Design methods of broadband circularly polarized patch antennas using artificial ground structure

This paper deals with broadband circularly polarized patch antennas using an Artificial Ground (AG) structure with rectangular unit cells as a reflector. The AG structure has no band gap unlike the mushroom structures for electromagnetic band gap (EBG) and changes the reflection phase in accordance with the polarization state of the incident wave. By properly combining the transmitted wave from the antenna and the reflected wave from the AG structure, broadband circular polarization can be obtained. On the other, the antennas have a rectangular or circular patch and are tested at around 6 GHz and show some simulated and measured in impedance, axial ratio and radiation patterns. The results show typically an impedance bandwidth of 48.6% and 3-dB axial ratio bandwidth 20.4%, for example, which are significantly wider than these of conventional patch antennas.