Circularly Polarized Wave Research Articles

Metasurface-Assisted Broadband Circularly Polarized Folded Reflectarray Antenna

In this article, a novel design of broadband circularly polarized (CP) folded reflectarray (FRA) antenna is proposed. The CP FRA consists of two kinds of metasurfaces (MSs) and a linearly polarized (LP) open waveguide antenna as the feeding source. The bottom MS functions as the main reflector, which is capable of realizing cross-polarization conversion and beam focusing simultaneously. The upper MS is utilized as a subreflector, which could reflect LP wave coming from the feeding source and transmit its orthogonal counterpart into CP wave. For demonstration, the MS-assisted CP FRA antenna is fabricated and measured. Numerical results are consistent with experimental ones, illustrating a peak gain of 24.1 dBi and a peak aperture efficiency of 51% at 9.9 GHz. The 3 dB gain bandwidth and 3 dB axial ratio (AR) bandwidth are achieved as 27.5% (8.8–11.6 GHz) and 43.9% (8–12.5 GHz), respectively. The proposed CP FRA provides a new avenue to realize broadband high-efficiency CP antenna, which may find great potentials in modern wireless communication systems.

Circularly Polarized Double-Folded Transmitarray Antenna Based on Receiver-Transmitter Metasurface

In this communication, a circularly polarized (CP) double-folded transmitarray antenna (DFTA) is proposed and experimentally verified for the first time in the open literature. It is designed based on a receiver–transmitter metasurface (RTMS) and a polarization rotating (PR) metasurface (MS). A linearly polarized (LP) patch antenna is integrated on the RTMS instead of a horn antenna to feed the DFTA. Through double-folded reflecting, twice PR, LP wave receiving, CP wave transmitting, and transmission phase manipulating, the LP spherical wave from the feed is transformed into the high-gain pencil-shaped CP beam. The strategies innovatively break the restriction that the previous folded reflectarray (FRA) and folded transmitarray (FTA) antennas are only LP. Moreover, the double-folded design further reduces the antenna profile to about 1/4 of the focal length. The simulation and experiment results are in good agreement, which exhibits a peak gain of 21.8 dBic at 9.8 GHz and a maximum aperture efficiency of 40%. Meanwhile, the DFTA obtains a −1 dB gain bandwidth of 6% (9.6–10.2 GHz), in which the axial ratio is lower than 1.5 dB.

Nonresonant propagation phase based metasurface design for independent manipulation of dual circularly polarized waves

Pancharatnam–Berry (PB) phase has attracted significant attentions due to its phase control characteristic for circularly polarized (CP) waves. PB phase structure usually provides equal but inverse phase shifts for the left-handed CP (LCP) and right-handed CP (RCP) waves. In this article, a method is proposed to decouple this correlation and to manipulate the wavefronts of interacting LCP and RCP waves independently and simultaneously. Nonresonant propagation phase realized through open-ended transmission line is introduced as an additional degree of freedom to achieve totally independent phase responses of the orthogonal CP waves. A metasurface is presented to shape the reflected orthogonal CP waves into vortex beam and pencil beam independently. Simulation and measurement results confirm with each other and demonstrate the proposed method.

3D-printed cavity backed crossed dipole antenna for high gain, wideband circular polarization in sub-6 GHz

Triple-arm crossed dipole antenna (CPDA) backed by 3D printed cavity exhibits high gain over wideband axial ratio for sub-6 GHz applications is presented. To improve peak gain and axial ratio bandwidth performance, multiple radiating arms are introduced. The arms are cascaded using vacant quarter rings to obtain circular polarization. Unlike the conventional CPDAs that yield single circular polarized (CP) wave, two CP waves produced by double-arm or triple-arm CPDAs enhances overall gain performance across wideband axial ratio. The length and orientation of the multiple arms in the CPDA determine the maximum current generated on the crossed dipole antenna, resulting in an improved gain since two CP waves are combined in the free space. To further increase boresight gain, 3D printed cavity is placed beneath the triple-arm CPDA. Unbalance impedance line presented in this work extends impedance bandwidth of the triple-arm CPDA to cover 3-dB axial ratio bandwidth. For validation purpose, a prototype was fabricated and measured. The measurement results demonstrate that the triple-arm CPDA has a boresight gain of 8.91–11.7 dBic within 3-dB axial ratio bandwidth of 51.4% (3.25–5.5 GHz). The proposed antenna produces a stable gain within sub-6 GHz bands.

Design investigation of dual-band dual-circularly polarized hybrid antenna array using semi-hexagonal HMSIW cavity

This paper presents a novel dual band, dual Circularly Polarized (CP) hybrid antenna consisting of a microstrip patch radiator and semi-hexagonal half mode substrate integrated waveguide (HMSIW) cavity. The hexagonal HMSIW cavity operates at its fundamental TM010 mode and excites two rectangular radiating patches with different sizes to provide multiband operation. An inclined slot with suitable size and position is placed on top of each patch to provide CP with different types including right-handed CP (RHCP) wave at the first band and a left-handed CP (LHCP) wave for the other band. Antenna structure is numerically simulated using High Frequency Simulator Structure Simulator (HFSS) and results including reflection coefficient, axial ratio (AR), and radiation patterns are reported. Moreover, a linear array of two elements of the proposed hybrid antenna is designed and simulated. A prototype of the proposed single element and two elements array is made and successfully tested. The measured results show that for the proposed two elements array 3 dB AR bandwidth and peak gain for the low- and the high-band are 1%, 9.2 dBi and 3.1%, 8.8 dBi respectively, which agrees well with those obtained by simulation.

Wideband low‐profile endfire circularly polarized antenna using mode superposition technique

In this article, a wideband low-profile endfire circularly polarized (CP) antenna using magnetoelectric dipole is proposed. Designing a wideband electric dipole element is easy and well-studied in the literature. However, designing a compact wideband magnetic dipole element is still a challenge. In this paper, the impedance bandwidth (IBW) of the magnetic dipole is enhanced by reducing the resonance frequency of higher-order mode half-TE310 with the help of rectangular slots placed at the null of mode half-TE310. By combining the resonance frequency of mode half-TE110 and mode half-TE310, the magnetic dipole can yield a larger IBW (6.86–7.67 GHz, 11.14%) with smaller planar dimensions of 1.259λ0 × 0.363λ0 × 0.038λ0 (λ0 is the free space wavelength at the centre frequency). To generate a wideband endfire CP wave, a horizontally polarized electric dipole with a feed line is combined with the vertically polarized magnetic dipole. The measured IBW and axial ratio bandwidth (ARBW) are 11.65% and 12.02%, respectively, with a measured peak endfire gain of 5 dBic. The overall dimension of the proposed wideband low-profile endfire CP antenna is 1.11λ0 × 0.66λ0 × 0.033λ0.

Broadband and thermally switchable reflective metasurface based on Z-shape InSb for terahertz vortex beam generation

In this paper, a broadband and thermally switchable reflective metasurface based on InSb Z-shape resonator (ZSR) structure was proposed for the vortex beam generation in terahertz (THz) region. Numerical simulation results indicate that the operation frequency range and efficiency will be basically unchanged when the external environment temperature increases from 300 K to 340 K, but gradually decreased when the temperature decreases from 300 K to 240 K. More specifically, the proposed InSb metasurface can transform the normal incident circular-polarization (CP) wave to its orthogonal component with conversion coefficient over 0.8 from 0.65 THz to 1.66 THz (relative bandwidth of 87.4%) after reflection when the temperature is changed from 300 K to 340 K. However, the bandwidth will be narrowed and conversion coefficient will be limited with the temperature decreases from 300 K to 240 K. The full 2π phase shift could be obtained at operation frequency by rotating the InSb ZSR structure along the wave propagation direction. Taking advantages of the above characteristics, the reflective THz vortex beams carrying orbital angular momentum (OAM) with topological charge of l = ±1, ±2, and ±3 at the temperature of 300 K over a broadband range can be achieved. In addition, thermal switchable effect of the vortex beams with topological charge of l = 2 at three different frequencies also can be observed. The further numerical results also indicate that the generated reflective THz vortex beams have high mode purity by the designed InSb metasurface. Our work provides a potentially efficient method for the development and integration of the broadband and switchable wavefront controlling devices.

3-D Printed Millimeter-Wave Metal-Only Dual-Band Circularly Polarized Reflectarray

This article presents 3-D printed metal-only dual-band millimeter-wave circularly polarized (CP) reflectarrays (RAs). The RAs’ unit cell (UC) is made of an anisotropic metal brick mounted on a full metal ground. In-plane rotating the metal brick introduces geometric Pancharatnam–Berry (PB) phase shifting, and vertically adjusting the position of the UC provides propagation phase shifting. The geometric PB and propagation phase shifting offer two different degrees of freedom, enabling independent wavefront shaping of CP wave over dual-band. Specifically, the low-band CP beam shaping solely depends on the propagation phase. In contrast, the high-band CP beam shaping depends on the geometric PB and the propagation phases. The coupling issue between dual-band is minimal because of the unique dual-band phase-shifting methods. In addition, 3-D printed dual-band left-hand CP (LHCP) horn antennas are designed, printed, and used as the feed. To demonstrate, two RA antennas with different dual-band CP beam directions are fabricated and measured.

Trapping wide-angle circularly polarized waves with giant circular dichroism using a single-channel coherent perfect graphene meta-surface absorber.

We propose a single-channel coherent perfect graphene meta-surface absorber to trap circularly polarized (CP) waves perfectly through cascading a polarization converting meta-array and a monolayer graphene sheet. To be more specific, the incident CP waves will be reflected into dual sets of orthogonally linearly polarized (LP) waves, where each group of the same polarized reflecting components can achieve identical amplitudes and a 180° phase difference at a certain frequency to have coherent absorption. In particular, we show that such a single-channel coherent perfect graphene meta-surface absorber possesses the merits of the wide-angular chiral absorbing capacity of CP waves with giant circular dichroism, thus should pave the way for building up more advanced coherent absorbers and offer more freedom to manipulate CP waves.

Muon pair production via e + e − annihilation in the presence of a circularly polarized laser field

In this paper, we have investigated the elementary particle reaction that results from the electron–positron interaction, at the leading order, with an intense laser wave of circular polarization. We have derived, by analytical means, the laser-assisted differential cross section expression by using the scattering matrix approach. We have analysed the energy and the number of exchanged photons dependence of muon pair production in electron–positron annihilation at different centre of mass energies including the Z-boson peak. For this reason, a wide range of high centre of mass energies relevant to future collider were covered to study the cross section behaviour. We have found that, for a given number of exchanged photons, laser field strength and frequency, the circularly polarized laser field decreases the total cross section by several orders of magnitudes.

Dual-band high-gain microstrip antenna with a reflective focusing metasurface for linear and circular polarizations

This paper proposes a dual-band high-gain microstrip antenna with a reflective metasurface (MS). The initial designed coaxial-fed laminated microstrip antenna can realize linear polarization (LP) radiation at the lower frequency of 5 GHz and circular polarization (CP) radiation at the higher frequency of 11 GHz, with a relatively low gain of about 5.8 dBi and 5.4 dBic, respectively. To enhance the radiation performance of the microstrip antenna, a reflective focusing MS is proposed, which can focus LP and CP waves at 5 GHz and 11 GHz, respectively. The MS antenna system is constructed by placing the initially designed microstrip antenna on the focal point of the reflective focusing MS, which can achieve the high-gain performance of 13.4 dBi for the LP radiation at 5 GHz, and 18 dBic for the CP radiation at 11 GHz, respectively. The proposed MS and feed antenna were designed and fabricated, and the experimental data were consistent with the simulation results, which verifies the feasibility of the proposed scheme. The proposed reflective focusing MS antenna could provide potential application in the modern wireless communication system.

C‐/Ka‐band circularly polarized shared‐aperture antenna array

A C-/Ka-band circularly polarized (CP) shared-aperture scanning antenna array has been proposed in this paper. Here, the antenna array working in the C-band (6.48–6.52 GHz) is composed of 4 × 4 cross-dipole antenna elements, and each cross-dipole antenna element is fed by a 1-to-2 power divider with 90° phase difference, so that it can induce left/right-hand CP wave. As for the antenna array working in the Ka-band (27.5–28.5 GHz), it is made up of 16 × 16 CP antenna elements, in which each CP antenna element is an aperture-coupled chamfered patch fed by substrate integrated waveguide (SIW) structure. To realize the proposed scanning array, the C-band antenna array is set within the gap between adjacent antenna elements of the Ka-band antenna array, and the radiation apertures of all the antenna elements are printed on the same plane. Notably, such a layout can yield good isolation performance between the C-band antenna and the Ka-band antenna element. From the measured results, in the C-band, the proposed scanning array can achieve a beam scanning range of 0°–38° with axial ratio (AR) < 3 dB, a port isolation of greater than 45 dB, and a maximum gain of 18.2 dBic. On the other hand, in the Ka-band, the proposed scanning array can yield a beam scanning range of 0°–45° with AR <3 dB, a port isolation of greater than 37 dB, and a maximum gain of 26.2 dB.

Wide Bandwidth Axial Ratio Circularly Polarized Array Antenna based on External Resonator

This study introduces a wide bandwidth and wide axial ratio (AR), circularly polarised (CP), patch array antenna. By combining dual layers of a polarizer with dual layers of linearly polarized microstrip patch antenna, a novel method is created for generating circular polarization waves with a wide frequency range. The dual-layer 2 × 2 and 2 × 8 microstrip patch array antenna is employed to achieve linearly polarized waves and the external polarizer consists of a 3 × 3 and 3 × 12 four-layer dual rings polarizer that transforms linearly polarized (LP) waves into CP waves. The |S11| −10 dB bandwidth of small and large-scale circular polarized array antennas is 20% and 27.06% at 5 GHz, respectively, Simulations and testing show that the 3-dB axial ratio bandwidth (ARBW) at 5 GHz is 17%. The suggested antenna has a lot of potential for satellite communication applications because of its easy structure, wide ARBW, and wide impedance bandwidth.

Four-Port Orthogonal Circularly Polarized Dual-Band MIMO Antenna With Polarization and Spatial Diversity Using a Dual-Band Linear-to-Circular Polarization Converter

A dual-band circularly polarized (CP) four-port multiple-input-multiple-output (MIMO) antenna for K/Ka-bands fixed-satellite service is proposed in this communication. The single element of MIMO is composed of a cascade of two dipoles of different lengths resonating at around 20 and 30 GHz. An array of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$7 \times 7$ </tex-math></inline-formula> elements of the unit cell of the dual-band linear-to-circular polarization converter is placed at a distance of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda _{o}$ </tex-math></inline-formula> /4 ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda _{o}$ </tex-math></inline-formula> is calculated with respect to 19.51 GHz) in the endfire direction of MIMO antenna to obtain an orthogonal CP wave at the two frequency bands. The proposed CP antenna shows good MIMO performance with a correlation coefficient (CC) of less than 0.19 and diversity gain (DG) of better than 0.99 at both the frequency bands. The proposed MIMO also agrees with polarization and spatial diversity, and the CP nature at lower and upper frequency bands can be interchanged by exciting the orthogonal ports. A prototype of the MIMO antenna is fabricated, and the measured CP bandwidths of 11.51% and 3.69% are obtained in the lower (19.65–22.05 GHz) and upper (29.25–30.35 GHz) frequency bands, respectively. The proposed antenna can be used for the Ka-band: 29.5–30.0 and 19.7–20.2 GHz fixed satellite service as uplink and downlink frequencies, respectively.

Circularly Polarized Millimeter Wave Frequency Beam Scanning Antenna Based on Aperture-Coupled Magneto-Electric Dipole

Based on the newly suggested wideband circularly polarized (CP) aperture-coupled magneto-electric dipole (MED), a millimeter-wave (mm-wave) frequency-scanned array (FSA) is proposed in this article. The MED is printed on two substrate layers. The electric dipole is two metal patches with perturbation structure, while the magnetic dipole is two rows of metal vias passing through the top substrate layer. The electric and magnetic dipoles, fed by a coupling slot, excite CP wave. By loading an arc-shaped vias row (AVR) at both ends of the magnetic dipole, the CP bandwidth with axial ratio (AR) less than 3 dB is extended to 40.9%. A new compact wideband transition from the rectangular waveguide (RWG) to the substrate integrated waveguide (SIW) is suggested as the feed structure for the CP FSA. A slow wave structure is etched on the ground of SIW to widen the beam scanning range. A 16-element array is designed and measured. The measured results show that the beam scanning range is 56° over 23–33 GHz band with a peak gain of 19.5 dBi. The CP mm-wave FSA has the advantages of wide scanning angle, low profile, and easy fabrication.

Wideband and metal‐only linear to circular polarization converter using multi‐slot elements

A wideband, metal-only, and low-cost transmission-type polariser is proposed in which a plane wave with linear polarization impinging on the structure is converted to circular polarization wave on the other side and vice versa. The proposed structure is a quad-layer frequency selective surface that its unit cell is composed of two sets of multi-slot elements placed perpendicular to each other to achieve a wideband polariser. In this unit cell, by changing the length of the slots, the amplitude and phase of transmission coefficient can be controlled, which are used to create a 90-degree phase difference between vertical and horizontal components of the incident electric field. A 9 × 9 $9\times 9$ array of the proposed polariser with a quad-layer is simulated and fabricated that shows the bandwidth of 22% (11.7–14.7 GHz) for an axial ratio below −3 dB and a transmission efficiency of more than 85%.

A wide axial-ratio beamwidth circularly-polarized oval patch antenna with sunlight-shaped slots for gnss and wimax applications

This paper proposes a quadruple band stacked oval patch antenna with sunlight-shaped slots supporting L1/L2/L5 GNSS bands and the 2.3 Ghz WiMAX band. The antenna produces right-hand circular polarization waves with wide axial-ratio beamwidth of 223/216^{circ } and 231/203^{circ } at two orthogonal cutplanes at L5 and L2 GNSS bands, respectively. Firstly, the resonant modes TM_{110} and TM_{210} are excited inside a single layer oval patch antenna, where resonance frequencies are calculated using Mathieu functions. Meanwhile, it is shown that another version of the mode TM_{110} with similar distribution but orthogonal direction is excitable inside the same oval patch. Then, a second stacked oval patch layer is added, which splits the resonance frequency of each of the modes TM_{110} and TM_{210} into two different values. Depending on the probe feed position and the separation between the two layers, the phase shifts between modes versions in the upper and the lower layers change. Thus, by fine-tuning the probe feed position and the separation between layers, spatially-orthogonal with quadrature-phase-shift versions of the mode TM_{110} are obtained, producing a circularly polarized waves at L2 and L5 bands. Furthermore, sunlight shaped slots are etched into the upper and lower layer patches to fine tune the phase shifts between different modes versions, which enhances the overall axial-ratio beamwidth. Despite the simplicity of the overall structure and the feeding mechanism utilized in the proposed design, wide axial-ratio beamwidths are obtained, as compared to previous works. The proposed antenna shows low reflection coefficient values at 1.14–1.29 GHz (L2/L5), 1.45–1.6 GHz (L1), and 2.26–2.4 GHz (WiMAX). The antenna gains are 5.9, 5.6, 6, and 6.5 dBi/dBic at L5, L2, L1, and WiMAX bands, respectively. The half-power beamwidths are 99/96^{circ }, 102/96^{circ }, 112/85^{circ }, and 65/48^{circ } at two orthogonal cutplanes at L5, L2, L1, and WiMAX bands, respectively.

A Wideband 3-D-Printed Multibeam Circularly Polarized Ultrathin Dielectric Slab Waveguide Luneburg Lens Antenna

This letter presents a wideband three-dimensional (3-D)-printed circularly polarized (CP) ultrathin dielectric slab waveguide (DSW) Luneburg lens (LL) with multibeam application in X-band. The characteristic that DSW supports TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> and TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> waves to pass through with different phase constants is used to generate 90° phase difference to compose CP wave for the proposed structure. To prove the point, the prototype antenna is fabricated by 3-D printing and measured. The results show that the proposed LL supports multibeam application with 11 beams covering ±60° range in azimuth plane, and the 3 dB axial ratio bandwidth for multibeam antenna is 23.5% with reflection coefficient lower than −10 dB and gain higher than 13.7 dBi. The measured results show good coincidence with simulated ones.

In-plane symmetry breaking induced tunable spin-dependent responses and polarization states for terahertz wave

Dynamic manipulation of electromagnetic terahertz waves is tremendously desirable to boost the development of favorable functional components of terahertz systems. Reconfigurable chiral metadevices have emerged as promising platforms for active control of spin-dependent responses, however, conventional design principles are restrained by the breakage of out-of-plane symmetries. Here, a type of kirigami-based terahertz metamaterial (MM) is numerically simulated to modulate circular polarization differential transmittance (CPDT) based on the in-plane symmetry breaking. The un-deformed MM empowered with mirror symmetries exhibits indiscriminate propagation for left circular polarization and right circular polarization wave, while the deformed MM with the tensile strain as 24% dramatically facilitates the breakage of in-plane symmetries and retains the CPDT value as high as 0.89. Furtherly, as the tensile strain reaches to 45.5%, the CPDT value is suppressed back to a negligible level and achieves the off-on-off chirality switch function through the continuously stretchable deformation. Moreover, the effect of kirigami cuts, height difference and rotation angle of silicon pillars on the CPDT spectra are also parametrically analyzed. The combination of kirigami technique and terahertz device gives rise to a novel branch of reconfigurable principles, and demonstrates its promising applications of chirality switching, spin-selective manipulation, chiral detection and polarization control.

A Theoretical Proposal for an Ultrabroadband Metamaterial Absorber for the Circular Polarization Waves Based on Anapole Mode in the Near‐Infrared Region

AbstractThe absorber excited by anapole response is in the spotlight owing to its non‐radiating merits, whereas the existing designs suffer from poor bandwidth and absorption. Furthermore, the circular polarization (CP) wave promises numerous application scenarios; thus, the absorbers aimed at it are sorely called for. An ultrabroadband metamaterial absorber (MMA) for the CP waves based on anapole mode is proposed in this paper. In this structure, the symmetrical split‐ring resonators (SRRs) are acted as the resonant unit to excite the toroidal dipole (TP) and electric dipole (EP) moments in the near‐infrared region. By applying the perfect electric conductor mirror effect, the enhanced field energy results in the absorption peak in the given band. Aimed at optimizing the absorption performance of the designed MMA, the SRRs are rotated, introduce the cavity resonance, and add the nickel patch to excite more electromagnetic resonance. The final optimized MMA can achieve an absorption exceeding 90% in an ultrabroadband of 1228–2156.7 nm, whose relative absorption bandwidth is 54.9%. Meanwhile, on account of its highly symmetrical structure, the MMA is insensitive to the polarization state of the CP waves. These splendid properties make the MMA a good candidate for potential applications.