Dual-Band Dual-Circularly Polarized Holographic Metasurface Antenna With Mode-Selective Electromagnetic Band Gap

Abstract

This article presents a dual-band holographic metasurface antenna (HMsA) capable of generating steered beams with both right-hand (RH) and left-hand (LH) circular polarization (CP). The proposed unit cell consists of three stacked layers above a ground plane. The first layer features a mode-selective electromagnetic bandgap structure that effectively isolates transverse magnetic (TM) and transverse electric (TE) surface-wave modes. Such isolation allows independent operation at distinct frequencies for various beam directions, while maintaining radiation efficiency comparable to single-mode designs. The second layer employs split-ring elements designed for the TE mode, and the third layer utilizes split-patch patterns for the TM mode. The dual-port configuration provides distinct polarization control: the TM mode at 11 GHz, excited by a vertical monopole, achieves RHCP, while the TE mode at 14 GHz, excited by a horizontal dipole, produces LHCP. Each port supports directional beam radiation at 30 degrees and 20 degrees, respectively, with measured gains of 17.47 and 18.01 dBi, and corresponding axial ratios of 0.53 and 0.43 dB.