Son Xuat Ta

Multi-Band, Wide-Beam, Circularly Polarized, Crossed, Asymmetrically Barbed Dipole Antennas for GPS Applications

This communication presents a multi-band, circularly polarized (CP), wide beamwidth, highly efficient antenna for use in global positioning systems (GPS). The primary radiating elements are two crossed printed dipoles, which incorporate a 90° phase delay line realized with a vacant-quarter printed ring to produce the CP radiation and broadband impedance matching. To achieve multiple resonances, each dipole arm is divided into four branches with different lengths, and a printed inductor with a barbed end is inserted in each branch to reduce the radiator size. An inverted, pyramidal, cavity-backed reflector is incorporated with the crossed dipoles to produce a unidirectional radiation pattern with a wide 3-dB axial ratio (AR) beamwidth and a high front-to-back ratio. The multi-band antennas have broad impedance matching and 3-dB AR bandwidths, which cover the GPS L1-L5 bands.

Compact Circularly Polarized Composite Cavity-Backed Crossed Dipole for GPS Applications

In this paper, we present a circularly polarized (CP) composite cavity-backed crossed dipole antenna for global positioning system (GPS) applications. We produce the CP radiation by crossing two dipoles through a 90° phase delay line of a vacant-quarter printed ring, which also has a broadband impedance matching characteristic. Two techniques, insertion of meander lines in the dipole arm and arrowhead-shaped trace at its end, are employed to reduce the sizes of the primary radiation element. The compact radiator is backed by a cavity reflector to achieve a wide CP radiation beamwidth. The proposed antenna exhibits a measured bandwidth of 1.450～1.656 GHz for a voltage standing wave ratio (VSWR) < 2 and 1.555～1.605 GHz for AR < 3-dB. At 1.575 GHz, the antenna has a gain of 7 dBic, a frontto-back ratio of 27 dB, AR of 1.18 dB, and 3-dB AR beamwidths of 130° and 132° in the x-z and y-z planes, respectively.

Crossed Dipole Loaded With Magneto-Electric Dipole for Wideband and Wide-Beam Circularly Polarized Radiation

A crossed dipole that is loaded with a magneto-electric dipole to produce the wideband and wide-beam circularly polarized radiation characteristics is proposed. The crossed dipole is incorporated with double-printed vacant-quarter rings to feed the antenna. The antenna is backed by a metallic cavity to provide a unidirectional radiation pattern with a wide axial-ratio (AR) beamwidth and a high front-to-back ratio. Experimental results showed that the prototype with an overall size of 120×120×30.5 mm3 has a |S11|<;-10 dB bandwidth of 1.274-2.360 GHz and a 3-dB AR bandwidth of 1.39-1.82 GHz. The antenna showed a right-hand circular polarization (CP) radiation with a very wide 3-dB AR beamwidth (>165°) and a high radiation efficiency (>94%) within the operational bandwidth.

Circularly Polarized Crossed Dipole on an HIS for 2.4/5.2/5.8-GHz WLAN Applications

A triband circularly polarized (CP) crossed-dipole antenna is introduced for 2.4/5.2/5.8-GHz wireless local area network (WLAN) applications. It employs a single feed and only two crossed trident-shaped dipoles as the primary radiating elements. To achieve a compact radiator size, two techniques are utilized, namely, insertion of a meander-line segment in the middle branch of the tridents and termination of all trident arms with arrowhead-shaped tips. The crossed trident-shaped dipoles are backed by a high impedance surface (HIS) to achieve a broadband characteristic and unidirectional radiation pattern at three bands. The measured impedance bandwidths, based on the -10-dB reflection coefficient values, are 2.21-2.62 GHz (410 MHz), 5.02-5.44 GHz (420 MHz), and 5.62-5.96 GHz (340 MHz), and the measured 3-dB axial-ratio bandwidths are 2.34-2.58 GHz (240 MHz), 5.14-5.38 GHz (240 MHz), and 5.72-5.88 GHz (160 MHz). The proposed antenna exhibits right-hand circular-polarized radiation with high gain.

Dual-Band Low-Profile Crossed Asymmetric Dipole Antenna on Dual-Band AMC Surface

A dual-band, low-profile, circularly polarized antenna on an artificial magnetic conductor (AMC) is introduced in this letter. The antenna employs a single feed and two crossed asymmetric dipoles as the primary radiating elements. In order to achieve a low profile and broadband characteristics in terms of impedance matching and 3-dB axial-ratio (AR) bandwidths at both bands, a dual-band AMC is utilized as a reflector of the antenna. The AMC structure utilizes four T-shaped slits in a unit-cell patch to significantly reduce its first and second resonant frequency ratio, and consequently its first and second resonances are easily adjusted for the desired operating frequencies. For performance verification, an antenna prototype was fabricated with an overall 2.4-GHz frequency size of 0.576λ0 × 0.576λ0 × 0.088λ0 (72 × 72 × 11 mm3). The measurements resulted in impedance bandwidths of 2.20-2.60 and 4.90-5.50 GHz for 10 dB and 3-dB AR bandwidths of 2.30-2.50 and 5.05-5.35 GHz. Additionally, the antenna yields right-hand circular polarization and high antenna efficiency at both bands.

Low-Profile Broadband Circularly Polarized Patch Antenna Using Metasurface

A low-profile single-feed circularly polarized (CP) patch antenna using metasurface is proposed for broadband operation. The antenna is comprised of a truncated corner square patch sandwiched between a lattice of 4 × 4 periodic metal plates and the ground plane. Surface waves propagating on the metasurface are excited in the proposed structure. This phenomenon generates additional resonances and minimum axial ratio (AR) points for the radiating structure, consequently broadening the impedance-matching and AR bandwidths of the antenna. The final prototype, with an overall size of 32 mm × 32 mm × 3 mm (0.58λo × 0.58λo × 0.056λo at 5.5 GHz), was fabricated and tested. The measurements resulted in a IS11I<;-10 dB bandwidth of 4.70-7.48 GHz (45.6%) and a 3-dB AR bandwidth of 4.9-6.2 GHz (23.4%). In addition, the antenna yielded a good broadside left-hand CP radiation with a small gain variation (7.0-7.6 dBic) and a high radiation efficiency (>90%) within the operational bandwidth.

Crossed Dipole Antennas: A review.

Crossed dipole antennas have been widely developed for current and future wireless communication systems. They can generate isotropic, omnidirectional, dual-polarized (DP), and circularly polarized (CP) radiation. Moreover, by incorporating a variety of primary radiation elements, they are suitable for single-band, multiband, and wideband operations. This article presents a review of the designs, characteristics, and applications of crossed dipole antennas along with the recent developments of single-feed CP configurations. The considerations of profile miniaturization, radiation pattern control, bandwidth enhancement, and multiband operation are emphasized.

Wide-Beam Circularly Polarized Crossed Scythe-Shaped Dipoles for Global Navigation Satellite Systems

This paper describes composite cavity-backed crossed scythe-shaped dipoles with wide-beam circularly polarized (CP) radiation for use in Global Navigation Satellite Systems. Each branch of the dipole arm contains a meander line, with the end shaped like a scythe to achieve a significant reduction in the size of the radiator. For dual-band operation, each dipole arm is divided into two branches of different lengths. The dipoles are crossed through a 90° phase delay line of a vacant-quarter printed ring to achieve CP radiation. The crossed dipoles are incorporated with a cavity-backed reflector to make the CP radiation unidirectional and to improve the CP radiation beamwidth. The proposed antennas have broad impedance matching and 3-dB axial ratio bandwidths, as well as right-hand CP radiation with a wide-beamwidth and high front-to-back ratio.

Single-Feed, Wideband, Circularly Polarized, Crossed Bowtie Dipole Antenna for Global Navigation Satellite Systems

A wideband circularly polarized (CP) antenna with a single feed is proposed for use in global navigation satellite systems. Its primary radiation elements are composed of two orthogonal bowtie dipoles, which are equipped with double-printed vacant-quarter rings to allow direct matching of the antenna to a single 50-Ω coaxial line and to produce CP radiation. The crossed bowtie dipole is appropriately incorporated with a planar metallic reflector to produce the desired unidirectional radiation pattern as well as to achieve a wideband characteristic in terms of impedance matching and axial ratio (AR) bandwidths. The designed antenna was fabricated and measured. The prototype antenna with an overall 1.2-GHz frequency size of 0.48 λo×0.48 λo×0.25 λo produced a measured |S11| 93%) over the operational bandwidth.

Dual-band operation of a circularly polarized radiator on a finite artificial magnetic conductor surface

This paper proposes a new way of designing a dual-band circularly polarized (CP) antenna by using a single-band CP radiator on a finite artificial magnetic conductor (AMC) surface. The AMC surface consists of a lattice of square metal plates on grounded dielectric substrate while the single-band radiator is a compact crossed dipole, which employs a 90° phase-delay line consisting of a vacant-quarter printed ring to generate broadband CP radiation. The dual-band operation is obtained by utilizing the original band generated by the radiator and the first additional band caused by surface waves propagating on the finite AMC surface. For verifying the design method, the proposed antenna is optimized for the L1 and L2 bands of the global positioning system with low-profile broadband characteristics and excellent CP radiation. The final design with an overall size of 85 × 85 × 11.493 mm3 (~0.3485λo × 0.3485λo × 0.0471λo at the 1.23 GHz) yields a measured impedance bandwidth of 1.202–1.706 GHz for the |S11| < –10 dB and 3-dB axial ratio bandwidths of 1.205–1.240 GHz and 1.530–1.625 GHz, respectively. Furthermore, the antenna yields right-hand circular polarization and high radiation efficiencies in both bands.