Broadband circularly polarized antenna array for S-band wireless applications

A design of 2×2 broadband circularly polarized (CP) antenna array is proposed to resonate within S-band at 2.4 GHz for wireless applications. To realize broadband operation, multiple slots of variable length are embedded in antenna array patch geometry. The individual array patch is excited by microstrip feed lines, which are derived from power divider circuits. The whole feeding structure is designed with sequential phase (SP) of 00, 90, 180 and 2700. The proposed multi-slot array structure gives the advantage of being wide impedance and axial ratio bandwidth with high gain. The -10 dB reflection coefficient bandwidth and 3 dB axial ratio (AR) bandwidth are 86% (1.68 GHz-4.22 GHz) and 29% (2.99 GHz-4.02GHz), respectively. Good radiation characteristics with gain more than 10 dBi in the operating region are obtained.