Design of Dual-Circularly Polarized Antenna with Cross Slot Coupling

A dual-circularly polarized microstrip antenna was designed by using cross slot coupling structure. The orthogonal slot coupled feeding structure not only broadens the bandwidth, but also avoids the problem of complex feed network in the design of antenna. The circularly polarized axial ratio can be improved effectively by a similar slot coinciding with the cross slots on the circular radiation patch. Two feeding ports were introduced to broaden the AR bandwidth, and respectively achieve left-hand circular polarization and right-hand circular polarization. Reflecting plate layer in the antenna structure improves the gain of antenna significantly. With the help of CST microwave simulation software, the result shows that: the gain of the antenna reaches 7.3 dB and the circularly polarized antenna has a 3-dB axial ratio (AR) bandwidth of 11.3% and a -10-dB impedance bandwidth of 18.1 %. The antenna was constructed and measured with its measured results compared to its simulated ones. Reasonable good agreements are observed between the measurement and simulation. As a result of the feeding structure symmetry, the antenna can be used in conformal array antenna, achieving the purpose of reducing cross polarization by different feeding weight.