A Partially Reflective FSS-Based Superstrate as a Decoupling Structure for Reducing the Mutual Coupling of Circularly Polarized Antennas

A frequency-selective surface (FSS)-based superstrate is proposed in this article, which helps to reduce the mutual coupling between closely spaced circularly polarized (CP) antennas. The decoupling structure is capable of reducing the mutual coupling from −8.7 to −26 dB while maintaining a good impedance match and having an axial ratio (AR) bandwidth of 2.5% (5.13–5.26 GHz). A direct design approach for the design of an FSS-based superstrate is also presented in this article to realize the best possible decoupling. The introduction of the decoupling structure reduces the envelope correlation coefficient (ECC) while improving the gain.