Wideband beam-forming metasurface with simultaneous phase and amplitude modulation

Achieving simultaneous controls of the amplitude and phase for electromagnetic waves is essential when shaping a complete wave-front aimed at forming an arbitrary beam. Here a strategy of manipulating the reflected amplitude and phase is proposed using a bi-layered metasurface element. The metasurface unit cell, consisting of a modified I-shape particle and one all-metal ground, achieves broadband phase- and amplitude control by tuning the gap size and rotating the modified I-shape particle, respectively. As a proof of concept, we design a fan-shaped beam metasurface antenna using the genetic algorithm to obtain the optimal phase and amplitude distributions. A Vivaldi antenna with less blockage effect is chosen to illuminate the metasurface, and then the amplitude and phase are compensated by the elements to achieve the optimized distributions. Finally, the beam-forming metasurface antenna is simulated, fabricated, and measured. The results show that the metasurface can generate a flat top beam under rectangular coordinate within the frequency range of 9-12 GHz. Our findings not only provide a universal way for generating beams with arbitrary shapes using metasurfaces but also offer an economical and simple alternative for a beam-forming array antenna.