Sense Of Polarization Research Articles

Cascaded circular‐polarisation‐selective surface based on bisected split rings

A cascaded circular-polarisation-selective surface (CPSS) based on bisected split rings is presented. The proposed CPSS allows the transmission of one sense of circular polarisation while reflecting the other sense. To validate the proposed design, a nine-layer prototype that operates in the Ka band has been designed, fabricated and tested. Experimental results show that transmission coefficients higher than −1 dB and axial ratios lower than 3 dB are obtained for one sense of circular polarisation, whereas transmission coefficients lower than −20 dB are obtained for the opposite sense over the frequency band from 26.39 to 35.43 GHz.

A CPW-fed reconfigurable patch antenna with circular polarization diversity

This paper presents a simple and compact coplanar waveguide (CPW)-fed circular-shaped reconfigurable patch antenna with a switchable circular polarization (CP) sense. The circular patch is cut at the ends vertically and switches are introduced to connect the patch ends. By controlling the ON/OFF status of the two switches, the polarization of the antenna can be switched between two states: left-hand circular polarization and right-hand circular polarization. The patch is designed on a very thin RT Duroid substrate of dielectric constant (εr) of 2.2 and thickness of 0.254 mm. The overall antenna dimensions are 35 × 30 mm. The antenna is designed and simulated using finite-element method -based EM simulator, HFSS. For each switching condition the return loss curve, radiation pattern are obtained. Axial ratio curves for polarization diversity cases are also plotted. Parametric studies have been made in order to get optimized values for certain antenna dimensions such as thickness, CPW ground to feed gap, etc.

Effect of Alfvén waves on the growth rate of the electron-cyclotron maser emission

By using the non-relativistic approximation for the calculation of growth rates, but taking account of the weakly relativistic modification for the electron-cyclotron resonance condition, it is shown that the effect of Alfvén waves (AWs) on the electron-cyclotron maser emission leads to the significant increase of the O-mode growth rate, but has little effect on the X-mode growth rate. We propose that this is because the O-mode wave has the field-aligned polarization sense in the same as the field-aligned oscillatory current, which is created by the field-aligned oscillatory motion of the energetic electrons caused via the presence of AWs. It is this field-aligned oscillatory current that contributes a novel growth rate to the O-mode wave but has little effect on the X-mode wave.

Chiral Fibers: Microformed Optical Waveguides for Polarization Control, Sensing, Coupling, Amplification, and Switching

Microformed optical waveguides, made by tapering and/or twisting fibers as they are passed through a miniature heat zone, possess unique properties that may be exploited for polarization control, harsh-environment sensing, dense multichannel coupling, spatial division multiplexing, amplification, and optical switching.

Bidirectional Same-Sense Circularly Polarized Slot Antenna Using Polarization Converting Surface

An asymmetric frequency selective surface (FSS) based on Jerusalem cross-slot (JC-SL) unit cell is used as a polarization converting surface (PCS) to change the sense of the circularly polarized (CP) wave as it passes through it. This is achieved by introducing 0 ° and 180 ° phase shifts for the two perpendicular linear polarized components of the CP wave. Without adding any extra phase shift, the transmitted CP wave will encounter a change in its sense of polarization. The PCS is then combined with a bidirectional CP slot antenna to achieve right-hand CP (RHCP) signal on both sides of the antenna. The overall size of the structure is about 0.75λ×0.75λ×0.15λ, where λ is the free-space wavelength. The structure is designed to operate at the GPS L1 band ( f = 1.575 GHz).

A MONOPOLE ANTENNA WITH DUAL-BAND RECONFIGURABLE CIRCULAR POLARIZATION

This paper describes a monopole antenna with dual-band switchable circular polarization (CP) sense in WLAN and WiMAX bands. The proposed antenna consists of a rectangular patch fed by a microstrip line and a ground plane embedded with a T-shaped slot integrated with PIN diodes. The slotted ground is capable of exciting CP sense around 2.45 GHz for WLAN and around 3.4 GHz for WiMAX, respectively. Two triangular strips are added to improve impedance matching. The CP sense of the proposed antenna can be reconfigured between the right-handed circular polarization (RHCP) and left-handed circular polarization (LHCP) by switching the states of PIN diodes in the slot. The lower band 3-dB axial ratio (AR) bandwidth is 8.6%, and the upper band 3-dB AR bandwidth is 20.8%, in which the return loss is less than −10-dB. Simulated analysis and measured results are carried out and good agreement is achieved.

ELECTRON CYCLOTRON MASER EMISSION IN CORONAL ARCHES AND SOLAR RADIO TYPE V BURSTS

Solar radio type V bursts were classified as a special spectral class based on their moderately long duration, wide bandwidth, and sense of polarization opposite of associated type III bursts. However, type V bursts are also closely related to the preceding type III bursts. They have an approximately equal source height and the same dispersion of position with frequency. Electron cyclotron maser (ECM) instability driven by beam electrons has been used to explain type III bursts in recent years. We propose ECM emission as the physical process of type V solar radio bursts. According to the observed properties of type V and III bursts, we propose that energetic electrons in excited type V continuum are trapped in coronal loops, which are adjacent to the open field lines traced by type III electrons. With the proposed magnetic field configuration and the ECM emission mechanism, the observed properties of type V bursts, such as long duration, wide bandwidth, and opposite sense of polarization can be reasonably explained by our model.

Dependence of the oblique propagation of ULF foreshock waves on solar wind parameters

AbstractAccording to theory, foreshock ultra‐low frequency (ULF) waves are allowed to propagate mainly along the ambient magnetic field; however, waves obliquely propagating at a noticeably large angle can be easily observed. Although the mechanism of wave refraction was proposed to resolve the disagreement, doubts on the application of wave refraction to oblique propagation still remain. With the Time History of Events and Macroscale Interactions during Substorms (THEMIS) data, we examine the dependence of the oblique propagation of the ULF waves on solar wind parameters. The distributions of the oblique propagation angle θkB2 are spread out over a wide range of the solar wind parameters. From the mechanism of wave refraction, we derive the θkB2 as a function of the upstream propagation angle θkB1, the ratio of solar wind speed to upstream and downstream wave phase speed , and the angle between the interplanetary magnetic field (IMF) and solar wind velocity θBV. Both of the prediction and the observation show the irrelevance of the wave frequency, the sense of polarization, the strength of the IMF, and solar wind speed to the oblique propagation. We find that the prediction from wave refraction is in good agreement with the observation, especially along the track of prediction lines with the same θkB1 and .

KINETIC PLASMA TURBULENCE IN THE FAST SOLAR WIND MEASURED BYCLUSTER

The k-filtering technique and wave polarization analysis are applied to Cluster magnetic field data to study plasma turbulence at the scale of the ion gyroradius in the fast solar wind. Waves are found propagating in directions nearly perpendicular to the background magnetic field at such scales. The frequencies of these waves in the solar wind frame are much smaller than the proton gyro-frequency. After the wave vector ${\bf k}$ is determined at each spacecraft frequency $f_{sc}$, wave polarization property is analyzed in the plane perpendicular to ${\bf k}$. Magnetic fluctuations have $\delta B_\perp>\delta B_\parallel$ (here the $\parallel$ and $\perp$ refer to the background magnetic field ${\bf B}_0$). The wave magnetic field has right-handed polarization at propagation angles $\theta_{\bf kB}<90^\circ$ and $>90^\circ$. The magnetic field in the plane perpendicular to ${\bf B}_0$ however has no clear sense of a dominant polarization but local rotations. We discuss the merits and limitations of linear kinetic Aflv\'en waves (KAWs) and coherent Alfv\'en vortices in the interpretation of the data. We suggest that the fast solar wind turbulence may be populated with KAWs, small scale current sheets and Alfv\'en vortices at ion kinetic scales.

Co-continuous morphology on spin coating produced thin TiO2 films

Biological research has shown good cell response to dense TiO2 films. Good surface chemistry of the implant can be further improved by introducing optimal topology, which in the case of osseointegration means porosity features in the nm and μm range. TiO2 films are produced by spin coating and the obtained morphologies are characterized qualitatively and quantitatively from the scanning electron microscope images of the surface and in focused ion beam cross-sections. Infrared spectroscopy, thermogravimetry/differential thermal analysis, and X-ray diffraction were used to characterize chemical changes and crystallization processes in the bulk gels and thin films. Mechanical properties of the films are characterized using Nano Scratch Test. Results show that the increase in acetyl acetone (ACAC) concentration from 1 mol ACAC:1 mol Ti(IV) n-butoxide used for dense films to 1.5:1 and simultaneous polyethylene glycol (PEG) presence led to a change in morphology from a dense to highly porous, co-continuous morphology. This is a result of pronounced phase separation with respect to gelation due to (1) the presence of uncomplexed ACAC, which is highly dissimilar, in a sense of polarity, to the other components of the sol and (2) the additional reaction between PEG and TiO2 oligomers. This porous morphology is found to be very sensitive to production parameters such as viscosity, spinning velocity and the amount of PEG added to the sol. It was also detected that, in addition to the phase separation, PEG also influences the crystallization process of the film.

Generalized van Cittert–Zernike theorem for the cross-spectral density matrix of quasi-homogeneous planar electromagnetic sources

A generalized van Cittert-Zernike theorem for the cross-spectral density matrix of quasi-homogeneous planar electromagnetic sources is introduced. We present theoretical examples of using this theorem to generate fields with interesting polarization and spatial coherence properties by choosing the appropriate spectral density distribution of the source. We found that under certain conditions, a quasi-homogeneous, polarized source may produce a beam in the far field that is unpolarized in the typical one-point sense but polarized in the two-point, mutual polarization sense.

Twisted nematic liquid crystal polarization grating with the handedness conservation of a circularly polarized state

We propose a liquid crystal (LC) polarization grating that conserves the polarization state of incident light, wherein the variation range of the twist angle is 2π. The design scheme for theoretically 100% diffraction efficiency of the first-diffraction order is derived, and a prototype LC grating is evaluated. Under zero voltage, the fabricated LC grating exhibits high efficiency of the first-order diffraction, validating the proposed design scheme. The high efficiency of the second-order diffraction can also be achieved under a high voltage so that the LC director in the midplane is vertical to the substrate plane. The circular polarization sense of the second-order diffraction is identical to that of the incident light as in the case of the first-order diffraction. This grating functions as a beam deflector, steering the input beam in three different directions (zeroth-, first-, and second-order diffractions) by adjusting the applied voltage.

A miniaturized switchable circularly polarized patch antenna controlled by a single diode operation

A novel switchable circularly polarized patch antenna with a compact size is proposed that uses only a single PIN diode. The proposed antenna consists of a corner-truncated square radiating patch with a cross-shaped slot on the ground, a triangular conductor, and one PIN diode. Because of the cross ground slot which is embedded on the diagonal direction, the resonant frequencies of each circular polarization sense are lowered about 41% for right-hand circular polarization and 38% for left-hand circular polarization. Moreover, by alternating the states of only one diode, a circular polarization sense is easily reconfigured without a radiating degradation. The simulated and measured results show that good CP characteristics are obtained with symmetrical radiation patterns at the lowered resonant frequencies. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:2375–2378, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27070

High e-vector acuity in the polarisation vision system of the fiddler crabUca vomeris

Polarisation vision is used by a variety of species in many important tasks, including navigation and orientation (e.g. desert ant), communication and signalling (e.g. stomatopod crustaceans), and as a possible substitute for colour vision (e.g. cephalopod molluscs). Fiddler crabs are thought to possess the anatomical structures necessary to detect polarised light, and occupy environments rich in polarisation cues. Yet little is known about the capabilities of their polarisation sense. A modified polarisation-only liquid crystal display and a spherical rotating treadmill were combined to test the responses of fiddler crabs to moving polarisation stimuli. The species Uca vomeris was found to be highly sensitive to polarised light and detected stimuli differing in e-vector angle by as little as 3.2 deg. This represents the most acute behavioural sensitivity to polarised light yet measured for a crustacean. The occurrence of null points in their discrimination curve indicates that this species employs an orthogonal (horizontal/vertical) receptor array for the detection of polarised light.

A design for circularly polarized ring slot antennas backed by thin grounded substrate

This article presents a design for circularly polarized ring slot antennas backed by a metal plate with a small separated distance.The antenna is excited through a shorted L-shaped coupling strip, and good circular polarization performance can be obtained as long as the vertical arm of the L-shaped coupling strip is properly stretched. Both simulated and measured results demonstrate that the reflector-backed slot antenna gives an opposite polarization sense to its counterpart without the reflector. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:1768–1770, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26885

Design of a polarisation reconfigurable patch antenna using ferrimagnetic materials

In this study the authors introduce the utilisation of ferrimagnetic compounds into an antenna design and investigate the capability of controlling the antenna properties by means of an external magnetic field. After intensive study of the material properties, the ferrimagnetic compound yttrium iron garnet (YIG) was found to be the best candidate for the proposed novel antenna design. The authors provide a patch antenna design with a part of the dielectric substrate replaced by YIG compound. They have investigated the influence of this compound on the antenna's polarisation properties under the application of an external magnetic field. The authors clearly demonstrate that the type and the sense of the antenna polarisation are strongly influenced by the YIG substrate, because they change with respect to the direction and the magnitude of the external magnetic field. Moreover, the authors have proved that the presence of this material induces non-reciprocal properties in the antenna's operation, changing the antenna properties with respect to receiving or transmitting mode.

A Switchable Circular Polarization Microstrip Antenna Using a Varactor Diode

In this letter a circular polarization microstrip antenna with switchable polarization is proposed. The switchable polarization sense characteristic is realized via a shunt connected varactor tuning diode. The appropriate capacitance of the diode at the reverse bias voltage can alter two circular polarizations, as the tuning diode, which is located near the rectangular slot in the circular patch, is utilized in a perturbation element. The switchable polarization is analyzed using the equivalent circuit model representing the resonances of each orthogonal mode. Simulation, calculated, and measured results agree well.

Waveguide Antenna Feeders With Integrated Reconfigurable Dual Circular Polarization

Waveguide antenna feeders with reconfigurable circular polarization sense are proposed in this paper. They can be switched between right and left hand circular polarization, without any mechanical rotation between the feeder and the antenna. Two types of feeders are presented. The polarizer works with a single switchable polarization for each state. The dual feeder can work with both polarizations at the same frequency band simultaneously, each one associated with a different rectangular waveguide port. The polarization sense is controlled by metallic posts that block or open the signal paths connecting the rectangular ports with a septum-orthomode polarizer. These posts are automated with piezo-motors integrated in the structure, leading to a very compact layout, reduced size, and practical for applications with diverse switching speed. The proof of concept and the automation are shown with experimental Ku-band prototypes.

On the dispersion features of whistler waves in almost pure ion plasmas

It is shown that in a multi-ion plasma of moderate density enriched by a large amount of negatively charged ions and/or heavy particulates, the lower cutoff frequencies of the electron whistler and the Z-mode (extraordinary) waves tend to each other, approaching the ion plasma frequency ωpi. The evolution of the dispersion curves ω(k, θ) of both wave modes is studied as a function of the relative electron density, beginning from the case of a moderate density plasma with comparable values of electron gyro- and plasma frequencies and ωpi essentially exceeding the ions’ gyrofrequencies. When the fraction of free electrons is very small the transparency frequency domain of the electron whistler mode becomes very narrow, being located in the vicinity of ωpi. If the negatively charged ions have the smallest specific charges among other ion species then, under similar conditions, the so-called crossover effect and the accompanying polarization sense reverse can occur at frequencies essentially greater than the ions’ gyrofrequencies. The revealed effects are characteristic of plasmas with excess of electronegative gas molecules or dust particulates highly adhesive to electrons, i.e., almost pure ion plasmas and/or pair-ion plasmas with extra small fractions of free electrons. Moreover, it is found that the vanishingly small electron fraction providing the same value of the electron whistler ion cutoff frequency normalized to the ion plasma frequency is essentially less for pair fullerene C60± than for pair hydrogen H± plasmas. The technique to determine ωpi using the evolution of the whistler wave magnetic field polarization ellipse is also described.

Corrugated-Conical Horn Analysis Using Aperture Field With Quadratic Phase

An approximation of the far-field radiation pattern of the corrugated-conical horn, by integration of the aperture field, augmented with perimeter-matched quadratic radial phase, is sufficient to establish a baseline design for the feedhorn of a satcom antenna system. The approximated far-field patterns compare well to more formal analysis methods, even reasonably so in the main beam with a semi-flare angle as wide as 45 deg for the first two angular modes. The field equations are presented in a compact complex exponential form, from which the components corresponding to excitation with any polarization sense may be obtained (either sense of circular/elliptical polarization or linear polarization with arbitrary orientation).