Gain enhancement of a circularly polarized microstrip patch antenna surrounded by a circular mushroom-like substrate

The performance of a circularly polarized microstrip patch antenna is improved using a circular mushroom-like substrate. The microstrip patch antenna is fed by a coaxial probe and is integrated within a circularly periodic structure to increase the antenna gain. The circular mushroom-like structure is a combination of two periodic structures with different periods. One is made of metallic rings and the other of grounding vias, which are disposed such as to form a radially and circularly periodic structure. With the proposed concept, an antenna prototype operating at 5.8 GHz was fabricated and tested. The axial ratio, radiation patterns and return loss obtained from measurements show a good circular polarization, impedance matching and a gain enhancement of the proposed antenna.