An advance design approach for circular polarization of the microstrip antenna with unbalance DGS feedlines

A novel design approach is offered to attain circular polarization of the microstrip antenna fed by unbalanced vertical feedlines. Usually, diagonally balanced-line feeds with hybrid couplers are used to attain circular polarization. Here, defected ground structures (DGSs) have been implemented under the unbalanced feedlines to achieve circular polarization. Adopting DGSs make it easy to tune antennas for circular polarization by varying the impedance of the feedlines.