Design of High-Gain Lens Antenna Using Pixelated Phase Gradient Metasurface

In this paper a novel systematic design method based on Genetic Algorithm (GA) for transmitting lens antenna design is introduced. The antenna consists of a dual-layer phase-gradient metasurface (PGMS). GA has been used to design the unit cells configurations incorporating in the cost function the performances of the main parameters of an antenna such as gain, bandwidth and side lobe level. To design a set of pixilation-based unit cells, a single bit with a binary value of 0 or 1 that indicates the presence or absence of copper at the pixel level, respectively, has been considered for each pixel. By setting the dimensions of each unit cell with a value of 0.4$\lambda\times 0.4\lambda$ ($\lambda$ being the wavelength at 12 GHz) and with binary optimization based on GA, appropriate transmission coefficient with suitable transmission phase in the range of [0,2$\pi$] has been achieved. The proposed PGMS antenna uses a 1.58 mm thick, RO4003C (lossy) transmission lens with a dimension of $110\times 110\times 35mm^{3}$ and a microstrip patch antenna acts as a radiation source. The proposed PGMS antenna has a 20.3 dB realized gain which is 13.5 dB greater than the single patch antenna one (6.8dB) and exhibits -15.5dB side lobe level (SLL) at 12 GHz. Simulation results of the proposed PGMS antenna verify the validity of the design method.