis algorithm for calculating the EM field distribution in general multilayer structures (i.e. inside a structure with an arbitrary number of layers). This algorithm is designed for spherical and circular-cylindrical geometries with elementary excitation. To model realistic lens antennas, we introduce additional flexibility that allows the analysis of actual feed antennas that usually do not follow the symmetry properties of the lens. Finally, by connecting the algorithm with an optimization subroutine, a powerful analysis and design tool is created. All the aspects of the proposed analysis approach are explained and illustrated with examples. Furthermore, some practical problems which are encountered in the design of these types of lens antennas are highlighted and common solutions are presented and compared to the ideal situations.

spherical lens antennas, cylindrical lens antennas, multi-shell lenses, spherical wave expansion, vector-Legendre transformation, cylindrical wave expansion

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