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This paper presents single-feed circularly polarized (CP) crossed dipole antennas on finite-sized artificial magnetic conductor (AMC) surfaces that show profile miniaturization and bandwidth enhancement. The antennas include a singleband radiator on a single-band AMC, a tri-band radiator on a single-band AMC, and a dual-band radiator on a dual-band AMC. The presence of the finite AMC surface results in generation of extra resonances for the radiating structures. These extra resonances can be favorably used to improve the performance of the antenna.

A circularly polarized (CP) antenna with a wideband characteristic is proposed for use in the Global Navigation Satellite System. Its primary radiation element is crossed bowtie dipoles, which are incorporated with double-printed vacant-quarter rings to allow the antenna to be matched directly to a single 50-Ω coaxial line and produce wideband CP radiation. The radiator is backed by a planar metallic reflector to achieve a desired unidirectional radiation pattern. The final design, with overall sizes of 0.48 λ 0 × 0.48 λ 0 × 0.25 λ 0 at 1.2 GHz, resulted in a |S11| 93%) within its operational bandwidth.

A crossed dipole antenna is incorporated with an AMC surface to achieve low-profile and broadband characteristics. Interactions between the crossed dipole and the AMC surface are meticulously considered for optimum design. The antenna yields an impedance bandwidth of 18.8% for |S 11 | < −10 dB and a 3-dB AR bandwidth of 10.9%.

Circularly polarized crossed dipole antennas are presented in this paper. A compact crossed dipole is realized with the use of a meander line and a barbed end in each dipole arm. A vacant-quarter printed ring is used as a 90° phase delay line to achieve circularly polarized radiation. For multi-band applications, each dipole arm is divided into multi-branches with different lengths to obtain multiple resonances. These radiators can be equipped with different reflectors, such as a finite planar metallic conductor, a cavity-backed metallic conductor, and a finite artificial magnetic conductor to obtain the desired antenna radiation characteristics. These antennas are quite practical for many wireless communication systems, such as satellite communications, global positioning systems, wireless local area networks, and radio-frequency identification devices.

In this paper, a wide-beam circularly polarized (CP) composite cavity-backed crossed scythe-shaped dipole is proposed. Each dipole arm contains a meander line whose end is shaped like a scythe chine to accomplish a significant reduction in the radiator size. The scythe-shaped dipoles are crossed through a 90° phase delay line of a vacant-quarter printed ring in order to generate CP radiation and broadband impedance matching. The crossed scythe-shaped dipole is incorporated with a cavity-backed reflector to improve the radiation pattern in terms of the CP radiation beamwidth and front-to-back ratio. The proposed antenna yields broad impedance-matching and 3-dB axial-ratio bandwidths, a high front-to-back ratio, and a wide beamwidth.

This paper presents a circularly polarized (CP) dual-band crossed dipole antenna incorporated with an artificial magnetic conductor (AMC) surface that serves as a reflector. Here, two crossed asymmetric dipoles are utilized as the primary radiation elements for a CP dual-band operation. Further, a novel AMC is designed with four T-shaped slits in a unit-cell patch to significantly reduce its second resonant frequency. Consequently, the first and second resonant frequencies of the proposed AMC structure are easily adjusted for the desired dual-band antenna operation.

This paper presents a closely spaced two-element folded-dipole-driven quasi-Yagi array with low mutual coupling between adjacent elements. The antenna utilizes a T-junction power divider as the feeding network with an input impedance of 50 Ω. A microstrip stub is added to the ground plane in the middle of the two elements to improve the mutual coupling characteristics. The folded dipole driver is connected to a 50 Ω microstrip line via a broadband microstrip-to-coplanar stripline transition with a quarter-wavelength radial stub. A mutual coupling of less than -21 dB is exhibited between two folded-dipole-driven quasi-Yagi antennas with a center-to-center spacing of 30 mm (0.55 λ0 at 5.5 GHz). The proposed quasi-Yagi array yields a bandwidth of 4.7-6.5 GHz for the -10 dB reflection coefficient and a gain of 6.6-7.6 dBi within the bandwidth range.

A dual-band printed dipole antenna with wide-beamwidth radiation patterns is introduced for 2.4/5 GHz bands wireless local area network access points. A printed dipole is designed at the center of circular ground plane and fed by a novel integrated balun consisting of a curved microstrip-line and a circular slot to allow broadband operation. An angled dipole and two vertical copper plates on the ground plane are used to achieve wide beamwidth in lower and upper bands, respectively. The proposed antenna has an impedance bandwidth of 2.395 - 2.50 GHz and 5.07 - 5.96 GHz for the -10 dB reflection coefficient. At 2.45 GHz, the antenna has gain of 6.86 dBi, front-to-back ratio of 21 dB, and half-power beam-width of 104° and 102° in the E- and H-planes, respectively. At 5.5 GHz, the antenna has gain of 6.92 dBi, front-to-back ratio of 27 dB, and half-power beam-width of 118° and 114° in E- and Hplanes, respectively.

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. © 2013 IEEE.

A dual-band, wide-beam, circularly-polarised crossed asymmetric dipole antenna is presented for global positioning system (GPS) applications. Each dipole arm has an asymmetrically barbed arrowhead and contains two different-sized printed-inductors to reduce the length of the primary radiating element and to achieve dual-band operation. At 1.575 GHz, the antenna has a gain of 7.5 dBic, a radiation efficiency of 97.4%, and a 3dB axial ratio (AR) beamwidth of 143° and 152° in the x-z and y-z planes, respectively. At 1.227 GHz, the antenna has a gain of 6.3 dBic, a radiation efficiency of 90%, and a 3dB AR beamwidth of 132° and 140° in the x-z and y-z planes, respectively. © 2012 The Institution of Engineering and Technology.

In this paper, a hybrid of T-dipole and quasi-Yagi antenna is presented for using in dual-band Wireless Local Area Network (WLAN) access point. The antenna is made up of combination of T-dipole and quasi-Yagi antenna structures, which are distinctly designed to operate at 2.4 and 5.5 GHz frequency bands. A simply integrated balun that consists of a curved microstrip line and a circular slot to allow broadband characteristic is used to feed the antenna. The final antenna design presents measured bandwidths (RL ≤ − 10 dB) of 2.35 – 2.55 GHz and 4.30 – 6.56 GHz which cover completely the two bands of WLAN. Simulated and measured results of peak gain and radiation patterns in both E- and H-plane validate potential of the design.

In this paper, a high gain printed quasi-Yagi antenna is introduced for 60 GHz wireless applications. The antenna is fed by a novel microstrip-slotline transition consisting of a curved microstripline and circular slot in order to allow wideband characteristics. A corrugated ground plane is employed as a reflector for improving gain and small gain variation. The proposed antenna has an impedance bandwidth of 49.8–68.5 GHz for a −10 dB reflection coefficient and a gain of 10.50–12.8 dBi within this bandwidth. In addition, the antenna exhibits a stable radiation pattern with half power beamwidths of 36°–50° and 41°–52° in the E- and H-planes, respectively.

This paper describes a wideband double dipole quasi-Yagi antenna fed by a microstrip-to-slotline transition. The transition feed consists of a microstrip radial stub and a slot radial stub, each with the same angle of 90°, but with different radii to achieve wideband impedance matching. Double dipoles with different lengths are utilized as primary radiation elements to enhance bandwidth and achieve stable radiation patterns. The antenna has a bandwidth of 3.65–8.90 GHz for a −10 dB reflection coefficient, and a flat gain of 6.4–7.6 dB across the bandwidth. The proposed antenna could be widely applicable to wideband wireless communication systems due to wideband characteristics, planar structure, and stable radiation pattern.