Entire Azimuth Plane Research Articles

Single/bidirectional pattern and beamwidth reconfigurable array antenna using reconfigurable reflecting surface

AbstractThis study describes an array antenna that allows for reconfiguration of the three significant antenna properties, that is, radiation pattern, half‐power beamwidth (HPBW), and single and bi‐directional beam. A reconfigurable reflecting surface (RRS) has been designed and incorporated with the array antenna on the top and bottom. The RRS works to reflect or pass the incident electromagnetic wave. It enables us to reconfigure from single to multibeam radiation in the ±z direction. It also provides two levels of HPBW, that is, 49.6° and 95°. Eventually, the same three sets of antennae have been stacked and rotated with a 60° angle to achieve the radiation pattern reconfiguration in the entire azimuth plane. It conforms to reconfigure all three antenna properties in six directions at an equal interval of 60° angle. The achieved maximum gain in a narrow beam is 9.56 dBi. The proposed reconfigurable antenna array can be used in modern wireless communication applications.

Low-Cost Beam Steering that Covers the Entire Azimuthal Plane Powered by Amplitude-Only Synthesis of a Quintuple-Dipole Source

Low-Cost Beam Steering that Covers the Entire Azimuthal Plane Powered by Amplitude-Only Synthesis of a Quintuple-Dipole Source

A compact frequency reconfigurable beam switching antenna based on a single‐layer FSS

AbstractA compact frequency reconfigurable beam switching antenna based on a single‐layer frequency selective face (FSS) is proposed in this paper. The proposed antenna consists of a dual‐band dipole antenna and a single‐layer FSS with hexagonally arrangement. The omnidirectional radiation pattern of the dipole antenna designed as a radiation source and surrounded by the FSS can be converted into directional radiation pattern sweeping along the entire azimuthal plane at two single frequency of 2.4 or 5 GHz. The frequency selection is achieved by controlling the diode state of the FSS unit, and the beam switching is realised by a specific combination of electromagnetic wave reflection or transmission from the hexagonal FSS. The novelty lies in applying the hexagonal arrangement to a dual single‐frequency single‐layer FSS unit. This will not destroy the reflection or transmission characteristics of the FSS unit, but also contribute to reduce the antenna size and achieve a low cost. To validate the design, a prototype is fabricated and measured. The single‐layer FSS antenna with a volume of 57 mm × 57 mm × 58.5 mm can be scanned in 12 steps along the azimuth plane at 2.4 and 5 GHz, respectively.

An Analytical Framework of Multisector Rectenna Array Design for Angular Misalignment Tolerant RF Power Transfer Systems

A design procedure is presented for an angular misalignment-tolerant multisector rectenna array used as a wireless energy harvesting (WEH) system. The proposed analytical framework derives constraints on the synthesized harvested dc power pattern of the rectenna element as a solution to completely mitigate the angular misalignment. The derived constraints determine the optimal number of sectors required to ensure uniform harvesting capability across the entire azimuth plane. This is analytically verified for a conventional patch antenna used in the rectenna element of the multisector WEH system. The design constraints give <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$N=8$ </tex-math></inline-formula> and 12 sectors the optimal solution for single patch and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2 \times 1$ </tex-math></inline-formula> patch array rectenna. Furthermore, a new multilayer wide-beam rectenna is proposed at 5.8 GHz requiring <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$N=6$ </tex-math></inline-formula> sectors to mitigate the angular misalignment with 36.5% size reduction when compared with the conventional patch WEH system. The prototype of the WEH systems using the conventional patch rectenna and the proposed rectenna is fabricated and measured. The measurement results corroborate the analytical and simulation results validating the capability of the proposed framework to achieve uniform energy harvesting in the entire azimuth plane.

Directive and Steerable Radiation Pattern using SASPA Array

This work examines the ability of a special type of smart antenna array known as Switched Active Switched Parasitic Antenna (SASPA) to produce a directive and electronically steerable radiation pattern. The SASPA array consists of antenna elements that are switchable between active and parasitic states by using P-Intrinsic-N (PIN) diodes. The active element is the element that is supplied by the radio frequency while short-circuiting the terminals of an element in the array results in a parasitic element. Due to the strong mutual coupling between the elements, a directional radiation pattern with high gain and a small beamwidth can be produced with only one active element operating at a time. By changing the parasitic state to the active state sequentially for all elements, the directed radiation pattern can be easily rotated. The antenna array structure used in this work is the uniform circular array (UCA) to achieve symmetrical radiation patterns and full coverage of the entire azimuth plane. Also, a novel method for reducing the mutual coupling effect in SASPA arrays is proposed in this work. By using this method, some parameters of the generated SASPA’s radiation pattern can be controlled. The simulated results obtained from this work depict that an N-element SASPA-UCA produces N-symmetrical, switchable, and steerable radiation patterns with high gain, small beamwidth, and a high Front-to-Back (F/B) ratio. Also, the results show that further improvements in these parameters can be achieved by increasing the number of elements in the array. Additional simulations demonstrate that by including decaying function weight in each element's circuitry, the mutual coupling between the components of the SASPA-UCA array can be minimized. The aforementioned parameters can then be efficiently modified using this mutual coupling reduction.

A Zeroth-Order Slot-Loaded Cap-Shaped Patch Antenna With Omnidirectional Radiation Characteristic for UHF RFID Tag Design

The zeroth-order resonance of a compact patch structure is explored for designing a metal-mountable tag antenna in the United States (US) ultrahigh-frequency (UHF) radio frequency identification (RFID) passband. This zeroth-order resonator (ZOR) structure comprises a cap-shaped patch loaded with two L-shaped slots. Also, the patch is coupled to the ground through two inductive stubs which provide enough parasitic reactance to support the zeroth-order resonance. The proposed single-element ZOR can generate sufficient antenna impedance for achieving a conjugate match with the RFID chip impedance. Good omnidirectional radiation characteristic with vertically polarized fields can be attained in the azimuth plane when the tag antenna is placed on a metallic surface. The proposed tag antenna’s realized gain at 915 MHz is −1.382 dB [effective isotropic radiated power (EIRP) 4 W]. A stable read distance of ~15 m is obtainable with even spatial coverage in the entire azimuth plane. The resonance frequency of the proposed tag does not vary much with the object being tagged.

Reduction of side lobes in the entire azimuth plane in a planar elliptical array antenna

SummaryA novel synthesis method to reduce the maximum side lobe in the entire azimuth plane and for achieving a desired value of directivity of a concentric elliptical array antenna is addressed in this paper. Three well‐performing meta‐heuristic optimization algorithms, teaching learning‐based optimization (TLBO), symbiotic organism search (SOS), and quantum particle swarm optimization (QPSO), are employed to optimize the cost function and to obtain the desired radiation pattern. Different simulation‐based experiments are performed to obtain the best possible set of angular positions and the distribution of isotropic antennas across the ellipses by rigorously maintaining non‐overlapping constraints. The major benefit of the proposed design is the deprecation of interference in all phi planes. The statistical analysis of the simulation results demonstrate perceptible improvement compared with that of a uniformly spaced concentric elliptical array and hence show the efficiency of the proposed algorithms. In both simulation studies, the results obtained using TLBO, SOS, and QPSO are compared. Analysis of the results exhibits that for the stated objective, the TLBO‐ and SOS‐based side lobe reduction approach performs superior to QPSO method. Proposed multi‐objective research work could lead to reduce payload and can simultaneously achieve isoflux coverage in entire azimuth plane on the earth surface which can essentially be utilized in (Low Earth Orbit) LEO and (Geostationary Earth Orbit) GEO satellites applications.

A Novel Dual-Band Beam Scanning Antenna Based on slot Active Frequency-Selective Surfaces [Antenna Applications Corner

A novel dual-band electronically beam scanning antenna based on a slot active frequency-selective surface (SAFSS) is proposed in this article. Each unit cell used in an SAFSS screen has two slots with four variable capacitors utilized to achieve high tuning ranges and dual modes. To achieve an adequate single mode, specific capacitances are used in each slot to overlap the two resonances. These dual modes in each unit cell create specific conditions for an antenna to control beams in dual bands simultaneously. An antenna prototype operating at the 1.5- and 2.45-GHz frequency bands is fabricated and measured. The results show that the fabricated antenna can scan its main beam in the dual band across the entire azimuth plane with a 45d resolution. The designed dual-band antenna is inexpensive, has easy fabrication, and is capable of sweeping beams across the full 360? angular range in dual bands simultaneously.

A Flexible Dual-Band Rectenna With Full Azimuth Coverage

This paper presents a novel cylindrical shaped dual-band flexible rectenna capable of harvesting RF energy from number of RF sources available in the entire azimuth plane. The proposed configuration is an array of four identical dual-band rectenna subsystems, printed on the lightweight flexible substrate. Here, each rectenna subsystem comprises of a dual-ring shaped dual-band monopole antenna and a dual-band rectifying circuit. The designed topology is good for popular bands of LTE 1.8 GHz and Wi-Fi 2.45 GHz. The robustness of the designed antenna in the proposed cylindrical shaped rectenna is also verified by testing it for different bending angles in the H-plane by simulation as well as measurement. The bending performance is tested for the antenna using S11 and farfield radiation pattern. Further, for extracting maximum RF signals in the entire azimuth plane, these four identical antennas are backed by a wide-band artificial magnetic conductor (AMC) placed in the inner region of the cylinder. The fabricated single rectenna unit is capable of converting power with 40% efficiency at very low input RF power −12 dBm. Finally, the overall rectenna array is fabricated and validated through measurements using two different test antennas as a RF sources in the real environment of lab. The proposed light weight, rectenna printed on a flexible substrate can extract RF signals from a number of randomly distributed RF sources simultaneously, while maintaining the overall compact configuration.

Azimuth-Pattern Reconfigurable Planar Antenna Design Using Characteristic Mode Analysis

In this paper, a patch antenna is proposed with reconfigurable patterns in the azimuth plane. The basic structure of the antenna is a circular patch upon which a vertical slot is etched. In addition, a row of shorting posts along the horizontal direction is placed underneath the patch. With the aid of characteristic mode analysis (CMA), reconfigurable patterns are achieved by synthesizing the currents of different modes. By switching over different sets of feeding ports, four steerable beams capable of covering the entire azimuth plane are obtained. One unique feature is that when the beam is switched to the direction orthogonal to it, the shape of the pattern will be switched accordingly. The antenna was fabricated and measured. The measured F/B ratio is close to 10 dB at 2.08 GHz, and the 3-dB beamwidth in the elevation (azimuth) plane is switchable from 82° (181°) to 190° (91°).

Electronically Controlled Beam Steerable Dual-Band Star-Shaped DRA for UAS and Wi-Fi Data Link Applications

This communication presents a low-cost dielectric resonator antenna (DRA) with beam steering capability in the ${S}$ - and ${C}$ -bands. A centrally fed star-shaped DRA (SDRA) is placed on a circular substrate with backside metallization. Four folded metallic parasitic strips are placed at each corner of the SDRA and grounded via four RF switches. The switches are controlled by an automated microcontroller circuit. It steers the beam in the entire azimuth plane. The antenna has multiple switching modes to carry out basic operations like searching and tracking in unmanned aircraft system (UAS) application. In basic debug mode, all RF switches are kept OFF or ON to check the working state of the antenna. In searching cum tracking (SCT) mode, the RF switches are used to steer the beam and to obtain bidirectional or unidirectional beam. The average peak gain of the antenna in SCT mode is more than 6 dBi. In basic mode, the antenna has a peak gain of ≈3.5 dBi. The measured results validate the beam steering concept.

High-Directivity, Compact, Omnidirectional Horizontally Polarized Antenna Array

Omnidirectional horizontally polarized (OTIP) X-band magnetic dipole (MD) antenna arrays are reported that simultaneously achieve high directivity and wide bandwidth while being compact in size. A major innovation is the seamless integration of several phase inverters into an electrically long TE0.5,0 mode open waveguide. The resulting open structure radiates as a collinear series of MD sections. The inverters facilitate the realization of in-phase electric fields along its entire length and, hence, phase coherence between all of these MDs. Each phase inverter is realized as a combination of a meandering slot on one metallic surface of the waveguide and several shorting vias surrounding it. Two such multistaged (six- and eight-element) collinear OTIP MD arrays were designed and optimized. Prototypes of both were fabricated with standard, low-cost PCB manufacturing technology. The volume of the six-element (eight-element) OTIP array is only 0.07 × 0.22 × 3.3 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> (0.07 × 0.22 × 4.3 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> ); it achieves a measured 8.2 dBi (10.4 dBi) peak realized gain (RG). The measured overlapping -10 dB impedance bandwidth and 3 dB RG bandwidth was 8% in both cases. These designs are ideal for wireless applications requiring thin high-directivity TIP sources covering the entire azimuthal plane.

A Novel Design of Radiation Pattern-Reconfigurable Antenna System for Millimeter-Wave 5G Applications

In this article, a novel design of dielectric resonator antenna (DRA) with a reconfigurable radiation pattern capability is presented. Reconfigurability in the azimuth plane is achieved by symmetrically placing six electromagnetic bandgap (EBG) sectors around the DRA. Each sector is composed of 26 circular-shaped mushroom-like EBG unit cell. In order to achieve 360° pattern reconfigurability with a minimum number of diodes, a network of metallic veins printed on a conductor-backed dielectric slab is used to group and connect the vias in each EBG sector. In addition, a switching p-i-n diode is integrated to the circuit to control the beam steering in the entire azimuth plane toward the respective desired sector by turning on and off the diode. Sixty GHz DRA prototype incorporating the EBG switching circuit is fabricated and tested. Results show 360° pattern reconfigurability in the azimuth plane, with a realized gain of 4.2 dBi, and less than −16 dB impedance matching level over the desired bandwidth are achieved.

Investigation on non‐linear aspects of pattern reconfigurable hexagon shaped planar loop antenna

A planar electronically pattern-reconfigurable antenna based on Alford-loop-type hexagon shaped radiator is presented. The antenna consists of three half-wavelength dipole radiators arranged on both sides of an FR-4 substrate. It has an overall profile of 0.47λ 0 × 0.47λ 0 × 0.012λ 0 (λ 0 free space wavelength at 2.35 GHz). The bottom ground layer is tapered to allow impedance matching. Three PIN diodes are used to control the direction of radiation pattern by switching them in a controlled manner. Thus the antenna provides reconfigurable radiation patterns in six spatial directions with by switching three PIN diodes in ON and OFF states. The antenna has a measured impedance bandwidth of 2.35-to 2.45 GHz (4.16% fractional Bandwidth) and steers the beam in six directions 0°, 60°, 120°, 180°, 240°, and 300° covering the entire azimuthal plane. The antenna offers a maximum measured gain of 2.66 dB with simulated efficiency over 75%. Further, an investigation of non-linear effects due to PIN diodes shows that the antenna operates in the linear region up to an input power level of 27 dBm where the strength of received spurious harmonic and intermodulation signals is negligible. It makes the antenna suitable for indoor and short-range communication applications in the 2.4 GHz band.

Pattern Reconfigurable, Vertically Polarized, Low-Profile, Compact, Near-Field Resonant Parasitic Antenna

A vertically polarized, low-profile, compact, near-field resonant parasitic antenna with pattern reconfigurability is demonstrated. The antenna has three dynamic end-fire states facilitated with only three p-i-n diodes. The radiation pattern in each state covers more than 120° in its azimuth plane and, hence, it achieves beam scanning that covers the entire azimuth plane. The antenna height and transverse size are, respectively, only $0.048\lambda _{0}$ and $0.1\lambda _{0}^{2}$ . Measured results, in good agreement with their simulated values, demonstrate that the antenna exhibits a ~11% fractional impedance bandwidth, and a ~6.6 dBi peak realized gain in all three of its pattern-reconfigurable states. Stable and high peak realized gain values are realized over its entire operational band surrounding 2.22 GHz.

Center-Fed Unilateral and Pattern Reconfigurable Planar Antennas With Slotted Ground Plane

A center-fed, single-layer, planar antenna with unilateral radiation patterns is investigated. The antenna consists of a turnstile-shaped patch and a slotted ground plane, which function as a vertical magnetic dipole and a horizontal electric dipole, respectively. By combining the two orthogonal dipoles with the same radiation intensities and antiphases, unilateral patterns with wide beamwidth and high front-to-back (F/B) ratio are achieved. As the unilateral radiation pattern can be easily steered in the horizontal plane by changing the slot location, a pattern reconfigurable antenna is further designed by using p-i-n diodes to control the connection states of the radial slots on the ground plane. Four steerable beams are obtained, capable of covering the entire azimuthal plane. For demonstration, both the unilateral and pattern reconfigurable antennas operating at 2.4 GHz WLAN band (2.40–2.48 GHz) were fabricated and measured. The measured overlapping bandwidths, with $\vert S_{11}\vert dB and F/B ratio >15 dB, are given by 7.0% (2.33–2.5 GHz) and 6.3% (2.32–2.47 GHz), respectively.

Compact Orientation Insensitive Dipolar Patch for Metal-Mountable UHF RFID Tag Design

An orientation insensitive dipolar patch antenna, which has a dimension of 30 mm $\times30$ mm $\times1.6$ mm ( $0.0915\lambda \times 0.0915\lambda \times 0.0049\lambda $ ), is proposed for designing a metal mountable tag. It consists of two pairs of orthogonal dipolar patches, which are placed in such a way that their inherent blind spots and null points are all removed. The tag antenna is readable in all directions in the boresight. Highly inductive thin stubs are inserted into the patches, and they are stub shorted to ground for increasing the tuning range of the operating frequency. A simple equivalent circuit model has been derived for visualizing the tag impedance characteristics. The proposed tag antenna can be read in the range of 2.9–3.5 m (at effective isotropic radiated power of 4 W) covering the entire azimuth plane when mounted on a metal plate with a dimension 20 cm $\times20$ cm. It can also be read from at least 2 m omnidirectionally when used for dielectrics with $\varepsilon _{r}$ in the range of 1–12.

An ultra-wideband pattern reconfigurable antenna based on graphene coating**Project supported by the National Natural Science Foundation of China (Grant Nos. 61661012, 61461016, and 61361005), the Natural Science Foundation of Guangxi, China (Grant Nos. 2015GXNSFBB139003 and 2014GXNSFAA118283), Program for Innovation Research Team of Guilin University of Electromagnetic Technology, China, and the Dean Project of Guangxi Key Laboratory of Wireless Wideband Communication

An ultra-wideband pattern reconfigurable antenna is proposed. The antenna is a dielectric coaxial hollow monopole with a cylindrical graphene-based impedance surface coating. It consists of a graphene sheet coated onto the inner surface of a cylindrical substrate and a set of independent polysilicon DC gating pads mounted on the outside of the cylindrical substrate. By changing the DC bias voltages to the different gating pads, the surface impedance of the graphene coating can be freely controlled. Due to the tunability of graphene's surface impedance, the radiation pattern of the proposed antenna can be reconfigured. A transmission line method is used to illustrate the physical mechanism of the proposed antenna. The results show that the proposed antenna can reconfigure its radiation pattern in the omnidirectional mode with the relative bandwidth of 58.5% and the directional mode over the entire azimuth plane with the relative bandwidth of 67%.

Frequency Selective Surfaces for Beam-Switching Applications

A novel design of a beam-switching antenna based on reconfigurable frequency selective surfaces (FSSs) is presented. The antenna is composed of a cylindrical FSS with PIN diodes and divided into six equal sectors by metallic sheets. Metallic cones at the top and bottom of the structure are used to create a directive beam. The antenna is fed by a simple dipole at its center. To switch the radiation pattern of the antenna, the diodes in one FSS-sector are set off to be transparent to the incident EM waves, whereas the diodes in other sectors are on to reflect the incident wave. The direction of the radiation pattern is defined by the off-state sector. In this design, the beam-switching is achieved with only one layer and minimum size of the cylindrical active FSS in order to decrease the number of active elements, and the amount of the power supply. The antenna can sweep the entire azimuth plane with 60° radiation beamwidth in six steps. The fabricated antenna prototype operates from 2.3 GHz to 3 GHz with maximum measured gain of 10 dBi and 3-dB beamwidth of 60°. This antenna can be used in the base station of the wireless communication systems.

Concentric circular-shaped electronically steerable parasitic array radiator antennas for full-azimuth directions of arrival estimation with reduced computational load

This study proposes a new uniform concentric circular (UCCA) shape of electronically steerable parasitic array radiator (ESPAR) antennas for directions of arrival (DoAs) estimation problem. The well-known estimation of signal parameters via rotational invariance techniques (ESPRIT) algorithm is adapted to this special shape of UCCA and the authors demonstrate that the resulting algorithm yields better DoAs estimation accuracy and solves the failure of estimation problem when the signals&apos; DoAs are in some particular sectors: notably for [0°–30°] and [160°–180°]. This approach has shown interesting performances since it can ensure good DoAs estimation over the entire azimuth plane with a low extra computational overhead. The constraints are the same imposed to the ESPRIT algorithm allowing about 66% reduction on the required computational efforts. The Cramer Rao bound on the variance of DoAs estimated by the proposed array geometry is analysed. Through simulation results, the authors demonstrate that applying ESPRIT in conjunction with the proposed antennas shape not only provides superior high-resolution localisation capabilities but also it drastically reduces computations compared with previous works.