Eight-port Octagonal-shaped Metasurface-based MIMO Antenna with Radar Cross Section Reduction

This paper explains the design of a wideband and circularly polarized (CP) eight-element octagonal-shaped Multiple-Input Multiple-Output (MIMO) antenna for C-band applications. The antenna provides higher gain due to stacking of multiple antenna layers. The CP radiation and in-band radar cross section (RCS) reduction is obtained due to the loading of perfect electric conductor (PEC) reflector and metasurface (MS) based polarization converter. The intended eight-port MIMO antenna consists of five layers; the layer-1 is the polarization converter MS, the layer-2 consists of Teflon substrate, layer-3 consists of an eightelement co-planar waveguide feeding structure, layer-4 is an air dielectric layer and layer-5 consists a PEC metal reflector. The antenna provides a wider impedance bandwidth of (3.86-7.72) 66.6% and axial ratio bandwidth of(4.31–4.63 GHz) 7.15%, isolation better than $15\mathrm{~dB}$, maximum gain of 9.18 dBi at 5.2 GHz, efficiency better than 78%, in-band minimum RCS of $37.5\mathrm{~dB}$, and ECC less than 0.07. Hence the proposed eight-port MIMO antenna is useful for C-band applications.