Dual-Beam LHCP/RHCP Beamforming Using a Holographic Metasurface Antenna

A dual-beam dual circularly polarized (CP) holographic metasurface antenna (HMSA) with an isotropic unit cell topology is proposed in this work. The unit cells in the MS are periodically arranged with a progressive phase modulation, excited by a near-edge quarter-wave monopole antenna placed at its center. The HMSA has dimensions of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{3 7 5} \mathbf{m m} \times \mathbf{3 7 5 ~ m m}$</tex>, and the unit cells are nonlinearly distributed in <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{5 0} \boldsymbol{\times} \mathbf{5 0}$</tex> matrix. The overall impedance profile of the MS is designed to generate two simultaneous CP beams: one with left-hand circular polarization (LHCP) and the other with right-hand circular polarization (RHCP), radiated at two directions <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(\theta, \phi)=\left\{\left(30^{\circ}, 0^{\circ}\right),\left(-30^{\circ}, 0^{\circ}\right)\right\}$</tex>, respectively. Further, the LHCP and RHCP beams achieve peak gains of 18.69 dB and 18.75 dB, respectively, with corresponding axial ratios of 1.88 dB and 1.72 dB. The proposed dual-beam dual-CP HMSA can provide independent links for multiple users, making the design highly suitable for next-generation wireless communication systems.