A circularly polarised phased array for land-mobile satcoms

A number of techniques have been investigated, aimed at producing a low cost steerable phased array for use with land-mobile satcoms. A sub-array geometry has been developed which allows convenient and accurate path length matching from each element to the centre of the array. Symmetrical phasing has been used in conjunction with 2-bit phase shifters to enable the array to be controlled by just 18 bits, thus reducing control system complexity and improving array agility. An entirely adaptive control system has been proposed to achieve beamforming and tracking without the aid of any costly open-loop technique. Predicted and experimental results have confirmed the feasibility of these techniques and have shown that there is little sacrifice in array performance. A prototype planar array has demonstrated the beamforming capability of the system and has shown that good performance is achievable over a ±45° range of beam deflections from zenith