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Because Pancharatnam-Berry (PB) geometrical phase can only be generated in the co-polarized reflection coefficient under circular polarized (CP) incidence for a reflective metasurface, the design of a reflective PB coding metasurface must be based on an appropriate polarization conversion metasurface (PCM) which can achieve CP-maintaining reflection. In this work, to design a reflective 2-dit PB coding metasurface for radar cross section (RCS) reduction, an ultra-wideband PCM is proposed at first, numerical simulation shows that the PCM can realize ultra-wideband CP-maintaining reflection from 8.6 to 35.9 GHz; moreover, PB phase will be generated in its co-polarized reflection coefficient under CP incidence by rotating its unit structure. Thus, an ultra-wideband reflective 2-dit PB coding metasurface is constructed successfully based on the PCM. The simulation and experiment results show that the coding metasurface has excellent performance in RCS reduction under arbitrary polarized incidences, compared with a pure metallic plate with the same size, its RCS can be reduced more than 10 dB in the frequency band 8.2–35.2 GHz with a relative bandwidth of 124.4%, in addition, the RCS reduction performance is kept well when the incident angle is increased to 45°. [ABSTRACT FROM AUTHOR]

In this work, one 8-shaped metasurface (MS) is proposed, which consists of a square array of 8-shaped conducting patches printed on a grounded dielectric substrate and covered by a top dielectric layer. Because the MS is symmetric with respect to both the x- and y-axes, and the phase difference between the reflection coefficients rxx and ryy is close to + 90° in an ultra-wide frequency band, it can be used as an ultra-wideband linear-to-circular polarization converter. Simulation results show that the MS can realize high-efficiency and ultra-wideband linear-to-circular polarization conversion under both u- and v-polarized incidences; the axial ratio (AR) of the reflected wave is below 3 dB in the ultra-wide frequency band of 6.45–24.20 GHz, which is corresponding to a relative bandwidth of 116%; in addition, the polarization conversion rate (PCR) can be maintained larger than 99.5% in the frequency range of 6.78–23.70 GHz, which occupies 95.3% of the 3 dB-axial-ratio-band. Finally, an experimental verification is carried out, a good agreement between the experimental and simulation results is observed. [ABSTRACT FROM AUTHOR]