Annular slot antenna for high-precision GPS applications

This paper presents the design of a printed antenna with annular slot geometry for GNSS applications. Two prototypes were built in order to meet the requirements of these systems. Different feeding techniques have been proposed in order to obtain the right-hand circular polarization. Electrical walls were added in the prototypes to avoid losses by parallel plate modes, to improve the radiation efficiency, gain and axial ratio. The proposed geometries were designed and built with two different feeding schemes: the first one is based on a series feed, whereas the other is based on the integration of a 90°-hybrid. The results showed that the synthesized antenna has all features required to operate in the Global Navigation Satellite Systems (GNSS).