EBG Navigation Antenna for Geosynchronous Satellite Applications

Conventional Navigation antennas designed for global Earth coverage from a Geosynchronous Satellite are usually using a direct radiating array configuration requiring between 8 to 19 elements. The use of electromagnetic band gap technology can potentially lead to a significant simplification of this type of antenna. Using this technology it may be possible to reduce the number of radiating elements and simplify the beam forming network while providing similar RF performances. A single radiating element located under a superstrate EBG layer is in principle sufficient to obtain the desired directivity, gain and axial ratio performances, but, in that case, the antenna phase center location exhibits wide variations over frequency and field of view. The phase center stability can be largely improved by replacing the single source element by a 2times2 array of radiating elements and by decreasing the EBG layer reflectivity. Two different designs, a single patch and a 2times2 array of patches feeding the EBG superstrate, have been compared in terms of RF performances. Tighter control of the phase centre position over the frequency bandwidth and the antenna field of view has been achieved with the array configuration.