Left-hand Circular Polarization Research Articles

Design of an Anisotropic Reconfigurable Reflective Polarization Converter for Realizing Circular Polarization-Reconfigurable Antenna

A polarization-reconfigurable antenna is presented here with the help of an anisotropic reconfigurable reflective polarization converter (RRPC). Proposed design consists of a monopole antenna as a source and an electronically switchable polarizer. Depending on the conducting states of only eight PIN diodes, which are placed on the top surface of the polarizer, linearly polarized (LP) wave generated by the monopole can be converted into left-hand circularly polarized (LHCP), right-hand circularly polarized (RHCP), and LP wave. Proposed RRPC has a ground plane on the back side and it is positioned below the source antenna with an air gap of 0.13 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> where λ is calculated at the antenna's operating frequency of 3.5 GHz. Overall configuration of the antenna is compact with a dimension of (0.31×0.31×0.19) λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> . As fewer active elements are used in the proposed design, complexity of the circuit for biasing and losses would be less. To the best of authors’ knowledge, it is first time reported work on active reflective polarizer, which not only has LP-to-CP polarization conversion ability but also it possesses electronic polarization switching ability in between LHCP, RHCP, and LP states.

Polarization-Reconfigurable Compact Wideband Slot Antenna by Using Liquid Metal

In this letter, a compact, low-profile, and wideband slot antenna with polarization reconfigurability is presented by using liquid metal (LM). A small rectangular ring placed below the microstrip line of a symmetric coplanar waveguide (CPW) is used for bandwidth enhancement. Three horizontal currents performed by LM injection are inserted for wide circular polarized excitation. The channel realized by three-dimensional printed technique is loaded on the antenna to provide reconfiguration conditions. By injecting the LM into the left or right channels, the radiation of right-hand circular polarization or left-hand circular polarization is achieved. While when the two channels are empty or both LM injections, the linear polarization (LP) radiations at two operating frequency bands are obtained. A prototype was fabricated and measured. Measurements show that the proposed antenna exhibits a wide impedance bandwidth (IBW) of 67% and an overlapped axial ratio bandwidth of 39.2% for the CP modes. While in the LP states, the overall reconfigurable IBW is 39.7%. Besides, the size of the antenna is 0.30 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">λ</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> × 0.32 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">λ</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> × 0.03 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">λ</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> , which is quite compact and low-profile.

Dual-Band Ultrathin Polarization Converter for S-Band Microwave Transmission

In this letter, a low-profile dual-band frequency selective surface (FSS) is designed as a polarizer for satellite communication. This single-layered FSS with a meandered open loop intersected by a metallic strip behaves as a dual sense polarizer. It converts linearly polarized (LP) EM waves of frequency range 2.01–2.64 GHz into left-hand circularly polarized (LHCP) EM waves. Similarly, the LP waves in the frequency range of 3.26–3.68 GHz are converted into right-hand circularly polarized (RHCP) EM waves. The unit cell dimension of the compact polarizer is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.075\lambda _{0} \times 0.075\lambda _{0} \times 0.005\lambda _{0}$ </tex-math></inline-formula> , where <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda _{0}$ </tex-math></inline-formula> stands for free space wavelength at the lowest cut-off frequency. This study explores the structural design evolution of the proposed polarizer and verifies the frequency behavior of the structure using a circuit model. The simulated performance of the dual-band polarizer is experimentally tested. Good concordance is observed between the simulated and measured results.

Dual Circularly Polarized Broadband Antenna Array for Millimeter-Wave Applications

A planar dual circularly polarized (CP) broadband array is proposed in this letter. The antenna consists of two semicircular patches and two suspended metal posts. According to the investigation of our previous work, the circularly polarized mode generated by combining the patches and the metal posts can achieve very wideband CP radiation. In order to achieve dual CP radiation with similar performance, a new antenna element is proposed with a centrally symmetrical configuration. The orthogonally crossed slot etched on the substrate-integrated waveguide cavity is used to excite the antenna element. A 4×4 array is designed, fabricated, and tested. Measured results show that a 3 dB AR bandwidth of 28.28% (26–34.6 GHz) and 30.61% (26–35.4GHz) is achieved for left-handed CP (LHCP) and right-handed CP (RHCP) radiation, respectively. The 3 dB gain bandwidth of 22.81% (26.4–33.2 GHz) and 24.50% (26–33.26 GHz) for these two polarizations is obtained. The proposed array demonstrates the feasibility of dual-polarized radiation. It features the advantage of wide bandwidth, easy integration, and low cost, which is very suitable for millimeter-Wave system applications.

Dual-function polarization converter of an all-dielectric metasurface with a chiral L-type meta-atom

We propose a dual-function metasurface with a chiral double L-type silicon meta-atom that works in the near-infrared band. On one hand, the designed metasurface can achieve the function of a quarter-wave plate in the wavelength of 1660–1840 nm, and convert y -linear polarization (LP) light into right-hand circular polarization (RCP) light. The polarization conversion ratio (PCR) is above 90%, up to 98%, and the ellipticity of the transmitted light is 0.9–1.0. On the other hand, for a wavelength of 1497 nm, the designed structure can also convert LP in any direction to left-hand circular polarization (LCP) light by using the circular dichroism of chiral structures. The PCR is above 99%, and the ellipticity of the transmitted light is equal to approximately − 1 . Moreover, when incident in the opposite direction, the wave plate can convert LP to RCP light. At present, the all-dielectric metasurface has important application potential in polarization conversion and photonic integration.

Directional Chiral Optical Emission by Electron-Beam-Excited Nano-Antenna

Manipulating directional chiral optical emissions on a nanometer scale is significant for material science research. The electron-beam-excited nanoantenna provides a favorable platform to tune optical emissions at the deep subwavelength scale. Here we present an L-shaped electron-beam-excited nanoantenna (LENA) with two identical orthogonal arms. By selecting different electron-beam impacting sites on the LENA, either the left-handed circularly polarized (LCP) or the right-handed circularly polarized (RCP) emission can be excited. The LCP and RCP emissions possess different emission directionality, and the emission wavelength depends on the arm length of the LENA. Further, we show a combined nanoantenna with two LENAs of different arm lengths. Induced by the electron beam, LCP and RCP lights emit simultaneously from the nanoantenna with different wavelengths to different directions. This approach is suggested to be informative for investigating electron-photon interaction and electron-beam spectroscopy in nanophotonics.

Directional Chiral Optical Emission by Electron-Beam-Excited Nano-Antenna

Abstract Manipulating directional chiral optical emissions on a nanometer scale is significant for material science studies. The electron-beam-excited nanoantenna provides a favorable platform to tune optical emissions at the deep subwavelength scale. Here we present an L-shaped electron-beam-excited nanoantenna (LENA) with two identical orthogonal arms. By selecting different electron-beam impacting sites on the LENA, either the left-handed circularly polarized (LCP) or the right-handed circularly polarized (RCP) emission can be excited. The LCP and RCP emissions possess different emission directionality, and the emission wavelength depends on the arm length of the LENA. Further, we show a combined nanoantenna with two LENAs of different arm lengths. Induced by the electron beam, LCP and RCP lights emit simultaneously from the nanoantenna with different wavelengths to different directions. We suggest this approach is informative for investigating electron-photon interaction and electron-beam spectroscopy in nanophotonics.

A Low-Profile and Compact Multi-Functional ENG-TL Inspired Antenna with Hybrid Polarizations for LTE/UMTS, WiMAX, and WLAN Applications

A novel low-profile, compact tri-band linearly and dual-sense circularly polarized (CP) antenna realized using via-less epsilon negative transmission line (ENG-TL) is investigated in this paper. The antenna miniaturization has been achieved by the zeroth-order resonance (ZOR) property of ENG-TL, which is actuated by connecting closed-loop octagonal ring radiator to an elliptical stub through a meandered-line structure. Circular polarization is accomplished by etching an L-shaped slot in the partial ground plane. The measured S11 result demonstrates that the proposed antenna features triple-band characteristics spanning from 2.42 to 2.50 GHz, 3.29 to 3.59 GHz and 5.43 to 5.55 GHz with centre frequencies of 2.46, 3.44, and 5.49 GHz, respectively. The antenna is offering linear polarization (LP) in the first and third bands while radiates left-handed CP in the + Z direction in the second band. An exceptional axial ratio (AR) of 0.062 dB has been achieved at 3.49 GHz with 3 dB axial ratio bandwidth (ARBW) extending from 3.35 to 3.67 GHz. This antenna offers an average simulated gain of 1.7 dBi across the CP band while 2.06, 1.75 and 3.67 dBi are acquired at 2.59, 3.53 and 5.62 GHz, respectively. Beside low-profile (0.013λ0 height) and miniaturized size (0.287λ0 × 0.205 λ0 ), intended antenna exhibits extended −10 dB impedance bandwidth, wide 3 dB AR bandwidth and reasonable radiation performance. It covers relevant frequency bands; therefore, it has the potential to be employed in 2.5 GHz LTE/UMTS, 3.5 GHz WiMAX, and 5.5 GHz WLAN applications.

A circularly polarized pyramidal horn antenna based on substrate integrated waveguide

A circularly polarized pyramidal horn antenna based on substrate integrated waveguide (SIW) technology is proposed and developed for Ku-band applications. The proposed horn antenna is excited by the upper and lower SICL differential feed networks placed vertically to each other, so that two orthogonal waveguide modes with the equal amplitude are generated at the horn aperture. A 90° coupling network based on SICL technology is proposed to achieve a 90° phase difference between the two orthogonal waveguide modes, thus realizing the function of left-hand circular polarization (LHCP) and right-hand circular polarization (RHCP) of the horn antenna. In addition, in order to make the phase distribution of the horn aperture more uniform, a cross metal strip structure at the horn aperture is proposed, thereby improving the radiation efficiency. The proposed horn antenna is manufactured by using low-cost printed circuit boards (PCBs) process. The measured results show that the proposed circularly polarized pyramidal horn operates at center frequency 12.5 GHz, the measured gain is 8.4 dBi, the relative standing wave and axial ratio (AR) bandwidth are approximately 24% and 5%, respectively. And the radiation aperture efficiency is as high as 78.5%. The developed circularly polarized pyramidal horn antenna can be applied in the field of satellite communications.

A high efficiency ultra-wideband circular-to-linear polarization conversion metasurface

In this work, an 8-shaped metasurface is proposed for circular-to-linear (CTL) polarization conversion, which is an orthotropic anisotropic structure composed of an array of 8-shaped metal patches printed on a grounded dielectric substrate and covered by a top dielectric layer. Because the 8-shaped metasurface has an appropriate anisotropy, which can make the reflection phase difference under u- and v-polarized incidences close to +90∘ in an ultra-wide frequency range, it can be used as an ultra-wideband CTL polarization conversion metasurface. Numerical simulated results show that the 8-shaped metasurface can achieve high-efficiency ultra-wideband CTL polarization conversion, it can convert right-handed circular-polarized (RHCP) wave to a y-polarized one and convert left-handed circular-polarized (LHCP) wave to a x-polarized one in the ultra-wide frequency band from 8.34 to 26.06 GHz with a relative bandwidth of 103.0%, and the polarization conversion rate (PCR) can be kept larger than 99.6% in the total working band. Finally, an experimental verification is carried out, and a reasonable agreement is observed between the simulated and experimental results.

Circular-Polarization-Selective Metasurface and Its Applications to Transmit-Reflect-Array Antenna and Bidirectional Antenna

In this article, a cascaded metasurface (MS) with circular-polarization-selective properties is proposed, which can achieve high reflection for left-handed circular polarization (LCP) and high transmission for right-handed circular polarization (RCP). Such MS, constructed by cascading two kinds of MS sheets, can conduct decoupled geometric phase modulations for the LCP reflection channel and RCP transmission channel by respectively rotating the two elements in the two MS sheets. In order to show its practical applications, first, the proposed MS is applied to design a reconfigurable circularly polarized (CP) transmit-reflect-array antenna (TRA) that can be switched between a high-gain LCP transmitarray antenna and a high-gain LCP reflectarray antenna (RA) dependent on the polarization state of the feed antenna. The simulated results validate its function-switchable and high-gain characteristics. Second, a CP bidirectional antenna is designed utilizing the proposed MS and validated by a fabricated prototype with good agreement between the measured and simulated performances. The results indicate that the joint bandwidth (BW) for both forward and backward aperture efficiencies larger than 20% and axial ratios smaller than 3 dB is about 16% (9.4–11 GHz), across which the antenna realizes bidirectional high-gain and high-purity LCP radiations.

Electrically Small Circularly Polarized UWB Intraocular Antenna System for Retinal Prosthesis.

This paper presents the design of an electrically small circularly polarized (CP) 3 × 3 mm2 antenna system as an intraocular unit for retinal prosthesis application. The system is operating in ISM and ultra-wideband (UWB) bands to target high programmability of retina stimulation and recording, respectively. The electrical dimensions, including the ground plane, are λ0/41 × λ0/41 × λ0/191. Physical limitations of the antenna are discussed based on Hansen and Collin's limitations. The proposed wire patch antenna exhibits wideband characteristics by combining multiple modes of the patch antenna in the presence of an interface PCB circuit. By loading polyimide encapsulated patch with stubs, dominant TM010 mode is combined with the higher order modes TM020-TM070 to exhibit wide -10 dB impedance bandwidth of 2-11 GHz. Annular rings and shorting pins in the ground plane provide CP radiation at 2.45, 5.8, and 8 GHz with 3-dB axial-ratio bandwidth of 0.3, 0.16, and 1.2 GHz, and far-field left hand circularly polarized (LHCP) gain of -18.4, -7.6, and -4.7 dBic, respectively, in broadside direction. A biocompatible antenna system is designed using Ansys HFSS in the presence of a detailed multilayer canonical eye model. Additionally, it is examined in an anatomical HFSS head model. Near and far-field electric field distribution is studied along with peak 1-g average specific absorption rate (SAR) calculations. The proposed antenna is fabricated, and the performance, including coupled power from an external antenna, is measured in a custom made eye model including head phantom. A reasonable agreement is obtained between simulated and measured results. To generate an artificial vision, image perception capability could be improved with implantable UWB communication systems that feature particularly high data-rate and small size.

Circularly Polarized Beam-Steering Microstrip Leaky-Wave Antenna Based on Coplanar Polarizers

A periodic frequency-scanning one-dimensional microstrip leaky-wave antenna with circular polarization is proposed in this letter. The introduction of the novel square patch and stub, which are printed on the same layer of the microstrip array, can effectively transform the polarization type into left-handed circular polarization (CP). The two parasitic elements in each unit cell can be excited by the host meandering microstrip line without extra feeding networks, which introduce one orthogonal polarized wave to satisfy the condition of CP radiation. A prototype includes nine modified unit cells is fabricated and measured. The designed antenna covers an impedance bandwidth over 26.1% with | <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> | < −10 dB and a CP bandwidth over 11.2% with |AR|< 3 dB in the measurement. The main beam scans from −4° to 18° in the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">yoz</i> plane (beam scanning plane) through broadside direction (0 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> ) while maintaining good CP property.

Coupling receiver–transmitter metasurface-based Fabry–Pérot resonant antenna with dual circular polarization

AbstractThis study presents a dual-circularly polarized (CP) Fabry–Pérot (FP) antenna, employing a novel receiver–transmitter (RT) metasurface (MS). The RT-MS unit cell consists of two identical neighboring substrates, with a three-layer metal coating printed on their surfaces. The bottom patch is adopted as a receiver to transfer electromagnetic waves to the top-corner cut patch, passing through the coupling cross-slot sandwiched in the middle. The RT-MS has high reflectivity to achieve a high gain. Through energy and a cross-slot, high aperture efficiency can be realized. A conventional corner cut patch can excite a CP mode of equal magnitude and a 90° phase difference. The RT-MS is arranged in 12 × 12 unit cells and used as a superstrate for a dual-CP antenna. Two orthogonally etched slots fed by two branch-matched orthogonally arranged feed lines are used as feeders to produce perpendicular linearly polarized waves. To enhance the bandwidth and improve the gain, double identical stack substrate patches are placed at the top side of the slot with no air gap, for a wide impedance band and high gain. Two wide CP bands, left-hand circular polarization and right-hand circular polarization, of 12.21–13.1 GHz (7.03%) and 12.35–13.1 GHz (5.89%), respectively, have maximum high gains of 16.5 and 15.97 dBic at 12.58 and 12.7 GHz, respectively, with a compact size of 2.6λ0 × 2.6λ0, suggesting better properties than recent antennas. The aperture efficiency can reach 63.2%. Thus, the RT-MS-based FP antenna is a good candidate for commercial and military communication systems.

Generation of multi-OAM beams using a compact dual-mode source and a 3D-printed Luneburg lens.

In this paper, a Luneburg lens-based multi-beam orbital angular momentum (OAM) antenna is proposed to achieve the 2D beam scanning capability of dual-mode OAM beams. The proposed design is composed of nine compact dual-mode antennas as sources, and a 3D-printed Luneburg lens. The sources, i.e., octagonal patch antennas, can radiate both right-handed circularly polarized (RHCP) and left-handed circularly polarized (LHCP) OAM beams with mode number l = ±1 by switching the input ports. Then, the sources are put at multiple focal points of the Luneburg lens to generate the OAM beams in different directions, and the directivities of the OAM beams are also enhanced by the Luneburg lens. The proposed design can realize nine dual-mode OAM beams with ±30° beam scanning range in two orthogonal planes. It should be noted that the proposed design can be expanded to achieve a larger number of beams with a periodic extension of the source antennas, also a wider beam scanning range with a Luneburg lens of a larger radius.

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.

Three-Dimensional Printed, Dual-Band, Dual-Circularly Polarized Antenna Array Using Gap Waveguide Technology

A gap waveguide (GW)-based 4 × 4 dual-band, dual-circularly polarized antenna array is proposed. The antenna is composed of two stacked layers which are responsible for right-handed circularly polarized (RHCP) radiation in K-band and left-handed circularly polarized (LHCP) radiation in Ka-band. Each stacked layer consists of a GW power distribution network to excite 16 radiating units from a single input. A waffle grid is mounted on top of the array structure to increase effective aperture areas and reduce grating lobes. A prototype was fabricated using stereo lithography appearance (SLA) 3D printing and metallization technology, which significantly decreased the fabrication cost and complexity. Measurement results for the antenna prototype demonstrate the operating bandwidths of 19.91–20.52 GHz in K-band and 28.26–29.19 GHz in Ka-band, over which the reflection coefficients of &lt;−10 dB and axial ratios of &lt;3 dB are achieved. The prototype provides peak gains of 20.1 and 20.3 dB with total efficiencies of &gt;90% in the two respective bands. The combination of dual-band, dual-circularly polarized capability, high gain, high efficiency, lightweight, low cost and compact size renders the proposed design a potential candidate for commercial millimeter wave communication applications.

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.

Stokes polarimetry with Poincaré–Hopf index beams

Polarization structured beams have immense potential in various applications. Poincaré–Hopf (PH) index beam contains structured polarization distribution represented by a ring corresponding to a constant latitude on the standard Poincaré sphere. These structured beams can be represented by points on a recently introduced higher order Poincaré sphere (HOPS). For every PH index, HOPS can be constructed. Beams exhibit diverse properties depending on the polarity and magnitude of the PH index. Two examples of positive PH index beams are the most commonly encountered beams with radial and azimuthal polarization distributions. Negative PH index beams are polarization structured optical beams in which the symmetry in the polarization distribution is not readily discernible. There can be a set of holonomically constrained polarization transformations that can be represented as trajectories on the surface of HOPS. With the advent of nanostructured metasurface optics, it is possible to fabricate elements that perform this set of holonomically constrained transformations. This mapping is useful in the study of the acquisition of topological phases of these beams. Further identifying the coordinates of the input and output beams can be useful in the study of chirality and dichroism. Chirality is due to differential phase shifts, whereas circular dichroism is due to differential absorption between the right and left handed circular polarization components. We present here a method called Stokes polarimetry on HOPS beams that can precisely locate the HOPS latitude and longitude coordinates for a given beam. This method is based on single intensity measurement and is envisaged to play a paramount role in the practical use of HOPS and unveiling its potential.

A simple coplanar waveguide fed polarization reconfigurable antenna design

A coplanar waveguide (CPW) fed polarization reconfigurable antenna for WLAN 2.4 GHz operation is studied. To achieve reconfiguration between left-hand circular polarization (LHCP), right-hand circular polarization (RHCP), and linear polarization (LP) with broad CP and LP operating bandwidths, the technique of switching only two PIN diodes embedded between the CPW feeding line and an open square-ring radiating element is introduced. As the radio frequency (RF) and direct current (DC) signals must be fed from the same feeding line (input port), during the experiment, an additional Bias-Tee element is introduced to the input port for combining the two signals.