Dual-band multiple beam reflector antenna for broadband satellites

Description

A broadband communication satellite antenna is offered that is able to generate full dual-band multiple beam coverage using only a single main reflector whose size is small enough to fit into the fairing of current launch vehicles. The design also maintains a high RF performance, namely an efficiency higher than 50% and a C/I better than 15 dB over the full transmit coverage and the full receive coverage. The antenna is based on an offset dual-optics configuration and the two frequency bands, one for transmitting (BTX) and one for receiving (BRX) do not overlap.

Innovations and advantages

• The compact dual-optics geometry allows a reduction in focal length of about 30% in comparison to a conventional offset configuration using a flat FSS sub-reflector in which the focal length of the main reflector would be set by the lower frequency band.
• Another attractive feature of, and improvement due to, the antenna geometry is the design of the MFB feed systems. It is well known that feeds in the lower diameter range tend to have poor efficiency while feeds in the higher diameter range tend to produce degraded main reflector illumination. With the new antenna configuration, it is possible to implement the optimum feed diameter in the two bands and still maintain congruent coverage.
• As an additional advantage of the antenna configuration, the numerous degrees of freedom left in the design may be used to further optimise several performance features, namely the amplitude and phase distributions in the MFB feed systems  as well as the design of the selective frequency elements of the FSS which may be tuned to cope with the variation of the incidence angle.

Domain of application

• Telecommunications satellites systems
• Earth observation Instrument
• Payloads, space-borne and ground antennas