A Broadband Circularly Polarized Square Slot Antenna

A new broadband circularly polarized slot antenna with a rotated slot for bandwidth enhancement is proposed. The antenna has a simple structure, consisting of a microstrip feed line, a substrate, and a rotated rectangular slot with two opposite slots etched on the plane. By appropriately adding the rotated rectangular slot and two opposite slots on the ground-plane, the impedance bandwidth of the antenna is enlarged, and its wide axial-ratio (AR) bandwidth is achieved. Experimental results show that the proposed antenna has good right-hand circular polarization (RHCP) characteristics. The measured −10-dB return loss impedance bandwidth and 3 dB axial-ratio bandwidth are 38.8% (1.5 GHz∼2.2 GHz) and 25.6% (1.56 GHz∼2.02 GHz) at the center frequency of 1.8 GHz.