Broadband Circularly Polarized Antenna with Stable Flat-Top Radiation Based on Metasurface

A novel broadband circularly polarized (CP) antenna is proposed. The operating principle of this CP antenna is different from those of conventional CP antennas. An off-center-fed dipole is introduced to achieve the 90° phase difference required for circular polarization. The new CP antenna consists of two off-center-fed dipoles. Combining such two new CP antennas leads to a bandwidth enhancement for circular polarization. A T-shaped microstrip probe is used to excite the broadband CP antenna, featuring a simple planar configuration. It is shown that the new broadband CP antenna achieves an axial ratio (AR) bandwidth of 55% (1.69-3.0 GHz) for AR <; 3 dB, an impedance bandwidth of 60% (1.7-3.14 GHz) for return loss (RL) > 15 dB, and an antenna gain of 6-9 dBi. The new mechanism for circular polarization is described and an experimental verification is presented.

This paper proposes a new broadband circularly polarized (CP) antenna for 5G millimeter waves based on the integrated substrate gap waveguide (ISGW). The broadband circularly polarized antenna etches a rectangular slot on the PEC on the upper surface of the ISGW, and then adds two rectangular perturbation patches of different shapes on the rectangular slot, thereby realizing circularly polarized wave radiation. To expand the 10dB return loss bandwidth and axial ratio bandwidth of the slot circular polarization antenna based on the substrate integrated gap waveguide, a new dielectric plate is added above the ISGW, and a cross-shaped patch is added above the dielectric plate. This cross-shaped patch not only functions as a parasitic patch but also circularly polarized radiation, thereby achieving the purpose of expanding the 10dB return loss bandwidth and axial ratio bandwidth of the circularly polarized antenna.

A new type of broadband circularly polarized (CP) antenna is proposed. The new CP antenna consists of two folded off center-fed dipoles. The operating principle of this type of CP antenna is different from those of conventional CP antennas. The 90° time-phase difference required for circular polarization is obtained by the off-center feed of a half-wave dipole. This type of CP antenna features a simple planar configuration. It is shown that the new CP antenna achieves an overlapped bandwidth of 46% (1.7-2.73 GHz) for axial ratio 15 dB. The broadband CP antenna has a gain of 8.5 dBi on average.

This paper presents a circularly polarized (CP) rectenna with the advantage of achieving high efficiency in both wide operating power and frequency ranges. The proposed rectenna is composed of a high-efficiency rectifier and broadband CP antenna. In the proposed rectifier, a novel wideband resistance compression technique is presented, highly improving the matching performance of the circuit in a wide range of input power and frequency. The technique is achieved by an impedance manipulation network and a coupled-lines-based resistance compression network (RCN). Theoretical analysis is carried out and closed-form equations are derived for the design of the rectifier. Simulated and measured results show that over 60% (up to 76%) conversion efficiency is achieved for the input power range of 5-17 dBm and frequency band of 1.7-2.9 GHz (mobile, Wi-Fi and ISM bands). Subsequently, unlike the conventional half-wavelength slot antenna, a compact CP antenna with a side length of quarter wavelength is designed by using a 1-wavelength loop slot and a coupled-line-based phase shifter. It has wide axial-ratio bandwidth and good radiation pattern. At last, by integrating the proposed rectifier together with the CP slot antenna, a broadband CP rectenna is completed with higher efficiency by about 18.6% than that without wideband RCN.

We report on the design of a low-profile integrated millimeter-wave antenna for efficient and broadband circularly polarized electromagnetic radiation. The designed antenna comprises a chiral dielectric metasurface built with a arrangement of dielectric cylinders with slanted-slots at the center. A broadbeam high-gain with wide axial ratio ( dB bandwidth was reached by pairing the electric and magnetic resonances of the dielectric cylinders and the slanted slots when excited by an elliptically polarized driven-patch antenna. This electric-magnetic pairing can be tuned by varying the cylinders diameter and the tilting and rotation angles of the slanted slots. The simulation results indicate impedance-matching bandwidths up to 22.6% (25.3–31.6 GHz) with 3-dB AR bandwidths of 11.6% (26.9–30.2 GHz), which in terms of compactness () and performance are superior to previous antenna designs. Since the simulations were performed by assuming materials and geometries easily implementable experimentally, it is hoped that circularly polarized antennas based on chiral metasurfaces can be integrated into 5G and satellite communications.

A broadband CP (circularly polarized) antenna with reflector folding up is proposed in this work. The antenna is consists of two pairs of dipoles with fan shape. To enhance the gain, an upturned reflector is set quarter wavelength under the dipoles. And by etching rectangular slots and chamfering the corner of the dipoles, the AR (axial ratio) bandwidth could be broadened to higher frequency. The simulated impedance $(\vert \mathbf{S11\vert \leq-10dB})$ and 3-dB AR bandwidths of the proposed antenna are 119% $(\mathbf{1.88GHz\sim 7.4GHz})$ and 73.1 % $(\mathbf{3.02GHz \sim 6.5GHz})$ respectively. The peak gain is about 10.6dB at 4.73GHz.

This paper presents a broadband high-efficiency circularly polarized (CP) active integrated antenna, and a broadband CP active array at 2 GHz. To realize the broadband CP antenna, a circular patch is aperture coupled by crossed slots in the ground plane, which are fed by an L-shaped microstrip feed line below the ground. The antenna is designed to serve the functions of both a radiator and a harmonics-terminated load for class-E high-efficiency power-amplifier (PA) integration. The broadband CP active antenna is realized by directly integrating the broadband CP antenna with the class-E PA. It achieves a 9% bandwidth (1.84-2.01 GHz) for axial ratio (AR) below 3 dB, and a 12% bandwidth for power-added efficiency (PAE) over 60%. To form the broadband CP active array, four active antenna elements are sequentially rotated, and each element is directly integrated with broadband class-E PA. A low-cost printed-circuit-board technology is employed in fabrication and a pseudomorphic high electron-mobility transistor is used. A peak drain efficiency of 71.5% for the class-E amplifier is measured at 1.95 GHz. The active array achieves a peak-effective radiated power of 39.7 dBm, and PAE is over 50% within a 22.6% bandwidth (1.72-2.16 GHz). The AR is below 3 dB over a 27% bandwidth (1.72-2.26 GHz).

A novel broadband circularly polarized antenna is proposed, designed, and measured. Basically, the antenna consists of a PIFA and a square ground with an arrow‐like branch at its corner, which permit the antenna both broadband and circular polarization characteristics. For ease integration with active devices and design facilitation, the radiating element and ground are etched on the same layer of the substrate. Prototypes of the proposed antenna are fabricated and tested. The obtained −10‐dB return loss bandwidth and 2‐dB axial ratio (AR) bandwidth reach as large as 39.8 and 41.7%, respectively. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:204–208, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25633

This paper presents a circularly polarized (CP) broadband high efficiency active integrated antenna (AIA). To realize the broadband CP antenna, a circular patch is coupled by crossed slots in the ground plane, which are fed by an L-shaped microstrip feed line below the ground. The antenna is designed to serve as the harmonics-terminated load for class-E high-efficiency power amplifier (PA). The broadband CP active antenna is realized by directly integrating the broadband CP antenna with a broadband class-E PA.

A novel broadband circularly polarized (CP) antenna with unique feeding method is proposed. It is composed of four sequentially rotating U-shaped dipole arms, two half-circular rings, two three-quarter circular rings and a pair of L-shaped patches. The sinusoidal property of current is employed to achieve CP radiation by feeding the four U-shaped dipole arms with 0°, 270°, 90° and 0° phases in accordance with the counterclockwise direction. The U-shaped dipole arm allows for the distribution of current over a longer radiating path, thereby enhancing the axial-ratio bandwidth (ARBW). The L-shaped patch is designed to improve the impedance-matching bandwidth (IBW) and ARBW of the antenna. The overall dimensions of the antenna are 0.95λ<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub>×0.95λ<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub>×0.32λ<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub>, where λ<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> is the wavelength of the center frequency in free space. The proposed antenna was designed, fabricated and tested, exhibiting a measured impedance bandwidth of 79.60% (2.42-5.62 GHz) and an axial ratio bandwidth of 75.16% (2.45-5.40 GHz). The operating bandwidth was found to be 75.16% (2.45-5.40 GHz), with a maximum gain of 12.5 dBic. These properties make the antenna suitable for modern 5G wireless communications.

This letter presents a circularly polarized (CP) broadband high‐efficiency active integrated antenna, where the broadband CP antenna is integrated directly with a broadband high‐efficiency class‐E power amplifier (PA). To achieve CP operation, a series feed using an L‐shaped microstrip feed line below the ground plane is used to provide a 90° phase shift between crossed slots. The antenna serves both functions of a broadband CP radiator and a broadband harmonics‐termination load network for the class‐E PA. Measures results demonstrate both broadband CP radiation and high efficiency. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 2145–2148, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21940

In this work, the design and the characterization of a broadband circular polarized monopole having low-profile and wide axial ratio beamwidth were presented. The antenna was designed on readily available, inexpensive glass-reinforced epoxy substrate having an overall size of 0.56λ0×0.50λ0×0.029λ0 (at center frequency 5.5 GHz). The proposed antenna was a modification of a square-shaped monopole antenna, which incorporates a pair of peripheral slits and an off-center slot for a elliptical polarized radiation. A v-shaped notch below the feed line was introduced and extended as antenna ground to generate broadband circular polarization characteristics. The −10 dB reflection coefficient bandwidth and 3-dB axial-ratio bandwidth of the proposed antenna were measured to be of 47.6 and 27 %, respectively. The 3-dB axial ratio beamwidth of the antenna was 93.5°. The antenna proposed in this work covers multiple application frequency bands including HiperLAN/2 IEEE 802.11a (5.15 - 5.35 GHz / 5.47 - 5.725 GHz) band, WLAN frequency band (5.1 - 5.9 GHz), C-band uplink (5.925 - 6.325 GHz) and part of military application band (4.75 - 4.99 GHz). HIGHLIGHTS Design and characterization of a broadband circular polarized monopole having low-profile and wide axial ratio beamwidth Proposed antenna covers multiple application frequency bands including HiperLAN/2 IEEE 802.11a, WLAN, C-band uplink and part of military application bands Proposed antenna is compact, low-profile and exhibits good polarization purity GRAPHICAL ABSTRACT

In this paper, a circularly polarized antenna with a low radar cross section (RCS) based on nonuniform metasurfaces is proposed. The metasurface is composed of four elements, which are arranged orthogonally in a <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$2\times 2$</tex> array. Each element is a nonuniform metasurface of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$4 \times 4$</tex> metallic patches. By feeding with a 90° phase difference, the antenna achieves circular polarization radiation. For the radiation case, simulated results show that the proposed antenna possesses a -10 dB impedance bandwidth of 47.05%, 3 dB axial ratio of 42.35%. The peak gain of the antenna reached 12.74 dBic. For the scattering case, the RCS reduction under normal incidence is higher than 6 dB in the operating frequency band of the antenna.

A patch antenna with simple feeding structure for broadband circular polarization is proposed in this letter. The patch is first designed with horizontal L-shaped strip (HLS) feeding, which feeds the radiation patch at orthogonal orientations with 90 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> phase difference. Two minimum points can be seen in the axial-ratio (AR) curve. By loading a shorting pin to the patch, the minimum point of lower frequency moves to higher frequency, and wide AR band is obtained consequently. Measured results show that 10-dB return-loss bandwidth of 23.6% (2.09-2.65 GHz), 3-dB AR bandwidth of 17.9% (2.18-2.61 GHz), and average gain of 8.5 dBic across the operating band are achieved for the proposed antenna with a low profile of 0.09λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> ( λ <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 corresponding to 2.4 GHz).

A broadband circularly polarized (BCP) all-textile antenna and its wearable conformal antenna array (WCAA) are investigated for body-centric communications. Initially, a circularly polarized (CP) microstrip patch antenna loaded with a piece of the modified metasurface is designed to achieve wide impedance and axial ratio (AR) bandwidths. The characteristic mode analysis is employed to understand the operating mechanism, which provides clear physical insight into each mode at various frequencies. Due to the adoption of textile (i.e., felt) as substrate and nylon conductive fabric as conductor, the proposed antenna is flexible, totally conforming to the curve-shaped human body. The antenna with broadside radiation is suitable for off-body communications. For verification, the prototype operating at 5 GHz (5.15–5.825 GHz) band was fabricated. The measured −10 dB impedance and 3 dB AR bandwidths of 35.1% and 17.5% with a peak gain of 8.5 dBi are achieved. Furthermore, the BCP antenna is used as an element to constitute the WCAA, and the omnidirectional radiation pattern in the azimuth plane is achieved for on- and off-body communications. The considerations about how to achieve omnidirectional radiation and avoid radiation nulls are studied in detail. Finally, the WCAA was fabricated and tested; the measured results guarantee its potential for wearable applications.