Circularly Polarized Wave Research Articles

Optical isolation via one-dimensional magneto-photonic crystals containing nonlinear defect layer

In this paper we investigate the transmission properties of one-dimensional periodic structures containing magneto-optical (MO) material layers with a nonlinear defect layer using the transfer matrix method. It is shown that such structures can exhibit unidirectional resonant photon tunneling phenomena which can discriminate between circularly polarized (CP) wave of given handedness impinging from the same direction for specific incident field intensity. These structures may be utilized to design intensity dependent optical isolator for CP waves. Also it is demonstrated that the threshold intensity to achieve optical bistability depends on the bias magnetic field.

Dual-band circularly polarized monopole antenna

A printed dual-band circularly polarized (CP) antenna is presented. The antenna is composed of a strip monopole on one side of a substrate. On the other side of the substrate, there are a perturbed patch and a slotted ground plane. Two sleeves are extended from two edges of the ground plane. It is investigated that the perturbed patch is mainly responsible for the CP wave centered at 5.5 GHz and the sleeves are mainly responsible for the CP wave centered at 2.5 GHz. The measured boresight gains are 4 dBic at 5.5 GHz and 2.5 dBic at 2.5 GHz.

Wideband Magnetoelectric Dipole Antennas With Dual Polarization and Circular Polarization

A new 45 degrees dual-polarized magnetoelectric dipole antenna is proposed. The antenna is excited by two -shaped probes placed at a convenient location. The measured overlapped impedance bandwidth is 48% with standing-wave ratio (SWR) 1.5 from 1.69 to 2.76 GHz. The measured gains vary from 7.6 to 9.3 dBi and from 7.6 to 9.4 dBi for port 1 and port 2, respectively. The isolation between the two ports is larger than 30 dB. The proposed antenna achieves a low cross-polarization level of less than 21 dB and a low back radiation level of less than 29 dB over the operating frequency range. With a broadband 90 phase shifter and a power divider, the proposed antenna can radiate circularly-polarized (CP) wave and exhibit a wide impedance bandwidth (SWR 2) of 90% from 1.23 to 3.23 GHz, which covers the whole 3-dB axial-ratio (AR) bandwidth of 82% from 1.28 to 3.05 GHz. In this operation frequency band, the proposed CP antenna has a broadside gain of larger than 5 dBi above 1.45 GHz. Considering the common overlapped bandwidth limited by the impedance, AR, and gain, the proposed antenna exhibits an effective bandwidth of 71%.

Nonlinear dispersion and transverse profile of intense electromagnetic waves, propagating through electron-positron-ion hot magnetoplasma

Self-guided nonlinear propagation of intense circularly-polarized electromagnetic waves in a hot electron-positron-ion magnetoplasma is studied. Using a relativistic fluid model, a nonlinear equation is derived, which describes the interaction of the electromagnetic wave with the plasma in the quasi-neutral approximation. Transverse Eigen modes, the nonlinear dispersion relation and the group velocity are obtained. Results show that the transverse profile in the case of magnetized plasma with cylindrical symmetry has a radially damping oscillatory form. Effect of applying external magnetic fields, existence of the electron-positron pairs, changing the amplitude of the electromagnetic wave, and its polarization on the nonlinear dispersion relation and Eigen modes are studied.

A novel broadband circularly polarised monopole antenna

A novel broadband circularly polarised (CP) monopole antenna is designed and implemented in this article. The antenna consists of a radiating patch that is composed of an annular-ring linked by a square ring over the corner and a modified ground plane. The broadband property is achieved based on a novel monopole structure that is connected by two perturbed loops, so the CP wave is generated due to the perturbation. Besides, by cutting a rectangular slit and embedding a vertical stub on the ground plane, the impedance and axial-ratio (AR) bandwidths can be greatly enhanced. The measured results reveal that the proposed monopole antenna has an impedance bandwidth of 4.575 GHz from 2.3 to 6.85 GHz, reaching the particularly broad bandwidth of 99.5%. Furthermore, a wide 3-dB AR bandwidth of 34.6% (1.53 GHz, 3.65–5.18 GHz) centred at 4.42 GHz is achieved. The radiation characteristics of the designed antenna are also presented.

A Frequency and Polarization Reconfigurable Circularly Polarized Antenna Using Active EBG Structure for Satellite Navigation

This paper presents a broadband frequency tunable and polarization reconfigurable circularly polarized (CP) antenna, using a novel active electromagnetic band gap (EBG) structure. The EBG surface employs identical metallic rectangular patch arrays on both sides of a thin substrate, but rotated by 90 $^{\circ}$ from each other. The active bias circuits are also orthogonal for each surface, enabling the reflection phases for orthogonal incident waves to be tuned independently in a wide frequency range. By placing a wideband coplanar waveguide (CPW) fed monopole antenna above the EBG surface, and properly tuning the bias voltages across the varactors in each direction, CP waves can be generated at any desired frequency over a broad band. In accordance with simulations, the measured 3 dB axial ratio (AR) bandwidth reaches 40% (1.03–1.54 GHz), with good input matching $(S_{11})$ and radiation patterns at six presented sampling frequencies. The polarization reconfigurability is verified by simulations and measurements, and shown to be capable of switching between left hand circular polarization (LHCP) and right hand circular polarization (RHCP).

A Comb-Line Antenna Modified for Wideband Circular Polarization

A sequential rotation technique is newly applied to a circularly polarized (CP) comb-line antenna. The antenna is analyzed using the moment method. First, a novel loop antenna is proposed as a CP radiation element. Next, the loop element is used for a comb-line antenna to radiate a CP wave. This reference antenna shows a bandwidth of 3% for a 3-dB axial-ratio criterion. Last, the comb-line antenna is modified for wideband CP radiation. It is both numerically and experimentally revealed that the CP wave bandwidth is wider than that of the reference antenna by a factor of five.

Broadband circularly polarized antenna with high gain and wide axial ratio beamwidth

ABSTRACTA broadband circularly polarized (CP) antenna with simple structure and wide angular coverage is proposed. The interlaced coplanar dipole is excited by a coaxial cable to achieve the CP wave. To obtain a high gain and low backward radiation, a rectangular cavity‐backed reflector is used. An initial design at around 6.0 GHz is presented to show the performance of this configuration. An impedance bandwidth and axial ratio bandwidth of about 35.6 and 33.5% can be achieved at this frequency. Also, a stable gain of about 10 ± 0.5 dBi and a wide axial ratio beamwidth of about 200° over the frequency of interest are obtained. Then, a parametric analysis is conducted to estimate the significance of the design parameters that affect the antenna's performance. Finally, a prototype at 11.0 GHz is fabricated to validate the design. The measured results are in good agreement with the simulated ones, which shows that the design can be easily applied to other frequency and that the design may be a good candidate for the CP antenna family. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:377–381, 2015

Defect modes in a one-dimensional photonic crystal with a chiral defect layer

We investigate the propagation of electromagnetic waves in a one-dimensional photonic crystal containing a defect layer made of an isotropic chiral medium. Using the invariant imbedding method, we calculate the transmission spectrum for both linearly- and circularly-polarized incident waves. In the normal incidence case, there is one defect mode, which does not depend on the chiral index and the polarization of the incident wave. When the waves are incident obliquely, however, we find that there appear double defect modes regardless of the polarization. The interval between the two defect frequencies increases monotonically as the chiral index or the incident angle increases. We argue that this phenomenon occurs due to the coupling and conversion between s and p waves inside the chiral defect layer.

A New Design of Ka-Band Circularly-Polarized Antenna

A new ka-band circularly-polarized antenna is presented in this paper, in which a linearly-polarized wave is conversed into a circularly-polarized wave with a circular waveguide polarizer. After simulation and optimization with HFSS (High Frequency Structure Simulator), a compact circularly-polarized antenna is designed with a total height less than 25mm. More simple and easier structure is adopted to achieve a low-profile circularly-polarized antenna.

Broadband circular and linear polarization conversions realized by thin birefringent reflective metasurfaces

Broadband circular and linear polarization conversions have been proposed in the paper by using thin birefringent reflective metasurfaces, which are composed of two orthogonal I-shaped structures placed on the top of a printed circuit broad with grounded plane on the bottom. We show that the metasurface manipulates the reflective phases of two orthogonal linearly-polarized waves independently by changing the dimensions of I-shaped structure. Hence, the polarization states of a linearly-polarized incident wave with normal incidence can be manipulated as desired after reflected by the anisotropic metasurface. Two polarization conversions have been presented by using such thin birefringent reflective metasurfaces: from linearly-polarized wave to circularly-polarized wave, and from linearly-polarized wave to cross-polarized wave. The metasurfaces work at microwave frequency, and the axial ratio better than 1dB is achieved within fractional bandwidth of 15% for circular polarization. Numerical and experiment results demonstrate good polarization conversions in a broad frequency band, which have excellent agreements with the theoretical calculations.

Design of a CPW-fed slot antenna with small size and ultra-broadband circularly polarized radiation

In this research, a coplanar waveguide (CPW)-fed slot antenna is proposed with a compact size and an ultra-broadband circularly polarized (CP) radiation. The proposed antenna, just with a small size of 40 mm × 40 mm × 1 mm in overall configuration, achieves an ultra-broad CP bandwidth of 68.1% from 3.05 to 6.2 GHz, suitable for both WiMAX (3.3–3.8 GHz) and WLAN (5.15–5.35 GHz/5.725–5.825 GHz) systems. The presented antenna proposes two linked rectangular slots in the ground to obtain CP radiations. The linked slots can also be considered as a square slot with two perturbations in the corners. The perturbations can split the fundamental resonant mode into two near-degenerate modes, leading to CP waves. The adjacent excited CP modes are merged for ultra-wideband CP radiation. With a symmetric series impedance line connected to CPW feedline, broadband input impedance matching from 2.65 to 6.8 GHz can be obtained. The proposed design has been verified by the simulated and measured results. The future MIMO potential of the proposed CP antenna has also been studied.

Optical isolation via unidirectional resonant photon tunneling

We show that tri-layer structures combining epsilon-negative and magneto-optical material layers can exhibit unidirectional resonant photon tunneling phenomena that can discriminate between circularly polarized (CP) waves of given handedness impinging from opposite directions, or between CP waves with different handedness impinging from the same direction. This physical principle, which can also be interpreted in terms of a Fabry-Perot-type resonance, may be utilized to design compact optical isolators for CP waves. Within this framework, we derive simple analytical conditions and design formulae, and quantitatively assess the isolation performance, also taking into account the unavoidable imperfections and nonidealities.

Effect of laser polarization on quantum electrodynamical cascading

Development of quantum electrodynamical (QED) cascades in a standing electromagnetic wave for circular and linear polarizations is simulated numerically with a 3D PIC-MC code. It is demonstrated that for the same laser energy the number of particles produced in a circularly polarized field is greater than in a linearly polarized field, though the acquiring mean energy per particle is larger in the latter case. The qualitative model of laser-assisted QED cascades is extended by including the effect of polarization of the field. It turns out that cascade dynamics is notably more complicated in the case of linearly polarized field, where separation into the qualitatively different “electric” and “magnetic” regions (where the electric field is stronger than the magnetic field and vice versa) becomes essential. In the “magnetic” regions, acceleration is suppressed, and moreover the high-energy electrons are even getting cooled by photon emission. The volumes of the “electric” and “magnetic” regions evolve periodically in time and so does the cascade growth rate. In contrast to the linear polarization, the charged particles can be accelerated by circularly polarized wave even in “magnetic region.” The “electric” and “magnetic” regions do not evolve in time, and cascade growth rate almost does not depend on time for circular polarization.

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 NOVEL SINGLE FEED OMNIDIRECTIONAL CIRCULARLY POLARIZED ANTENNA WITH WIDE AR BANDWIDTH

A novel omnidirectional circularly polarized (CP) antenna with single feed is proposed for 2.4GHz WLAN applications. Based on the zeroth-order resonance (ZOR) mode of epsilon negative (ENG) transmission line (TL), the antenna excites uniform vertically polarized E-fleld just as the monopole does. A modifled Alford loop with electromagnetic coupling fed by L-shaped strip consists of four curved branches, which is placed on the top of the antenna and generates an equivalent horizontally polarized magnetic dipole mode. Once the two orthogonally polarized components are equal in amplitude but difierent in phase by 90 - , omnidirectional CP wave can be obtained. The measured results show that the impedance bandwidth (S11 < i10dB) is 6% (2.38{2.53GHz), and the 3-dB axial ratio bandwidth in the azimuth plane is very wide which achieves 54% (1.60{2.80GHz). Additionally, the 3-dB axial ratio beamwidth is over 50 - for radiation pattern in elevation plane. Moreover, the antenna achieves excellent omnidirectional right-hand CP performance with a variation of 0.5dB in the azimuth plane and an average gain over 1.5dB across the operating band, which are well applied to the wireless system.

Screw split ring resonator as building block of three-dimensional chiral metamaterials

We proposed and numerically investigated the influence of spatial topology on the infrared frequency region response of chiral metamaterials based on discrete deformed split ring resonators. Compared with the well studied continuous helix, the proposed metamaterials with discrete topology exhibit broad band chiral electromagnetic response. It is shown that the conversion between left and right circular polarization waves for our model is much broader than the continuous helix model. The observed cross-coupling between electric and magnetic fields results from the chiral electric currents on the resonators due to the broken mirror symmetry. The findings are useful for the design of future real three-dimensional chiral metamaterials with tunable optical response.

The interference effect in electron scattering on a nucleus in the field of two pulsed laser waves of circular polarization

Electron scattering on a nucleus in the field of two unidirectional pulsed laser waves of circular polarization is considered. The interference effect was detected if an electron scatters in the plane determined by the direction of laser wave propagation and the initial electron momentum. In this kinematics the electron emits and absorbs photons of both waves in a correlated manner. Broadening of partial differential cross sections is studied near the interference outgoing angle of the electron. It is shown that the partial probability of stimulated processes in the interference region may be five orders of magnitude greater than the corresponding probability of processes in any other geometry. The results may be experimentally verified, for example, in the framework of the FAIR (Facility for Antiproton and Ion Research, Darmstadt, Germany) project.

Circular Polarization in Defected Hexagonal Shaped Microstrip Antenna

A novel circular polarization (CP) design of a single-feed Hexagonal shaped microstrip antenna for enhanced antenna parameters is presented. The CP design is obtained by placing three isosceles triangular defects at proper locations in the hexagonal radiating patch as well as in the square ground plane. By adjusting one of the side lengths of the triangular defect, slightly longer or shorter than that of the others, two orthogonal near degenerate resonant modes for CP radiation are excited. Moreover, the 3 dB axial ratio bandwidth is surrounded by the 10 dB impedance bandwidth, to ensure that the antenna radiates CP waves in its impedance band. The antenna gain of the proposed antenna has increased by 5.34 dB (7.93 vs. 2.59 dB), as compared to the hexagonal microstrip antenna with triangular truncations in patch but without triangular defects in the ground plane having same substrate material, height and same radiating patch size and shape. Prototype antenna is fabricated for experimental evaluation. Simulated and measured results are in good agreement with each other.

A comparison of parametric decay of oblique Langmuir wave in high and low density magneto-plasmas

The parametric decay instability of an obliquely propagating Langmuir wave into the low-frequency electromagnetic shear Alfven wave and the Left-Handed Circularly Polarized wave has been investigated in an electron-ion plasma, immersed in a uniform external magnetic field. Quantum magneto-hydrodynamic model has been used to find the linear and non-linear response of a high density quantum magneto-plasma. Going to the classical limit (ℏ→0) retrieves the results for low density classical plasma. Nonlinear dispersion relations and growth rates are derived with analytically and numerically. It is observed that growth rate in the high density degenerate magneto-plasma increases exponentially, while in the low density classical case it increases logarithmically.