Circularly Polarized Rectangular Slot Antenna with Trapezoidal Tuning Stub for UWB Application

A new wideband circularly polarized rectangular slot antenna is proposed which employs a symmetrical trapezoidal tuning stub located at the centre of the slot fed by a coplanar waveguide. The rectangular slot is slightly perturbed by metallic arcs each placed along the diagonal end position with varying radii. These perturbation along with the geometry of the feed line and widened tuning stub with appropriate arrangements of gap spacing between the centre feed line, surrounding ground plane and tuning stub, the orthogonal surface currents which are generated in the slot and centre feed line have equal magnitudes but opposite phases to obtain circular polarization (CP). The broad band CP radiation is obtained mainly due to the widened trapezoidal tuning stub which is protruded in to the rectangular slot from the transmission feed line until the centre of slot. All the optimization on the prototype proposed antenna are performed to achieve an axial ratio band less than 3dB of 1.12GHz (29.01%) with respect to the centre frequency of 3.86GHz lying within 10dB impedance bandwidth of 1.797GHz (41%) with respect to centre frequency of 4.41GHz providing a good impedance matching in the whole 3dB Axial Ratio band.