A low-cost broadband circularly polarized antenna with integrated feeding network

A broadband directional circularly polarized (CP) antenna is investigated by placing two pairs of parallel dipoles orthogonally in a square plane. The proposed antenna is printed on a planar structure, which integrates a sequential-phase (SP) network on a single substrate. Parasitic stepped-patches are introduced beside the two arms of each dipole to improve the axial ratio (AR) bandwidth. Measurements show that the antenna has a |S₁₁|<;-10-dB bandwidth of 1.76-2.64 GHz (40%), a 3-dB AR bandwidth of 1.83-2.65 GHz (36.6%), and a 1-dB gain bandwidth of 1.77-2.6 GHz (38%). These three bandwidths almost cover the same frequency band. In addition, the antenna exhibits a right-hand circular polarization with a peak gain of 8.7 dBic at 2.43 GHz.