CPW-Fed Stair-Shaped Slot Antennas With Circular Polarization

The design is described of a coplanar-waveguide (CPW)-fed circularly polarized slot antenna. The slot antenna and the feeding structure are fabricated on the same plane of the substrate so that circuit process and position alignment could be simplified. By etching a longitudinal slot at a middle point of a stair-shaped slot and tuning geometrical parameters, two orthogonal electric fields with quadrature phase difference excite a circularly-polarized wave. A bandwidth of 31.2% (2.30-3.15 GHz) is achieved with an axial ratio < 3 dB and reflection coefficient < -10 dB. Details of the design procedure for the proposed antenna are described, and the results of the antenna performance are presented and discussed.