LOW PROFILE, HIGH GAIN AND WIDEBAND CIRCULARLY POLARIZED ANTENNAS USING HEXAGONAL SHAPE PARASITIC PATCHES

This paper proposes low profile, high gain and wideband circularly polarized (CP) microstrip antennas (MSA), using gap coupled parasitic patches (PPs) on superstrate layer. Printed and suspended probe fed, CP MSAs are designed on a 1.59 mm thick FR4 substrate, and an array of closely spaced hexagonal PPs are printed on the bottom side of the 1.59 mm thick FR4 superstrate and placed at a height about λ0/8 above the ground plane, where λ0 is the free space wavelength, corresponding to the central frequency of the operating frequency band. The gap coupled hexagonal PPs are not only used to enhance the axial ratio bandwidth (AR BW) and gain of the antenna, but also used to reduce impedance and gain variation of the antenna over the operating frequency band. ‘Ant9’ is a suspended MSA with 7 hexagonal PPs. A prototype ‘Ant9’ is fabricated and tested, which provides a peak gain of 9 dBi, S11 < −10 dB, gain variation < 1 dB, and AR < 3 dB over 4.9 to 6.45 GHz frequency band. ARBW of 27.3% is achieved. The proposed ‘Ant9’ covers three frequency bands viz., 5.15 to 5.35 GHz, WLAN band, 5.725 to 5.875 GHz, ISM band, and 5.9 to 6.4 GHz, Satellite C band. The space fed antenna configuration reduces the cross polar radiation level (CPL) and increases the efficiency of the antenna. The measured results agree with the simulation ones. The overall size of ‘Ant9’ is 0.96λ0 × 0.96λ0 × 0.136λ0.