Fast synthesis of shaped reflector antennas

For systems requiring a shaped (non-focused) antenna radiation pattern, a single shaped reflector illuminated by a simple feed can provide a light-weight, low loss and cost effective solution. Terrestrial applications include surveillance radar and point to multipoint transmission services. In space, communication and broadcast satellites increasingly employ contoured beam antennas to achieve efficient coverage of irregularly shaped geographical service areas. The design methods for shaped reflector antennas generally fall into two classes; those which are accurate and flexible but require extensive computation times, and those which are computationally efficient but are based on many simplifying approximations and frequently introduce sub-problems. This paper describes a method aimed at meeting the need for an accurate and fast shaped reflector synthesis. The essence of the design approach is to improve the computational efficiency by making use of the known physics of the problem, and wherever possible relying on an analytical treatment in preference to numerical methods. The method is based on an aperture plane formulation; it relies on synthesising a complex aperture field distribution which produces the required contoured beam. The shaped reflector surface is then determined from the aperture field using geometrical optics