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In this paper, to achieve ultra-wideband radar cross section (RCS) reduction, a coding phase gradient metasurface (CPGM) is proposed by using Pancharatnam-Berry (P-B) phase. The CPGM is composed of eight types of CPGM elements, and a series of phase gradients with different directions or starting-values will be introduced in these types of CPGM elements under the same EM-wave incidence, so it can not only achieve anomalous reflection to reduce its specular RCS but also reduce the maximum bi-static RCS due to phase cancelation. The simulation results demonstrate that the CPGM has an excellent performance in RCS reduction, compared with a pure metallic plate with the same size, its specular RCS under normal incidence with arbitrary polarization can be reduced more than 10 dB in the ultra-wide frequency band of 8.8–34.8 GHz with a relative bandwidth of 119.3%, and its maximum bi-static RCS can also be reduced effectively in the ultra-wide frequency band; moreover, when the incident angle is increased to 45°, the RCS reduction can still be achieved in an ultra-wide frequency band. Finally, an effective experimental verification is carried out. [ABSTRACT FROM AUTHOR]

In this work, an anisotropic metasurface is proposed for linear-to-circular (LTC) and circular-to-linear (CTL) polarization conversions, which is composed of a square array of two-corner-cut square patches printed on a grounded dielectric substrate and covered by a dielectric layer. Numerical simulation results show that the anisotropic metasurface can act as a high-efficiency ultra-wideband reflective polarization converter to achieve both LTC and CTL polarization conversions. Under x- and y-polarized incidences, its reflected wave will be converted to left-handed and right-handed circular-polarized (CP) waves, respectively, in the ultra-wide frequency band between 7.14 and 25.66 GHz with a relative bandwidth of 113%, and the polarization conversion ratio (PCR) can be kept larger than 99.73% in the frequency range of 7.72–25.08 GHz; in addition, the reflected wave under CP incidence will be converted to an x- or y-polarized wave, and the bandwidth and PCR of the CTL polarization conversion are almost the same as those of the LTC polarization conversion. Finally, the working principle of the polarization converter is illustrated, moreover, an effective experimental verification is carried out, and a reasonable agreement is observed between the simulation and experimental results. [ABSTRACT FROM AUTHOR]

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]