Retroreflector With Polarization Isolation Based on Nonreciprocal Metasurface

This letter proposes a nonreciprocal metasurface retroreflector, which introduces isolation between two orthogonal polarizations. The proposed metasurface is based on the transistor-loaded nonreciprocity mechanism and receiving-reradiating structure. Benefitting from this design, the nonreciprocal polarization response introduced by the backloaded transistor amplifier can provide isolation between the two orthogonal polarizations. Besides, the unit cross-polarized reflection phase can be designed arbitrarily to realize desired phase gradient. As a result, the metasurface converts vertically polarized waves to horizontally polarized waves with amplification and retroreflects at a specific incident angle. Meanwhile, absorption occurs when horizontally polarized waves are incident at the same angle. A prototype is fabricated and measured. The measured results prove that the proposed metasurface can realize retroreflection at a 30° incident angle with cross-polarization isolation of 29.42 dB at 5.44 GHz. The proposed metasurface is expected to expand applications of planar retroreflectors.