Planar superstrate made with meta-material particles for dual-polarized dual-frequency antennas and circularly polarized antennas

In recent years, two-dimensional arrangements of metamaterial particles have been used as superstrates to overcome the main disadvantages of planar antennas (mainly patch antennas or printed dipoles) such as, low directivities and bandwidths. These structures can be used either as metasurfaces or partially reflecting surfaces (PRS) of Fabry-Perot cavities, In this way,the radiation performance of planar antennas, [1], [2] such as directivity, mutual coupling on array configuration and bandwidth, can be improved. Most these superstrates usually work in a single frequency band and a single linear polarization. The increasing number of applications require dual-frequency, dual-polarization or circularly polarization operation. For these reasons, in this paper, we propose two superstrates to improve the directivity of patch antennas. The first one works with dual-polarized and dual-frequency patch antennas (rectangular patch excited orthogonally for instance) while the second one works with circularly polarized patch antennas.
As shown in the figure below, a Fabry-Perot cavity is mainly formed by a radiating element between a complete reflecting screen (PEC), and a partially reflecting surface (PRS). In this paper a patch antenna covered with a PRS is used.