High Circular Polarization Research Articles

Simulation of Pol-SAR Imaging and Data Analysis of Mini-RF Observation From the Lunar Surface

High circular polarization ratio (CPR) characteristics were found in permanently shaded regions (PSRs) near the lunar poles. High CPR was regarded as a water ice index. The compact-polarimetric (CP) miniature radio frequency (Mini-RF) radar transmits left-circularly polarized signals and receives horizontally polarized ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$S_{\text {HL}}$ </tex-math></inline-formula> ) and vertically-polarized ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$S_{\text {VL}}$ </tex-math></inline-formula> ) echoes from the lunar surface. Statistics of the CPR data show its relations with the relative phase ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\delta$ </tex-math></inline-formula> ) between <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$S_{\text {HL}} $ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$S_{\text {VL}} $ </tex-math></inline-formula> and the degree of polarization ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$m$ </tex-math></inline-formula> ) but few interpretations were provided. The average CPR data reach the maximum and minimum at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\delta =\pm 90^{\circ }$ </tex-math></inline-formula> , respectively. As <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$m$ </tex-math></inline-formula> becomes very small, the CPR approaches 1. It has been found that CPR is also affected by surface roughness and incidence angle of radar waves. The CPR is now expressed in CP mode to explain the Mini-RF observation. Full-polarimetric radar echoes and CP parameters of the lunar surface are numerically simulated using the bidirectional analytic ray-tracing method. Single-bounce and multiple-bounce scattering components are included in the simulation. Radar images of the lunar crater are simulated with the digital elevation model (DEM) data. The <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$H-\alpha $ </tex-math></inline-formula> decomposition derived from the full-polarimetric simulation is presented to analyze <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\delta $ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$m$ </tex-math></inline-formula> . Simulated radar images with different surface roughness are analyzed statistically to study the functional dependences of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\delta $ </tex-math></inline-formula> , <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${m}$ </tex-math></inline-formula> , and CPR on incidence angle and roughness. Relationships among <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\delta $ </tex-math></inline-formula> , <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$m$ </tex-math></inline-formula> , and CPR are used to analyze the effects of incidence angle, roughness, TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , and rock abundance on the scattering components. The CPR, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$m$ </tex-math></inline-formula> , and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\delta $ </tex-math></inline-formula> of PSR craters of different ages are compared with those of nonpolar craters. The results indicate that the CPR, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$m$ </tex-math></inline-formula> , and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\delta $ </tex-math></inline-formula> are unlikely to be unambiguous evidence of water ice.

Regulating Circularly Polarized Luminescence of Axially Chiral Anthracene Derivatives through Solvatochromism and Supramolecular Self‐assembly

AbstractTwo axially chiral fluorophores derived from anthracene were designed and synthesized, and the chiroptical behaviour were thoroughly investigated including solvent‐dependent emission and circularly polarized luminescence (CPL). Interestingly, unexpected supramolecular self‐assembly of the chiral molecules driven by strong π−π interaction can enable significant hypsochromic shift and fluorescence intensity enhancement. Meanwhile, the luminescence dissymmetry factor of CPL activity exhibited significant enhancement through self‐assembly process. This work provides a novel approach to achieve the supramolecular CPL materials possessing both high luminescence quantum efficiency and high circular polarization.

Dual Mode Dual-Band Circularly Polarized Modified Square Ring Antenna

This paper proposes a dual-band circularly polarized (CP) modified square ring antenna. The resonate structure of this antenna consists of a modified square ring patch and a ground plane, and the antenna is fed by a modified L probe with two unequal branches. A low order CP mode (TM11 Mode) and a high order CP mode (TM12 Mode) are both excited in this simple structure for the dual band operation. The truncated corners of the ring and the embedded corners of the slot are used to obtain the dual band CP operation. The overall size of the antenna is 150 × 150 × 11.7 mm3. The measured 10-dB return loss bandwidths are 13.0% for the lower 2.45 GHz band and 37.4% for the upper 5.8 GHz band. The measured 3-dB axial ratio bandwidths are 2.1% and 5.8% for the lower band and upper band respectively. The measured peak gains of the lower band and upper band are 8.19 dBic and 9.44 dBic respectively.

Achieving Circularly Polarized Surface Emitting Perovskite Microlasers with All-Dielectric Metasurfaces.

Micro- and nanolasers are miniaturized light sources with great potential in optical imaging, sensing, and communication. While various micro- and nanolasers have been synthesized, they are mostly linearly polarized and thus strongly restricted in many new applications, e.g., chiral resolution in synthetic chemistry, cancerous tissue imaging, information storage, and processing. Herein, we experimentally demonstrate the circularly polarized surface emitting perovskite lasers by integrating the as-grown perovskite microcrystals with an all-dielectric metalens. The perovskite microcrystal serves as an optical microcavity and produces linearly polarized laser emission, which is collected by a geometric phase based TiO2 metalens. The left-handed circularly polarized components are collimated by the metalens into a directional laser beam with a divergent angle of <0.9°, whereas the right-handed components are strongly diverged by the same metalens. Consequently, the right-handed circularly polarized components are filtered out, and perovskite lasers with high directionality and pure circular polarization have been experimentally realized.

High Performance Circularly Polarized MIMO Antenna with Polarization Independent Metamaterial

This paper presents a high performance circularly polarized multiple input multiple output microstrip patch antenna which is suitable for current high data rate requirements. Circular polarization has been achieved by dual feeding the signals in phase quadrature to the patch antenna. A polarization independent metamaterial has been designed. The designed metamaterial is used to enhance the gain of the antenna and used as a superstrate of this patch antenna. Using metamaterial superstrate, a gain as high as 13.6 dBi with a bandwidth of 15.4% has been achieved at 11 GHz. The structure has been fabricated and the simulated results are in good agreement with the measured results. Circular polarized antenna also reduces the delay spread due to multipath environment and provides high latency.

A Broadband High Gain Circularly Polarized Antenna System for Cognitive Radio

A Broadband High Gain Circularly Polarized Antenna System for Cognitive Radio

High circular polarization of near-infrared light induced by micron-sized dust grains

ABSTRACT We explore the induction of circular polarization (CP) of near-infrared light in star-forming regions using three-dimensional radiative transfer calculations. The simulations trace the change of Stokes parameters at each scattering/absorption process in a dusty gas slab composed of aligned grains. We find that the CP degree enlarges significantly according as the size of dust grains increases and exceeds ∼20 per cent for micron-sized grains. Therefore, if micron-sized grains are dominant in a dusty gas slab, the high CP observed around luminous young stellar objects can be accounted for. The distributions of CP show the asymmetric quadrupole patterns regardless of the grain sizes. Also, we find that the CP degree depends on the relative position of a dusty gas slab. If a dusty gas slab is located behind a star-forming region, the CP reaches ∼60 per cent in the case of 1.0 µm dust grains. Hence, we suggest that the observed variety of CP maps can be explained by different size distributions of dust grains and the configuration of aligned grains.

Design of High-Gain Circularly Polarized Antennas Based on Vehicle Application Environment

In this paper, a novel circularly polarized (CP) antenna that achieves high gain by maximizing the radiation aperture utilization is proposed for vehicle applications. The realization of increasing the radiation aperture is based on the application environment, making full utilization of the vehicle roof, a large metal reflector beneath the antenna, which is indispensable in the vehicle application. Developed from the structure of typical microstrip patch antenna, the design extends the radiation patch to cover the side of the dielectric substrate, which increases the size of the radiating patch without increasing the antenna's outline size. To make CP antennas more suitable for special working environments with large reflecting surface, a sequential rotation feeding structure with 90° progressive phase difference is uniquely designed based on the active port impedance of the four-ended radiation structure. This co-design method introducing the active port impedance of a multi-port radiator into the design of feeding network as the loads can effectively guarantee the CP performance of the antenna, and can greatly simplify the optimization work in the subsequent stage. Based on this design idea, a prototype working at 1.48 GHz with a 50-MHz bandwidth is designed for vehicle satellite broadcasting application. Experimental results show that the antenna achieves a high CP gain greater than 7 dBic with a compact size of $50 \times 50 \times 10\,\,mm^{3}$ ($0.247\lambda _{0} \times 0.247\lambda _{0} \times 0.05\lambda _{0}$ , $\lambda _{0} $ is the wavelength of working frequency in free space).

Dual-Band and High-Efficiency Circular Polarization Convertor Based on Anisotropic Metamaterial

In this paper, a dual-band and high-efficiency circular polarization (CP) convertor based on anisotropic metamaterial (AMM) was proposed and investigated in microwave region. The proposed AMM based CP convertor is composed of a sub-wavelength metal grating sandwiched with bi-layered disk-split-ring (DSR) structure array, which can convert the normal incident CP wave to its orthogonal one around two adjacent frequency ranges. Based on the intrinsic anisotropic and Fabry-Perot-like cavity-enhanced effect, a high CP conversion efficiency can be achieved by applying the proposed AMM. Numerical simulation results indicate that the cross-polarization transmission coefficients can achieve maximum values of 0.84 at 4.5 GHz, and 0.92 at 7.9 GHz, respectively, which is in well agreement with experiment. In addition, the measured CP conversion efficiency is beyond 99% at resonance frequencies. The mechanism of the CP conversion properties can be explained by the electromagnetic (EM) interference model and the simulated electrical field distribution. Due to its excellent polarization conversion properties, the proposed CP convertor based on AMM structure shows potential application in such as radar, remote sensing, and satellite communication.

A low‐profile circularly polarized transmitarray antenna using rotated cross dipole elements

A low profile circularly polarized (CP) transmitrarray using double-layer cross dipole elements is presented in this letter. The proposed element exhibits an overall thickness of only 0.22λ0, which offers the advantages of light weight, easy fabrication, and low cost compared to conventional transmitarray elements. The transmission coefficient of the element is analyzed by Ansys HFSS, and the results show that the element manifests a high transmission rate and good CP performance. Then, by using angular rotation technique, transmitarray with this type of element is designed, fabricated, and tested. The size of the transmitarray is 6.6 × 6.6λ0 at the center frequency of 10 GHz. The measured peak gain is 22.5 dB at 9.5 GHz, resulting in an aperture efficiency of 36%. The measured 1-dB gain and 3-dB axial ratio bandwidths are 10.2% and 12%, respectively.

Beam-Switching High Gain CP Graphene ME-Dipole Antenna for 5G MIMO Communications

A wideband circularly polarized (CP) graphene-based magneto-electric (ME) antenna with reconfigurable radiation characteristics for 5G MIMO communications is presented in this paper. It consists of graphene patches deposited on silicon oxide substrate arranged horizontally and vertically to act as a ME-antenna. The reconfigurable conductivity of graphene is used to control the operating bandwidth of the antenna. The single element has an impedance matching bandwidth of 78.3 % with the circular polarized band of 61.2% for applying chemical potential, µc=2 eV. The effect of changing the graphene reconfigurable conductivity on the radiation characteristics of the ME-antenna is investigated. The operating bandwidth is controlled by proper biasing the graphene sheet. The peak gain and the antenna efficiency are increased with increasing the chemical potential value due to the increase in graphene conductivity. The mutual coupling between ME-antenna elements is investigated for linear and circular arrangement. Octagonal array consists of 8-similar elements are constructed to produce electronic beam switching in different directions. Single beam, dual-beams, and omni-directional beam is achieved by controlling the graphene conductivity of single, two, and all the ME-elements in the array. Three ring array are designed to switch the beam in different angles for highest coverage area.

High Green Brightness Circularly Polarized Electroluminescence Regulated by Rigid Chiral D-A Type Emitters

In this paper, a pair of rigid chiral D-A type enantiomers (S-/R-2) incorporating the pyrene moiety as the donor and 1,8-naphthalimide as the acceptor was chosen as circularly polarized electrolumi...

Optical observations and cyclops post-shock region modelling of the polar V348 Pav

ABSTRACT Post-shock regions (PSR) of polar cataclysmic variables (CVs) produce most of their luminosity and give rise to high circular polarization in optical wavelengths and strong variability on the white dwarf (WD) rotation period, which are distinctive features of these systems. To investigate the polar candidate V348 Pav, we obtained a comprehensive observational set including photometric, polarimetric, and spectroscopic data, which was used to constrain the post-shock properties of the system. The object presents high circular polarization (∼30 per cent) and high He ii 4686 Å to H β line ratio, confirming it is a polar. From both radial velocities and light curves, we determined an orbital period of 79.98 min, close to the orbital period minimum of CVs. The H β radial velocity curve has a semi-amplitude of 141.4 ± 1.5 km s−1. Doppler tomography showed that most of the spectral line emission in this system is originated in the region of the companion star facing the WD, possibly irradiated by the emission related to the PSR. We modelled the PSR using the cyclops code. The PSR density and temperature profiles, obtained by a proper solution of the hydrothermodynamic equations, were used in a 3D radiative transfer solution that takes into account the system geometry. We could reproduce the V348 Pav B, V, R, and I photometric and polarimetric data using a model with a WD magnetic field of ∼28 MG, a WD mass of ∼0.85 M$\odot$, and a low (∼25°) orbital inclination. These values for the WD mass and orbital inclination are consistent with the measured radial velocities.

High efficiency active wavefront manipulation of spin photonics based on a graphene metasurface.

Metasurfaces have been widely studied for manipulating light fields. In this work, a novel metasurface element is achieved with a high circular polarization amplitude conversion efficiency of 88.5% that creates an opposite phase shift ranging from -180° to 180° between incidence and reflection for different spin components. By arranging the elements according to different requirements, spin-dependent reflection, focusing and scattering are demonstrated. It is also demonstrated that tuning of the Fermi energy is an viable way to active control the circular polarization conversion efficiency and expand the applicable bandwidth. The results open a new route for modifying and designing the wavefront of circular polarized light.

A High-Gain Circularly Polarized Antenna Using Zero-Index Metamaterial

In this letter, a novel high-gain circularly polarized (CP) antenna based on the zero-index metamaterial (ZIM) is presented. A square ring with two asymmetrical splits is used as a unit cell to achieve high gain and circular polarization. The 9 × 9 periodic array unit cells act as an aperture efficient focusing metasurface lens and polarization converter for a primary source antenna. The focusing effect of the ZIM enhances the gain of the microstrip patch antenna placed above it by an amount of 5–6 dB. Also, the ZIM converts the linearly polarized wave emitted by the patch antenna into circularly polarized waves. The circular polarization is achieved by optimizing the two split gaps on the ring of the unit cell, which gives two orthogonal polarizations with the required phase. The proposed design is fabricated and verified experimentally. The prototype has measured impedance bandwidth from 7.04 to 7.68 GHz. The 3 dB axial ratio is achieved from 7.11 to 7.56 GHz, with a peak gain of 12.31 dBic at 7.45 GHz. The gain of around 11.5 dBic is achieved over the entire CP bandwidth with a good cross-polarization level.

3-D Printing and CNC Machining Technologies for Exploration of Circularly Polarized Patch Antenna With Enhanced Gain

This paper presents a gain-enhanced circularly polarized (CP) patch antenna, where 3-D printing and computer numerical control machining technologies are employed for the fabrication of its dielectric and metal parts, respectively. In order to assemble the whole structure effectively and accurately, a hybrid strategy and pin-loaded example are here proposed to deal with the detached dielectric and metal. On the one hand, asymmetrically 3-D printed substrate with the mesh-grid architecture is formed with resin chunks to introduce the perturbation and produce the CP radiation. On the other hand, its metal part likewise possesses the 3-D structure with four metal screws to be symmetrically placed in the two diagonals of square patch, thus making the patch and ground as a whole. More importantly, the screws have dual functions, which can not only integrate the dielectric and metal parts, but also work as shorting pins. Therefore, due to the shunt inductive effect of shorting pins, the dominant mode of patch is excited at higher frequency, resulting in the enlarged antenna area and enhanced gain. As a result, the gain-enhanced CP patch antenna is realized, and an antenna prototype is then fabricated and tested, exhibiting a high CP gain of about 10 dBic.

Dual-band and high-efficiency circular polarization conversion via asymmetric transmission with anisotropic metamaterial in the terahertz region

In this paper, we present an anisotropic metamaterial (AMM) composed of a sub-wavelength metal grating sandwiched with bi-layered double-arrow-shaped (DAS) structure array, which can achieve high-efficiency circular polarization (CP) conversion via giant asymmetric transmission (AT) in terahertz (THz) region. Numerical simulation results indicate that near complete CP conversion with cross-polarization transmission coefficients can reach 0.91 and 0.93, which can be observed at 0.31 and 0.55 THz, respectively. Based on the combination of polarization conversion effects and Fabry-Perot-like cavity-enhanced effect of AMMs, the AT parameter for CP wave can reach a maximum of 0.83 at 0.30 THz, and 0.87 at 0.56 THz, respectively. With appropriate geometric parameters design of each unit-cell, embedded in the proposed AMM, the cross-polarization transmission coefficient and AT parameter for CP waves can be increased to the maximal values of 0.98 and 0.9, respectively. The proposed AMM shows great potential applications in high performance dual-band CP convertor and isolator in THz region.

Micro-strip antenna with high bandwidth, cone pattern, circular polarization, and slit

ABSTRACTThis paper presents a micro-strip antenna with cone pattern, circular polarization, and optimized impedance dimensions and bandwidth. It consists of an antenna radiation plane (patch), two Lange couplers dividing the Wilkinson power, and a circular substrate including defected ground structure elements. Scattering and pattern of the proposed antenna are measured after optimization. Also, a circular micro-strip antenna with a slit is designed. This antenna results in an increase of 32% in impedance bandwidth and a decrease of 44% in the antenna dimensions because of slitting the radiation plane (patch) and circulating the substrate antenna construction and substrate antenna feed. Finally, the simulation result and practical measurements demonstrate the validity of the proposed antenna for practical applications.

A Low Profile High Gain Ultra Lightweight Circularly Polarized Annular Ring Slot Antenna for Airborne and Airship Applications

In this paper a low profile circularly polarized annular ring slot antenna (CPARSA) with high gain is presented. An inverted U-shaped meandered slot is cut at the inner patch of annular ring to obtain the circularly polarized (CP) radiation. This annular slot loaded ground plane on a substrate thickness of 0.5 mm results in a very low profile (0.009λ 0 ) antenna in term of free space wavelength at its center operating frequency. The largest side lengths of octagonal shaped antenna are 0.89λ 0 × 0.89λ 0 according to its center frequency. Measured impedance bandwidth of 23.54% from 5.4 GHz - 7.0 GHz (for |S 11 | ≤ -10 dB) and AR bandwidth (AR<; 3 dB) of 5.15% from 5.67 GHz - 5.97 GHz are achieved by the antenna. Meanwhile, stable radiation pattern is observed throughout the entire bandwidth with peak gain of 7.6 dBi at the center frequency of 5.8 GHz. A defected ground plane is employed in the design which results in reduction of surface waves leading towards higher gain of antenna. The proposed antenna operating at 5.8 GHz band is fabricated on low cost substrate with standard printed circuit board (PCB) process. The proposed design provides favorable characteristics for various lightweight applications including miniaturized drones and airborne applications. To validate the prototype, measured results are compared with simulation outcomes and good agreement is obtained.

High Brightness Circularly Polarized Organic Light-Emitting Diodes Based on Nondoped Aggregation-Induced Emission (AIE)-Active Chiral Binaphthyl Emitters.

A pair of chiral binaphthyl enantiomers ( S-/ R-6) incorporating a tetraphenylethene (TPE) moiety as an aggregation-induced emission (AIE) active group exhibits bright yellow circularly polarized electroluminescence (CP-EL) emission with a remarkable gEL value, low turn-on voltage, and high brightness in the nondoped CP organic light emitting diodes (CP-OLEDs). This work provides a new strategy to develop doping-free CP-OLED materials.