Multiband and multifunctional polarization converter using an asymmetric metasurface

Abstract

A compact and asymmetric multi-band reflective polarization converter metasurface has been offered in this paper. The proposed simple converter can effectively convert an incident linearly polarized EM wave to its orthogonal counterpart and circular polarized waves (RHCP and LHCP) at two frequency bands. The design consists of a square with two curves on the top right and lower left corners and a square Split Ring Resonator (SRR) responsible for linear-to-linear and linear-to-circular polarization conversions, respectively. The simulated results show that the converter successfully transforms a y-polarized incident wave to its orthogonal counterpart in a frequency range of 15.5–16.5 GHz with unity conversion at 16 GHz and circularly-polarized (RHCP) wave at 13 GHz and (LHCP) at 18 GHz, verified through the fabricated and measured sample. Wide angular stability up to 60° oblique incidence along with high efficiency reveals the good applicability of the structure. Moreover, the root cause of the cross-polarization conversion has been analyzed and confirmed through Bi-Mode Foster equivalent circuit and surface current distribution as well. Finally, a fabricated prototype is tested to validate the simulated results through measurement.

Ultrawideband Cross-Polarization Converter Using Anisotropic Reflective Metasurface

“…For EM waves absorption, isotropic reflective metasurfaces are typically used with low co− and cross−polarized reflection components. If we break the symmetry of the isotropic unit cell, its cross−polarized coefficient increases due to the anisotropic effect faced by the geometry [35]. It signifies that EM waves convert from x−polarized to y−polarized or (y−polarized to x−polarized).…”

“…The polarization conversion results are relatively efficient, up to 90%, and the operating bandwidth is also high (Figure 2d). Mathematically, the relation between effective electric and magnetic dipole moments i.e., 𝒑 and 𝒎 respectively, and the incident fields (E and H) can be described through the following equations [35]:…”

“…where 𝑃 𝑒𝑚 represent for electric-magnetic polarizability and 𝑃 𝑒𝑒𝑥𝑥 can be defined as 𝑃 𝑒𝑒𝑥𝑥 = 𝑝 𝑥 𝐸 𝑥  𝐸 𝑦 ,𝐻 𝑥 ,𝐻 𝑦 = 0 . Moreover, the relation between effective surface electric current and magnetic current densities i.e., 𝑱 𝒔 and 𝑴 𝒔 respectively, and the incident fields can also be written as [35]:…”

“…Considering the Ey polarized incidence wave i.e., Mathematically, the relation between effective electric and magnetic dipole moments i.e., p and m respectively, and the incident fields (E and H) can be described through the following equations [35]:…”

“…. Moreover, the relation between effective surface electric current and magnetic current densities i.e., J s and M s respectively, and the incident fields can also be written as [35]:…”