Polarization Conversion Bandwidth Research Articles

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%\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\%$$\\end{document} across frequencies ranging from 7.9 to 22.7 GHz. The PCR remains effective even when oblique incidence angles of up to 30∘\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^\\circ$$\\end{document} 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 ×\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ imes$$\\end{document} 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∘\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^\\circ$$\\end{document} orientations. The robustness and practicality of the design are demonstrated by creating 12 ×\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ imes$$\\end{document} 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.

Genus Plasma-Based Self-Complementary Reconfigurable Intelligent Metasurfaces

AbstractThis paper investigates the radiation properties of plasma-based intelligent reflectarray surface (IRS) that utilizes self-complementary elements. The elements of the surface employ reconfigurable plasma conductivity to manipulate the polarization of electromagnetic waves in various Ka-band applications. The unit-cell of the IRS is composed of 2 × 2 sub-cells of 0.5 λo × 0.5 λo × 0.078 λo mm3. Each sub-cell contains three glass containers arranged in a triangle-rectangular-triangle configuration and filled with ionized plasma gas. When the IRS illuminated by a linearly polarized (LP) plane wave, the surface converts it into circularly polarized (CP) waves based on the plasma ionization state. It achieves dual-band polarization conversion at 7.3 GHz with bandwidth of 200 MHz and at 8.6 GHz with a bandwidth of 1.15 GHz. To enhance the polarization conversion bandwidth, a sequential arrangement of self-complementary unit-cell elements with different sizes is employed. An 8 × 8 genus reconfigurable IRS is utilized to generate both left-hand circularly polarized (LHCP) and right-hand circularly polarized (RHCP) waves from the upper and lower sides of the structure. The axial ratio (AR) bandwidth is maintained at 2.1 Hz for both surfaces. An LP horn antenna is used with the 8 × 8 genus reconfigurable IRS, resulting in a peak gain of 13.2 dBi, a side lobe level (SLL) of 6 dBi, and an AR bandwidth of 500 MHz. To further enhance the radiated gain, the ionized plasma within the self-complementary elements is controlled to focus the radiated power into a directive beam, resulting in an increased gain of 19.4 dBi.

A polarization conversion metasurface for reducing radar cross section and enhancing radiation performance of circularly polarized array antennas

In this paper, we present a metasurface for ultra-wideband polarization conversion. The unit structure of the PCM consists of a metallic pattern layer, an air layer, and a grounded dielectric layer, which can achieve a polarization conversion bandwidth (PCR) from 6.17 GHz to 19.5 GHz (103.9%). According to the phase cancellation principle, the PCM cells and their mirror cells are arranged in a checkerboard fashion to form a metasurface. Applying it to a circularly polarized patch array antenna for RCS reduction. With the addition of PCM, the impedance matching (S11) bandwidth of the antenna is broadened from 7.2 to 8.3 GHz (14.2%) to 6.2–8.4 GHz (30.1%), the axial ratio (AR) bandwidth is broadened from 6.9 to 8.25 GHz (17.8%) to 6.75–8.32 GHz (20.1%), the peak gain to 11.1 dBi and the antenna's monostatic RCS achieves more than 5 dB reduction from 6.4 to 18.6 GHz (97.6%) under x- and y-polarized plane wave irradiation.The current distribution of the antenna is used to explain the gain improvement. Finally, we fabricated and tested a prototype of the proposed metasurface antenna.

Hybrid dual-mode tunable polarization conversion metasurface based on graphene and vanadium dioxide.

We present and numerically verify a functionally hybrid dual-mode tunable polarization conversion metasurface based on graphene and vanadium dioxide (VO2). The tunable polarization converter consists of two patterned graphene layers separated by grating which is composed of gold and VO2. Due to the existence of phase change material VO2, the polarization conversion mode can be switched flexibly between the transmission and reflection modes. Theoretical calculations show the proposed polarization conversion metasurface can obtain giant asymmetric transmission (AT) at 0.42 and 0.77 THz when VO2 is in the insulating state. Conversely, when VO2 is in the metallic state, the converter switches to the reflection mode, demonstrating broadband polarization conversion for both forward and backward incidences. Furthermore, the conductivity of graphene can be modulated by changing the gate voltage, which allows dynamic control polarization conversion bandwidth of the reflection mode as well as the AT of the transmission mode. The robustness of the metasurface has also been verified, the high polarization conversion efficiency and AT can be maintained over wide incidence angles up to 65° for both the xoz plane and yoz plane. These advantages make the proposed hybrid tunable polarization conversion metasurface a promising candidate for THz radiation switching and modulation.

Polarization-Independent Ultra Wideband RCS Reduction Conformal Coding Metasurface Based on Integrated Polarization Conversion-Diffusion-Absorption Mechanism

An ultra wideband (UWB) radar cross-section (RCS) reduction metasurface has received attention in recent years. However, the majority of the research has concentrated on the physics and design of planar surfaces, which do not meet the standards of modern aerodynamics and aesthetics. In this paper, we offer a sophisticated strategy for designing a metasurface that can conform to the shape of any object, even those of moderate curvature, and can also achieve UWB RCS reduction by combining absorption, polarization conversion, and diffusion mechanisms. Firstly, an absorbing-polarization converter is designed, composed of a square patch with a truncated diagonal strip and ring. A thin Rogers RT/Duroid 5880 dielectric substrate layer is used in the structure, which is also appropriate for conformal conditions. The substrate layer and the ground plane are separated by an air gap to enhance the polarization conversion bandwidth (PCBW). For normal incident electromagnetic (EM) waves, the PCBW ranges from 10.8 to 31.3 GHz with polarization conversion ratio (PCR) values greater than 0.9 dB. Up to a 45∘ oblique incidence angle over the aforementioned band, the PCR efficiency is well maintained. Then, the optimized coding metasurface is formed by the Pancharatnam–Berry (PB) phase, consisting of meta-atoms “0” and “1” of the same size but different orientations, to realize the concept of cross-polarization diffusion. A theoretical investigation has been performed to analyze the RCS reduction performance of planar as well as conformal cylindrical surfaces. The results show that more than 10 dB of RCS reduction is experienced over UWB (10.8–31.3 GHz) for planar metasurfaces under linearly and circularly polarized incidence waves. Furthermore, the RCS reduction for cylindrical surfaces can be achieved in a similar frequency band above 10 dB up to an angle of 90∘. It can be deduced that our proposed flexible metasurface can be used as an absorber or a polarization converter and provide broadband RCS reduction, which is essential for multi-function and conformal stealth applications.

Low RCS, Broadband Polarization Conversion Metasurface Antenna Based on Reactance Loading

A reactance-loaded polarization conversion metasurface (PCMS) is presented and exploited to realize a metasurface antenna (MTA) with both low radar cross section (RCS) and broadband radiation. Distinct from the conventional low-RCS PCMS, a metallic surface with etched open and closed slits is integrated into a PCMS consisting of double L-shaped particle pairs. Due to the edge capacitance induced by open slits and the surface inductance imposed by closed slits, the PCMS is endowed with reactance features that act as a perturbation to modulate the near-field interactions, thereby expanding the polarization conversion bandwidth. Besides, the reactance-loaded metallic surface, which has the same period as L-shaped particle pairs, combined with the grounded substrate, constitutes a broadband metasurface radiator. With the help of characteristic mode analysis, a linearly polarized aperture-coupled PCMS antenna is proposed, which effectively stimulates two resonant modes with broadside radiation to help bring about a broad operating bandwidth of 45.52%. Subsequently, the checkerboard-layout PCMS array is coupled to a sequentially feeding network through apertures on the ground plane, implementing a circularly polarized MTA with a broad 3 dB axial ratio bandwidth of 20.11%. Relying on phase cancellation and outstanding polarization conversion behaviors, an ultrawideband RCS reduction bandwidth of 7–39 GHz (139.13%) is also available.

Coding Engineered Reflector for Wide-Band RCS Reduction Under Wide Angle of Incidence

This communication presents the design of 1 bit coding engineered reflector for wideband monostatic/bistatic radar cross section (RCS) reduction under a wide angle of incidence by redirecting the backscattered electromagnetic (EM) energies into wide and countless angles. The proposed surface can achieve an excellent monostatic/bistatic RCS reduction performance of more than 10 dB over a wide frequency range from 60 to 120 GHz under wide angles of incidence up to 75°. This is achieved by designing a wideband anisotropic polarization rotator unit cell with a relative polarization conversion bandwidth of 66.7% and polarization conversion efficiency of more than 99%. The unit cell and its mirrored version are used to represent the “0” and “1” coding states of an optimized 1 bit coding sequence. The distribution of the “0” and “1” coding states and the dimensions of the anisotropic unit cell are optimized carefully, such that the unit cell will have 180° ± 30° reflection phase difference between the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$x$ </tex-math></inline-formula> - and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$y$ </tex-math></inline-formula> -axes over the whole three frequency bands (V-, E-, and W-bands) and obtains ultrawideband and wide-angle diffusion scattering patterns under oblique incidence up to 75°. The simulation and experimental results show that the proposed coding engineered reflector has nearly uniform diffusive scattering characteristics under normal and wide-angle off-normal incidences of EM waves up to 75° over the three frequency bands.

Ultrabroadband RCS Reduction Design by Exploiting Characteristic Complementary Polarization Conversion Metasurfaces

A new design method for ultrabroadband radar cross section (RCS) reduction by exploiting characteristic complementary polarization conversion metasurfaces (PCMs) is proposed and validated. The proposed method lifts the conventional bandwidth limitation enforced by the performance of a single PCM and expands the RCS reduction bandwidth. A systematic strategy for ultrabroadband RCS reduction design is developed and an effective reflection coefficient amplitude of the composite surface ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Gamma _{ {eff}}$ </tex-math></inline-formula> ) is derived as a new RCS reduction indicator. Based on this indicator, complete polarization conversion (CPC) frequency points of PCM are identified as important characteristics, and PCM pairs with interleaved CPC points, termed as initial PCM (I-PCM) and complementary PCM (C-PCM), are designed to compensate each other for ultrabroadband RCS reduction. A scaling-and-tuning two-step method for designing the C-PCM of a specific I-PCM is developed and validated. To further improve RCS reduction performance, taking the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\Gamma _{ {eff}}}$ </tex-math></inline-formula> as an indicator, the particle swarm optimization (PSO) algorithm is used to select the optimal I-PCMs, C-PCMs, and their area ratios. Finally, an ultrabroadband RCS reduction surface is designed, fabricated, measured, and validated. It realizes 10-dB monostatic RCS reduction ranging from 7.6 to 26.2 GHz (110.7% relative bandwidth) which exceeds the polarization conversion bandwidth of each individual PCM. Besides, good polarization insensitivity and bistatic RCS reduction performance are also obtained. The proposed method provides a new route for designing broadband RCS reduction surface based on PCMs with unsatisfactory characteristics and greatly alleviates the performance requirement for PCMs.

Ultrawideband RCS Reduction of Planar and Conformal Surfaces Using Ultrathin Polarization Conversion Metasurface

A metasurface-based polarization converter for ultrawideband radar cross-section (RCS) reduction of planar and conformal surfaces is presented in this paper. Initially, a polarization converter is designed which consists of a modified concentric double (MCD) square ring resonator-based unit cell along with an air gap in between the substrate and the ground plane. This air gap enhances the polarization conversion bandwidth (PCBW) of the converter. An ultrawide PCBW ranging from 6.3 – 20.5 GHz (106%) is obtained with a high polarization conversion ratio (PCR) of 0.9 for normal incident EM waves. The conversion efficiency is also found to be stable for oblique incidences over the aforementioned band with a PCR of above 0.8 upto ±35° angles of incidence. Later on, a checkerboard configuration of the polarization conversion metasurface (PCMS) array and its mirror array is applied on a planar as well as on a cylindrical conformal surface for reducing the radar cross section (RCS). It is observed that a consistent 10 - dB co-polarized monostatic RCS reduction is achieved with the planar PCMS surface over an ultrawideband (5.5 – 20.5 GHz). Even with the cylindrical surface, nearly 10 dB RCS reduction is obtained upto central angles of 60° over a wideband. Both the structures are simulated and measured after fabrication, and a reasonably good agreement is obtained between them.

Characteristic Modes Analysis of a Near-Field Polarization-Conversion Metasurface for the Design of a Wideband Circularly Polarized X-Band Antenna

A metasurface (MS) based on loop elements operating in the near field of a linearly-polarized microstrip antenna is employed to realize a circularly polarized radiated field. The properties of the loop unit cell are highlighted with the help of the Characteristic Mode Analysis that is employed for investigating the achievable linear to circular polarization conversion bandwidth and providing the guidelines for the design of the final antenna. A finite structure comprising 4&#x00D7;4 unit cells is tailored for achieving a circularly polarized far field within the whole X-band adopted for satellite communications (7.25 GHz-7.75 GHz, 7.9 GHz-8.4 GHz). A simple but effective single-port excitation scheme is adopted, and the overall performance are assessed by measurements on the fabricated prototype. The good agreement between simulated and measured results confirms the reliability of the proposed approach as well as the meaningful insight provided by Characteristic Modes Theory.

Ternary optimization for designing metasurfaces

A fully automated approach for designing metasurfaces whose unit cell may include metallic vias is proposed. Towards this aim, a ternary version of the particle swarm optimization (PSO) algorithm is employed in order to find the optimal metallic pattern and via-hole positions simultaneously. In the proposed design method, the upper surface of the unit cell is first pixelated. One of the possible three states of a metallic covered pixel, an uncovered etched pixel and a pixel containing a centered metalized via-hole is assigned to each pixel. The optimal state of each pixel is then determined by utilizing a ternary PSO algorithm to achieve favorable design goals. This method can be used for designing various metasurfaces as well as other via-assisted electromagnetic structures. As a proof of concept, the proposed method was applied to design two surfaces: a frequency selective surface with a minimum resonance frequency, and a linear-to-circular polarization converter with a maximum polarization conversion bandwidth. Comparison of the results with previous works confirms the efficiency and capability of the proposed method to design diverse metasurfaces in an automated fashion without the need for any theoretical or physical model.

Tunable broadband polarization converters based on coded graphene metasurfaces

In this paper, two optimization algorithms (randomly initialized hill climbing and genetic algorithms) are considered to design broadband polarization converters based on coded metasurfaces. A pixeled graphene patch with an elliptic structure is proposed for the initial solution. Each pixel can be 1 and 0 which represents the presence and absence of the graphene. The initial guess tends to the optimum configuration after several optimization processes. Four broadband polarization converters are designed utilizing the optimization algorithms. By changing the chemical potential of graphene, the operation frequency of the polarization converters can be adjusted. Furthermore, the effects of relaxation time of graphene and incident angle on the polarization conversion bandwidth of the four designed structures are investigated.

A metasurface‐based broadband quasi nondispersive cross polarization converter for far infrared region

A broadband nondispersive cross polarization converter (CPC) structure using metasurface for far infrared region has been proposed in this article. The structure is transmittive in nature, which converts a linearly polarized incident wave to its mutually orthogonal linearly polarized wave over a band of frequency ranging from 10.25 to 22.7 THz maintaining a high polarization conversion ratio (PCR) of more than 0.95. The fractional bandwidth of 75.6% corresponding to the center frequency of PCR bandwidth having more than 0.9 PCR value has been realized. The structure is also studied for oblique incidences where it shows wide band polarization conversion up to 45° for both TE and TM polarized oblique incident waves. The electric field distributions at the top and bottom surfaces of the structure close to the center frequency of polarization conversion bandwidth indicate the orthogonal rotation of incident linearly polarized wave at the frequency of interest. For the given set of media interface a separate study on polarization conversion through Brewster angle concept has been carried out simultaneously. The structure exhibits high PCR by maintaining the compactness in thickness (~ λ/5) as well as periodicity (~ λ/3) compared to the existing reported ones.

Wideband Linear-to-Circular Polarizer Based on Orthogonally Inserted Slot-Line Structures

This letter presents a printed wideband linear-to-circular polarizer for X -band applications. The proposed polarizer consists of a periodic array of orthogonally inserted slot-line structures, which are treated as two independent transmission paths for two orthogonal components of a linearly polarized incident plane wave, respectively. In order to effectively realize linear-to-circular polarization conversion, the orthogonal slot-line structures are loaded with inductive strips and pairs of open-circuited strips, respectively. This arrangement can maintain equal magnitude and 90° phase difference between these two transmission paths in a wideband frequency range. With the aid of equivalent circuit models, an operation principle of the proposed polarizer is extensively explained, and a design example is then conducted based on the prescribed specifications. Finally, the designed polarizer is fabricated and measured. The measured results confirm the theoretical predictions that the insertion loss is less than 1 dB from 8.27 to 13 GHz, and the axial ratio is less than 1 dB over entire band ranged from 7.92 to 12.16 GHz. This kind of polarizer indeed features great design flexibility, low insertion loss, and wide polarization conversion bandwidth.

Merging bands of polarization convertors by suppressing Fano resonance

In this letter, we propose to extend the bandwidth of polarization conversion (PC) by merging the bands of different polarization converters. Intuitively, it is quite natural that the bands of two polarization converters be merged if they are close enough. Unfortunately, there is always a narrow band with low efficiency between the two bands, which results from Fano resonance. We establish a theoretical model to analyze the underlying mechanism of the Fano resonance. We find that the Fano resonance can be suppressed by reducing the resonant frequency of the converter operating at a higher frequency band. In this way, the anti-symmetric surface current can be eliminated and the two PC bands can be merged as a wide band. We designed, fabricated, and measured a prototype. Both the simulation and experimental results verify this method. This work provides an effective alternative to the design of wide-band or even ultra-wideband polarization converters.

An ultra-broadband and highly-efficient tunable terahertz polarization converter based on composite metamaterial

A near perfect, ultra-broadband and highly-efficient terahertz reflective polarization converter based on multilayer metamaterial is proposed in this paper. The hybrid metamaterial unit structure consists of a split-ring metal pattern and a metal sheet separated by a dielectric resonator spacer. The polarization conversion ratio (PCR) is above 90% from 2.06 to 4.26 THz, with an optimal range between 2.98 and 4.16 THz where the efficiency is above 98% for normal incidence. It also shows excellent performance for oblique incidences. Moreover, the working band and the optimized frequency range for the polarization conversion can be manipulated by changing the open angle between the metallic arcs and the substrate thickness, respectively. Based on this design, two types of hybrid metamaterial converters are also investigated to swith off polarization conversion altogether or modify the polarization conversion bandwidth. A polarization converter with temperature controlled PCR is realized by adding a vanadium oxide (VO2) mask on the designed structure. In addition, by integrating photoconductive silicon islands between the split-ring and metal bar a dual-band polarization converter can be realized. Combining with a polarizer, this window can act as an active THz filter.

Ultra-wideband polarization conversion metasurface and its application cases for antenna radiation enhancement and scattering suppression

A double-layer complementary metasurface (MS) with ultra-wideband polarization conversion is presented. Then, we propose two application cases by applying the polarization conversion structures to aperture coupling patch antenna (ACPA). Due to the existence of air-filled gap of ACPA, air substrate and dielectric substrate are used to construct the double-layer MS. The polarization conversion bandwidth is broadened toward low-frequency range. Subsequently, two application cases of antenna are proposed and investigated. The simultaneous improvement of radiation and scattering performance of antenna is normally considered as a contradiction. Gratifyingly, the contradiction is addressed in these two application cases. According to different mechanism of scattering suppression (i.e., polarization conversion and phase cancellation), the polarization conversion structures are utilized to construct uniform and orthogonal arrangement configurations. And then, the configurations are integrated into ACPA and two different kinds of metasurface-based (MS-based) ACPA are formed. Radiation properties of the two MS-based ACPAs are improved by optimizing the uniform and orthogonal arrangement configurations. The measured results suggest that ultra-wideband polarization conversion properties of the MS are achieved and radiation enhancement and scattering suppression of the two MS-based ACPAs are obtained. These results demonstrate that we provide novel approach to design high-performance polarization conversion MS and MS-based devices.

Wideband and high efficiency reflective polarization rotator based on metasurface

A wideband and high efficiency reflective polarization rotator (PR) based on metasurface is presented. The unit cell of the PR consisting of two oblique symmetry triangle split rings and simulated results show the PR has more than 90% polarization conversion efficiency from 9.24 to 17.64 GHz (a relative bandwidth of 62.50%) under normal incidence. The broad polarization conversion bandwidth and high efficiency results from multiple plasmon resonances and nearly 100% polarization conversion is obtained at three plasmon resonances. The mechanism of the proposed PR is analyzed by surface current distributions. Electric and magnetic resonances generate broad polarization conversion bandwidth and high polarization conversion ratio within the operating band. In addition, we analyze the polarization states of the PR unit numerically based on the reflected fields, which serves as theoretical predictions of polarization conversion. To verify the simulation results and analysis, a sample was fabricated and measured. The measured results are in good agreement with simulated results and numerical analysis.

High-efficiency polarization conversion phase gradient metasurface for wideband anomalous reflection

An ultra-wideband polarization conversion metasurface based on S-shaped metallic structure is designed and prepared. The simulation results show that the polarization conversion bandwidth is 14 GHz for linearly polarized normally incident electromagnetic waves and the cross-polarized reflectance is more than 99% in the range of 10.3 GHz–20.5 GHz. On the premise of high reflection efficiency, the reflective phase can be regulated by changing the geometrical parameter of the S-shaped metallic structure. A phase gradient metasurface composed of six periodically arrayed S-shaped unit cells is proposed and further demonstrated both numerically and experimentally. The specular cross-polarization reflection of the phase gradient metasurface is below −10 dB, which shows a good performance on manipulating the direction of the reflected electromagnetic waves.

Broadband and wide-angle reflective polarization converter based on metasurface at microwave frequencies

We propose to realize a broadband and wide-angle reflective polarization converter in microwave regions. The proposed converter can convert a linearly polarized (LP) wave to its cross-polarized wave at three resonant frequencies. It can also convert the LP wave to a circularly polarized wave at other two resonant frequencies. Furthermore, the proposed converter can achieve broad bandwidth with incident angle up to 45°. The simulated and measured results are in agreement in the entire frequency regions, and the bandwidth of polarization conversion over 75 % can be obtained from 7.6 to 15.5 GHz under normal incidence and from 7.8 to 13.0 GHz under incident angle of 45°. The surface current distributions of the proposed converter are discussed to analyze the physical mechanism. The converter tolerance to wide angle of incidence and the broad bandwidth could be useful in the range of applications in the microwave regions.