Dual-broadband high-isolation circularly polarized Low-RCS shared-aperture antenna array based on mushroom-type metasurface

In this paper, a metasurface (MS)-based dual-broadband high-isolation circularly polarized (CP) shared-aperture antenna array with in-band radar cross section (RCS) reduction is proposed. The higher-band antenna consists of a metasurface composed of four surrounded subarrays and a center driven patch. The lower-band antenna is composed of four patch antennas fed by a sequential-rotated feeding network. The mushroom-type metasurface works as additional radiators for extending the operating band in the higher-band and reducing the mutual coupling in the lower-band simultaneously. The working bands are broadened to 15.4% (5.40–6.30 GHz) and 12.9% (4.13–4.70 GHz) at the higher and the lower bands, respectively. Over 22 dB isolation is obtained by reusing the electromagnetic bandgap property of the mushroom-type metasurface. Moreover, the RCS of the antenna array is reduced due to the diffusion of the metasurface. Over 5 dB in-band RCS reduction is achieved. A sample is fabricated and measured. The experimental and simulated results are in good agreement, indicating that the proposed shared-aperture antenna array can find application in synthetic aperture radar, aircraft, and stealth platforms.