Wideband Circularly Polarized Research Articles

Circularly Polarized Beam-Steering Microstrip Leaky-Wave Antenna Based on Coplanar Polarizers

A periodic frequency-scanning one-dimensional microstrip leaky-wave antenna with circular polarization is proposed in this letter. The introduction of the novel square patch and stub, which are printed on the same layer of the microstrip array, can effectively transform the polarization type into left-handed circular polarization (CP). The two parasitic elements in each unit cell can be excited by the host meandering microstrip line without extra feeding networks, which introduce one orthogonal polarized wave to satisfy the condition of CP radiation. A prototype includes nine modified unit cells is fabricated and measured. The designed antenna covers an impedance bandwidth over 26.1% with | <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> | < −10 dB and a CP bandwidth over 11.2% with |AR|< 3 dB in the measurement. The main beam scans from −4° to 18° in the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">yoz</i> plane (beam scanning plane) through broadside direction (0 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> ) while maintaining good CP property.

High Gain Wideband Circularly Polarized Microstrip Antenna Array

A wideband high gain circularly polarized microstrip antenna (CP MSA) array is presented in this communication. In the proposed CP MSA array, the elements are designed at 3.5 and 5.8 GHz, which are sequentially rotated to form a planar array. The array elements are fed using the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$TM_{110}$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$TM_{210}$ </tex-math></inline-formula> modes of a center CP MSA. This arrangement achieves an axial ratio (AR) bandwidth of 63.7% (3.25–6.29 GHz) and improves gain over a wide bandwidth. The peak gain of the array is 17.77 dBic with a 3-dB gain bandwidth of 53.9%. The center MSA of the array is fed using four orthogonal printed L-probes with quadrature phase difference. The proposed CP MSA array has an <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$|S_{11}|\leq -10$ </tex-math></inline-formula> dB bandwidth of 63.3% (3.32–6.4 GHz).

Wideband Circularly Polarized Filtering Hybrid Antenna

In this paper, a wideband circularly polarized (CP) filtering hybrid antenna is presented. The liquid dielectric resonator (DR) is excited by a microstrip-coupled cross-slot to generate CP radiation. Four inverted L-shaped strips are loaded on the ground plane to introduce an additional CP resonant point, then two adjacent axial ratio (AR) minima are combined to improve the bandwidth of the single-feed CP antenna. By etching a U-shaped slot and loading a C-shaped microstrip stub on the microstrip line, two tunable radiation nulls near the edges of the working band can be obtained without any extra filtering circuits. To verify the design, a filtering CP antenna is designed, fabricated, and tested. Measured results show that the antenna provides wider 3-dB AR and an impedance bandwidth of 38.8% from 1.36 to 2.02 GHz and 39.4% from 1.37 to 2.04 GHz, respectively. The realized gain of the proposed antenna is stable at about 7.8 dBi within the whole working band. A reasonable agreement between measured and simulated results is observed.

3D-printed cavity backed crossed dipole antenna for high gain, wideband circular polarization in sub-6 GHz

Triple-arm crossed dipole antenna (CPDA) backed by 3D printed cavity exhibits high gain over wideband axial ratio for sub-6 GHz applications is presented. To improve peak gain and axial ratio bandwidth performance, multiple radiating arms are introduced. The arms are cascaded using vacant quarter rings to obtain circular polarization. Unlike the conventional CPDAs that yield single circular polarized (CP) wave, two CP waves produced by double-arm or triple-arm CPDAs enhances overall gain performance across wideband axial ratio. The length and orientation of the multiple arms in the CPDA determine the maximum current generated on the crossed dipole antenna, resulting in an improved gain since two CP waves are combined in the free space. To further increase boresight gain, 3D printed cavity is placed beneath the triple-arm CPDA. Unbalance impedance line presented in this work extends impedance bandwidth of the triple-arm CPDA to cover 3-dB axial ratio bandwidth. For validation purpose, a prototype was fabricated and measured. The measurement results demonstrate that the triple-arm CPDA has a boresight gain of 8.91–11.7 dBic within 3-dB axial ratio bandwidth of 51.4% (3.25–5.5 GHz). The proposed antenna produces a stable gain within sub-6 GHz bands.

A wideband circularly polarized monopole antenna with elliptic ring slot patch using characteristic mode analysis

This article presented a wideband circularly polarization (CP) monopole antenna with elliptic ring slot patch using characteristic mode analysis (CMA). By analyzing the characteristic modes of elliptical patch and elliptical ring patch in turn, it is found that the elliptical ring slot patch can meet the phase requirement of CP. Then, the parasitic elliptical ring slot patch is used to broaden the impedance bandwidth and polarization bandwidth of the antenna. The broadband is obtained by the modal significance (MS) analysis, and the CP is realized by analyzing the characteristic current of two modes are orthogonal and the characteristic angle (CA) close to 90°. The proposed antenna was fabricated and measured with the size of 0.59λ0 × 0.59λ0 × 0.02λ0. The measured 3-dB axial ratio (AR) band is from 5.3 to 9.4 GHz (55.8%), and the −10 dB impedance band is from 4.5 to 9.7 GHz (73.2%).

A metasurface enabled dual band antenna exhibiting dual polarizations with reduced beam squint and cross polarization

A compact, dual-band metasurface-based microstrip patch antenna with both linear and circular polarization (CP) for multiband communication is reported in this work. The ingredients in the antenna design consist of a combination of metasurface and metamaterial inspired structures that are demonstrated as an effective technique to correct the beam squint problem and reduce the cross-polarized radiation, usually experienced by thick substrate-based broadband CP antennas. A fractal boundary metasurface is introduced to achieve CP over a small frequency band. Eight Electric-LC resonators are symmetrically placed in the same plane of the radiating patch to widen the CP bandwidth, correct the beam squint, reduce the cross-polarized radiation, and realize a subwavelength resonance of λ0/5.15 order. The measured impedance bandwidths (|S11| < −10 dB) of the proposed antenna are 7.8% (3.7–4.0 GHz) and 27.58% (5.05–6.65 GHz) in the lower and upper-frequency band, respectively. The measured 3-dB axial ratio bandwidth (ARBW) is 24.8% (5070–6510 MHz) at 5.8 GHz. The fabricated prototype has an overall size of 55 × 55 × 4.08 mm (0.696λ0 × 0.696λ0 × 0.051λ0 at 3.8 GHz or 1.063λ0 × 1.063λ0 × 0.078λ0 at 5.8 GHz) with a realized peak gain of 4 dBi in the lower band and 7.1 dBic in the upper band. The measured results are consistent with the simulation results.

A novel circularly polarized patch antenna based on polarization conversion metasurface for radiation and scattering performance improvement

A new design based on sequential-rotation arranged polarization conversion metasurfaces (PCMs) is proposed for reducing backscattering and improving radiation performance of circularly polarized (CP) patch antennas. The proposed antenna is composed of a conventional corner-truncated patch antenna loaded with a PCMs. The configuration of the PCMs increases the operating bandwidth and realized gain, as well as reduce radar cross section (RCS). The relative CP bandwidth (both |S11| < −10 dB and AR <3 dB) is improved to 13.65% due to achieving an additional mode by the PCMs. Also, the peak gain is enhanced by 6.6 dB. Moreover, an in-band and out-of-band RCS reduction is achieved compared with the conventional CP patch antenna due to the polarization conversion characteristic of the PCMs. The maximum RCS reduction is 27.5 dB within the band. This design enables an effective strategy for wideband, high-gain, and low-RCS CP patch antennas. A sample operating at C-band was fabricated and measured, demonstrating a satisfactory match between simulation and measurement results, so verifying the proposed idea.

Terahertz Wave Conversion From Linear to Circular Polarization by Graphene Metasurface Featuring Ultrawideband Tunability

This paper reports a detailed study of a graphene-based metasurface to function as tunable broadband linear to circular polarization converter in the terahertz gap. This device provides a wide polarization conversion band of 2.25 THz (3.75 THz to 6 THz) with an enhanced fractional 3-dB axial ratio bandwidth (FARBW) of 46.15%. The proposed structure consists of a simple tri-layer configuration where the meta-atom comprises a patterned graphene layer on a gold-backed silicon dioxide substrate. The proposed reflective-type linear to circular polarization converter (RLCPC) exhibits both right-handed and left-handed circular orientations of the reflected wave in two halves of the operating spectrum, further validated in terms of polarization ellipses developed by an inhouse code. The lack of experimental setup at the above said frequencies available to the authors in their country has been paid off by verifying the response using a detailed circuit model. The RLCPC maintains a thickness of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">λ_o</i> /7.69 with a lattice size of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">λ_o</i> /8.33. The structure also promises a stable wideband circular polarization conversion up to 20° and a dual-band circular polarization conversion up to 40° incident angle of the electromagnetic wave. This device can be useful for THz beam scanning antennas, RCS reduction and THz antennas for space and military radar applications.

High-Gain Wideband Circularly Polarised Fabry-Perot Resonator Array Antenna Using a Single-Layered Pixelated PRS for Millimetre-Wave Applications.

In this paper, a wideband and high-gain circular polarised Fabry–Perot Resonator Antenna (FPRA) with a single partially reflective surface (PRS) layer is automatically generated and optimised using a VBA-based interface system between CST Microwave studio and Matlab. The proposed PRS layer is a promising superstrate for wideband and high-gain FP resonator antennas due to its relatively high reflection coefficient magnitude and positive phase gradient, which resemble that of the optimum PRS over the relevant frequency band. The circular polarisation was achieved using a sequential feeding network for a 2 × 2 array air-gapped slot-coupled elliptical patch antenna. The proposed design achieved an impedance bandwidth of 48.58% (15.3 GHz) ranging from 23.84 GHz to 39.14 GHz, and the −3 dB gain bandwidth was 22.42% (6.25 GHz) from 24.75 to 31 GHz, with a peak gain of 17.12 dB at 29 GHz, and an axial ratio bandwidth of 21.75% (6.2 GHz). In addition, the achieved radiation efficiency was 90%. Consistent and almost invariant radiation patterns are achieved over the millimetre-wave frequency band of interest. The experimental and simulated results are in good agreement, justifying the feasibility of the proposed design as a high-gain and wideband FP resonator array antenna for Mm-wave applications.

Wideband low-RCS circularly polarized antenna with metasurface combining wave diffusion and polarization conversion

A novel and simple low-profile high-gain wideband circularly polarized (CP) slot antenna with low radar cross section (RCS) is presented. The proposed antenna is composed of a traditional linearly polarized (LP) slot antenna and an integrated metasurface-based superstrate. The superstrate consists of a center array with metasurface (MS) unit cells and four surrounding arrays with 4×4 MS unit cells. On the one hand, a wideband and high-gain CP radiation in the frequency band of 5.27-6.18 GHz (a relative bandwidth of 15.9%) is achieved by the polarization conversion property of the MS and four surrounding arrays. On the other hand, a broadband RCS reduction in the frequency band of 4.5-20 GHz (a relative bandwidth of 126.5%) is obtained by the combination of two electromagnetic wave diffusion principles. Inspired by C-band, X-band and Ku-band radar applications, a low-cost stealthy prototype with broadband low RCS and CP radiation is realized.

Circularly Polarized Millimeter Wave Frequency Beam Scanning Antenna Based on Aperture-Coupled Magneto-Electric Dipole

Based on the newly suggested wideband circularly polarized (CP) aperture-coupled magneto-electric dipole (MED), a millimeter-wave (mm-wave) frequency-scanned array (FSA) is proposed in this article. The MED is printed on two substrate layers. The electric dipole is two metal patches with perturbation structure, while the magnetic dipole is two rows of metal vias passing through the top substrate layer. The electric and magnetic dipoles, fed by a coupling slot, excite CP wave. By loading an arc-shaped vias row (AVR) at both ends of the magnetic dipole, the CP bandwidth with axial ratio (AR) less than 3 dB is extended to 40.9%. A new compact wideband transition from the rectangular waveguide (RWG) to the substrate integrated waveguide (SIW) is suggested as the feed structure for the CP FSA. A slow wave structure is etched on the ground of SIW to widen the beam scanning range. A 16-element array is designed and measured. The measured results show that the beam scanning range is 56° over 23–33 GHz band with a peak gain of 19.5 dBi. The CP mm-wave FSA has the advantages of wide scanning angle, low profile, and easy fabrication.

210–365 GHz 90° Differential Phase Shifter for Wideband Circular Polarizer

In this article, a wideband 90° differential phase shifter in the 210–365 GHz band with a fractional bandwidth of 54% was designed, fabricated, and measured to develop a wideband circular polarizer for millimeter/submillimeter wavelengths. To achieve a wide bandwidth, we designed a 90° differential phase shifter with a flat phase-difference characteristic by combining three different types of 90° differential phase shifters to cancel out the frequency dependence of the phase difference between the two polarizations. The developed phase shifter has a phase difference of 90 ± 6° and a return loss better than 17 dB for both polarizations over the frequencies 210–365 GHz, in addition to waveguide transitions necessary for <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</i> -parameter measurements. The developed phase shifter can be used as an alternative for achieving simultaneous observations of dual-polarization signals at 230 and 345 GHz, as proposed by the next-generation event horizon telescope, which aims to observe black holes.

Four-Port Orthogonal Circularly Polarized Dual-Band MIMO Antenna With Polarization and Spatial Diversity Using a Dual-Band Linear-to-Circular Polarization Converter

A dual-band circularly polarized (CP) four-port multiple-input-multiple-output (MIMO) antenna for K/Ka-bands fixed-satellite service is proposed in this communication. The single element of MIMO is composed of a cascade of two dipoles of different lengths resonating at around 20 and 30 GHz. An array of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$7 \times 7$ </tex-math></inline-formula> elements of the unit cell of the dual-band linear-to-circular polarization converter is placed at a distance of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda _{o}$ </tex-math></inline-formula> /4 ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda _{o}$ </tex-math></inline-formula> is calculated with respect to 19.51 GHz) in the endfire direction of MIMO antenna to obtain an orthogonal CP wave at the two frequency bands. The proposed CP antenna shows good MIMO performance with a correlation coefficient (CC) of less than 0.19 and diversity gain (DG) of better than 0.99 at both the frequency bands. The proposed MIMO also agrees with polarization and spatial diversity, and the CP nature at lower and upper frequency bands can be interchanged by exciting the orthogonal ports. A prototype of the MIMO antenna is fabricated, and the measured CP bandwidths of 11.51% and 3.69% are obtained in the lower (19.65–22.05 GHz) and upper (29.25–30.35 GHz) frequency bands, respectively. The proposed antenna can be used for the Ka-band: 29.5–30.0 and 19.7–20.2 GHz fixed satellite service as uplink and downlink frequencies, respectively.

Axial ratio tuned disk‐shapedS‐bandtriple notch circularly polarized slot antenna

Microstrip-line fed annular ring circularly polarized antenna is proposed in this work. The antenna is fabricated on a disk-shaped FR-4 substrate with annular ring slots etched in the ground. The overall space requirement of the antenna is 25 × 25 × 1.6 mm3. The antenna is modeled for triple notch wide band circular polarization operation in the frequency range from 2–4 GHz. A wide impedance band operation is be obtained by the introduction of slots and stubs. An impedance band- width of 1.8 GHz is accomplished with three notches at 2.4, 2.8, and 3.3 GHz.

A Low-RCS and Wideband Circularly Polarized Array Antenna Co-Designed With a High-Performance AMC-FSS Radome

In this letter, we investigate a low radar cross-section (RCS) wideband circularly polarized microstrip array antenna co-designed with a high-performance artificial magnetic conductor and frequency selective surface (AMC-FSS) radome. Compared with the absorbent frequency selective radome-based antenna, the proposed co-designed antenna can achieve a relatively low gain loss in an extremely wide frequency range with wideband in-band and out-of-band RCS reduction, due to the introduction of a novel AMC-FSS radome which can achieve low insertion loss and wideband transmission by combining a double-layer miniaturized bandpass FSS and a single-layer chessboard AMC surface. We demonstrate the effectiveness of the proposed AMC-FSS radome and co-designed antenna through simulations and measurements. The results show that the gain deterioration of the co-designed antenna is only 0.42 dB at the central frequency of 4.8 GHz and less than 1 dB in the wide frequency band, ranging from 4.23 to 5.38 GHz with a relative bandwidth of 23.9%. At the same time, the monostatic RCS for a normal incidence is greatly reduced from 4 to 18 GHz.

Compact Wideband Circularly Polarized Loop Antenna Based on Dual Common and Differential Modes

This letter presents a novel design method of a compact wideband loop antenna for circularly polarized (CP) radiation based on two sets of common modes (CMs) and differential modes (DMs). Different CMs and DMs are excited in the loop antenna with the same amplitude of radiated electric fields by using equal-amplitude and in-phase excitation. A wideband CP radiation performance is achieved through the combination of two sets of CMs and DMs with an innate 90° phase delay. Moreover, the shared-aperture configuration of CMs and DMs achieves a size reduction. An experimental prototype was fabricated and measured to verify the design concept for CP operation. The experimental results indicate that an overlapped bandwidth of 2.30–3.40 GHz (38.6%) with | <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> |<–10 dB, axial ratio <3 dB, and gain variation <1 dB is obtained within compact size of 0.4 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">λ</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> × 0.4 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">λ</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> × 0.009 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">λ</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">λ</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> is the wavelength in free space at the center operating frequency). Such a compact, wideband, and stable-gain CP antenna with a simple feed strategy is a promising candidate for wireless communication.

A Circularly Polarized Dielectric Resonator Antenna Based on Quasi-Self-Complementary Metasurface

In this communication, a circularly polarized (CP) dielectric resonator antenna (DRA) based on quasi-self-complementary metasurface (MS) has been proposed. Due to the quasi-self-complementary characteristic of the proposed MS, the phase difference of the transmission coefficients between two orthogonal linear polarizations is 90° in the frequency band from 25.5 to 26.5 GHz. The DRA with the proposed MS can realize the transformation from linear polarization to circular polarization at 25.6–25.99 GHz. The proposed MS significantly increases the gain and CP bandwidth of the DRA. The working bandwidth of the proposed antenna is included in the New Radio FR2 frequency band totally, which is considered as the follow-up expansion frequency of fifth-generation (5G) communication. The proposed MS-based antenna has realized the linear-to-circular polarization transformation in millimeter frequency band without additional substrate, which has not been researched yet.

A Novel Design and Development of a Strip-Fed Circularly Polarized Rectangular Dielectric Resonator Antenna for 5G NR Sub-6 GHz Band Applications.

In this article, a rectangular dielectric resonator antenna (RDRA) with circularly polarized (CP) response is presented for 5G NR (New Radio) Sub-6 GHz band applications. A uniquely shaped conformal metal feeding strip is proposed to excite the RDRA in higher-order mode for high gain utilization. By using the proposed feeding mechanism, the degenerate mode pair of the first higher-order, i.e., at 4.13 GHz and at 4.52 GHz is excited to achieve a circularly polarized response. A circular polarization over a bandwidth of ~10%, in conjunction with a wide impedance matching over a bandwidth of ~17%, were attained by the antenna. The CP antenna proposed offers a useful gain of ~6.2 dBic. The achieved CP bandwidth of the RDRA is good enough to cover the targeted 5G NR bands around 4.4–4.8 GHz, such as n79. The proposed antenna configuration is modelled and optimized using computer simulation technology (CST). A prototype was built to confirm (validate) the performance estimated through simulation. A good agreement was observed between simulated and measured results.

Gain-Enhanced Wideband Circularly Polarized Antenna with a Non-Uniform Metamaterial Reflector

In this paper, a gain-enhanced wideband circularly polarized (CP) antenna with a non-uniform metamaterial (NUM) reflector is presented, which is composed of a modified wide S-shaped slot antenna and a NUM reflector. To achieve a wideband CP operation, a modified S-shaped slot is fed by an L-shaped microstrip feedline that ends with a triangular patch to improve axial ratio (AR) bandwidth and impedance bandwidth. A NUM reflector composed of rectangular metal units with different sizes is employed and its units are unevenly distributed. The proposed CP antenna is designed, fabricated, and measured. The measured results show that the impedance bandwidth covers 3.0-6.0 GHz (66.7%) and a 3-dB AR bandwidth covers 3.1-5.6 GHz (57.4%). A peak gain of 6.0 dBi is obtained at 3.8 GHz by using the reflector. The advantages of the proposed antenna are the simple structure, high gain, and broad CP bandwidth.

Wideband Circularly Polarized Cavity-Backed Dielectric Resonator Antenna With Low RCS for Aerial Vehicle Communications

This letter explains the design of a wideband circularly polarized dielectric resonator antenna (DRA) with a dual-cylindrical conformal cavity for aerial applications. The proposed dielectric resonator (DR) element uses multilayer cross-shaped elements of varying dimensions with an off-centered circular slot that is inserted inside the DR geometry. Combining the wideband DRA with a conformal cavity (bending angle, α = 5°) that provides wider impedance bandwidth of 111% from 5.02 to 17.52 GHz and axial ratio bandwidth of 32.29% from 6.18 to 8.56 GHz. The proposed antenna provides a higher gain of 10.77 dBi at 8.5 GHz, gain values better than 7.21 dBi, and radiation efficiency better than 90% for the complete band. Also, the proposed antenna provides good radar cross-section reduction mechanism for the entire working band.