Low-Profile Multibeam Antenna Based on Modulated Metasurface

Linearly polarized (LP) multiport multibeam antennas (MBAs) based on modulated metasurface (MTS) are presented in this article. A key challenge for MTS to generate multiple independent beams is the mutual interference of different impedance modulations. This interference can lead to reduced directivities of main beams and high sidelobe levels (SLLs). A full-wave-based optimization for a large number of beams is significantly time-consuming and practically ineffective. The source locations are optimized here by employing the aperture field calculated from a zeroth-order approximation (ZOA) of the currents on the surface. This provides a good preliminary accuracy without any full-wave analysis. The relevant design method is verified by two examples of three-beam and seven-beam MTS antennas. Furthermore, the seven-beam MTS antenna is fabricated and successfully measured. The measurements show a measured realized gain of 20 dBi at 14.10 GHz with a beam coverage (10-dB overlap) up to ±36°. It is seen that the same performance requires larger areas with conventional summation of apertures.