Low-RCS Low-Profile Four-Element MIMO Antenna using Polarization Conversion Metasurface

This letter presents a novel polarization conversion metasurface (PCM) which is used for the design of a low-profile low-radar cross section (RCS) multiple-input–multiple-output (MIMO)-slot antenna operating at 7.72 GHz. The PCM and its orthogonal units are arranged in checkerboard pattern to cancel out the scattered fields in far-field and applied directly atop a four-element MIMO slot antenna for RCS reduction. The reference slot antenna has the peak realized gain of 5.11 dBi. The proposed MIMO slot antenna, which is operating in 7.56–7.93 GHz frequency band has low-profile, i.e., 0.12 λ0 at the frequency 7.56 GHz, and the peak realized gain of 5.34 dBi. The RCS reduction at the broadside for normal incidence is more than 4 dB in 5–10 GHz frequency band, whereas the in-band RCS reduction of the antenna is greater than 11 dB, and the isolation of the proposed MIMO antenna is maintained to greater than 20 dB. These results are verified with the fabrication of a prototype antenna and measurements.