Low-Profile Beam-Steering Metasurface Lens Antenna Utilizing Defocused Array Feed Without Amplitude–Phase Network

The present study introduces a low-profile beam-steering metasurface lens antenna (MLA) that is excited by a defocused array antenna (DAA), eliminating the need for amplitude and phase excitation modulation. First, we modify an ultrathin Huygens' unit cell to provide greater angular stability, which is intended for use in beam-steering lens antennas. Subsequently, we analyze the effect of the focal–diameter ratio (F/D) on the beam-steering performance of the lens. Further, a one-dimensional (1D) MLA equipped with a DAA is modeled. Based on this model, we investigate the influence of DAA distance from the lens, DAA diameter, and F/D on radiation directivity and scanning capability. By adjusting the distance between the DAA and the lens, sub-arrays located in different regions of the DAA can be excited with uniform amplitude and phase, enabling dual-polarized single-beam scanning radiation. This excitation technique eliminates the need for amplitude and phase modulation networks, thereby reducing beam-steering costs and the complexity of the feed network. Finally, a 10${\lambda }_0\times$10${\lambda }_0$ MLA prototype excited by a 52-unit dual-polarized DAA is simulated and fabricated. The simulation and measurement results demonstrate that the proposed MLA achieves a scanning range of ± 15°/± 16° in the E/H-plane at 10.3 GHz, with a gain fluctuation of less than 2.35/2.25 dB.