Hand Circular Polarization Research Articles

Dual band four port MIMO antenna with dual circular polarization for Wi-Fi/WiMAX applications

The planar compact four port circularly polarized printed MIMO antenna described in this article is small and intended to support Wi-Fi and WiMAX applications. Suggested four E-shaped monopole elements make up the dual circularly polarized (CP) MIMO antenna that has two left hand CP (LHCP) elements and two right hand CP (RHCP) elements. An I shaped strip is used to join separate ground planes of designed E shaped monopole antenna to have same voltage levels. A good diversity performance is achieved with an envelope correlation coefficient (ECC) of less than 0.15. The 60 mm × 60 mm antenna is designed from FR4 material, which is inexpensive and has a 1.6 mm thickness. Using a high-frequency structure simulator (HFSS), the suggested MIMO antenna is designed and optimized. The measured findings demonstrate the circular polarization, 3-dB axial ratio beamwidth, impedance bandwidth of 2.11 GHz −2.42 GHz and 3.40 GHz-3.51 GHz, adequate axial ratio bandwidth (ARBW) of the suggested MIMO antenna along with high isolation of −17 dB, gain of 3.43 and 2.09 dBic at 2.4 GHz and 3.5 GHz respectively, TARC (Total active reflection coefficient) of less than 0 dB, a CCL (Channel capacity loss) of lesser than 0.4 bits/sec/Hz, and an MEG (Mean effective gain) value of less than 3 dB.

MeerKAT observations of pair-plasma induced birefringence in the double pulsar eclipses

ABSTRACT PSR J0737−3039A/B is unique among double neutron star systems. Its near-perfect edge-on orbit causes the fast spinning pulsar A to be eclipsed by the magnetic field of the slow spinning pulsar B. Using high-sensitivity MeerKAT radio observations combined with updated constraints on the system geometry, we studied the impact of these eclipses on the incident polarization properties of pulsar A. Averaging light curves together after correcting for the rotation of pulsar B revealed enormous amounts of circular polarization and rapid changes in the linear polarization position angle, which occur at phases where emission from pulsar A is partially transmitted through the magnetosphere of pulsar B. These behaviours confirm that the eclipse mechanism is the result of synchrotron absorption in a relativistic pair-plasma confined to the closed-field region of pulsar B’s truncated dipolar magnetic field. We demonstrate that changes in circular polarization handedness throughout the eclipses are directly tied to the average line of sight magnetic field direction of pulsar B, from which we unambiguously determine the complete magnetic and viewing geometry of the pulsar.

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.

Independent Phase Control in Gap‐Tuned Metasurfaces for Dual‐Function Switching

AbstractSeeking new ways to actively control the phase using metasurfaces has gained significant attention in recent years, which is the key to achieve controllable wavefronts under external stimuli. Among various active phase control mechanisms, a mechanical method based on gap tuning, termed as gap‐tuned metasurface here, has shown promise in continuous phase adjustment. However, previous studies face limitations in independent and complete phase control at different gap distances, which is crucial in dual‐function switching applications. In this study, a novel type of gap‐tuned metasurfaces are proposed, which can overcome the above limitations through simultaneously manipulating the Pancharatnam–Berry phase and gap‐induced dynamic phase under circularly polarized incidences. Two exemplary gap‐tuned metasurfaces capable of orbital angular momentum (OAM) switching and focusing‐polarity switching are experimentally demonstrated. Furthermore, the special dynamic phase design also exhibits phase conjugate property similar to the Pancharatnam–Berry phase, making circular polarization handedness an alternative route for dual‐function switching. This method provides a straightforward and effective means for the development of active wavefront control devices.

Kinetic numerical analysis of electromagnetic ion cyclotron instability in non-thermal Vasyliunas-Cairns distributed plasmas

Enhanced fluctuations driven by non-thermal features of particle-distributions are reported frequently in the variety of space plasma observations. In the rare-collisional plasmas, these amplified fluctuations scatter the particles in various direction and governs the dynamics of space plasma environments effectively. Electromagnetic ion cyclotron (EMIC) waves usually responsible for low frequency interplanetary magnetic field fluctuations. These are natural emissions in numerous natural environments of plasmas which usually operates underneath the ion/proton cyclotron frequencies. These are identified as left hand circular polarization (L-mode) with a propagation directed towards the ambient magnetic field. Various space missions and in situ measurements unveil the perpendicular temperature anisotropies of non-thermal populations of ions/protons i.e. in heliospheric regions and solar wind. These proton temperature anisotropies excite EMIC instability which in turn the pitch angle scatters the ions and restrained the anisotropy in certain ranges. In Vasyliunas-Cairns distributed hybrid non-thermal electromagnetic proton plasma, the transverse dielectric response function (TDERF) is calculated for L-mode. It is then numerically solved in order to show the impact of non-thermal populations due to non-thermal parameters α and κ on the dispersion and growth rates of EMIC instability in low and high plasma beta β regimes. Possible variation in the real oscillatory and imaginary frequencies spectrum is also analyzed with the variation in the values of other pertinent parameters i.e. temperature anisotropy τ and β. The parametric numerical analysis of the present work has relevance about that plasma phenomena of space regions where non-thermal distributed populations are prevalent.

A broadband dual-polarized antenna for 5G wireless communication systems

This article presents a broadband dual-polarized antenna for the 5G wireless communication technology. A ring resonator is chosen with the purpose of enhancing the axial ratio (AR) and impedance bandwidth. Partial ground plane is chosen with a slot placed beneath the feedline. The dimensions of the antenna are 50 mm × 50 mm × 1.6 mm, and it is fabricated on a dielectric substrate made of FR4 material. The variation of antenna polarization is achieved through the function of PIN diode. When the diode is in the ON state, the antenna functions as a wideband antenna that exhibits right hand circular polarization (RHCP). The frequency range covered by this system spans from 4.5 GHz to 7.5 GHz. Conversely, it provides linear polarization (LP) within a frequency range that spans from 4.3 GHz to 5.3 GHz. The metrics of the prototype antenna are measured and tested. The CST full wave simulator is utilized for conducting simulations.

A Millimeter-Wave Broadband Multi-Mode Substrate-Integrated Gap Waveguide Traveling-Wave Antenna with Orbit Angular Momentum.

Orbit angular momentum (OAM) has been considered a new dimension for improving channel capacity in recent years. In this paper, a millimeter-wave broadband multi-mode waveguide traveling-wave antenna with OAM is proposed by innovatively utilizing the transmitted electromagnetic waves (EMWs) characteristic of substrate-integrated gap waveguides (SIGWs) to introduce phase delay, resulting in coupling to the radiate units with a phase jump. Nine "L"-shaped slot radiate elements are cut in a circular order at a certain angle on the SIGW to generate spin angular momentum (SAM) and OAM. To generate more OAM modes and match the antenna, four "Π"-shaped slot radiate units with a 90° relationship to each other are designed in this circular array. The simulation results show that the antenna operates at 28 GHz, with a -10 dB fractional bandwidth (FBW) = 35.7%, ranging from 25.50 to 35.85 GHz and a VSWR ≤ 1.5 dB from 28.60 to 32.0 GHz and 28.60 to 32.0 GHz. The antenna radiates a linear polarization (LP) mode with a gain of 9.3 dBi at 34.0~37.2 GHz, a l = 2 SAM-OAM (i.e., circular polarization OAM (CP-OAM)) mode with 8.04 dBi at 25.90~28.08 GHz, a l = 1 and l = 2 hybrid OAM mode with 5.7 dBi at 28.08~29.67 GHz, a SAM (i.e., left/right hand circular polarization (L/RHCP) mode with 4.6 dBi at 29.67~30.41 GHz, and a LP mode at 30.41~35.85 GHz. In addition, the waveguide transmits energy with a bandwidth ranging from 26.10 to 38.46 GHz. Within the in-band, only a quasi-TEM mode is transmitted with an energy transmission loss |S21| ≤ 2 dB.

Chiroptical Switching of Electrochromic Polymer Thin Films.

The interaction between light and chiroptical polymers plays a crucial role in chiroptics, spintronics, and chiral-spin selectivity. Despite considerable successes in creating dissymmetric polymer films, the elucidation of chiroptical activities under electrochemical switching remains unexplored. Here homogeneous chiral electrochromics is reported using chiral assembly of conjugated polymers through a transient solidification process with molecular chiral templates. In their neutral state, the chiral electrochromic polymers directly produce a remarkably dissymmetric polarization-dependent transmittance. The circular dichroism (CD) and dissymmetric transmission can be tuned by adjusting the doping level of the electrochemically active polymer films. Under high levels of oxidation, the chiroptical activities are reversed with strong bleaching in the visible, leading to formation of monosignate CD spectra over the infrared region. The matching between circular polarization handedness and chirality of chiroptical polymers makes a distinct impact on optical contrast and color switching dynamics due to the flipped chiroptical activities through polymer redox reactions. The differential circularly polarized transmission in the chiral see-through display can make a well-resolved color change in human eyes, demonstrating proof-of-concept devices for 3D imaging and information encryption. This work serves as a foundation to develop advanced on-chip fabrication of circular polarization-multiplexed display in flexible and highly integrated platforms.

Tidal harmonics retrieval using GNSS-R dual-frequency complex observations

Tidal analysis and methods for estimation and prediction of ocean tidal constitutes are essential in a large area of scientific disciplines, for example, navigation, onshore and offshore engineering, and production of green energy. Ground-based Global Navigation Satellite System-Reflectometry (GNSS-R) has been proposed as an alternative method for measuring sea surface height. We use 6 years of GNSS-R observations at In-phase and Quadrature levels from July 2015 to May 2021 obtained from a dedicated receiver and sea-looking left hand circular polarization antenna for estimating sea level (SL). In the first step, the multivariate least-square harmonic estimation (LS-HE) method is applied for SL estimation. Then, final SL time series are generated by combining estimated SL from all satellites at L1 and L2 frequencies in the averaging step. The 6-year root-mean-square error between GNSS-R L12 sea surface heights and a collocated tide gauge (TG) is 5.8 cm with a correlation of 0.948 for a high temporal resolution of 5 min with 15 min averaging window. Afterward, using the univariate LS-HE, we detect tidal harmonics with periods between 30 min to 1 year. The detection results highlight a good match between GNSS-R and TG. Higher harmonics, i.e., the periods shorter than 3 h, show stronger signatures in GNSS-R data. Finally, we estimate the amplitude and phase of standard tidal harmonics from the two datasets. The results show an overall good agreement between the datasets with a few exceptions.

Dual-sense slot-based CP MIMO antenna with polarization bandwidth reconfigurability

In this letter, a compact, planar circularly polarized (CP) sub-GHz slot-based multiple-input-multiple-output (MIMO) antenna with dual sense CP along with polarization bandwidth reconfigurability is presented. The pentagonal reactively loaded slot is fed by two folded tapered feedlines to achieve CP. The antenna offers left-hand-circular polarization (RHCP) with the as well as right hand circular polarization (LHCP). The antenna exhibit linearly polarization (LP) by exciting two ports simultaneously. Moreover, the antenna CP resonance can be reconfigured by varying the capacitance of the varactor diode. The antenna has a wide −10 dB operating frequency band from 578–929 MHz. while the axial ratio (AR) bandwidth ranges from 490–810 MHz. Moreover, the two elements MIMO are optimized and placed on compact dimensions 100 × 100 × 0.76 mm3 to realize pattern diversity. The antenna’s key characteristics are compact size, wide-band sub-GHz operation, dual sense CP, polarization bandwidth reconfigurability and good MIMO performance. Thus, it is a suitable candidate to be utilized in CubeSats applications in sub-GHz bands.

Wideband single-feed dual circularly polarized multi-beam transmitarray antenna based on receiver–transmitter metasurface

In this paper, a novel metasurface (MS) as well as a generalized dual-circular-polarized (CP) decoupled modulating method are proposed. The proposed MS can realize high-efficiency dual-spin transmissions with equal-magnitude upon left handed circular polarization (LCP) incidence across 9–12.5 GHz. This MS is constructed based on the receiver–transmitter configuration, and the receiver layer composed of an LCP patch resonator while the transmitter layer is a linearly polarized patch resonator. Rotating the receiver and transmitter patches separately can impose identical and conjugated geometric phase modulations for the dual-CP transmission waves, respectively. Hence, through an elaborate combination of the dual geometric phases, totally decoupled and dispersion-less phase modulations for transmitted dual-spin waves can be obtained. As the proof of its uses in practical applications, we have designed a single-feed dual-CP dual-beam transmitarray antenna (TA) and a dual-CP quad-beam TA. The second TA is also fabricated and tested. The measured results are consistent with the simulated results, showing that the TA achieves peak aperture efficiency of 49% at 9.5 GHz, with 1 dB gain bandwidths (BWs) of the dual-CP quad-beams all larger than 24.5% while 3 dB axial ratio BWs all larger than 54.5%. The proposed wideband and high-gain dual-CP multi-beam TAs may have promising prospects for many applications such as vehicle-satellite communication systems, satellite broadcasting and coverage systems.

A broadband circularly polarized Fabry Perot antenna with spatially separated superstrate area excitation for CubeSat applications

This article describes the development of a high-gain, broadband, circularly polarized Fabry–Perot cavity (FPC) antenna for high-data-rate communication in CubeSat/SmallSat applications. In this work, the concept of spatially separated superstrate area excitation is developed for the first time in FPC antennas. This concept is then validated and applied to increase the gain and the axial ratio bandwidth of a conventional narrowband circularly polarized source patch antenna. The antenna’s design leverages independent control of polarization at different frequencies, resulting in a large overall bandwidth. The fabricated prototype antenna provides right hand circular polarization with a peak measured gain of 15.73 dBic over a common bandwidth of 1.03 GHz ranging from 7.99 GHz to 9.02 GHz. The gain variation over the bandwidth is less than 1.3 dBic. The antenna measures 80 mm × 80 mm × 21.14 mm and is simple, lightweight, easily integrable with CubeSat body, and useful for X-Band data downlink. When integrated with the metallic body of a 1U CubeSat, the simulated gain of the antenna increases to 17.23 dBic, with a peak measured gain of 16.83 dBic. A deployment method is proposed for this antenna that results in a total stowed volume of only 2.13λo × 2.13λo × 0.084λo (0.38 {lambda }_{o}^{3}).

Design of a dual‐CP gap waveguide fed aperture array antenna

AbstractA slot array antenna with dual‐circular polarisation (CP) is presented in this paper. To overcome the fabrication and loss challenges in mm‐wave frequencies, the gap waveguide technique is utilised. The right and left hand circular polarisation (RHCP and LHCP) radiations are achieved using slots‐fed stepped septum polariser on the longitudinal slot arrays. The waveguides and feeding layer are based on ridge gap waveguide. The experimental results demonstrate the |S11| and axial ratio of proposed antenna array are lower than −10 and 2 dB, respectively over the frequency range of 29.1–31.7 GHz. The proposed antenna exhibits the measured peak gain of 27.2 dBic at 30.2 GHz. The results prove that the proposed array antenna is a brilliant choice for 30 GHz‐band applications and could be developed to realise larger dual‐polarised planar arrays.

A Multioctave 8 GHz$-$40 GHz Receiver for Radio Astronomy

Accurate measurement of angular positions on the sky requires a well-defined system of reference, something that in practice is realized by the International Celestial Reference Frame (ICRF) with observations of distant (typical redshift <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\sim$</tex-math></inline-formula> 1) Active Galactic Nuclei (AGN). At such great distances a subset of these objects exhibit as little as 10 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$-$</tex-math></inline-formula> 50 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mu$</tex-math></inline-formula> as/year observed parallax or proper motion, thus giving the frame excellent spatial and temporal stability. Until fairly recently the majority of AGN centered imaging was accomplished in the S (2.3 GHz) and X (8.4 GHz) radio frequency bands, however S-band observations for reasons such as sensitivity “plateauing”, increased source structure (jets), and radio frequency interference (RFI) have become less productive. Following spacecraft telemetry moves to higher frequencies and a desire to strengthen JPL's leadership in defining the next-generation of celestial reference frames has motivated the development of a “Quad-band” prototype receiver that operates in X, Ku, K, and Ka band in both right hand (RCP) and left hand (LCP) circular polarization. The goal of this receiver is to achieve less than a 20 % increase in noise over the Jansky Very Large Array (JVLA, NRAO) performance specification, which in such a wide bandwidth represents a revolutionary capability. To evaluate the various technical developments of the 8 GHz <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$-$</tex-math></inline-formula> 40 GHz receiver the feedhorn optical beam was designed to interface to the US based Very Long Baseline Array (VLBA). The receiver's intermediate frequency (IF) spans 4 GHz <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$-$</tex-math></inline-formula> 8 GHz, giving rise to up to eight 4 GHz IF channels for a fully populated instrument. This paper outlines the technical development of a 2 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{1}$</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">$_{2}$</tex-math></inline-formula> octave wide (8 GHz <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$-$</tex-math></inline-formula> 40 GHz) X-Ka band prototype receiver, fulfilling a need for super broadband technology within the VLBI network. An important additional benefit of the wideband receiver approach is its simplicity and low cost of operation.

Quad Port Multipolarized Reconfigurable MIMO Antenna for Sub 6 GHz Applications

Recent reconfigurable technological advancements for wireless communication systems provide various global solutions. This research work presents a quad port multipolarized switchable multiple input multiple output (MIMO) antenna for sub 6 GHz applications. It covers the frequency range from 3.1 to 5.1 GHz, including the 5G NR band n78 (3.3 to 3.8 GHz) and 5G NR band n79 (4.4 to 5 GHz). The proposed antenna comprises four offset-fed monopole antenna elements with an overall dimension of 60 mm × 65 mm. To achieve circular polarization (CP), a parasitic meandering resonator is integrated with antenna elements using four PIN diodes. The polarization diversity is obtained by controlling the bias states of four PIN diodes. The radiating element −1/−3 offers left hand circular polarization (LHCP), while element −2/−4 procures right hand circular polarization (RHCP) when all diodes are ON. Consequently, the proposed antenna provides linear polarization (LP) under reverse bias conditions. Moreover, the designed antenna acquires a wide axial ratio bandwidth (ARBW) of 36.1%. In addition, the developed MIMO antenna exhibits isolation greater than 15 dB using the common ground plane, and the obtained ECC is less than 0.13. The prototype is fabricated, and the simulated responses are in good correlation with the measured results.

Mechanically Tunable Terahertz Circular Polarizer with Versatile Functions

AbstractCircular polarizers that selectively transmit only one handedness of circular polarization are useful for imaging and wireless communications. Conventional circular polarizers involve 3D chiral structures, which impose fabrication challenges, while typically introducing chirality within a limited bandwidth. To overcome the limitations associated with conventional non‐planar designs, a three‐layer metasurface‐based planar circular polarizer exhibiting strong and broadband chirality is presented here. Its superiority over existing multilayer designs is derived from a systematic design procedure. Measurement results reveal that the proposed structure maintains a 15‐dB extinction ratio from 251 to 293 GHz for the preferred handedness of circular polarization, leading to a fractional bandwidth of 15.4% with a transmission efficiency above 92.7%. Furthermore, the proposed structure is mechanically tunable to alter its functionality or operation bandwidth. Specifically, through simply rotating the top or bottom metallic layer by 90°, the structure can function as a transmissive quasi‐half‐wave plate that reverses the sense of circular polarization. Moreover, the presented structure can operate at nearby frequency ranges for the aforementioned functionalities by mechanically adjusting the air gap spacings between the metallic layers. Further calculations based on the measured results of each layer suggest that the proposed structure is robust to deviations in the air gap spacings.

Design and Analysis of Circular Polarized Two-Port MIMO Antennas with Various Antenna Element Orientations

This article presents the circularly polarized antenna operating over 28 GHz mm-wave applications. The suggested antenna has compact size, simple geometry, wideband, high gain, and offers circular polarization. Afterward, two-port MIMO antenna are designed to get Left Hand Circular Polarization (LHCP) and Right-Hand Circular Polarization (RHCP). Four different cases are adopted to construct two-port MIMO antenna of suggested antenna. In case 1, both of the elements are placed parallel to each other; in the second case, the element is parallel but the radiating patch of second antenna element are rotated by 180°. In the third case, the second antenna element is placed orthogonally to the first antenna element. In the final case, the antenna is parallel but placed in the opposite end of substrate material. The S-parameters, axial ratio bandwidth (ARBW) gain, and radiation efficiency are studied and compared in all these cases. The two MIMO systems of all cases are designed by using Roger RT/Duroid 6002 with thickness of 0.79 mm. The overall size of two-port MIMO antennas is 20.5 mm × 12 mm × 0.79 mm. The MIMO configuration of the suggested CP antenna offers wideband, low mutual coupling, wide ARBW, high gain, and high radiation efficiency. The hardware prototype of all cases is fabricated to verify the predicated results. Moreover, the comparison of suggested two-port MIMO antenna is also performed with already published work, which show the quality of suggested work in terms of various performance parameters over them.

Reconfigurable graphene-gold-based microstrip patch antenna: RHCP to LHCP

In the designed study, a reconfigurable graphene-gold-based microstrip patch antenna is proposed. Designed antenna has the ability to access a variety of right hand circular polarization, and left hand circular polarization polarizations by switching the positions of its slots. The central frequency of the antenna is adjusted to 0.92 THz according to the conditions. The main approach of the article is based on the principle that if the position of the slot is rotated 90°, the polarization will be switched from right hand circular polarization to left hand circular polarization. In the design outputs of S11 below −10 dB for the range of 0.8 THz through 1.1 THz is observed, which is desirable. Incidentally, the axial ratio is less than 3 dB in the direction of the antenna axis according to the simulation outputs. Important parameters of the antenna such as efficiency, directivity radiation pattern, matching, E-field distribution, H-field distribution, current density distribution, polar radiation pattern, 3D radiation pattern, and S11 sweep based on chemical potential changes (frequency reconfigurable) in the desired frequency domain are analysed. While for the range of 0.6 THz to 1.4 THz, the results obtained from the point of view of matching and polarization are good conditions. The chemical potential in the designs is 0.6.

A high gain dual circularly polarized X‐band antenna for CubeSat applications

AbstractIn this article, a dual circularly polarized high gain superstrate integrated X‐band antenna is designed and analyzed for CubeSat applications. The proposed antenna consists of a metallic patch, multilayer space qualified printed circuit boards, and a dielectric superstrate with a high relative permittivity on top of the patch to establish a suitable resonance condition for high‐gain operation. The driven patch is fed by a 3‐dB hybrid coupler for the generation of dual (left hand circular polarization and right hand circular polarization) circular polarization. The antenna exhibits an impedance bandwidth of &gt;18.5% (7.75–9.4 GHz) with a peak gain of &gt;16 dBiC. The achieved antenna performance makes it suitable for CubeSat missions at X‐band.

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.