Left-hand Circular Polarization Research Articles

An inverted F-shaped slotted broadband metasurface-based circularly polarized patch antenna for 5G application

This paper presents an inverted F-shaped slotted broadband metasurface (MS)-based circularly polarized (CP) microstrip patch antenna. The host antenna comprises a truncated corner square patch with an inverted F-shaped slot, positioned on a 1.6 mm thick FR-4 substrate backed by ground plane. Concurrently, the MS layer is composed of a 4 × 4 square ring array, constructed on a separate 1.6 mm thick FR-4 substrate with net compact dimensions 0.54λo × 0.54λo × 0.027λo at 5.13 GHz, serving as a superstrate layer. The proposed antenna exhibits impressive performance, including a −10-dB impedance bandwidth from 4.40 GHz to 7.38 GHz as well as a 3-dB axial ratio (AR) bandwidth from 4.74 GHz to 5.52 GHz. Furthermore, at 5.13 GHz, it achieves a notable maximum radiation efficiency and realized gain of 85 % and 6.95 dBic respectively. Moreover, polarization of the antenna is observed as left-handed circularly polarized (LHCP). To validate the impedance response, the antenna’s equivalent circuit model has been sequentially developed, followed by the fabrication of a prototype. The measured results closely resemble with the simulated responses, indicating strong consistency between theory and experimental results. With its overall compact dimension of 0.65λo × 0.65λo × 0.027λo at 5.13 GHz, the proposed CP antenna is well-suited for 5G application.

Multi-band ultrathin reflective metasurface for linear and circular polarization conversion in Ku, K, and Ka bands

Linear polarization (LP) and circular polarization (CP) holds paramount importance in Ku, K, and Ka bands for satellite based communication, and remote sensing applications. Satellite based remote sensing applications face challenges like atmospheric attenuation, noise & interference, and signal degradation. Moreover, satellite based communication application demands CP in two distinct, non-adjacent frequency bands with orthogonal polarizations at greater oblique angles, considering the unpredictable incidence angles of electromagnetic (EM) waves. Addressing these challenges, an innovative metasurface polarization converter is proposed to operate efficiently across the Ku-band (13.5–18.0 GHz), K-band (18.0–26.5 GHz), and Ka-band (26.5–38.5 GHz) frequency ranges. The converter achieves left-handed circular polarization (LHCP) in the Ku- and Ka-bands within the frequency ranges of 14.57–15.65 GHz and 27.47–33.85 GHz for y-polarized incident EM waves. Additionally, it provides right-handed circular polarization (RHCP) in the K- and Ka-bands at 17.27–23.92 GHz and 35.87–38.32 GHz for y-polarized incident EM waves. The LP conversion ratio exceeds 95% in the frequency bands of 15.97–16.85 GHz, 24.70–26.65 GHz, and 34.37–35.45 GHz for y-polarized, LHCP, and RHCP incident EM waves, respectively. The metasurface exhibits robust performance up to incidence angles of 45 degrees under oblique conditions. Experimental validation using traditional board-circuit manufacturing demonstrates close agreement between measured co- and cross-polarized reflection coefficients and simulations in the 13.5–18 GHz, and 24–38.5 GHz frequency range. Thin metasurface with a thickness of only 0.64 = 0.013λo mm, the proposed design outperforms existing studies in the literature, establishing its competitive edge in terms of structure and performance.

On the characterization of reflective surfaces using dual-polarization GNSS-R

Global navigation satellite systems reflectometry (GNSS-R) is a technique to extract information from reflecting surfaces by the reflected GNSS signals. GNSS-R has garnered increasing attention in the scientific literature due to its continuous global coverage and its superior spatial resolution. Moreover, operating in the L-band renders GNSS-R relatively immune to adverse weather conditions and affords high sensitivity to soil electrical properties. This work introduces a new approach with a dual-polarization antenna, left-hand circular polarized (LHCP) and right-hand circular polarized (RHCP), receiving the reflected signal from a sufficiently smooth surface so that all reflected energy arrives from the specular reflection point. The objective is to characterize the reflecting surface by extracting the relative permittivity and conductivity from the reflected signal. In contrast to other studies found in the literature, the reflection of the GNSS signal on different materials, including dielectric and conductive materials is considered. We derive a maximum likelihood estimator (MLE) for estimating the dielectric parameters of the reflective surface and other parameters of the reflected signal. We also derive the respective Cramer–Rao Lower Bound (CRLB) evaluating the performance of the MLE. The attained results are assessed based on the signal-to-noise ratio (SNR) and the angle of reflection of the reflected signal, which are the parameters that predominantly influence the proposed approach. Lower elevation angles, for instance, lead to higher estimation accuracy, while for reflective surfaces composed of metallic materials a higher SNR is needed to yield favorable estimation performance. Regarding dielectric materials, the estimation results are encouraging and thus enable diverse remote sensing applications by GNSS-R using the proposed setup.

Propagation of circularly polarized electromagnetic wave in magnetized spin plasma

The spin effects on the propagation characteristic of circularly polarized electromagnetic (EM) wave in high density strongly magnetized plasma are discussed based on the the classical hydrodynamical model of relativistic spin plasma. The dielectric coefficients for right-hand circularly polarized (RCP) and left-hand circularly polarized (LCP) waves are obtained. Results show that the spin effects can affect the propagation characteristic of circularly polarized EM wave dramatically. Provided the spin effect is strong enough, LCP waves can also propagate in the magnetized over-dense plasma, while RCP waves may not. The strength of spin effects can be enhanced by increasing the plasma density or/and EM wave intensity.

Design of high flexible multi-band conformal printed patch antenna for sub 6 GHz 5G-based vehicular communication

ABSTRACT Vehicular communications (VCs) play a major role in intelligent transportation systems (ITS). In addition to preventing unintentional collisions and traffic jams, this system can lower fuel and energy usage in the transportation system. The Internet of Vehicles emerges by integrating the IoT with vehicles for smooth communication. In IoV, vehicular communications may be from vehicle to infrastructure (V2I), vehicle to vehicle (V2V), vehicle to pedestrian (V2P), and vehicle to network (V2N) or vehicle to roadside unit (V2R). The antenna used in vehicular communication has some problems, such as less efficiency and high return loss. The frequency response in the existing methods should not give sufficient data for selecting a better band. To avoid this kind of issue and improve the performance by selecting a better frequency band, this work presents a highly flexible multi-band conformal printed patch antenna for sub-6 GHz 5 G-based vehicular communication application. The substrate used to design the antenna is polyimide, and the microstrip patch antenna is designed with cross-shaped slots. The multi-band circularly polarised antenna is designed to operate in vehicular communication bands such as 2.4 GHz, 4.7 GHz, 5.3 GHz, and 5.9 GHz. The proposed work is simulated in HFSS, and the results of directivity, gain, reflection coefficient, Voltage Standing Wave Ratio (VSWR), radiation pattern, axial ratio, Left-Hand Circular Polarisation (LHCP), Right-Hand Circular Polarization (RHCP) and surface current distribution are evaluated for the conformal antenna.

Pattern reconfigurable UHF RFID universal reader antenna array

In response to the rising demand for adaptable and versatile RFID reader antenna, this paper presents an integrated reader system featuring an array of four antennas. The primary objective is to design four identical, circularly polarized, high-gain, wide-band antennas that cover the 860–960 MHz UHF RFID band. Each antenna consists of three layers, the radiator and director layers, designed as patch antennas with trimmed edges and a central slot, while the reflector layer is constructed from a copper material. These layers are assembled with four Teflon spacers, and a coaxial connector is utilized for feeding the antenna. An open-circuit stub is used to improve impedance matching. CST Microwave Studio was employed for design optimization. The four sector antennas achieve a 150 MHz bandwidth (833–983 MHz) and a maximum gain of 8.4 dBi. When combined with a four-port RFID reader (ThingMagic M6E), the antenna system generates four electronically switchable beams in the azimuth plane. The proposed antenna exhibits left-hand circular polarization (LHCP) within the RFID ISM band, maintaining an axial ratio (AR) between 1 dB and 3 dB. The antenna array, including the reader and control unit, measures 255 × 255 × 210 mm. Simulation and measurement results confirm the system's performance and functionality.

A 27 ​GHz, simple 2-Bit 1 × 8 phased array

This study demonstrates a simple 2-bit phased array operating at 27 ​GHz that supports one-dimensional beam scanning with left-handed circular polarization (LHCP). The antenna is constructed using a compact four-layer printed circuit board (PCB) structure, consisting of a 90° phase shifter layer with microstrip structures, a ground (GND) layer, a direct current (DC) control layer, and a circularly polarized annular radiation patch layer with 1-bit phase shifting. Based on the proposed unit structure, a 1 ​× ​8 array with half-wavelength inter-element spacing was designed and validated. Experimental results show that the array achieves a peak gain of 10.23 dBi and is capable of beam scanning within ±50°.

Ultra-Thin Metasurface Polarization Converter with Linear and Circular Polarization Features for RCS Applications

AbstractIn this study, an attractive ultra-thin metasurface (MS) converter is proposed for both K-band (18–27 GHz) and Ka-band (27–40 GHz) having the superior performance of the linear-to-linear polarization (LP-LP) conversion and the linear-to-circular polarization (LP-CP) conversion. Its operating bandwidth for the LP-LP conversion is approximately over 18.6–26.7 GHz (lower part of the K-band) with a conversion efficiency of more than 90% and over 19.55–24.8 GHz (upper part of the K-band) with a polarization conversion ratio (PCR) value of more than 99%. In addition, its operating bandwidth for the LP-CP conversion (a left-handed circular polarization (LHCP)) is nearly between 31.8 and 40.5 GHz (Ka-band) with a PCR value of more than 99%. The converter can achieve a PCR value greater than 90% for both the LP-LP and LP-CP conversions for an oblique incidence wave with an incidence angle up to $$ 40^\circ $$ 40 ∘ . The design also provides mono-static radar cross section for the 18.6–26.7 GHz frequency range, where the LP-LP conversion is provided. The proposed structure can be considered to be ultra-thin having a thickness of 1 mm corresponding to 0.075$$\lambda $$ λ in the LP-LP and 0.12$$\lambda $$ λ in the LP-CP cases concerning the center frequency. The cost-effective bandwidths (BWCEs) are 210 and 34 for the LP-LP and LP-CP conversions, respectively. Free-space experiments were carried out at X-band and Ku-band to validate our design.

Achievement splitting for topological states with pseudospin in phase modulation by using gyromagnetic photonic crystals

As we know, valley-Hall kink states or pseudospin helical edge states are excited by polarized-momentum-locking [left-handed circular polarization (LCP) and right-handed circular polarization (RCP)] because the valley-Hall kink modes or pseudospin polarized modes have intrinsic and local chirality, which is difficult for these states to achieve phase modulation. Here we theoretically design and study a compatible topological photonic system with coexistence of photonic quantum Hall phase and pseudospin Hall phase, which is composed of gyromagnetic photonic crystals with a deformed honeycomb lattice containing six cylinders. A typical kind of hybrid topological waveguide states with pseudospin-characteristic, magnetic field-dependent, and strong robustness against backscattering and perfect electric conductor (PEC) is realized in the present system. Furthermore, we re-design a structure with intersection-liked, achieve splitting for one-way pseudospin quantum Hall edge states by using phase modulation. Robustness of the one-way pseudospin-quantum Hall edge states in splitting has been demonstrated as well. Additionally, PEC inserted in transport channel brings optical path difference in waveguide transmission, which would influence splitting for hybrid topological waveguide states in phase difference modulation. This work not only provides a new way for manipulation (i.e., phase modulation) of hybrid topological waveguide states in compatible topological photonic system from distinct topological classes but also has potential in various applications, such as sensing, signal processing, and on-chip communications.

Broadband vortex beam generation by a reflective meta-surface based on a metal double-slit resonant ring

Recently, the meta-surface (MS) has emerged as a promising alternative method for generating vortex waves. At the same time, MS also faces the problem of a narrow bandwidth; in order to obtain a broad bandwidth, the MS unit cell structure becomes more and more complex, which will bring many inconveniences to the preparation process of MS devices. Therefore, we want to design a simple MS unit cell with a multi-frequency selection. In this paper, based on the principle of geometric phase, we design a simple reflective MS unit cell based on a metal double-slit resonant ring. We elaborate on the resonance mechanism of the MS unit cell. Under the normal incidence of circularly polarized (CP) waves, the reflection coefficient of the same polarization was greater than 85%. By rotating the orientation angle of the resonator on the MS unit cell, the continuous 2π phase coverage was satisfied in the frequency range of 0.52–1.1 THz, and the relative bandwidth becomes 71.6%. Based on this, we construct a vortex generator by using a 15×15 MS unit array. The right-handed circularly polarized (RCP) waves and left-handed circularly polarized (LCP) wave are separately incident on MS with topological charges of l=+1,+2,+3 under multiple resonant frequencies. The generated RCP vortex wave has topological charges of l=−1,−2,−3 and the generated LCP vortex wave has topological charges of l=+1,+2,+3. The numerical simulation results demonstrate that our designed MS, capable of achieving multiple resonance outcomes, can effectively operate in a multi-broadband mode and produce a wide-band vortex beam. In addition, we also calculate the pattern purity. Through theoretical analysis and numerical simulation, we prove that our designed MS can generate a broadband vortex wave.

Tunable and strong circular dichroism mediated with graphene-Weyl semimetal planar scheme

Strong circular dichroism (CD) has been observed in Weyl semimetals (WSMs) because of the extremely large gyrotropic optical response. However, traditional proposals cannot tune the wavelength of CD peaks continuously without changing the geometric parameters or external magnetic field, which limits the practical application. This study presents a lithography-free platform exhibits near-unity CD in a WSM-graphene-dielectric structure. It is theoretically shown that the proposal possesses different reflectance properties for right-hand circular polarization and left-hand circular polarization light in the mid-infrared range. The merits of the wide-angular chiral capacity of CP waves can also be maintained. The CD of the chiral structure can be tuned not only by adjusting the structural parameters, but also the chemical potential of graphene, which may also facilitate the design of more efficient chiral optical devices.

Substrate-Integrated Cylindrical Cavity Controlled Hexa-Polarization Flexible Cylindrical Dielectric Resonator Antenna for Ku-Band Applications

A substrate-integrated cylindrical cavity (SICC) fed polarization flexible cylindrical dielectric resonator antenna (CDRA) is presented in this literature. To excite the CDRA, a unique and simple feeding approach based on substrate-integrated waveguide (SIW) technology is demonstrated. This SICC is fed by two 50Ω microstrip lines, oriented orthogonally to each other. The SICC with a cross slot on its top metalized surface and the TM110 mode excites inside it act together to couple energy efficiently to the CDRA. Applying different phase combinations signals at the two input ports of the SICC, the CDRA can radiate in four different orientations linear polarization (LP) (along φ = 0°, 45°, −45°, and 90° ), left-handed circular polarization (LHCP), and right-handed circular polarization (RHCP). A conventional cylindrical dielectric resonator having relative permittivity ϵd = 10 is preferred. Its diameter, height, and cross-slot dimensions are optimized to operate the CDRA over Ku-band with 12% impedance bandwidth, 2-dB axial ratio (AR) bandwidth of 11%, and 3-dB gain bandwidth of 12%. In this operating band, CDRA resonates at three different higher-order modes (HEM32δ, HEM113, and HEM12δ+2) with 8 ± 1.6 dBi/dBic gain for all the polarization states. The measurements of this antenna are conducted using two external phase shifters and one power divider.

A tunable versatile metasurface in terahertz frequency based on graphene–metal hybrid structures

The increasing demands for device integration and reusability have led to the development of freely switchable and dynamically tunable diverse functions in both modern optics and wireless communications. This study proposes a versatile metasurface that integrates with four tunable functions in the terahertz region based on graphene patch and metal split-ring hybrid structures. By adjusting the Fermi level of the graphene patches through electrostatic gating, the proposed metasurface can effectively achieve free switching among four different functions and dynamic tuning of each function's characteristics over a broad frequency band. Moreover, the metasurface operates smoothly in reflection mode for x-polarization, y-polarization, and left-hand and right-hand circular polarization illuminations. All expected performances, including resonant absorption with tunable frequency (relative bandwidth is about 20 %) and regulable absorbance (from 10 % to 100 %), arbitrary interconversion of four polarization states (relative bandwidth is over 48 %), regulation of cross-polarization conversion rate (from 0 % to 100 %), tunable spatial power division (three-way outputs), and dual-channel high-efficiency signal modulation (modulation depth is over 81 %), are demonstrated through full-wave simulation experiments. This study opens up a new avenue for exploring tunable multifunctional integrated devices with graphene materials, with potential applications in various domains, such as wireless communication, terahertz sensing, and imaging.

Compact Dual-Band Circularly Polarized Shared-Aperture Antenna for Satellite Communication Systems

A compact dual-band circularly polarized (CP) shared-aperture antenna is proposed for satellite communication. The antenna enables simultaneous dual-band functionality and CP radiation with right-handed CP in the Ku band and left-handed CP (LHCP) in the Ka band. The shared-aperture is implemented by integrating two independent subapertures, which function through frequency-multiplexed, resulting in a minimized profile (0.04 λ 0 ) and reduced complexity, making it an ideal choice for array applications. To enhance inter-frequency isolation, a circular arrangement of metal vias is incorporated. The measured results indicate that the antenna effectively encompasses a 3 dB axial ratio (AR) bandwidth of 15.6–16.5 GHz in Ku and 26.5–27.5 GHz in Ka bands. Additionally, it exhibits a broader 10 dB impedance bandwidth (IBW) and superior port isolation bandwidth exceeding 30 dB.

Single-fed Ku/Ka dual-band aperture shared planar antenna array for satellite communication

This paper presents a single-fed Ku/Ka dual-band aperture-shared planar antenna array designed for satellite communication. The need to enhance data transmission speeds has driven the exploration of higher frequency bands, such as the Ku-band and Ka-band. Researchers have been investigating the design of multiband antennas to achieve space miniaturization and cost-effectiveness in these higher frequency bands. However, previous works faced challenges, including spatial efficiency limitations, complex radiator structures, band isolation issues, and increased complexity in the feeding network. To address the abovementioned challenges, this paper proposes a single-fed Ku/Ka dual-band shared-aperture planar antenna array. By combining a patch antenna for the Ku-band and a cavity antenna for the Ka-band, a simple and single-fed network is realized. The proposed antenna element is further extended to a linear array antenna and a sequentially rotated array antenna. The implemented sequentially rotated array antenna exhibited a measured impedance bandwidth of 17.4–19.7 GHz (12.4%) and 27.0–29.0 GHz (7.1%). Moreover, the proposed sequentially rotated array antenna demonstrated measured peak gains of 13.7 dBi for right-hand circular polarization in the Ku-band receiver and a measured peak gain of 15.6 dBi for left-hand circular polarization in the Ka-band transmitter, making it highly suitable for satellite communication.

High quality factor and unity circular dichroism enabled by dielectric-Weyl semimetal-dielectric stack

A mid-infrared (mid-IR) chiral absorber based on multilayer films of silicon (Si)/Weyl semimetal (WSM)/Si is proposed and numerically studied. The proposal exhibits high quality factor circular dichroism (CD) with different absorptance properties for right-hand circular polarization (RCP) and left-hand circular polarization (LCP) light. The absorption characteristics have been explored with the generalized 4 × 4 transfer matrix algorithm, and the effects of structural parameters on the circularly polarized (CP) absorptance are systematically investigated. The circular polarization efficiency (η) and CD are defined as crucial parameters for quantifying the chirality response. The results prove that the chiral absorber exhibits extraordinary efficiencies of 1 and 0 for LCP and RCP light at a wavelength of 11.5 μm, respectively. Thus a maximum CD in absorption of unity with a resonant quality factor (Q-factor) of 295 can be obtained. The performance of dual-band chiral responses can be engineered via the thickness of each layer. Moreover, it is identified that the design results in angle-independent performance, which is essential trait for an efficient chiral absorber.

A dual-band dual-sense circularly polarized patch antenna using hybrid capacitive-inductive proximity-coupling feed

This paper presents a new proximity-coupling mechanism between a rectangular patch and a microstrip line with an open circuit terminal. The patch is located to cover both adjacent maximum-voltage (capacitive coupling) and maximum-current (inductive coupling) points of the standing wave on the feedline, and consequently, two orthogonal resonant modes with 90° phase difference are excited on the patch for generating a circularly polarized (CP) radiation. Based on this feeding mechanism, a dual-band dual-sense CP antenna is designed, which is composed of two linear rectangular patch arrays coupled to an open-ending microstrip line. It is realized on a single-layer substrate and its CP rotating sense in each band is opposite to each other. For verification, the antenna operating at 5.0 and 8.0 GHz are designed, fabricated, and tested. Noting that the design concept can be easily implemented to other frequency bands. The measurements result in an impedance-matching bandwidth of 4.72 – 5.10 GHz and 7.50 – 8.20 GHz. The antenna is left-hand CP for the lower band and right-hand CP for the upper band. In addition, the prototype shows a 3-dB axial ratio bandwidth of 4.93 – 5.02 GHz and 7.40 – 8.10 GHz and peak gains of 11.4 and 12.7 dBic at the lower and upper bands, respectively.

Thermally tunable broadband circular dichroism with Weyl semimetal/vanadium dioxide planar structure

Weyl semimetals (WSMs) have lately attracted significant interest because of the intrinsic large gyrotropic optical response and strong chiral anomaly. This study presents a mid-infrared (mid-IR) lithography-free platform exhibits broadband near-unity circular dichroism (CD) with WSM-vanadium dioxide (VO2) dual layers. The optical responses with mid-IR radiation have been explored with the generalized 4 × 4 transfer matrix algorithm. It is theoretically shown that the proposal possesses different absorption characteristics for right-handed circularly polarized (RCP) and left-handed circularly polarized (LCP) light. Theoretical results show that a CD in absorption reaching 0.936 and a g factor of 1.76 under 300 K temperature. The merit of the wide-angular chiral capacity can be maintained. The magnitude and resonance of CD can be tuned not only by adjusting the structural parameters, but also the insulator-to-metal transition (IMT) of VO2, which may facilitate the design of more efficient chiral optical devices.

Broadband intelligent programmable metasurface with polarization-modulated self-adaptive electromagnetic functionality switching

Programmable metasurfaces have received a great deal of attention due to their ability to dynamically manipulate electromagnetic (EM) waves. Despite the rapid growth, most of the existing metasurfaces require manual control to switch among different functionalities, which poses severe limitations on practical applications. Here, we put forth an intelligent metasurface that has self-adaptive EM functionality switching in broadband without human participation. It is equipped with polarization discrimination antennas (PDAs) and feedback components to automatically adjust functionalities for the different incident polarization information. The PDA module can first perceive the polarization of incident EM waves, e.g., linear or circular polarization, and then provide the feedback signal to the controlling platform for switching the EM functionality. As exemplary demonstrations, a series of functionalities in the 9–22 GHz band has been realized, including beam scanning for x-polarization, specular reflection for y-polarization, diffuse scattering for left-handed circular polarization (LCP), and vortex beam generation for right-handed circular polarization (RCP) waves. Experiments verify the good self-adaptive reaction capability of the intelligent metasurface and are in good agreement with the designs. Our strategy provides an avenue toward future unmanned devices that are consistent with the ambient environment.

Decoding the Nature of Coherent Radio Emission in Pulsars I: Observational Constraints

Radio observations from normal pulsars indicate that the coherent radio emission is excited by curvature radiation from charge bunches. In this review, we provide a systematic description of the various observational constraints on the radio emission mechanism. We have discussed the presence of highly polarized time samples where the polarization position angle follow two orthogonal well-defined tracks across the profile that closely match the rotating vector model in an identical manner. The observations also show the presence of circular polarization, with both the right and left handed circular polarization seen across the profile. Other constraints on the emission mechanism are provided by the detailed measurements of the spectral index variation across the profile window, where the central part of the profile, corresponding to the core component, has a steeper spectrum than the surrounding cones. Finally, the detailed measurements of the subpulse drifting behaviour can be explained by considering the presence of non-dipolar field on the stellar surface and the formation of the partially screened gap (PSG) above the polar cap region. The PSG gives rise to a non-stationary plasma flow that has a multi-component nature, consisting of highly energetic primary particles, secondary pair plasma, and iron ions discharged from the surface, with large fragmentation resulting in dense plasma clouds and lower-density inter-cloud regions. The physical properties of the outflowing plasma and the observational constraints lead us to consider coherent curvature radiation as the most viable explanation for the emission mechanism in normal pulsars, where propagation effects due to adiabatic walking and refraction are largely inconsequential.