Cobham Technical Services has undertaken a number of feasibility studies of compact VSAT terminals based around the use of novel flat-plate array antenna concepts. These include the design, development and test of a complete two-way man-portable terminal operating at Ku-band.
The terminal was similar in size to a laptop computer and incorporated a 30cm x 30cm high-efficiency 11/14 GHz array antenna based on a patented stripline array technology. A spread spectrum modulation scheme was employed to reduce adjacent satellite interference effects associated with the relatively broad antenna beam. The system was trialled using an existing satellite transponder and provided exceptional performance in terms of downlink and uplink data rates.
The same stripline array technology was also used in a larger 60cm x 60cm antenna terminal design. In this case, conventional modulation standards were adopted and the suppression of interference to adjacent satellites was achieved as a result of the reduced antenna beamwidth. Novel beam alignment techniques were devised which ensure that the antenna always remains pointed at its target satellite.