Reflector antennas for high power, near field elliptical spot beams with circular polarisation

A set of three reflectors using elliptical surfaces to provide near field focusing, each having a cluster of circularly polarised feeds providing multi-band performance has been developed. Frequency bandwidth at any one band is typically 10%. The antenna configuration was dictated heavily by system needs for bandwidth, spot size and overall efficiency. Spot size and shape were set after a trade- off including achievable power density, spot vertical and horizontal dimensions, spot alignment under worst case environmental conditions, etc. In order to minimise cost, the design was taken directly from computer model to hardware. Reflectors were analysed using physical optics and GTD, feeds were designed using mode matching techniques with finite element analysis used for certain feed components