Multifunctional full-space metasurface with asymmetric transmission

In this paper, an asymmetric multifunctional full-space metasurface (FS-MS) is proposed. Utilizing the principle of anisotropy, the designed unit has independent phase modulation in transmission and reflection modes. The metasurface unit is composed of three layers of dielectric substrates and four layers of metal, featuring traditional cross-shaped, slotted cross-shaped, and four longitudinal arm branch structures. Through the action of an isolation layer with a slotted cross-shaped structure in the center, the unit can realize asymmetric transmission. Based on the units, combined with the generation principles of focusing beam, Bessel beam, orbital angular momentum (OAM) beam, as well as the phase superposition principle, an FS-MS was designed. By varying the polarization, frequency, and direction of the incident wave, the metasurface can achieve four functions on the same PCB. Different functions can be realized when electromagnetic (EM) waves are from both sides of the metasurface. The simulation experiments are verified at 15 GHz and 27 GHz. The results show that the metasurface can realize a zero-order double Bessel beam, a bifocal with a focusing efficiency of 36.71% and a l=+1 OAM beam with a mode purity of 74.33%, and a l=+2 OAM beam with a mode purity of 73.44%. The proposed metasurface, characterized by a simple structure and bidirectional radiation capability, is a promising candidate for bidirectional wireless communication applications.