[Show abstract][Hide abstract] ABSTRACT: 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.
[Show abstract][Hide abstract] ABSTRACT: A novel approach is proposed for reflectarray antenna design which makes use of planar near field measurements to characterize the scatterers and the incident field on the structure. This method is based on an equivalent transmission line model of a unit cell in an infinite periodic array. A monopole probe is used to sense a scattered signal in the near field of a reflectarray illuminated by a primary source. These measurements are introduced in the model and provide all the necessary data to accomplish the design. The method has been validated experimentally with four prototypes based on different levels of approximation, at a central frequency of 15 GHz. The results indicate that the proposed near-field based technique allows the design of reflectarrays having similar or better performance than those obtained when numerical modeling is used to obtain the phase response of the unit cells.
Preview · Article · Jul 2006 · IEEE Transactions on Antennas and Propagation