Planar arrays for MSAT and INMARSAT land mobile satellite communications

Conformal phase scanned microstrip patch arrays have been in use for several years on aircraft for satellite communications over INMARSAT satellites. These arrays achieve very low drag but unfortunately suffer from high noise temperature due primarily to losses in the phase shifters. Phase scanned arrays are also very expensive due to the large number of PIN diodes or other control elements used and the use of multiple layers of microwave substrate material. The need for reliable communications on large aircraft may justify the expense of phase scanned arrays whereas the land mobile market demands much less expensive antenna configurations. This paper describes a planar array which has the low profile of a phase scanned array while achieving the low noise temperature and low manufacturing cost of a mechanically steered antenna. The array has been developed for use with INMARSAT-M transceivers. Derivatives of this design for use with MSAT and Mini-M transceivers are currently under development.