High-gain Antenna Research Articles

A compact antipodal vivaldi antenna for modern surveillance systems

ABSTRACT Recent breakthroughs in modern surveillance systems combined with stealth and jamming technologies have led to the development of high-directional and high-gain antennas. This paper presents a compact-sized antipodal Vivaldi antenna (AVA) consisting of an elliptical shaped radiating flare with rectangular slots at the flare edges for modern surveillance systems. The proposed antenna provides improvements in the antenna characteristics, including a higher front-to-back ratio, increased main lobe gain, reduction in the side lobe level (SLL), and lower frequency limit. The results reveal that at 20 GHz, an improved gain of 3.8 dB and a front-to-back ratio of more than 40 dB have been realised. Additionally, in contrast to the antenna without edge slots, the impedance bandwidth, |S11| < −10 dB of 15 GHz, and a reduction in the lower operating frequency by 36.7% have also been achieved. The prototype antenna is developed and tested to verify with simulation results. The proposed antenna with the miniaturised structure may be suitable for surveillance applications in modern radar systems because of its ultrawide fractional bandwidth, high directive gain, and reduced SLL.

An ultra-thin high-efficiency plasmonic metalens with symmetric split ring transmitarray metasurfaces

Metasurface lenses (or metalenses) have aroused great attentions and efforts in the community of metamaterials or metasurfaces due to its ultrathin device dimension and superior focusing performances. High-efficiency transmissive metalenses with an ultra-thin device thickness are an important aspect especially in the low frequency by using plasmonic transmitarray antennas. In this paper, an ultra-thin plasmonic metalens with only 0.1λ (λ is working wavelength, the aperture size is 7λ) device thickness is designed by changing the radius of the proposed symmetric complementary split ring resonator antenna metasurfaces. Thanks to its high transmittance and large phase shift of the plasmonic meta-atoms, the designed metalens achieves both high transmissive efficiency of 80% and high focusing efficiency of 50% on the focal plane of F = 4.6λ in the simulations. The designed ultra-thin plasmonic metalens has a moderate large numerical aperture of 0.67 (NA = 0.67). In order to verify its high working efficiency of the proposed plasmonic metalens, a sample is also fabricated and a much higher focusing efficiency of 65% is realized in the measurements. The influence of the open angles of the symmetric split ring transmitarray metasurface on the focusing performances such as working efficiency and NA of the designed metalens is also studied and analyzed finally, which can add new degree of freedoms to optimize its focusing performance. The presented studies can facilitate the development of high-efficiency metalenses in the low frequency and have significant potential applications in high-resolution microwave imaging, high-gain metalens antennas and others.

Evolution of gain enhancement techniques in dielectric resonator antenna: applications and challenges

AbstractDielectric resonator antennas (DRA) are advantageous due to their small size, high radiation efficiency, ease of excitation, and minimal metallic losses. Enhancing the gain of DRA will make them suitable for a variety of applications such as wireless communication technology. High-gain antennas are required for wireless communication to overcome the difficulties of high path loss. The researchers have presented numerous techniques, including stacked DRA, DRA array, and higher-order mode excitation for enhancing the gain. This article provides a comprehensive summary of the state of art techniques and geometries including stacking, frequency-selective surfaces superstrate, electromagnetic band gap structures, hybrid techniques, arrays, etc., for increasing DRA gain. Techniques to improve other parameters like bandwidth and radiation efficiency along with gain are also discussed. The challenges in each technique and the possible applications are presented. Based on the studies, it is observed that the DRA array technique is suitable for obtaining gains up to 19 dBi for radar-based applications. For low-profile DRA requirements, hybrid DRAs prove prolific in enhancing gain up to 16 dBi.

High-gain reconfigurable polarization antenna based on metamaterial array for Terahertz applications

This paper suggestsproposes a high-gain reconfigurable polarization antenna using a metasurface polarizaer. The metasurface polarizer is a rectangular array that consists of similar 25 unit-cell elements. Each metamaterial (MM) unit-cell element consists of a circular copper patch attached to two copper arrow-shaped strips installed at its circumference. The circular patch and two arrows are installed between a rectangular superstrate at the top and a rectangular substrate at the bottom, which is backed with a perfect electric conductor with a relative permittivity of εsub = 3.38. The MM characteristics are obtained in a wide range of frequencies from 1.4 to 2.1 THz. The metasurface polarizer array is installed at an optimized height of 25 μm under a linear polarized dipole antenna that operates at 1.81 THz with a bandwidth (BW) of 0.2 THz from 1.75 to 1.95 THz (11.05%, − 10 dB BW) and gain of 2.27 dBi. The incident-plane wave from the antenna can be converted into a reconfigurable left- or right-hand circular polarization according to the directions of the arrow of the MM unit-cell element. Moreover, the operating − 10-dB BW of the dipole antenna increases to 30.93%, and the gain is enhanced to 6.18 dBi at the same operating frequency. A reconfigurable polarization conversion for the dipole antenna can be obtained over wide 3-dB axial ratio BW from 1.45 to 1.95 THz (33.3% BW).

Monopole Cavity Resonator Antenna with AMC and Superstrate for 5G WiMAX Applications

For 5G and WiMAX applications, a coplanar waveguide (CPW)-fed monopole antenna sandwiched between an artificial magnetic conductor (AMC) and a superstrate is investigated. Because traditional planar antennas have low gains, they are unsuitable for a wide range of applications. This paper explores scientific strategies for increasing radiation gain in low-gain antennas such as planar monopoles. We use AMC in conjunction with superstrate to achieve a high gain antenna, with the monopole antenna serving as the primary radiator. However, a superstate like this demands the use of materials with high permittivity, and most of such materials are not readily available on the market. Even if such materials are available, they are mostly expensive and unsuitable for commercial systems. We investigate various superstrates and elaborate on which way these superstrates can be used interchangeably without compromising antenna performance. In the end, we fabricate one of these three superstrates. The antenna, which also employs AMC in tandem with the superstrate, has an impedance bandwidth ranging from 3.2 GHz to 3.75 GHz with 7 dBi gain, so it can be a viable candidate for 5G and WiMAX applications

Aperture-Shared All-Metal Endfire High-Gain Parabolic Antenna for Millimeter-Wave Multibeam and Sub-6-GHz Communication Applications

This communication demonstrates an endfire aperture-shared antenna for millimeter-wave (mm-wave) multibeam and sub-6-GHz communication applications. High-gains are achieved based on the parabolic reflectors (PRs) that can collimate the electromagnetic (EM) wave radiated from the feeds at the focal points. In contrast to the full metal-based PR in the sub-6-GHz band, the mm-wave PR is implemented using periodic metal gratings, which shows a bandgap in the mm-wave band while allowing the sub-6-GHz EM wave free to pass. In this way, the sub-6-GHz and mm-wave parabolic antennas share the same radiating aperture with near 100% aperture reuse efficiency and tiny mutual interference. Multiple mm-wave feeds are used to achieve multibeam radiation without a complicated feed network. The radiating aperture is gradually enlarged in a flared structure to enhance the gain further while maintaining a high aperture efficiency. In contrast to the state-of-the-art printed circuit board (PCB) designs, the proposed antenna is an all-metal one with the advantage of no dielectric loss. A prototype operating at the C- and Ka-bands is designed, prototyped, and measured.

Design of Dual-Band MIMO antenna for 5G applications

MIMO antenna are widely used in many areas for the great reception of signals. In transport industry for the development of automation and for the advancement they required efficient and high gain antenna transceivers. In this paper, single-element dual band antenna is used for 5G Vehicle to Everything (5G-V2X) application but the design will be enhanced to six-element for full coverage, on analysing single element. Three antennas of same structure as specified in this paper are arranged in a single substrate as a shape of triangle of combining all three, and similar structure is made in another substrate such that both are separated by a strip like structure and arranging both substrates that both triangularly arranged substrate forming a hexagonal structure from the top view. These will increase the coverage over 360° surrounds these will increase the gain over 9dB at mm-Wave range.

Focusing and Linear-to-Circular Polarization Conversion of a Hemispherical Metasurface

With the aim of enhancing the radiation of the antenna system conventionally containing a protective dome, a transmission-type linear-to-circular polarization conversion electromagnetic metasurface lens which approximates a hemispherical shell profile is presented in this study. The presented design bearing structural compatibility with the existing dome geometry can facilitate the link enhancement of compact system through its potential for a circularly-polarized high gain antenna. To fulfill both the focusing and polarization conversion requirements, transmission phase distribution on the hemispherical surface is analyzed first. Then, polarization-dependent unit cell geometry is designed to achieve the objective transmission phase distribution. The hemispherical metasurface is thus obtained through building all unit cells with determined dimensions and orientations onto the corresponding hemispherical surface positions. Finally, using an aperture-coupled linearly-polarized patch antenna as the primary radiating source of the metasurface, enhanced main lobe gain and circularly-polarized secondary radiation is observed within a wide band. The agreement between simulation and measurement validates the design.

Optimization of Coherent Dynamics of Localized Surface Plasmons in Gold and Silver Nanospheres; Large Size Effects

Noble metal nanoparticles have attracted attention in recent years due to a number of their exciting applications in plasmonic applications, e.g., in sensing, high-gain antennas, structural colour printing, solar energy management, nanoscale lasing, and biomedicines. The report embraces the electromagnetic description of inherent properties of spherical nanoparticles, which enable resonant excitation of Localized Surface Plasmons (defined as collective excitations of free electrons), and the complementary model in which plasmonic nanoparticles are treated as quantum quasi-particles with discrete electronic energy levels. A quantum picture including plasmon damping processes due to the irreversible coupling to the environment enables us to distinguish between the dephasing of coherent electron motion and the decay of populations of electronic states. Using the link between classical EM and the quantum picture, the explicit dependence of the population and coherence damping rates as a function of NP size is given. Contrary to the usual expectations, such dependence for Au and Ag NPs is not a monotonically growing function, which provides a new perspective for tailoring plasmonic properties in larger-sized nanoparticles, which are still hardly available experimentally. The practical tools for comparing the plasmonic performance of gold and silver nanoparticles of the same radii in an extensive range of sizes are also given.

Topology optimization design of antennas with complex radiation characteristics

AbstractAntennas with complex radiation characteristics can enhance the adaptability of radiofrequency systems in complex electromagnetic environments. However, The realization of complex targets is extremely challenging for conventional antenna design methods. It is difficult to find a suitable initial topology of the antenna with complex radiation characteristics. Therefore, in this paper, topology optimization is used to explore the initial structure with complex radiation properties. A two‐dimensional lossy thin layer model based on the transitional boundary condition is constructed, and target field functions for complex radiation are proposed. To verify the effectiveness of the algorithm, a high gain antenna with 10.2 dBi is realized, which has the highest aperture efficiency compared with the literature in similar directions. Then, for more complex targets, the radiation patterns of arbitrary direction null, arbitrary direction beam, and equal‐amplitude dual beam are realized, respectively. The topology optimization algorithm provides a new approach for the design of complex multitarget antennas.

A Compact Mu-Near-Zero Metamaterial Integrated Wideband High-Gain MIMO Antenna for 5G New Radio Applications.

This article demonstrates a compact wideband four-port multiple-input-multiple-output (MIMO) antenna system integrated with a wideband metamaterial (MM) to reach high gain for sub-6 GHz new radio (NR) 5G communication. The four antennas of the proposed MIMO system are orthogonally positioned to the adjacent antennas with a short interelement edge-to-edge distance (0.19λmin at 3.25 GHz), confirming compact size and wideband characteristics 55.2% (3.25-5.6 GHz). Each MIMO system component consists of a fractal slotted unique patch with a transmission feed line and a metal post-encased defected ground structure (DGS). The designed MIMO system is realized on a low-cost FR-4 printed material with a miniature size of 0.65λmin × 0.65λmin × 0.02λmin. A 6 × 6 array of double U-shaped resonator-based unique mu-near-zero (MNZ) wideband metamaterial reflector (MMR) is employed below the MIMO antenna with a 0.14λmin air gap, improving the gain by 2.8 dBi and manipulating the MIMO beam direction by 60°. The designed petite MIMO system with a MM reflector proposes a high peak gain of 7.1 dBi in comparison to recent relevant antennas with high isolation of 35 dB in the n77/n78/n79 bands. In addition, the proposed wideband MMR improves the MIMO diversity and radiation characteristics with an average total efficiency of 68% over the desired bands. The stated MIMO antenna system has an outstanding envelope correlation coefficient (ECC) of <0.045, a greater diversity gain (DG) of near 10 dB (>9.96 dB), a low channel capacity loss (CCL) of <0.35 b/s/Hz and excellent multiplexing efficiency (ME) of higher than -1.4 dB. The proposed MIMO concept is confirmed by fabricating and testing the developed MIMO structure. In contrast to the recent relevant works, the proposed antenna is compact in size, while maintaining high gain and wideband characteristics, with strong MIMO performance. Thus, the proposed concept could be a potential approach to the 5G MIMO antenna system.

Millimeter-wave coding radial-periodic metasurface for manipulating beam-pointing angle of conical-beam radiation

In this article, a millimeter wave coding radial-periodic metasurface conical-beam (CB) antenna for manipulating beam-pointing angle (BPA) is presented. The proposed structure is excited by a high-gain CB planar antenna. The novelty of the proposed design lies in its BPA manipulating mechanism, obtained by radial-periodic metasurfaces (MS) located on the top of the source CB antenna. Full-wave analysis and experimental validation verified the proposed design performance, achieving simulated 10.2% 10-dB impedance bandwidth (BW) covering 27.19–30.12 GHz, whereas the measured BW is 11.7%, covering 26.86–30.2 GHz; as well as 6–18° BPA coverage in the elevation plane with a measured peak gain of 7.7–9.86 dBi in the 27–28 GHz range. The proposed structure exhibits good CB radiation performance with wide BW, flexible BPA control capability, and stable gain variation. Consequently, the proposed structure can be a potential candidate for applications that need wide beam coverage.

Design of Rectangular Patch Antenna on the Hilbert Fractal-shaped High Impedance Surface

The high Impedance Technique has emerged as a modern approach for high-gain microstrip antennas. A high impedance surface minimizes surface waves and provides increased gain. Instead of, a typical mushroom to design High Impedance Surface (HIS), fractal geometry can be used. Hilbert curve-based Fractal geometry minimizes physical length and keeps electrical length the same. In this work, three iterations of Hilbert curve-shaped HIS geometry are studied with emphasis on HIS application. Fractal facilitates multi-frequency operation from GSM 1800 MHz to 6 GHz Wireless applications. The antennas have a peak gain of 5.3 dbi. The simulation is conducted in HFSS, and the analysis is performed using reports like reflection coefficients, radiation patterns, and gain plots

High-Gain Millimeter-Wave Antenna-in-Display Using Non-Optical Space for 5G Smartphones

This article presents a high-gain display-integrated antenna topology, for the first time, embedding radiating traces into a nonoptical space, referred to as the dead space (DS), which is the edge part of the display panel; however, it does not perturb the optical illumination of the display. Thus, the proposed antenna topology is denoted as antenna-in-display (AiD). To fit the extremely narrow embedding conditions of the given DS (= <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.03 \lambda _{0}$ </tex-math></inline-formula> at 28 GHz), a new-shape coplanar waveguide (CPW)-fed folded dipole antenna was devised and efficiently tailored in the DS area. The bottom side of the panel was modified to render the effect of a coplanar defected ground structure (CDGS) for antenna minimization, and a new asymmetrical antenna geometry was proposed for wideband impedance matching and broadside radiation pattern. Compared with conventional studies, the proposed antenna concept provides an improved gain resulting from the good conductive metal in DS, the complete display visibility, and touch sensor compatibility, whereas the previous antenna-on-display (AoD) approaches inherently suffer from the limited gain obtained at the expense of lower conductivity of the optically invisible antenna electrodes. Because the proposed AiD concept enables the direct fabrication of antenna traces into the DS area of the display panel, eliminating need for an additional film, a lower package profile, and cost reduction can be achieved. The proposed prototype was fabricated and verified using an actual smartphone. The measured data confirm 12.32 dBi gain, 54.3% radiation efficiency, and 3 dB gain bandwidth larger than 3 at 28 GHz.

A Wideband High-Gain Dielectric Horn-Lens Antenna for Wireless Communications and UWB Applications

A wideband high-gain dielectric horn-lens antenna (DHLA) for wireless communications and ultra-wideband (UWB) applications, featuring 122% fractional bandwidth, is presented. The antenna, consisting of a dielectric horn equipped with a spherical-axicon dielectric lens that increases and equalizes the gain within the operating band, is placed on a PCB featuring a wideband eight-shaped slot fed by a tapered microstrip line employed to excite the radiating system. The lens, integrated within the body of the dielectric horn, has the property of focusing the RF energy near its vertex on an extended frequency band, thus ensuring compact size, excellent field coupling with the antenna excitation system, and a significant increase of antenna gain. The antenna operates in the 3–12.4 GHz frequency range with relatively flat group delay, making it suitable for operating with narrowband, broadband, and impulsive UWB signals. The antenna can work properly without or with a metal reflector useful to enhance gain (up to 19 dBi), improve the front-to-back ratio, and reduce the impact of the antenna characteristics from the installation site. CST Studio Suite, implementing a full-wave locally conformal finite integration technique (FIT), was employed to design and characterize the antenna. The antenna characteristics estimated numerically were found to be in good agreement with the experimental results performed on an antenna prototype.

High-Gain and Wideband Planar Endfire Antenna Implemented via Spoof Surface Plasmon Polaritons and Dielectric Lens for X-Band Applications

This letter proposes a wideband, high-gain, and planar endfire antenna using odd-mode spoof surface plasmon polaritons (SSPPs) and dielectric lens. The SSPPs of the odd mode are excited via a novel asymmetric coplanar waveguide feeding configuration, consisting of a row of gradient slots etched inside of one ground plane. Symmetric SSPPs structure serves as a radiator element to realize stable endfire radiation. By extending a planar elliptical dielectric lens at the end of the substrate, the gain and front-to-back ratio (FBR) of the proposed antenna are further enhanced. The proposed endfire antenna is fabricated and measured to certify the design concept. Measured results indicate the endfire antenna obtains a desired operating band of 7.9–13 GHz, a high peak endfire gain of 14.8 dBi, and an average efficiency of 80%. Moreover, the FBR is better than 20 dB over the wide bandwidth with an optimal peak FBR up to 40 dB.

Gain Enhancement of Horn Antenna Using a Metal Lens

A compact wideband open-horn antenna is proposed for point-to-point wireless communications. The antenna consists of a spatial power divider and an <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$H$ </tex-math></inline-formula> -plane lens. Both the power divider and lens are metallic, fabricated by using 3-D-printing technology. Our proposed lens has wrinkled subchannels of different lengths to convert the original quasi-cylindrical wavefront into a nearly planar wavefront across a wide frequency range, giving a wideband high-gain antenna. The operating principle and the design guideline are given. Using the guideline, two design examples with different <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$E$ </tex-math></inline-formula> -field magnitude distributions are studied and fabricated for Ku-band applications. The first design has a uniform <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$E$ </tex-math></inline-formula> -field magnitude distribution, with its maximum measured gain and normalized sidelobe level (SLL) being 18.1 dBi and −9.4 dB, respectively. The second design has a tapered <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$E$ </tex-math></inline-formula> -field magnitude distribution. In this case, the maximum measured gain and normalized SLL are 19.6 dBi and −15.0 dB, respectively. The overall measured 3-dB gain bandwidths of the two designs are more than 46.7%. It is found that the sizes (axial lengths) of the proposed designs are smaller than those of optimum horn antennas by more than 60%.

High Gain and Wide-Angle Continuous Beam Scanning SIW Leaky-Wave Antenna

A novel substrate integrated waveguide (SIW) adopting a leaky-wave antenna (LWA) for continuous beam scanning for tri bands is presented. For continuous beam scanning (CBS), optimization of different parameters associated with the unit cell has been carried out. Apart from this, optimal impedance matching is also obtained with the help of the characteristic impedance of the waveguide. The proposed SIW LWA scans from −58° to + 59° along with 14.50 dBi gain when the frequency changes from 10 GHz to 18.22 GHz and provides a scanning rate of 14.23. The beauty of the suggested antenna is its smaller size and high gain, along with a wider scanning range (117°) capability. This antenna’s final prototype has been fabricated, and the measurement results are matched with the simulation results.

Artificial Magnetic Conductor as Planar Antenna for 5G Evolution

A 5G wireless system requests a high-performance compact antenna device. This research work aims to report the characterization and verification of the artificial magnetic conductor (AMC) metamaterial for a high-gain planar antenna. The configuration is formed by a double-side structure on an intrinsic dielectric slab. The 2-D periodic pattern as an impedance surface is mounted on the top surface, whereas at the bottom surface the ground plane with an inductive narrow aperture source is embedded. The characteristic of the resonant transmission is illustrated based on the electromagnetic virtual object of the AMC resonant structure to reveal the unique property of a magnetic material response. The characteristics of the AMC metamaterial and the planar antenna synthesis are investigated and verified by experiment using a low-cost FR4 dielectric material. The directional antenna gain is obviously enhanced by guiding a primary field radiation. The loss effect in a dielectric slab is essentially studied having an influence on antenna radiation. The verification shows a peak of the antenna gain around 9.7 dB at broadside which is improved by 6.2 dB in comparison with the primary aperture antenna without the AMC structure. The thin antenna profile of λ/37.5 is achieved at 10 GHz for 5G evolution. The emission property in an AMC structure herein contributes to the development of a low-profile and high-gain planar antenna for a compact wireless component.

Triple-band stub loaded patch antenna with high gain for 5G Sub-6 GHz, WLAN and WiMAX applications using DGS

Microstrip antennas have become ubiquitous in today's wireless communication world due to their low profile, low cost, and simplicity in fabricating on circuit boards. However, poor performance characteristics, such as limited bandwidth, low power handling capabilities, and low gain, limit their applicability in various instances. Path loss will be substantial in 5th generation (5G) wireless communication due to the utilization of high-frequency bands. A high-gain antenna with a small size is necessary to address this issue. A compact tri-band, slotted monopole antenna with high and consistent gain employing a defected ground plane structure (DGS) has been investigated and implemented in this study. This proposed antenna uses three inverted L-shaped stubs connected to the radiating element to cover the desired bands while keeping the antenna size small. The designed antenna has two key characteristics: (i) wide bandwidth and (ii) reasonable gain. The antenna covers 2.45 and 5.6 GHz WLAN, 2.4 GHz Wi-Fi, 2.5 and 5.2 GHz WiMAX and 3.7 GHz Sub-6 GHz of 5G for mobile communication. The overall substrate size of the antenna is 30 ? 17 ? 1.6 mm3and the electrical dimensions are 0.49 ?L ? 0.28 ?L ? 0.026 ?L, where ?L is the free space wavelength at 2.45 GHz. The measured reflection coefficient (S11 &lt; -10dB) covers 2.4 - 2.52 GHz (bandwidth 112 MHz) and 3.4 - 4.1 GHz (bandwidth 700 MHz) and 5.2 - 6.6 GHz (bandwidth 1359 MHz) with a fractional bandwidth of 5.1 % at lower frequency band, 18.6 % at mid frequency band and 23.7 % at high frequency band. A prototype antenna has also been developed using an inexpensive, low-profile 1.6 mm thick FR-4 (?r = 4.4) substrate. The measured peak gains achieved are 1.35 dB at 2.45 GHz, 2.55 dB at 2.65 GHz and 3.8 dB at 5.5 GHz. The simulated results have been validated against actual experimental measurements, and the outcomes are consistent and match with certainty. The proposed antenna design is very compact and easy to fabricate due to the absence of vias.