A Novel Bi-Directional Absorber Design with Polarization Selective Capability

Perfect metamaterial absorber (PMA) is crucial for many applications, such as stealth technology, solar energy capture, and spatial filters in wireless communication.Conventional PMA adopts the metal-insulator-metal (MIM) configuration.It can only absorb waves propagating in one specific direction, which puts constraints on some potential usage.We proposed here a novel PMA structure that can absorb y-polarized waves bidirectionally.On the other hand, the x-polarized waves are reflected regardless of their propagation direction.We chose an FR4 printed circuit board (r = 4.4; loss tangent = 0.02) as the dielectric substrate because it is cheap and easy to obtain.We cascaded two FR4 circuit boards and the structure presented here has three conductor layers.The different loop patterns are located at each layer.The thickness of our PMA design is only 3.2mm (0.046 free space wavelength at the absorption frequency), which is far less than the operation wavelength.In addition, the absorption rate is near unity (99.1 %) at the assigned frequency of 4.28GHz, so the unwanted scattering waves are suppressed completely.Our proposed PMA design is compact, low cost, easy to fabricate and can operate with a unique polarization selection.Moreover, our design can absorb and reflect waves with specific polarization bidirectionally.Such a PMA design can work as an intelligent reflective surface.It can be used as the polarization filter and route the path of propagating waves.It can also be used to enhance the performance of Fabry-Perot cavity antennas because of its capability to reflect co-polarized waves and absorb cross-polarized waves.