Fast analysis of a compound large reflector antenna

[摘要] ENGLISH ABSTRACT: The o set Gregorian dual reector antenna is eminently well suited to a radio telescopeantenna application as it o ers a narrow beam width pattern (i.e high gain) and goode ciency. The focus of this work is on the analysis of characteristics of such a Gregorianantenna.The design of the class of reector antennas is normally based on the use of ray-optics,with this simpli ed approach being able to predict antenna performance based on approximateformulas for example the beam width against aperture size. However for compoundantennas such as the Gregorian reector there are several interdependent parameters thatcan be varied and this reduces the applicability of the simple ray-optic approach. It wasdecided that, if a fast enough analysis of a con guration can be found, the technique ofdesign through interactive analysis would be viable.To implement a fast analysis of the main beam performance of such a Gregorian antenna,a solution algorithm has been implemented using a plane wave spectrum approach combinedwith a custom aperture integration formulation. As this is able to predict the beam performancewithin about a second on a PC, it is suitable for iterative design. To implementthe iterative design in a practical manner a user interface has been generated that allowsthe user to interactively modify the geometry, see the physical layout, and thennd theantenna pattern. A complete working system has been realised with results comparing wellto a reference solution. The limitations of the technique, such as its inaccuracy in predictingthe side lobe structure, are also discussed.

[发布机构] Stellenbosch University