Single-layer series-fed planar array with controlled aperture distribution for circularly polarized radiation

We propose a compact circularly polarized series-fed patch array with enhanced radiation performance at S -band. To our best knowledge, no similar single-layer structure has been designed, measured, and reported in the literature with equivalent radiation performances in terms of reduced sidelobe level (SLL) and aperture efficiency as well as compactness and simplicity. The planar array consists of a 50- Omega microstrip single feed point, offering uniform and efficient excitation of all its elements that enable a broadside beam with high-gain and low sidelobes. A feeding network for such aperture control is designed and optimized to provide good impedance matching with a two-point excitation per radiating element, which is based on 0° and 90° meander lines to enable circularly polarized radiation. A structure made by a 4!! imes !!1 arrangement of square patches is simulated, optimized, and manufactured, providing a realized gain of about 10 dBic and an SLL below -15 dB. Very good axial ratios and high efficiencies are obtained. The proposed antenna may be of interest for next-generation far-field wireless power transmission systems and other applications including target tracking, radar, and internet of things technologies requiring efficient circularly polarized radiation.