Ultra-wideband Compact Circularly Polarized Antenna Using Coupled Dipoles

Abstract

Novel ultra-wideband compact circularly polarized (CP)antenna with 5:1 CP < 1 dB bandwidth and 3:1 VSWR < 3:1 bandwidth is designed by coupling four standard half-wave dipoles capacitively in a square loop fashion. The performance of the antenna is demonstrated in free space, with metallic and electromagnetic band gap (EBG)metamaterial ground planes. In the case of metallic ground plane the total height of the antenna is 3 cm, which is 0.15 of the wavelength at the lowest frequency of operation of 1.5 GHz. Significant reduction in the height, 0.015 of wavelength, is achieved with EBG ground plane which is almost 10 times less as compared to metallic case. The CP antenna with a feed structure including a balun and 100 Ω to 160 Ω impedance transformer has been simulated and is being fabricated currently. The measured results of the coupled dipole antenna will be presented in the IEEE- APS meeting.