Dual-Circularly Polarized Patch Antenna Using Field Transformation Medium

In this letter, a dual-circularly polarized antenna based on the field transformation (FT) method is presented. The antenna consists of a dual-linearly polarized feeding patch antenna, and an FT waveplate as a reflector. The FT waveplate enables the realization of a circularly polarized antenna that has a very wideangle band and unidirectional radiation pattern in both polarizations. At 2.4 GHz, the axial ratio of the proposed patch antenna is below 3 dB with the angle band from -44° to +50° in yz plane and from -42° to 41° in xz plane. The gain of the proposed dualcircularly polarized patch antenna is 7.7 dB. The isolation between the two ports is better than 15 dB.