Compact Circularly Polarized Slot Antenna with a Wide Impedance Bandwidth for VSWR≤ 1.5

Abstract

A new design of circularly polarized (CP) slot antenna is presented in this paper that operates across 3.09–11.31 GHz with an impedance
bandwidth (IBW) of 114.1% for VSWR≤2. Moreover with applying a tuning stub to the feed line the impedance matching of the antenna is
enhanced that leads to a bandwidth of 107.5% (3.32-11.04 GHz) for VSWR≤1.5. The CP antenna consists of a rectangular radiation patch
which is fed through a coplanar waveguide (CPW), three asymmetric rectangular slots on the ground plane and a tuning stub added to the
feed-line. Furthermore two slots at center of the patch have been used to excite two orthogonal resonant modes for circular-polarization
radiation, also to widen the CP bandwidth a rectangular branch strip is attached to top end of the radiation patch. The proposed antenna
exhibits CP bandwidth of 41.93% across 4.88–7.52 GHz, which incorporates the WLAN band. In addition, the antenna has a significantly
compact volume of 25×25×0.8 mm3. The measured and simulated results confirm the usefulness of the antenna for practical applications.