Simple design of efficient broadband multifunctional polarization converter for X-band applications

Design, optimization, and comparative analysis of wide-band polarization conversion along with dual coding sequences for RCS reduction

In this paper, a wideband polarization conversion metasurface is designed. Additionally, coding and chessboard metasurfaces are specifically tailored for radar cross-section reduction (RCS). Initially, a compact unit cell demonstrating exceptional polarization conversion performance is introduced, achieving a polarization conversion ratio (PCR) exceeding 90 % across frequencies ranging from 7.9 to 22.7 GHz. The PCR remains effective even when oblique incidence angles of up to 30∘ are utilized across this frequency band. Roger RT5880, with a thickness of 0.254 mm, serves as the substrate. An airgap is introduced between the substrate and the ground plane to enhance the polarization conversion bandwidth. This unit cell serves as the fundamental building block for subsequent metasurface configurations. To assess the scalability and effectiveness, a 36 × 36 unit array is assembled, confirming efficient polarization conversion capabilities extending to larger structures. Moreover, a 1-bit coding unit "0" and "1" are formed by the Pancharatnam-Berry phase based on the same-sized meta-atom with 90∘ orientations. The robustness and practicality of the design are demonstrated by creating 12 × 12 lattices and evaluating their RCS reduction potential under two distinct scenarios: a chessboard pattern and a coding-based scheme. Notably, its results indicate substantial RCS reduction across a broad frequency spectrum (7.9 to 22.7 GHz) for both configurations. This study demonstrates the wide-ranging applicability of metasurface design, making it a valuable contribution to the fields of microwave engineering, polarization control, and radar stealth technology. Owing to its simplicity, bandwidth, and versatility, this approach offers innovative solutions for diverse real-world applications.

Cheaper, Wide-Band, Ultra-Thin, and Multi-Purpose Single-Layer Metasurface Polarization Converter Design for C-, X-, and Ku-Band Applications

This article presents the design of wide-band, ultra-thin, and multi-purpose polarization converter utilizing metasurface for C-, X-, and Ku-band applications. Having a topology on a FR-4 substrate with metasurface metallic patterns on the front and an all-metallic surface finish on the back, the unit cell of converter design has symmetry in the x−y plane with unique features of having both linear polarization (LP) and circular polarization (CP) property. While the polarization conversion ratio (PCR) of converter in normal incidence case is more than 90% in three different frequency bands of 6.46–6.78 GHz, 10.52–11.85 GHz, and 16.49–17.37 GHz, it shows linear-to-linear polarization feature and a linear-to-circular polarization feature with left-handed circular polarization (LHCP) for the frequency range between 7.28 and 9.40 GHz and right-handed circular polarization (RHCP) for the frequency range between 13.38 and 15.19 GHz. It is also seen that the converter has a PCR value of around 90% for oblique incidence case with incidence angles up to 45°. Extensive simulations have been conducted to prove the performance of suggested converter with the aid of a commercially-available simulation platform, called CST Microwave Studio. The advantages of suggested polarization converter are low-cost, wide-band, ultra-thin, and having both LP and CP conversion in C-, X-, and Ku-bands.

Dual-Band Wide-Angle Reflective Circular Polarization Converter with Orthogonal Polarization Modes

Herein a dual-band wide-angle reflective circular polarization converter, based on a metasurface was developed. The unit cell is composed of a split square ring and a nested square patch. The split square ring plays the role of creating polarization conversion. The square patch is useful for improving the quality of axial ratio. It was verified that the structure could transform the x-polarized incident wave into left-hand circular polarization in the lower frequency band, and to right-hand circular polarization in the higher frequency band. For y-polarized incidence, the transformation has orthogonal modes to that for x-polarized incidence. Moreover, the 3 dB axial ratio takes place in the ranges of 8.42-12.32 GHz and 18.74-29.73 GHz, corresponding to a relative bandwidth of 37.61%, and 45.35%, respectively. In addition, the polarization conversion efficiency is greater than 99% in the ranges of 8.65-11.83 GHz and 19.55-29.36 GHz. Furthermore, for oblique incidence, the axial ratio remains stable, even at 50° incidence, for the lower frequency band. Lastly, a prototype is fabricated and measured for experimental verification. The measured and simulated results were in good agreement. Compared with other designs in the literature, the proposed converter operates with good performance in dual-band, with high-efficiency, and with angular stability.

Reconfigurable broadband metasurfaces with nearly perfect absorption and high efficiency polarization conversion in THz range

Reconfigurable metasurfaces (RMSs) that enable the switching function of absorption and polarization conversion have attracted increasing attention. However, the design of RMSs to achieve wideband and high efficiency for both absorption and polarization conversion functions simultaneously remains a great challenge. Here, we propose the design of a RMS structure with a high-efficiency cross-polarization conversion and nearly perfect absorption. The reconfiguration between different functions of polarization conversion and absorption is obtained based on the reversible insulator-to-metal phase transition of Vanadium dioxide (VO[Formula: see text]). When the VO[Formula: see text] is in insulator state, the RMS realizes the cross-polarization conversion function in the wideband of 1.04-3.75 THz with a relative bandwidth up to 113 [Formula: see text] due to the multi-resonant modes of electric and magnetic resonances. Meanwhile, the nearly-perfect absorption is achieved in the range of 1.36-3.38 THz with the corresponding relative bandwidth up to 85 [Formula: see text] for the VO[Formula: see text] in metallic state. Specially, the wideband and high-efficiency performance of these functionalities is maintained for a wide angle incidence. The capability of bi-functional switch and integration with polarization conversion and absorption in a single metasurface structure endowed with both wideband and high-efficiency characteristics for a wide incident angle is very promising for emerging RMS devices in the terahertz region.

Ultra-broadband Pancharatnam-Berry phase metasurface for arbitrary rotation of linear polarization and beam splitter

A systematic study of a robust angular tolerance ultra-broadband metasurface for arbitrary rotation of linear polarization is demonstrated. The proposed method combines the spin-dependent Pancharatnam-Berry phase and the generalized Snell's law to achieve an arbitrary angle linear polarization rotator and beam splitter. Numerical results of one terahertz example show that a 90° polarization rotator has a polarization conversion ratio of more than 90% from 1.3 to 2.3 THz in the ultra-broadband range. This method represents a significant advance in versatile, flexible design and performance compared to previously reported birefringent material wave plates, grating structures, and multi-resonance-based polarization rotators.