CPW-Fed S-Shaped Slot Antenna for Broadband Circular Polarization

In this letter, a new broadband circularly polarized (CP) printed-slot antenna fed by a coplanar waveguide (CPW) is designed and fabricated. To achieve a broadband CP wave, an S-shaped slot is employed in the ground to produce orthogonal surface currents for right-hand circular polarization (RHCP). Furthermore, an L-shaped radiator is introduced to obtain a broad impedance bandwidth that can cover the whole CP bandwidth completely. Good agreement is achieved between the simulation and measurement, which shows that the presented antenna covers an impedance bandwidth (S₁₁ <; -10 dB) of 104% from 1.78 to 5.64 GHz, and a 3-dB axial-ratio bandwidth (ARBW) of 58.6% from 2.85 to 5.21 GHz. The surface current analysis and a parametric study of the design are also carried out to explain the mechanism of circular polarization.