A Low-Profile and Low-Cost Dual Circularly Polarized Patch Antenna

This paper presents a low profile and low-cost patch antenna with dual circularly polarized (CP) capability in X-band at a canter frequency of 8.3 GHz. The dual-CP antenna is divided into three layers, composed of a parasitic square patch, a radiation square patch with four equal arms, and a 90 degrees patch coupler. Two arms of the radiation patch are connected to the 90 degrees hybrid coupler using two metalized vias. Right-handed circular polarization (RHCP) and left-handed circular polarization (LHCP) are achieved by exciting two different ports. To validate the proposed design, the prototype of the dual-CP antenna is fabricated and measured. Based on the measurement, the structure of the proposed antenna has an excellent circular-polarization purity of less than 3 dB over the whole operational frequency bandwidth of the antenna (8 GHz-8.47 GHz) with a wide 3-dB axial ratio (AR) beamwidth of 133 degrees across the angular range from -55 degrees to +78 degrees at 8.3 GHz.