Tri-band shared aperture MIMO metantenna with broadband low scattering characteristics.

In this paper, a triple band shared aperture multiple input multiple output (MIMO) antenna is proposed, with each antenna capable of reducing radar cross section (RCS). The RCS reduction (RCSR) of 4-14 GHz is accomplished through a chessboard-distributed dual-layer polarization conversion metasurface (PCM). The PCM is fed directly by an L-shaped branch, forming a metantenna covering 5.3-6.9 GHz and is assembled into a 4×2 ±45° dual-polarized MIMO antenna, with isolation exceeding 20 dB without extra decoupling technology. A low-frequency and four mid-frequency antennas are loaded in the vacant area of the metantenna, forming a shared aperture MIMO antenna covering 2-3.36 GHz and 3.37-5.11 GHz, respectively. Frequency selective surfaces (FSSs) with band-pass characteristics are loaded on the arms of dipole to enable electromagnetic wave transmission of 5.3-6.9 GHz, minimizing its impact on the high-frequency antenna's radiation characteristics. The scattering characteristics of dipoles also allow for RCS reduction within 2-4 GHz. Besides, additional layers controlling RCS (ALCR) are loaded on the edges of the MIMO metantenna to further reduce RCS within 2-4 GHz. Ultimately, a radiation bandwidth of 110.1% covering 2-6.9 GHz is achieved, covering almost S and C bands, with a low-scattering bandwidth of 2-12.2 GHz covering S, C and X bands, achieving an RCSR of 9 dB within the frequency band.