An Artificially Anisotropic Antenna Substrate for the Generation of Circular Polarization.

The purpose of this communication is to present the design of an artificially anisotropic antenna substrate (AAAS) for the generation of circular polarization (CP) for a linearly polarized antenna. The AAAS can be manufactured by assembling thin sheets with certain relative permittivities for the host or environment \varepsilon e and inclusion \varepsilon i materials as a stack. Using two different stacking materials enables the generation of different effective permittivities $\varepsilon _{{{x{'}}}}$ and $\varepsilon _{{{y{'}}}}$ for the wave components propagating in-between an antenna and a ground. The idea is to modify the antenna polarization by exploiting reflections from a ground in a way that CP operation is obtained. By properly designing the AAAS, the radiator shape can be maintained simple. The operation of AAAS is demonstrated for substrates made of homogeneous anisotropic and thin sheets. It is shown that by using sufficient high inclusion permittivity (e.g., \varepsilon _{i} = 15 ), the AAAS is observed to even show axial ratio <2 dB with over 25 dBi higher right-hand CP gain than left-hand CP in the main beam of the antenna. A prototype with available low-lossy materials is manufactured and successful correlation with theory and simulation results is observed. [ABSTRACT FROM PUBLISHER]