Circularly polarized high gain antenna using array of parasitic patches on superstrate layer

Abstract

This paper proposes a circular polarized microstrip antenna fed high gain antenna using array of square and circular parasitic patches on a superstrate layer. Here parasitic patches are used to enhance the gain of antenna. The antenna structure consists of a microstrip antenna fabricated on FR4 substrate and placed at 1mm from finite ground plane. This MSA feeds array of square parasitic and circular parasitic patches fabricated on a FR4 superstrate. The patches on superstrate are suspended in air at about λ0/2. Circular polarization is obtained by diagonal feeding of microstrip antenna and using two shorting pins. The array size of parasitic patches is varied from 1×1 to 5×5. The printed MSA is fed by a 50 Ω coaxial probe. The VSWR is < 2 over 5.725 – 5.875 GHz, ISM frequency band. The antenna provides increase in gain from 8 dB to 14 dB gain as we increase the array of parasitic patches from MSA0 to MSA 4×4 over 5.725– 5.875 GHz. But gain decreases as we increase array of parasitic patches to 5×5. So maximum gain can be obtained in circular polarized antenna is by using 4×4 arrays of parasitic patches. The antenna structure also provides more than 70 % efficiency.