Multifunctional near field focusing transmission metasurface based on polarization sensitivity

In this paper, a near field focusing transmission metasurface (MS) based on polarization sensitivity is developed at microwave frequency. The MS unit cell has only three metal layers, which is less than the published dual-polarized transmission structure. And the phase shifting range can cover 320 degrees for x- and y-polarized waves. The biggest bright spot of the focusing MS made of the proposed units is its changeable focus point by rotating the horn 0 degrees-90 degrees round its central axis: focusing switching between one and two focusing points. In addition, the developed MS has the following advantages: multifunctional, low sidelobe, high focusing efficiency, small size, wideband, and less layer number. The focusing relative bandwidth is 9.7%, and the maximum focusing efficiency is 30% at center frequency 15.5 GHz. The efficiency is higher than that of published results in transmission orthogonal polarization mode. The proposed MS has potential applications in medical treatment, noncontact sensing system.