Directional Metasurface with Selective Polarization Using Antenna Elements

A new concept of a directional, non-reciprocal metasurface (MSF) where the polarization of the transmitted wave can be selected at will is presented. Each cell of the proposed MSF has a circularly polarized (CP) elliptical patch on side 1 and a reconfigurable orthogonal (either x- or y-) linear polarization (LP) square patch on side 2. Any random polarization incident wave on side 1 is collected by the array of CP antennas. The signal is transmitted to the reconfigurable LP antennas on side 2 through vias. The reconfigurable LP patches have orthogonal feed from two segments which are connected with the common microstrip line through single pole double through (SPDT) switches. The appropriate switch position results in the preferred polarization of the transmitted wave. Two transistors along the transmission lines of the two antennas ensure the non-reciprocity of the directional metasurface. The proposed design operates effectively in the frequency range 3.4-3.6 GHz and it presents nearly 20 dB enhancement of the transmitted wave with the selected linear polarization in the forward direction and 50 dB isolation as compared to the propagation in the opposite direction.