Ultrawideband High-Efficiency 2.5-Dimensional Polarization Conversion Metasurface and Its Application in RCS Reduction of Antenna

A linear-to-linear 2.5-dimensional polarization conversion metasurface (2.5-D PCM) with a high polarization conversion ratio (PCR) in ultrawideband is proposed. The unit cell of the 2.5-D PCM is composed of a superstrate etched with metal strips and a substrate attached with a metal ground. The 2.5-D PCM can efficiently convert the polarization of x-polarized or y-polarized wave to its cross direction after reflection. The PCRs are higher than 96% within a relative bandwidth of 99.5% for the x- and y-polarized vertically incident waves. In addition, the 2.5-D PCM can be applied to reduce the in-band and out-band radar cross section (RCS) of different antennas. A circularly polarized antenna is chosen as an example. Compared to the reference antenna, the monostatic and bistatic RCSs of the proposed antenna are decreased in an ultrawideband without the performance degradation of the antenna. The prototypes of the 2.5-D PCM and the antennas are fabricated, and the measurements are in reasonable accordance with the simulations.