Dual-Ring Circularly-Polarized Microstrip Patch Array Using Hybrid Feed

We describe the design of a new form of traveling-wave-fed, circularly polarized microstrip patch array at X -band. The antenna employs a dual-ring array structure in which the radiating elements are fed by non-radiating slots with sequential phase excitations to generate circular polarization. The antenna incorporates two novel features: firstly, two concentric ring sub-arrays of linearly polarized elements are used to improve the axial ratio and, secondly, development of a new model for power distribution to ensure that all the elements radiate the same power, thus ensuring pattern symmetry and high-quality circular polarization. The proposed design was validated through practical measurements, which showed a well-matched antenna with good axial ratio and well-defined radiation patterns.