Dual-band Circularly-polarized Antenna Research Articles

Dual-band Circularly Polarized Antenna with Wide Axial-ratio and Gain Beamwidths for High-precision BDS Applications

Dual-band Circularly Polarized Antenna with Wide Axial-ratio and Gain Beamwidths for High-precision BDS Applications

Dual-Band Circularly Polarized Omni-Directional Biconical Antenna With Double-Circular Parallelepiped Elements for WLAN Applications

This research proposes a novel dual-band (2.45/5.80 GHz) omnidirectional circularly polarized (CP) biconical antenna with double-circular parasitic parallelepiped elements for wireless local area network (WLAN) applications. The proposed dual-band CP antenna scheme consisted of a biconical radiating structure surrounded by inner- and outer-circular parallelepiped elements that convert linearly polarized electric fields into CP fields. Simulations were performed to optimize the antenna parameters, and an antenna prototype was fabricated and experiments were conducted. The measured impedance bandwidths (IBWs) were 44.4% (1.84 – 2.89 GHz) and 4.56% (5.73 – 5.99 GHz) for the lower- (2.4 GHz) and upper-frequency (5.80 GHz) bands, respectively. The corresponding 3-dB axial ratio bandwidths (ARBWs) were 11.22% (2.27 – 2.54 GHz) and 10.49% (5.6 – 6.2 GHz). The radiation patterns of the dual-band antenna scheme were omnidirectional left-hand circular polarization, with the measured antenna gains of 3.2 dBic and 8.5 dBic at 2.45 and 5.80 GHz, respectively. The simulated and measured results were reasonably agreeable. Despite the narrow IBW and ARBW for the upper-frequency band, the bandwidths adequately covered the target upper frequency band, rendering the proposed CP omnidirectional biconical antenna scheme operationally suitable for WLAN applications. Furthermore, the novelty of this research lies in the use of a biconical radiating structure augmented with double-circular parasitic parallelepiped elements to realize circular polarization for dual-band WLAN applications.

Dual-Band Circularly Polarized Antenna With Two Pairs of Crossed-Dipoles for RFID Reader

In this article, a low-profile high-efficiency dual-band 0.915/2.45 GHz circularly polarized (CP) antenna and its array are designed for radio frequency identification (RFID) reader applications. First, a dual-band antenna element is introduced to achieve dual-sense CP radiation using two pairs of crossed-dipoles for the first time. The right-hand CP (RHCP) wave at lower band is mainly produced by the first-order mode on longer dipole, while the left-hand CP (LHCP) wave at upper band is generated by the combination of first-order mode on shorter dipole and third-order mode on longer dipole. An artificial magnetic conductor (AMC) is used to improve the antenna directivity with low profile and makes this antenna easy to integrate into RFID system. Then, a rotated sequential phase feed CP array is proposed, fabricated, and measured. Measured impedance bandwidth (IBW) for <inline-formula> <tex-math notation="LaTeX">$\vert \text{S}_{11}\vert &lt; -10$ </tex-math></inline-formula> dB is more than 40.0&#x0025; at these two bands. Measured 3 dB axial ratio bandwidths (ARBWs) are 32.0&#x0025; (0.77&#x2013;1.06 GHz) and 27.8&#x0025; (2.22&#x2013;2.95 GHz). Compared with other dual-band CP reader antennas, which work in 0.915/2.45 GHz RFID systems, this new antenna array has a simpler configuration to achieve dual-band CP radiation. In addition, the 3 dB ARBWs are much wider than the previous antennas. Moreover, because the feeding network of this array is quite simple, the radiation efficiency is very high (&#x003E;90&#x0025;), and the peak gains are more than 9.0 and 15.0 dBic at corresponding bands.

Neural-Network-Based Multiobjective Optimizer for Dual-Band Circularly Polarized Antenna

A multiobjective optimization (MOO) technique for a dual-band circularly polarized antenna by using neural networks (NNs) is introduced in this paper. In particular, the optimum antenna dimensions are computed by modeling the problem as a multilayer feed-forward neural network (FFNN), which is two-stage trained with I/O pairs. The FFNN is chosen because of its characteristic of accurate approximation and good generalization. The data for FFNN training is obtained by using HFSS EM simulator by varying different geometrical parameters of the antenna. A two strip-loaded circular aperture antenna is utilized to demonstrate the optimization technique. The target dual bands are 835–865 MHz and 2.3–2.35 GHz.

Dual‐band circularly polarized crossed‐dipole antenna with double split‐ring resonators and a defected ground structure

A dual-band cavity-backed circularly polarized crossed-dipole antenna with double split-ring resonators (SRRs) is investigated in this paper. A pair of crossed dipoles connected by concentric ring-delay lines is firstly designed as a circularly polarized (CP) antenna with only one CP mode. To extend the operation of the original design, a pair of the λ/4-resonance SRRs are used to realize wider axial ratio bandwidth at higher band. At the same time, another pair of the λ/4-resonance SRRs with larger dimension is adopted to obtain a lower frequency band, although the effect is not very satisfying. Then the cavity-backed technology and a defected ground structure are both employed to improve the working bandwidth. The dual-band CP antenna can be tuned into a wide bandwidth one by changing the dimensions of the larger SRRs. A good agreement between the simulated and measured results can be observed. The measured impedance bandwidths are 6.90% (3.36-3.60 GHz) and 53.58% (4.40-7.62 GHz). The measured 3-dB AR bandwidth is 7.93% (3.39-3.67 GHz) and 59.15% (4.08-7.51 GHz).

A dual-band efficient circularly polarized rectenna for RF energy harvesting systems

A multilayered circularly polarized (CP), dual-band, stacked slit-/slotted-patch antenna with compact size and with compact rectifier is offered for RF energy harvesting systems. The compact dual-band CP antenna size is able to achieve by stacking slotted-circular-patch (SCP) on the substrate above the tapered-slit-octagon patch (TSOP). Dual-band CP radiation is realized by stacking the SCP on the TSOP and the microstrip feedline with metallic-via to SCP. Eight-tapered-slit with length difference of 6.25% are embedded along the octagonal directions symmetrically on the TSOP from the patch's center and two unequal size circular slots are embedded in diagonal axis onto SCP to produce dual-orthogonal modes with almost equal magnitude for CP waves. The designed antenna is realized measured gain of greater than 5.2 dBic across the band (0.908-0.922 GHz) with maximum gain of 5.41 dBic at 0.918 GHz and gain of greater than 6.14 dBic across the band (2.35-2.50 GHz) with maximum gain of 7.94 dBic at 2.485 GHz. An overall antenna volume is 0.36λ o × 0.36λ o × 0.026λ o (λ o is free space wavelength at 0.9 GHz). A compact composite right-/left-handed (CRLH) based rectifier with dual-band at 0.9 and 2.45 GHz is designed, prototyped, and measured. The right-handed (RH) part of the CRLH transmission line (TL) is formed by a microstrip line. The left-handed (LH) part of the CRLH-TL is formed by lumped components. The measured RF-DC conversion efficiency is 43% at 0.9 GHz and 39% at 2.45 GHz with rectifier size of 0.18λ o × 0.075λ o × 0.0002λ o at 0.9 GHz.

Dual-Band Circularly Polarized Antenna Using Mu-Negative Transmission Lines

A dual-band circularly polarized (CP) antenna based on artificial mu-negative transmission lines (MNG-TLs) is proposed in this letter. By etching dumbbell-shaped slots on the microstrip and narrow gaps on the ground plane, the zeroth- and first-order resonance (ZOR and FOR) modes of the MNG-TLs can be excited. Moreover, by introducing two parallel branches at the edge of metal strips in the ground plane, the CP fields are obtained at both resonance modes. The measured results show that the proposed antenna has the –10 dB impedance bandwidths of 6.3% (from 2.31 to 2.46 GHz) and 8.1% (from 3.32 to 3.6 GHz) in lower (ZOR) and upper (FOR) bands, respectively. Meanwhile, the 3 dB axial-ratio bandwidths of 10.2% (from 2.33 to 2.58 GHz) and 7.7% (from 3.35 to 3.62 GHz) can be obtained. Also, the CP radiation can be formed in the azimuth planes of 30° θ θ < 40° in two bands, respectively.

Dual-Band Dual-Sense Circularly Polarized Substrate Integrated Waveguide Antenna

A dual-band dual-sense circularly polarized (CP) antenna is presented in substrate integrated waveguide technology. The proposed antenna consists of four V-shaped asymmetrical resonators that are placed on a circular substrate symmetrically with respect to its center. The antenna is excited by a probe on the central axis. A dual-band CP antenna is designed and fabricated. The antenna provides left-hand circular polarization (LHCP) in the lower band and right-hand circular polarization (RHCP) in the upper band. Total size of the antenna is 1963.5 mm2 on a 0.787 mm thick RT/Duroid 5880 substrate. Measured axial ratios are below 3 dB over 8.78–8.90 and 9.52–9.66 GHz. Over the bands, the return loss is more than 10 dB. Measured cross-polarization levels are 31.1 and 24.65 dB, and front-to-back ratios are 14.93 and 18.35 dB over the LHCP and RHCP bands, respectively. Depending on application requirements, the band ratio can be tuned. Also, the sense of polarization can be interchanged. The antenna does not use any ground plane perturbation. Thus, it can be directly attached to a microwave circuit.

Dual-Band Circularly Polarized Antenna With Wide Axial Ratio Beamwidths for Upper Hemispherical Coverage

This paper presents a dual-band circularly polarized cross-dipole antenna with wide axial ratio beamwidths for full upper hemispherical coverage for GPS L1 and L2 bands. The antenna has curved radiating arms and a corrugated back cavity to enhance the beamwidth. A wideband hybrid coupler is used to feed the antenna at the two nearby frequency bands. Experimental results show that very wide 3-dB AR beamwidths of over 200° can be obtained, fully covering the upper hemisphere for the two GPS bands.

Dual-Band Circularly Polarized Split Ring Resonators Loaded Square Slot Antenna

A dual-band circularly polarized (CP) microstrip line fed slot antenna using a set of split ring resonators (SRRs) is proposed in this communication. Outer ring connected SRRs are placed on the back side of the slot to create the CP upper band. Diagonally opposite corners of the slot are truncated, which together with the SRRs give CP response in the lower band. The proposed dual-band CP antenna provides design flexibility to control the resonance frequency and sense of polarization at the dual bands, independently. The proposed antenna is designed to operate at 3.1 and 4.7 GHz, which is fabricated and tested. The experimental results show the −10-dB impedance bandwidths of 400 MHz in both the bands and the 3-dB axial ratio bandwidth of 3.1% (from 3.05 to 3.15 GHz) and 4.2% (from 4.65 to 4.85 GHz) in lower and upper bands, respectively. Finally, a metallic cavity is used with the antenna to achieve a unidirectional radiation pattern with front-to-back ratio of more than 15 dB without affecting the impedance bandwidth and CP performance of the antenna.

A Novel Design of Low-Profile Dual-Band Circularly Polarized Antenna With Meta-Surface

A low-profile dual-band circularly polarized (CP) antenna applied for WiMAX (2.5 and 3.5 GHz) is proposed in this letter. With a well-designed meta-surface placed atop a slot antenna, two circularly polarized bands can be excited. The annular folded slot antenna resonates at 2.5 GHz while the meta-surface is designed to excite another CP band around 3.5 GHz, and the meta-surface can also effectively enhance the front radiation. Two CP operation bands are 2.48–2.56 GHz and 3.48–3.63 GHz, with the low frequency ratio (FR) of 1.4 (2.5 GHz/3.5 GHz). The antenna is compact with a low profile of 3 mm, which can be easily integrated in the wireless communication system.

Serial Aperture-Coupled Dual Band Circularly Polarized Antenna

In this innovative method of producing circular polarized (CP) wave, we present a serial feed line which couples diamond-shaped slot to ring and cross-slot to patch. The feed line is used to feed the two parts in series. Then, the structure can easily be operated as a dual band circularly polarized antenna to cover both 0.915 GHz and 2.45 GHz bands. Experimental results show that the proposed antenna has good circular polarization characteristics.

Compact Circularly Polarized Dualband Zonal-Slot/DRA Hybrid Antenna Without External Ground Plane

A zonal slot antenna cut onto a conducting cavity is combined with a dielectric resonator antenna (DRA) to form a circularly polarized (CP) dualband hybrid antenna. The zonal slot antenna and DRA are located on the side wall and top face of the cavity, which are responsible for the lower and upper bands, respectively. No external ground planes are used for the hybrid antenna and, thus, the structure is very compact. An L-probe is placed inside the cavity to feed the zonal slot directly and to excite the DRA indirectly through a cross coupling slot beneath the DRA. In this paper, two symmetrical cuts are cut onto the zonal slot for exciting CP fields, and a third cut is introduced to the zonal slot to fine-tune the axial ratio (AR). The DRA is excited by its underlaid cross slot with unequal lengths, giving two orthogonal degenerate modes that generate CP fields. The frequencies and field polarizations of the zonal slot and DRA can be designed independently, which greatly facilitates designs of the dualband CP antenna. The reflection coefficient, AR, radiation pattern, and radiation efficiency of dualband antennas were measured, and the measured results agree reasonably well with our simulated results obtained using Ansoft HFSS.

Polarisation-dependent electromagnetic bandgap incorporating a slanted sheet via

This study describes a novel sheet via polarisation-dependent electromagnetic bandgap surface. The properties of the surface are shown to vary with the via angle and length selected. The former adjustment causes asymmetric behaviour to linear incident waves and the latter brings about a reduction in inductance and consequent increase in resonant frequency. A 45° inclined via is examined in terms of its response to linear and circularly polarised (CP) waves. It is shown via simulation that linear polarised plane waves can be converted to CP with an axial ratio better than 0.4 dB. The study also demonstrates that at the centre of the design band the surface reflects co-handed waves in response to CP incident waves. Finally, the study details a dual-band CP antenna with a single port, achieved by exciting the surface with a bazooka-balun dipole.

Compact dual-band GPS microstrip antenna

Recently, in order to satisfy the demand for precise and reliable global positioning system (GPS) applications, the dual-band circularly polarized (CP) antenna has been developed. This paper describes a new design of a probe-fed dual-band CP microstrip antenna with two corner-truncated square patches that overlap without an air gap. Compared with the conventional dual-band CP antenna with an air-gap layer between the two patches, the volume of this antenna is reduced and its fabrication is easier. Details of the proposed antenna design and experimental results are presented and discussed. The measured results confirm the validity of this design, which can meet the requirement of GPS application at 1575/1227-MHz frequencies. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 44: 58–61, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20547