Right-hand Circular Polarization Research Articles

Development of a Broadband and High-Gain Circularly Polarized Array of Multilayer Slot Antennas for X-Band Wireless Communication Networks

This paper presents a wideband cavity-backed slot antenna array designed for X-band wireless communication systems. The antenna element consists of a circular slot combined with a cross-slotted patch; both are fed by an L-shaped microstrip line through proximity coupling to extend the impedance bandwidth and gain. The reduction of beam squint in the radiation patterns, caused by the asymmetric feed line, is achieved through intelligent optimization of the dimensions and position of the cross slot on the patch. Additionally, a back cavity is included to provide unidirectional radiation and enhance gain. The antenna exhibits right-hand circularly polarized (RHCP) radiation patterns with high gain over a wideband frequency range. To further improve the axial ratio (AR) bandwidth and gain, the antenna is utilized in a 2 × 2 array configuration with a sequential rotation feed network. The overall dimensions of the proposed array are 1.42 λ 0 × 1.42 λ 0 × 0.45 λ 0 , where λ 0 represents the wavelength at the center frequency of 10 GHz. The fabricated array is then tested, and the measurements show an impedance bandwidth of 60% (7 GHz-13 GHz) with S 11 < − 10 dB, a 3 dB AR bandwidth of 42% (7.45-11.65 GHz), and a peak gain of 11.14 dB. The simulated and measured results exhibit good agreement, validating the effectiveness of the design.

A dual-band, beam steering and polarization reconfigurable 2-bit array antenna for satellite navigation/communication applications

A dual-band array antenna for satellite navigation/communication applications with beam steering and reconfigurable polarization functions is proposed in this paper based on four 2-bit antenna units. The 2-bit antenna unit works in the dual frequency range of 1.55–1.65 GHz (GPS L1, GLONASS L1, GSNS L1, Beidou-2 B1) and 2.0–2.2 GHz (Mobile Satellite Service, MSS, downlink), and its phase can be controlled by PIN diodes flexibly. Therefore, the proposed array antenna has dual-band and beam steering characteristics. Besides that, the polarization of the proposed array antenna can be changed by covering a metasurface and rotating it at different angles. The measured results indicate that the proposed array antenna can achieve linear polarization (LP), left-handed circular polarization (LHCP), and right-handed circular polarization (RHCP). The proposed array antenna can realize LP beam steering within 45° and CP beam steering within 30° at 1.6, 2.0, and 2.2 GHz.

Dual-mode vortex beam transmission metasurface antenna based on linear-to-circular polarization converter.

The generation of multi-mode vortex beams at the same aperture is currently emerging as a research hotspot. In this paper, a method based on a linearly polarized-circularly polarized translational transmission metasurface (TM) is proposed to enable a dual-circularly polarized dual-mode vortex beam generation. Through the judicious implementation of an additional rotational phase and the combination of the initial transmission phase, the phases of the left-hand circularly polarized (LHCP) and right-hand circularly polarized (RHCP) waves can be manipulated arbitrarily and independently. Meanwhile, the design of the array phase is utilized for the dual-mode dual-circularly polarized beam generation. Simulation and sample measurements provide validation data for the feasibility of this method, in which the measurement results are in excellent consistency with the simulation ones. This proposed method paves the way toward the enhancement of the channel capacity of mobile communication.

A printed tiny-RHCP antenna for direct broadcast application

The present study unveils a printed antenna design that achieves high gain and exhibits right-handed circular polarization (RHCP). The antenna is intended for use in direct broadcast satellite systems, operating within the frequency range of 12.20 to 12.70 GHz. The specified configuration is achieved by etching a pair of indistinguishable isosceles triangles from the vertex of a geometrically regular square. A circular geometric structure consisting of sixteen isosceles triangles scaled in proportion is meticulously engraved from the central point of the recently obtained geometry. The meticulous etching enhances the antenna’s effective length, which in turn helps achieve improved parametric performance at the desired frequency. The antenna under consideration was simulated using a SONNET EM simulator, cross-verified by the CST microwave studio, and afterward, it was fabricated using a cost-effective PCB laminated Rogger 5880 material. The antenna under consideration significantly reduces size, achieving miniaturization of 20.20%. The antenna is resonated at 12.52 GHz, and it exhibited a satisfactory circularly polarized gain of 8.46 dBic. It also provides a CP bandwidth of 0.54 GHz, capable of covering the entire DBS band. Additionally, it offers 97% radiation efficiency and 86% aperture efficiency. The antenna also offers 23 dB/m correction factor, which highlights its minimal EMI/EMC effects. All the measured outcomes align with the results achieved from the simulator.

Axial Ratio Improvement of Circularly Polarized Antenna Using Parasitic Elements for 5G Applications

A circular polarization (CP) antenna that can switch between right-handed circular polarization (RHCP) and left-handed circular polarization (LHCP) modes has been designed and introduced for 5G applications in the 3.5 GHz frequency band in this work. The proposed antenna comprises a crossed dipole fed by a 90° hybrid coupler. The axial ratio (AR) enhancement of 190 MHz is achieved by vertically stacking a substrate with a distance of λ / 4 from the ground plane, including an annular ring-shaped parasitic element above a circular-shaped disc. Consequently, by creating surface current rotation on the parasitic elements, the CP performance of the antenna is improved. According to the experiments, a wide impedance bandwidth of 930 MHz (3.19-4.12 GHz) and an overlapped AR bandwidth of 23.5% for both modes are achieved. The overall size of the antenna is 100 × 92.5 × 24 m m 3 , and the gain is stable across the operating frequency band with a peak value of 6.78 dBic.

Switchable terahertz orbital angular momentum Bessel beams based on spin-decoupled multifunctional reflective metasurfaces.

In this study, switchable terahertz (THz) multi-orbital angular momentum (OAM) Bessel beams (BBs) were developed based on a spin-decoupled reflective multifunctional metasurface (MTS). Switchability was achieved by switching the feed between left-hand circular polarization (LCP), right-hand circular polarization (RCP), and linear polarization (LP) incidences. A switchable physical model was established for calculating the beam direction, OAM mode, polarization, and non-diffractive distance of the outgoing BBs. As an example, a spin-decoupled MTS was designed to generate dual BBs under LCP incidence, which was subsequently switched to RCP or LP for switchability. The outgoing BBs could be switched among three types of beams: Type-1 under LCP incidence (LCP, θL = 40°, φL = 0°, lL = 1, dL = 18 cm) and (RCP, θR = -40°, φR = 0°, lR = -1, dR = 20 cm); Type-2 under RCP incidence (RCP, θR = 40°, φR = 0°, lR = 1, dR = 18 cm) and (LCP, θL = -19°, φL = 0°, lL = 3, dL = 16.4 cm); and Type-3 under LP incidence (LP, θ = 40°, φ = 0°, l = 1, d = 18 cm), (RCP, θR = -40°, φR = 0°, lR = -1, dR = 20 cm) and (LCP, θL = -19°, φL = 0°, lL = 3, dL = 16.4 cm). Compared with previous MTSs, the proposed spin-decoupled MTS has the advantages of switchability among BBs, high non-diffractive distance/aperture size ratio of 15, large beam deflection angle of up to 40°, and high BB conversion efficiency of up to 96%. The simulated results were consistent with those calculated using the physical model, thus validating the physical model. The designed switchable BBs have potential THz near-field applications, such as high-capacity near-field wireless communications, wireless power transfer, high-resolution imaging, non-destructive testing, and speed detection of high-speed rotating objects.

A Circularly-polarized Patch Antenna for BDS Applications

The BDS (Beidou) Navigation Satellite System has been a powerful tool in real-time navigation and positioning. In the transitional stage between BDS-2 and BDS-3, it would be a top priority to ensure the antenna is compatible with the two systems. In our investigations, a circularly-polarized (CP) patch antenna is proposed for receiving B1I signals. This antenna is a newly designed slit-loaded square patch structure. The T-shape structure with F-shape slots is deployed on each edge of the antenna, and a single feed is employed to excite right-hand CP radiation. In simulations, all the parameters of the antenna are optimized through Ansys HFSS. In experiments, the processed antenna is further testified, where the measured bandwidth is compared with the simulated one to verify the effectiveness of the antenna.

A novel dual-sense polarization reconfigurable dual-band microstrip antenna

In this paper, a novel dual-band, dual-sense, polarization reconfigurable dual coupled line square microstrip patch antenna is proposed. It comprises of a diagonal edge truncated square microstrip patch with a dual coupled line structure. The dual-band operation is realized by using dual coupled lines. They also aid in generating dual-sense of circular polarization (CP) at two resonances. The diagonal edge truncated square patch consists of four PIN diodes along with the bias circuit. It realizes a dual-sense of polarization reconfiguration like right-handed circular polarization (RHCP)/left-handed circular polarization (LHCP), linear polarization (LP)/LHCP, RHCP/LP at lower resonance f1 = 2.4 GHz and higher resonance f2 = 2.6 GHz respectively for different states of the diodes. The proposed antenna is designed, simulated, fabricated, and experimentally tested for validation. The experimental results of −10 dB reflection coefficient, 3 dB axial ratio for CP, gain, and radiation pattern characteristics at the two bands are acceptable and are found to be in concurrence with simulation results in all the states. The proposed antenna would be useful for multifunctional wireless communication applications.

Manipulating Spin‐Dependent Wavefronts of Vortex Beams via Plasmonic Metasurfaces

AbstractConventional metasurfaces based on geometric phase are constrained to spin‐locked phase profile, resulting in mirrored functionalities for different spins. A single flat device that enables independent manipulation of wavefronts in two orthogonal circularly polarized channels is of paramount importance in wireless and optical communications. In this work, by tuning the dimension and rotation angle of H‐shaped meta‐atoms to synthesize propagating phase and geometric phase, spin‐dependent plasmonic metasurfaces are presented to manipulate circularly polarized waves in the visible band. To verify the capability of spin‐dependent wavefront manipulation, three metasurfaces are implemented. The first metasurface generates vortex beams with orbital angular momentum (OAM) l = 1 under left‐handed circularly polarized (LCP) incidence and l = 2 under right‐handed circularly polarized (RCP) incidence. By introducing convolution operation, the second metasurface is capable of producing vortex beams with different OAMs and different directions for two spins. The third metasurface produces dual‐beam and quad‐beam with different OAMs for different circular polarizations. This scheme can provide a new pathway in ultracompact nanophotonic devices and systems.

A 1-bit electronically reconfigurable beam steerable metasurface reflectarray with multiple polarization manipulations

A 1-bit electronically controlled metasurface reflectarray is presented to achieve beam steering with multiple polarization manipulations. A metsurface unit cell loaded by two PIN diodes is designed. By switching the two PIN diodes between ON and OFF states, the isotropic and anisotropic reflections can be flexibly achieved. For either the isotropic reflection or the anisotropic reflection, the two operation states achieve the reflection coefficients with approximately equal magnitude and 180° out of phase, thus giving rise to the isotropic/anisotropic 1-bit metasurface unit cells. With the 1-bit unit cells, a 12-by-12 metasurface reflectarray is optimally designed and fabricated. Under either y- or x-polarized incident wave illumination, the reflectarray can achieve the co-polarized and cross-polarized beam scanning, respectively, with the peak gains of 20.08 dBi and 17.26 dBi within the scan range of about ±50°. With the right-handed circular polarization (RHCP) excitation, the left-handed circular polarization (LHCP) radiation with the peak gain of 16.98 dBic can be achieved within the scan range of ±50°. Good agreement between the experimental results and the simulation results are observed for 2D beam steering and polarization manipulation capabilities.

Modular Optical Diodes for Circular Polarization Based on Glass‐Supported Cellulose Nanocrystal/Polyethylene Glycol Composite Films

Depending on processing methods and conditions, cellulose nanocrystal (CNC) films exhibit linear birefringence or selective Bragg reflection. The latter means reflection of light with left‐handed circular polarization (LCP) due to CNC in a helicoidal microstructure of the same handedness. Herein, glass‐supported CNC/polyethylene glycol (CNC/PEG) composite films with PEG concentrations in the range of 0–30% w/w with selective Bragg reflection at wavelengths from 440 to 550 nm are prepared. A modular device comprised of a dip‐coated birefringent CNC‐glass sample sandwiched between two CNC/PEG‐glass samples shows different responses to light with LCP and to light with right‐handed circular polarization (RCP). The device suppresses selective Bragg reflection from the rear (front) CNC/PEG sample for incident light with LCP (RCP), even when the birefringent film does not meet the condition for a halfwave plate. This behavior resembles the performance of optical diodes for circular polarization. Polarization properties of composite films and optical diodes in terms of degree of polarization and ellipticity are discussed within the Stokes–Mueller formalism. Electromagnetic simulations of Mueller matrices reveal the equivalence of modular and in‐tandem film approaches of optical diodes.

3-bit reconfigurable THz metasurface based on structured light illumination for vortex beams and holographic imaging

Metasurfaces have attracted widespread attention due to their excellent control ability of terahertz wavefronts. Terahertz metasurfaces have made rapid progress in areas such as biological detection, high-speed communication, and imaging. However, terahertz metasurfaces currently have a single function, and the primary goal of this research is to create a reconfigurable and multifunctional terahertz metasurface. In this work, we designed a novel eight-gaps-splits-ring resonator (EGSRR). The EGSRR is filled with photosensitive semiconductor material, and the metasurface unit's amplitude-phase characteristics are controlled by different encodings of structured light. Finally, under the incidence of right-handed circularly polarized (RCP) waves, 3-bit phase encoding of its reflected wave with cross-polarization is achieved. To verify the ability of metasurface to control terahertz wavefronts, the 3-bit metasurface units are assembled into an array to achieve different-order vortex beams and reconfigurable holographic images. The novel optically controlled reconfigurable metasurface not only has promising applications in generating vortex beams and holographic imaging, but it also represents a novel approach to designing multifunctional and programmable terahertz metamaterials.

Circularly polarized MIMO filtering dielectric resonator antenna for 5G sub-6 GHz applications

This research presents an innovative hexagonal dielectric resonator antenna (DRA) with circular polarization and multi-input multi-output (MIMO) characteristics. The DRA consists of two dielectric layers, providing a fractional bandwidth of 9% (4.05 to 4.38 GHz).The antenna ground plane features has an S-shape slot, when coupled with a 50Ω microstrip line, enables the generation of right-hand circular polarization. To enhance performance, the feed line includes a bandpass filter with a semi-elliptical form, resulting in outstanding selectivity. The proposed design demonstrates a gain of 9.2 dBi and encompasses a 3 dB axial ratio bandwidth of 9.29%. The proposed design is fabricated, and a comparison is made between the simulated and the measured results. Furthermore, the study introduces a MIMO antenna system by combining two filter arrays. The MIMO antenna demonstrates a reasonable port isolation of >25 dB across the operating band with acceptable MIMO parameters.

The abruptly autofocusing characteristics of the circular Airyprime beam in a chiral medium

In this paper, the abruptly autofocusing characteristics of the circular Airyprime beam (CAPB) propagating in a chiral medium is investigated for the first time. The results show that the CAPB splits into the left-handed circularly polarized (LCP) and the right-handed circularly polarized (RCP) beams with different propagating trajectories in the chiral medium. The focal length Zf, the depth of focal length Zw and the peak intensity of two focal field spots in the chiral medium can be effectively manipulated by the combination of initial beam parameters of CAPB (the primary ring radius r0, the scaling factor w0 and the exponential decay factor a) and the chiral medium parameter h. In addition, the expression of Zf derived from CAB can be well applied to CAPB. The Zf and the Zw of LCP and RCP components of CAPB and CAB are the same, but the autofocusing ability of CAPB is about 7 times of that of CAB under the same condition in the chiral medium, almost the same as that in free space. Due to the abruptly autofocusing ability and the propagation properties in a chiral medium, the CAPB may have potential applications in many fields such as biomedical treatment and optical manipulation.

Compact wideband printed antenna with circularly polarized tilted beam radiation using a Quasi-Radiator

This paper presents a new compact wideband printed antenna with circularly polarized (CP) tilted beam radiation using a quasi-radiator. To achieve size compactness and tilted CP performance, the radiation patch of a conventional monopole is loaded by a fork-slot, and a shorting via is used to connect the corners of rectangular patch and partial ground plane together. The fabricated prototype has an |S11| < −10 dB of 60.9% (1.2–2.25 GHz), an AR < 3 dB of 25.7% (1.55–2 GHz), a peak gain of 3.7 dBi, a compact size of 0.186λ0 × 0.186λ0 × 0.008λ0 at the lowest frequency with CP radiation, a right-handed CP beam at θ = −42°, and a left-handed CP radiation at θ = −134° in the elevation plane. The antenna is analyzed using characteristic mode analysis (CMA) to figure out the orthogonal modes and working principle of CP radiation. The antenna benefits include low-profile, simple structure, easy fabrication, large tilt angle, and stable radiation patterns over entire bandwidth.

Spin-dependent and tunable perfect absorption in a Fabry-Perot cavity containing a multi-Weyl semimetal.

Spin-dependent absorption has been widely studied in metamaterials and metasurfaces with chirality since it develops significant applications in multiplexed holograms, photodection, and filtering. Here, the one-dimensional photonic crystal Fabry-Perot (FP) cavity containing a multi-Weyl semimetal (mWSM) defect is proposed to investigate the spin-dependent perfect absorption. Results denote that the distinct refractive indices of right hand circularly polarized (RCP) and left hand circularly polarized (LCP) waves are present due to the nonzero off-diagonal term of mWSM, thus supporting the perfect absorption of RCP and LCP waves at distinct resonant wavelengths. The different perfect absorption wavelengths of RCP and LCP waves reveal the spin-dependent perfect absorption. By altering the Fermi energy, tilt degree of Weyl cones, Weyl nodes separation, topological charge, and thickness of the mWSM layer, the perfect absorption wavelength of RCP and LCP waves can be regulated conveniently. Particularly, the linear tunable perfect absorption wavelength with thickness of the mWSM layer supports the accurate determination of perfect absorption wavelength at distinct mWSM thicknesses. Our studies develop simple and effective approaches to acquire the spin-dependent and adjustable perfect absorption without the external magnetic field, and can find practical applications in spin-dependent photonic devices.

(Invited) Photoluminescence-Based Circular Polarization Convertors for Multiplexing of Optical Information

Polarized light has a great potential to provide a variety of optical information at once such as light intensity (brightness), wavelength (color), and polarization. In particular, circularly polarized (CP) light is expected to be used not only for 3D display but also for optical data encryption and anti-counterfeiting, because the polarization plane of CP light rotates during light propagation resulting in no angular dependence on information transmission. The previously reported approaches for creating CP light from unpolarized light can be roughly classified into the filtration using a circular polarizer, the selective reflection by chiral liquid crystals, and the circularly polarized luminescence (CPL) from chiral luminophores. Meanwhile, we have recently proposed a new approach for creating highly-pure CP light by converting linearly polarized luminescence (LPL) using luminescence-based CP convertor (Figure 1a).[1] The unique advantage of the luminescence-based CP convertor lies in the spectral conversion properties of the LPL films which allows multiplexing of optical information by simply laminating LPL films. In this presentation, we introduce the multilayer-type luminescence-based CP convertors (Figure 1b) fabricated by using two or three LPL films showing different PL wavelength.In this study, we selected quantum rods (QRs) and π-conjugated luminescent polymers as one-dimensional (1D) luminophores. As a stretchable transparent polymer, poly(ethylene-co-vinyl acetate) (EVA) was used. LPL films were prepared by uniaxial stretching of the luminophore/EVA composite films. When yellow-, orange-, and red-color-emissive QRs were used as a luminophore, yellow-, orange-, and red-LPL were obtained as shown in Figures 1c-e. By laminating LPL film on the quarter-wave film with the angles between polarization plane of LPL and fast-axis of quarter-wave film were -45˚, 0˚, and +45˚, left-handed (LH-), parallel LP, and right-handed (RH-) CP light were produced, respectively. When the yellow-, orange-, and red-LPL films were laminated at three different angles (-45˚, 0˚, and +45˚) against the fast axis of the quarter-wave film, 3×3×3=27 different pieces of optical information were produced as shown in Figure 1f. Furthermore, time information on CP light can also be multiplexed theoretically by laminating several LPL films showing different fluorescence lifetimes. In this presentation, we will also discuss about time-multiplexing of optical information by multilayer-type luminescence-based CP light convertor consisting of multiple LPL films showing different PL lifetimes.[1] Y. Okazaki et. al., J. Mater. Chem. C, 2022. DOI: 10.1039/d2tc03955a. Figure 1

Design of a multi‐function global navigation satellite system and 5G cellular antenna structure for automotive applications using characteristic mode analysis

AbstractThis paper illustrates a single antenna structure that simultaneously satisfies the antenna requirement for 5G cellular and global navigation satellite systems (GNSS). The antenna has a linearly polarised omnidirectional radiation for the newly defined 5G sub‐6 GHz cellular bands in the 617–5000 MHz frequency range. In contrast, a right‐hand circular polarisation (RHCP) with a hemispherical radiation pattern at the GNSS L1 has a frequency range of 1559–1606 MHz. This multi‐function antenna would provide a simplified product design and better space utilisation, particularly suitable for flat antenna modules and automotive. The primary concept involves employing a planar inverted F antenna structure to generate radiation modes for cellular bands and incorporate U‐slot on the top plate to generate the GNSS radiation modes. The design methodology utilises the characteristic mode analysis tool to tune the desired radiation characteristic mode at the intended frequency range for each function. The antenna was fabricated, and the performance was evaluated on a 1‐m ground plane. The GNSS RHCP gain measures 5 dBc at boresight, with an axial ratio below 2 dB across the L1 bands, while the cellular gain maintains an excellent return loss and omnidirectional radiation pattern performance across the cellular bands.

Multimaterial Additively Manufactured Transmissive Spin‐Decoupled Polarization‐Maintaining Metasurfaces

AbstractTaking advantage of multimaterial additive manufacturing, this work demonstrates a kind of polarization‐maintaining metasurface (MS) for spin‐decoupled beam shaping. The wavefronts of the two spin states, i.e., the left‐hand circular polarization (LHCP) and the right‐hand circular polarization (RHCP), can be independently manipulated while the output spin state remains the same as the input. The meta‐atom is implemented with dual‐polarized antennas at the top and the bottom with phase delay lines connecting them. The dual‐polarized antenna on the receiving side is fixed to receive the LHCP/RHCP incident waves, while the dual‐polarized transmitting antenna is rotated, providing the opposite phase shifts for the LHCP and RHCP. The absolute value of the phase shift is the same as the transmitting antenna's rotation angle. Meanwhile, varying the length of phase delay lines introduces 2π phase shifts for both LHCP and RHCP inputs. Thus, combining the two phase‐shifting degrees of freedom, the LHCP and RHCP wavefronts can be independently controlled while the polarization is not flipped after transmitting through the MS. One MS produces vortex beams with different topological charges for LHCP and RHCP. The other achieves spin‐decoupled focusing. The multilayered MSs are conveniently printed using multimaterial additive manufacturing without postprocessing.

Focusing a vortex beam with circular polarization: angular momentum

Based on the Richards-Wolf formalism, we obtain two different exact expressions for the angular momentum (AM) density in the focus of a vortex beam with the topological charge n and with right circular polarization. One expression for the AM density is derived as the cross product of the position vector and the Poynting vector and has a nonzero value at the focus for an arbitrary integer number n. The other expression for the AM density is deduced as a sum of the orbital angular momentum (OAM) and the spin angular momentum (SAM). We reveal that at the focus of the light field under analysis, the latter turns zero at n = –1. While both these expressions are not equal to each other at each point of space, 3D integrals thereof are equal. Thus, exact expressions are obtained for densities of AM, SAM and OAM at the focus of a vortex beam with right-hand circular polarization and the identity for the densities AM = SAM + OAM is shown to be violated. Besides, it is shown that the expressions for the strength vectors of the electric and magnetic fields near the sharp focus, obtained by adopting the Richards-Wolf formalism, are exact solutions of the Maxwell's equations. Thus, Richards–Wolf theory exactly describes the behavior of light near the sharp focus in free space.