Circularly Polarized Wave Research Articles

A Low Cross-Polarization Configuration Method for Phased Array Radar Antenna

The cross-polarization isolation (CPI) is a key parameter to assess the dual-polarization antenna because the cross-polarization closely affects the antenna application. A polarization state configuration (PSC) approach is proposed to configure the polarization state of the polarimetric phased array radar antenna. Unlike the traditional fixed polarization states such as the linear polarization (LP) and the circular polarization (CP), the PSC method modulates the polarization state of the radiated wave continuously. In addition, the optimal excitation magnitude and phase of the dual-polarization element is calculated, thereby maximizing the CPI. Most of the configured polarization state is the elliptical polarization (EP), and a lower cross-polarization level and higher CPI could be obtained. This method could expand the acceptable angle range when compared with the LP and CP waves. Numerical simulations and comparisons are conducted to manifest the validity of the proposed method.

A Loop-Line Antenna with Enhanced Bandwidth of Circular Polarization

We investigate a circularly polarized (CP) transmission-line antenna composed of loop radiation elements, called a loop-line antenna. To enhance the CP wave bandwidth, an isolated loop radiation element is first analyzed using the method of moments. It is found that a CP wave bandwidth for a 3 dB axial-ratio criterion has a maximum value of 8%. On the basis of the analysis results, we design the loop-line antenna. It is found that the antenna shows a CP wave bandwidth of 6%, which is twice as wide as that of a conventional loop-line antenna. The analysis results are verified with experimental ones. In addition, a condition for wideband CP radiation is discussed and found to be a composite radiation element consisting of two CP loops.

Modified Crossed-Wire Antennas Radiating a Circularly Polarized Conical Beam

Two types of modified crossed-wire antennas are investigated to enhance a circularly polarized (CP) wave bandwidth. The wire length of each antenna is increased twice as long as that of the original antenna. First, a bent-type antenna is analyzed using the method of moments. It is found that the CP wave bandwidth for a 3 dB axial ratio criterion is twice as wide as that of the original antenna. Next, a spiral-type antenna is analyzed. It is revealed that the antenna shows a CP wave bandwidth of 28%, which is wider than that of the original antenna by a factor of 3.5. The analysis results are validated by experimental work.

Dual-Band Circularly Polarized Dielectric Resonator Antenna for WLAN and WiMAX Applications.

In this paper, a new dual-band circularly polarized (CP) dielectric resonator antenna for WLAN and WiMAX applications is proposed. The dielectric resonator has an asymmetric Y-shaped geometry. By properly selecting the length of the arms, the pairs of fundamental (TE) and second-order (TE) are excited separately at the design frequencies to radiate the CP wave. The measurement shows that the fabricated antenna exhibits a wide impedance bandwidth for |S−10 dB of 62.07% (2.2–4.18 GHz). The far-field measurements in the broadside direction demonstrated a dual-band CP response with 3 dB ARBWs of 4.92%(2.38–2.5 GHz) at the lower and 12.64% (3.26–3.70 GHz) at the upper band. The measured CP bands cover the entire frequency range of WLAN (2.401–2.495 GHz) and WiMAX (3.4–3.69 GHz) at the lower and upper bands, respectively.

Chiral coding metasurfaces with integrated vanadium dioxide for thermo-optic modulation of terahertz waves

ld of electromagnetics, there are many limitations to achieve simultaneous polarization conversion and wavefront control. The chiral coding metasurface based on the Pancharatnam-Berry (P–B) phase effectively helps to alleviate these restrictions and shows strong control over the terahertz radiation field. In this paper, the principle of chirality is theoretically analyzed and verified by simulation results. The circular dichroism ΔR (chiral effect) achieves 0.8. By combining the chirality and thermo-optic effect of vanadium dioxide (VO2), we propose three switchable metasurfaces for quantitative splitting and high-efficiency focusing (low-efficiency divergence) of terahertz beams. The amplitude switching efficiency of the circularly polarized (CP) and linearly polarized (LP) pencil beams is above 0.85. Under the excitation of LP waves, the first two chiral metasurfaces have one and two temperature-switchable reflective right-handed circularly polarized (RCP) pencil beams, respectively. The third chiral metasurface generates high-efficiency focusing for RCP waves and low-efficiency divergence for left-handed circularly polarized (LCP) waves. This work provides new methods for more flexible modulation of CP and LP waves and promotes the application of terahertz coding metasurfaces in communication.

Obtaining single mode spoof surface plasmon polaritons under circular polarized incidence

The study of spoof surface plasmon polaritons (SSPPs) has become one of the hotspots of electromagnetics because of their peculiar properties and broad application prospects. Compared with linear polarized (LP) waves, which can be efficiently coupled into single (TE or TM) mode SSPPs by phase gradient metasurfaces (PGMs), circular polarized (CP) waves are difficult for SSPPs devices to use. Although Pancharatnam–Berry (PB) phase manipulating metasurfaces can successfully couple CP waves into hybrid (TE and TM) modes SSPPs, arbitrary pure mode SSPPs are still unavailable under CP incidence. In this study, a new scheme of PGMs coupler was designed to solve the above problem. The multi-layered PGMs consist of V-shaped structure and patch structure, which play the roles of achieving circular-to-linear polarization conversion and providing phase gradient respectively. A plasmonic metasurface placed 10 mm below the PGMs can support the propagation of TE and TM modes SSPPs. As a result, arbitrary single mode SSPPs can be excited and propagate under CP incidence at 12 GHz, which means that we can convert CP waves into either TE or TM mode SSPPs we want through this PGMs coupler. Both simulations and measurements demonstrated novel ideas, and the calculated coupling efficiencies are all higher than 62.0%. The PGMs coupler we designed will break the limitation of incident waves on coupled SSPPs and provide a new method for the control and utilization of CP waves in engineering.

Cyclotron Emission with a Helical Wavefront from an Electron Accelerated by the Circularly Polarized Wave

Cyclotron Emission with a Helical Wavefront from an Electron Accelerated by the Circularly Polarized Wave

An Electronically-Switched Frequency-Agile Hybrid Dielectric Resonator Antenna With a Fixed Reconfigurable Circularly Polarized Band

In this article, an electronically-controlled frequency-agile hybrid dielectric resonator antenna is presented that also produces a reconfigurable circularly polarized (CP) wave over a specific frequency range. Two L-shaped metallic strips are placed adjacent to a partial ground plane that can be shorted/detached in four combinations using two PIN diodes (D1 and D2). Frequency reconfigurability is achieved by switching from both OFF to at least one ON state to yield a single and dual-band responses for the former and latter, respectively. The Eigen mode simulation reveals that the upper-band is mainly attributed to the quasi-TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">δ21</sub> mode of the rectangular dielectric resonator. The lower-band in one and two ON-states arises due to the dielectric-loaded monopole antenna and the strip-loaded partial ground plane, respectively. The ON-OFF state produces a right-handed CP wave at the lower band that can be reconfigured to a left-handed CP wave by switching to OFF-ON state. A fabricated sample is measured and simulation results are validated. The measured -10 dB impedance bandwidths for OFF-OFF, ON-ON, OFF-ON, and ON-OFF are 13.31% (4.42-5.05 GHz), 11.30% (2.17-2.43 GHz)/27.43% (3.68-4.85 GHz), 30.64% (2.46-3.35 GHz)/17.94% (4.16-4.98 GHz), and 26.57% (2.48-3.24 GHz)/18.7% (4.12-4.97 GHz), respectively. The measured 3 dB axial ratio bandwidths are 12.20% (2.54-2.87 GHz) and 10.95% (2.59-2.89 GHz) when D1 and D2 are turned-ON alternatively.

Broadband Vortex Beams Generation With Narrow Divergence Angle Using Polarization Insensitive Metasurface

In this paper, we propose a polarization insensitive metasurface to generate broadband vortex beams with narrow divergence angle. The metasurface is composed of $\mathrm {30\times 30 }$ I-shaped metal elements printed on the F4B substrate with metal ground plane. The wideband is realized by optimizing the parameters of I-shaped unit cell to adjust the resonant frequency. A 360° phase range is achieved by rotating the element along the central axis. The phase superposition method is used to design the metasurface to generate vortex beams with narrow divergence angle. The proposed metasurface can generate broadband vortex beams under circular polarization (CP) and linear polarization (LP) wave excitation. The far-field radiation patterns and near-field characteristics of the metasurface are simulated to verify the proposed design. The gain of vortex beams is better than 15 dBi within 12–20 GHz (relative bandwidth of 50%), and the maximum gains are 23.2 dBi, 25.3 dBi for CP and LP cases, respectively. The broadband metasurface is fabricated and measured, and the measured results agreed well with the simulated ones. The proposed design provides a convenient and flexible way to realize broadband vortex beams with narrow divergence angle.

45° Linearly Polarized and Circularly Polarized High-Scanning-Rate Leaky-Wave Antennas Based on Slotted Substrate Integrated Waveguide

A class of 45° linearly polarized and circular polarized high scanning rate leaky wave antennas are proposed in this paper, which is based on slow-wave substrate integrated waveguide structure. High scanning rate leaky wave antennas have recently become attractive for imaging applications and automotive radar. These applications also require a continuous scanning range without an open stopband, as seen at broadside for ordinary leaky wave antennas. Furthermore, both 45° linearly polarization and circularly polarization are required in practical applications. In this paper, we propose an all-in-one leaky wave antenna design, which features high scanning rate, continuous scanning capability across the broadside, 45° linear polarization or circularly polarization, single-layer configuration, and single-side radiation. Two design examples are provided to illustrate the proposed principle. Both simulation and experimental validation are given.

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.

Circular Polarization Antenna-Filter

A two-function filtering antenna device in the 1-2 GHz band is investigated. The device radiates or receives electromagnetic waves of circular polarization and simultaneously performs the function of a second-order bandpass filter. The considered design consists of a dual-mode printed antenna-resonator coupled with two non-radiating resonators which are fed by a quadrature balanced power divider. Using the model in the form of an equivalent circuit the main features of the structure synthesis and its tuning are analyzed including potentially achievable characteristics. The results of the numerical simulations using electromagnetic software are presented in comparison with the experimental characteristics for the prototype made of high-permittivity high-quality ceramics. It is found that the proposed design is characterized by an almost two-fold increase of the operating frequency band compared to the resonant antenna itself while maintaining a low level of cross-polarization within the passband. It is also shown that the design has the frequency response of the second-order bandpass filter.

Investigation of the null reconstruction effect of an orthogonal elliptical polarization hologram at a large recording angle

We report on the null reconstruction effect (NRE) of an elliptical polarization volume hologram with orthogonal elliptically, circularly, and linearly polarized waves, respectively. The NRE is a special phenomenon in polarization holography, which means the diffraction efficiency declines to zero when the hologram is reconstructed by an orthogonally polarized reading wave. In our previous work [Opt. Express24, 1641 (2016)OPEXFF1094-408710.1364/OE.24.001641; Opt. Lett.42, 1377 (2017)OPLEDP0146-959210.1364/OL.42.001377; Opt. Express23, 8880 (2015)OPEXFF1094-408710.1364/OE.23.008880], the NRE of polarization holography recorded by linear and circular polarization waves has been investigated. Compared with linear and circular polarization holography, elliptical polarization holography represents a more general and unified recording hologram. However, no work on the NRE of elliptical polarization holography, as far as we know, has been reported until now. In this paper, the NRE of elliptical polarization holography is investigated and demonstrated theoretically and experimentally. First, the conditions of achieving NRE in elliptical polarization holography are studied based on vector holography theory. The results indicate that the NRE is a common phenomenon in polarization holography written by linear, circular, and elliptical polarization waves. Then, a series of experiments of NRE in a polarization hologram written by orthogonal elliptically, circularly, and linearly polarized waves is carried out. The NRE of elliptical polarization holography is experimentally observed, and the results are in nice agreement with the theoretical analysis. The NRE of elliptical polarization holography is expected to be applied in high-density optical data storage and polarization-controlled holographic elements.

Low-RCS Multi-Beam Metasurface-Inspired Antenna Based on Pancharatnam–Berry Phase

Inspired by the checkerboard metasurfaces, we propose the design of low-RCS multi-beam linearly polarized (LP) array antenna based on Pancharatnam–Berry (P-B) phase. The antenna array is composed of a number of split-ring resonators (SRRs) with a rotation angle $\alpha $ difference. For circularly polarized (CP) waves, each two adjacent SRRs exhibit $\alpha $ and $2\alpha $ P-B phase differences under feeding and normally illuminating, respectively. Because of this, the SRR array exhibits different phase gradients for radiated and reflected waves. To obtain multiple LP beams, reversed phase gradients for CP waves are alternatively arranged in 1-D or 2-D on the array, leading to two or four beams, respectively. Under normally illuminating, the reflection phases along the array form the checkerboard configuration, which can reduce both the in-band RCS and out-of-band RCS of the antenna array. As an example, we demonstrate a low-RCS four-beam antenna operating in ${X}$ -band. Both the simulated and measured results show that the maximal realized gain of each beam reaches up to about 13.6 dB at 10.2 GHz. To evaluate the RCS reduction performance, we measured specular reflection of the prototype under normal incidence. The reflection is reduced by more than 10 dB in 9.7–10.3 GHz and by more than 5 dB out-of-band in 10.3–14.0 GHz. The design method provides an alternative to the design of low-RCS and low-profile antenna arrays.

Polarization conversion and phase modulation of terahertz electromagnetic waves via graphene-dielectric structure

In this paper, by using the 4 × 4 transfer matrix approach, the reflection and transmission of circularly polarized (CP) waves which are obliquely incident to the periodic structure comprising of graphene-dielectric layers are investigated. The results indicate that by applying a magnetic field in appropriate direction there exists an omni-directional band gap in the transmission spectrum either left or right CP wave. The given structure can convert the linearly polarized wave to CP wave in reflected and transmitted waves. Furthermore, the dependence of the ellipticity of the reflected and transmitted waves to the applied magnetic field and the chemical potential of the graphene is studied. Such structures can be used as a polarization converter and phase modulator in the terahertz frequency range.

A Simplified Model for Predicting the Installed Performance of Circularly Polarized Antennas

We propose a simplified equivalent model for predicting the installed performance of circularly polarized (CP) antennas. We use a set of infinitesimal sources to represent the irradiated fields of an antenna of interest; however, instead of using infinitesimal dipoles, our source is composed of a set of infinitesimal crossed dipoles, the most basic radiator that generates CP waves. This choice facilitates the optimization process and still maintains the analytical aspect of the model; the irradiated fields can be described analytically. We achieve a reduction in computational cost when comparing to direct modeling, without impairing the accuracy of the model during the antenna placement task, and a reduction of optimization time when comparing to classical dipole models. Also, the equivalent model building step has reduced a computational cost for CP antennas. In order to validate our model, we construct a scaled model of a circular cylinder with a top-mounted GPS antenna, and we measure its radiation pattern in an anechoic chamber. The experimental results are in remarkable agreement with those simulated using the proposed equivalent model.

Circularly Polarized Fabry-Perot Antenna Employing a Receiver–Transmitter Polarization Conversion Metasurface

This study presents a linear-to-circular polarization conversion metasurface (PCM) based on a novel unit cell for a circularly polarized (CP) Fabry-Perot (FP) antenna. The unit cell consists of a bottom linear-polarization patch and a top circular-polarization patch, which are separated by a metalized plane and connected by a metalized via. The bottom patch receives the power and transfers it to the top layer through the metalized via; the top layer then transmits the power into space. The metasurface is designed to have high reflectivity and an appropriate reflection phase to compose a resonate cavity with the ground plane. The capability of linear to circular polarization conversion is provided to the PCM by adjustment of the transmission magnitude and phase. A slot coupled patch antenna is used as the feeder due to its stable broadside radiation. The linearly polarized wave emitting from the feeder resonates in the cavity and then is converted into a CP wave when it comes out of the cavity. A prototype antenna is fabricated and measured. The measurement results show that the antenna has good circular polarization performance within the band of 9.8–10.2 GHz. The maximum gain of the antenna reaches 17.8 dBic at 10 GHz, with an aperture efficiency of 53%. The proposed antenna outperforms most of the previously reported CP FP antennas due to its low profile, high gain, and relatively high efficiency.

60 GHz Wideband Low-Profile Circularly Polarized Patch Antenna With an Asymmetric Inset

This letter presents a low-profile wideband circularly polarized (CP) patch antenna with a single layer of dielectric. An asymmetric inset is incorporated in the antenna structure using two parallel slots, each containing a patch, with a length difference of $\frac{{{\boldsymbol {\lambda }_{\boldsymbol {eff}}}}}{4}$ . The length difference leads to a 90° phase difference between the currents on the left- and the right-side patches, causing the antenna to radiate a CP wave. Additionally, a broad bandwidth is achieved because of the additional resonance point generated by a quarter-wave resonance from the asymmetric inset. The proposed antenna achieves a peak gain of 7.4 dBiC and fractional bandwidths of 17.2%, 15.1%, and 13.3%, respectively, for –10 dB $S_{11}$ bandwidth, 3 dB gain bandwidth, and axial-ratio bandwidth with a single-dielectric-layer structure.

A Single-Layer Wideband Circularly Polarized Antenna for Millimeter-Wave Applications

A wideband traveling-wave circularly polarized (CP) antenna printed on a single-layer PCB for millimeter-wave (MM-Wave) applications is presented in this communication. The proposed antenna radiates the CP wave on the basis of the principle similar to the classical endfire-mode helical antenna. The proposed antenna is terminated with an absorber to realize traveling-wave radiation. The traveling-wave working mechanism causes the proposed antenna to have a frequency scanning function and higher stability compared with resonant antennas. Curved microstrip transmission lines are adopted as the CP radiation elements; the whole array antenna is etched on a single-layer substrate. A prototype operating at 30 GHz is fabricated and measured. The radiation beam of the proposed antenna scans from − 14.5° (28 GHz) to +22.5° (34 GHz), the axial ratios are lower than 3 dB, and the measured gains show a maximum value of 21.9 dBi at 33 GHz and a minimum value of 20.3 dBi at 28 GHz. The measured $| \text {S}_{11} |$ and $| \text {S}_{21} |$ are lower than −10 and −16 dB, respectively, in the frequencies mentioned above.

Extraordinary spoof surface plasmon polaritons excitation by linear and circular polarization conversions phase gradient metasurface

To excite spoof surface plasmon polaritons (SSPPs), phase gradient metasurface (PGM) has been developed as an efficient scheme of couplers. While under circular polarization (CP) incidence, hybrid (TM and TE) modes SSPPs are inevitably excited. Most SSPPs applications are working with single mode, which limits the energy utilization for CP incidence. In order to solve the problem, a novel scheme of PGM was designed to convert the CP incident waves into single TM or TE mode SSPPs. The coupler is constructed with two parts: the PGM part is composed of I-shaped structure, provided with the function of SSPPs excitation and polarization conversions, the mushroom part plays the role to guide out the excited SSPPs with good wave vector matching. Appropriate reflection coefficients of the unit cells were found to make up phase gradient of the PGM at 10 GHz, then TM or TE mode SSPPs can be excited under RCP or LCP incident waves, respectively. Also, we will show that hybrid (TM and TE) modes SSPPs can be excited under linear polarization (LP) incidence, which is different from previous couplers and may find use in some special applications. The theoretic design is corresponding to both simulations and experiments results. It may open up a new way for polarization control of SSPPs, and broaden the utilization of CP waves and LP waves in SSPP devices.