Wideband bow‐tie antenna with increased gain and directivity by using high impedance surface

Metamaterial surfaces offer a wide range of advantages in terms of antenna design. One such metamaterial is designed to capture the benefits of both high‐impedance surfaces as well as artificial magnetic surfaces. The confluence of both these properties delivers an added advantage to planar antennas by delivering high gain and directivity simultaneously. Bidirectional radiation pattern has been transformed to a directional radiation pattern by placing the metamaterial as substrate beneath the antipodal bowtie antenna. In addition, zero separation between the antenna and metasurface ensures low profile. The proposed design has been verified both by simulation and measurement which have shown an improvement on gain of 3.2 dBi with an almost steady gain response inside the resonating band of the antenna which lies between 12 and 16 GHz.     

Study of miniaturized E‐patch antenna loaded with novel E‐shape SRR metamaterial for RFID applications

A new design of compact micro strip antenna, based on a newly structure "E"SRR of metamaterial is proposed and designed using CST Microwave Studio. It has been found that the characteristics of new micro strip antenna with novel designed metamaterials placed in the same plane as the radiating element are comparable to the conventional patch antennas, whereas its gain, directivity, and radiating efficiency are remarkably improved. For the design and fabricated antenna, it shows that with the addition of split ring resonator, the frequency has been shifted from 2.38 GHz to 2.4 GHz. The return loss of this antenna increased from ?60 dB to ?70 dB. The realized gain increased from 7.1 dbi for the antenna alone to 7.31 dbi for the meta‐material antenna. Prototype for all antennas are fabricated and measured. Good agreement between the measured and simulated results is achieved.     

Three-dimensional large-aperture lens antennas with gradient refractive index

We propose an accurate method for designing three-dimensional （3D） large-aperture metamaterial slab lens antennas with gradient refractive index （GRIN）. According to the geometric optics, Fermat principle, ray-tracing technique and impedance matching, the 3D GRIN slab lenses with large apertures are accurately designed and simulated. With the aid of the effective medium theory, an X-band and a Ku-band conical horn antennas loaded with the 3D GRIN slab lenses of 250-mm diameter are experimentally realized using the drilling-hole technique on the printed circuit boards （PCBs） as the unit cells of metamaterials. Compared to the traditional dielectric lens with the same aperture, the proposed antennas have very good performance with high directivity, and the gain is increased by 2 to 5 dB. Using the same method, we design and realize a huge-aperture GRIN lens in the X band with a diameter of 1000 mm, which is composed of nearly one millions of inhomogeneous unit cells of square-ring resonators and dielectric blocks with drilling holes. Due to the huge aperture size, the electromagnetic ray paths inside and outside of the GRIN lens are verified and optimized using the ray tracing technique. Measurement results show good performance of the proposed antenna with high directivity.     

Metamaterial covered modified antipodal Vivaldi antenna with lens

In order to obtain a narrower half power beamwidth (HPBW) and a higher antenna gain in a wide frequency band, metamaterial layers and constant refracting-index lens are used to optimize the antenna performance in this article. The proposed metamaterial covered modified antipodal Vivaldi antenna with lens (M-MAVA with lens) has an operating frequency band of 1–8 GHz, and the maximize gain here is 18.81 dBi at 8 GHz, which increase about 9 dB. The HPBW in the entire frequency range is decreased significantly. Beyond this, the simulation results are in good accordance with the measurements. Based on these characteristics, the proposed M-MAVA with lens has an application in optimizing the structure of ground penetrating radar, microwave imaging, UAV countermeasures system and other system which need the good radiation gain and directivity.     

基于零折射率超材料的高定向性微带天线

研究了一种基于平面网格状零折射率超材料的高定向性微带天线.利用超材料结构的平均效应实现了在10.24 GHz处介电常数为零,进而实现了超材料的折射率为零.实验结果表明,利用零折射率超材料对波束产生汇聚作用,使微带天线的定向性明显增强,E面、H面半功率波束宽度分别收缩了56.67°和26.60.,侧向辐射明显减弱,天线的...     

Millimeter‐wave antenna with wide‐scan angle radiation characteristics for MIMO applications

A three‐element quasi Yagi‐Uda antenna array with printed metamaterial surface generated from the array of uniplanar capacitively loaded loop (CLL) unit‐cells printed on the substrate operating in the band 25‐30 GHz is proposed. The metamaterial surface is configured to provide a high‐refractive index to tilt the electromagnetic (EM) beam from the two dipole antennas placed opposite to each other. The metamaterial region focuses the rays from the dipole antenna and hence increases the gain of the individual antennas by about 5 dBi. The antenna elements are printed on a 10 mil substrate with a center to center separation of about 0.5 λ ₀ at 28 GHz. The three‐element antenna covers 25‐30 GHz band with measured return loss of 10 dB and isolation greater than 15 dB between all the three ports. The measured gain of about 11 dBi is achieved for all the antenna elements. The three antenna elements radiate in three different directions and cover a radiation scan angle of 64°.     

Profile miniaturization and performance improvement of a rectangular patch antenna using magnetic metamaterial substrates

The idea of profile miniaturization and performance improvement of a rectangular patch antenna using a metamaterial substrate with large values in the real part of effective relative permeability is proposed in microwave frequency range. The volume profile of the antenna is minimized by tuning the effective relative permeability and thickness of the substrate material. The specific type of metamaterial which can be used as substrate material for the antenna miniaturization purpose is suggested. The proposed idea is validated through finite‐difference time‐domain (FDTD) simulations for sample rectangular patch antennas with metamaterial substrates at the frequency about 10 GHz. Improvement of the power directivity is found for the metamaterial substrate with large value in the real part of effective permeability. © 2016 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:254–261, 2016.     

Application of metamaterials for performance enhancement of planar antennas: A review

Metamaterials are assemblies of metallic and/or dielectric materials with properties that are not readily found in naturally existing materials. Hence, metamaterial structures are commonly loaded on/near the patch, embedded in the substrate, loaded/etched from the ground plane or placed as a superstrate layer for enhancing bandwidth and gain, and size miniaturization of conventional patch antennas. The demand for wide bandwidth, high gain, and compact antennas is highly contemplated in recent wireless communication research studies. Despite their lightweight, ease of fabrication, low profile, and simplicity for integration, patch antennas have performance limitations as result of their narrow bandwidth, lower gain, larger size, and lower power handling capacity. To address these problems, metamaterial‐based antennas have gained massive interest. There exist inadequate literatures about review of current state of extensive study reports on metamaterial application for patch antenna performance enhancement. Thus, this paper has reviewed and discussed latest research works on metamaterial applications for performance enhancement of planar patch antennas.     

基于超材料的低剖面宽带双极化天线设计

设计了一种基于超材料的低剖面宽带双极化天线。该天线采用复合左右手结构（CRLH）作为辐射单元,利用其色散曲线的非线性特点,实现两种模式谐振点的融合,拓展带宽;同时采用不连通的十字形缝隙改善异极化隔离与交叉极化。论述了宽带低剖面线极化天线、水平/垂直双极化天线、±45°双极化天线的设计方法,并给出了HFSS的仿真结果,仿真结果表明：该天线具有低剖面、宽频带的特点,可用作大型天线阵的阵元。     

树枝状结构超材料在微带天线上的应用仿真

针对普通微带天线增益低、方向性差的缺点,提出一种树枝状结构超材料微带天线模型,为提高性能,利用以有限积分为主的CST软件对树枝状结构负磁导率微带天线模型和树枝状结构左手材料覆层微带天线模型进行了仿真研究。仿真结果表明,相对于普通微带天线,负磁导率材料基板天线增益提高了,并使有效辐射功率得到提高。同时,树枝状结构左手材料覆层天线的增益提高了1.2dB,相当于天线的有效辐射功率提高了31.8%,E面和H面主瓣半功率波束宽度分别收缩了45.8°和44.8°。树枝状结构负磁导率材料和左手材料可以抑制天线激发的表面波,对天线发射的电磁波进行会聚效率更高。新型天线可用于导弹、卫星及飞机飞行器等。     

Integrated Vivaldi antenna for UWB/diversity applications in vehicular environment

This article presents the design of a three‐port diversity antenna capable of producing three‐directional radiation pattern for vehicular communications. The proposed antenna consists of three uncorrelated Vivaldi antennas that are interconnected and developed on a single printed circuit board. Unlike many other antennas reported for the vehicular environment, the proposed antenna offers ultra‐wideband characteristics with end‐fire radiation pattern leading to high realized antenna gain. The integrated antenna has a footprint of 65 × 40 × 1.6 mm³ and offers 6 GHz impedance bandwidth extending from 5 to 11 GHz. The port‐to‐port isolation is greater than 20 dB within the operating bandwidth. Furthermore, the diversity performance of the proposed three‐port antenna system is evaluated and presented. The calculated envelope correlation coefficient, diversity gain, and mean effective gain are well above the minimum requirement. The prototype antenna is fabricated and the experimental results are presented.     

Design of a metamaterial‐based linear insulated antenna using a genetic algorithm

Recent interest in the application of metamaterials to antenna design has shown some promise in terms of improving the performance of disadvantaged antennas. In this article, we shall consider the design of a linear insulated antenna with a metamaterial coating operating in a lossy surrounding medium. Performance shall be examined for two different embodiments of this antenna using a genetic algorithm as the design tool, and shall address designs based on maximum antenna bandwidth, gain, and gain‐bandwidth product. Practical implementation of such antennas shall also be discussed and some experimental data presented. © 2008 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2009.     

Gain enhancement of slot antenna using zero‐index metamaterial superstrate

This article presents a technique to enhance the broadside gain of a CPW fed slot antenna using a single layer metamaterial (MTM) superstrate. A finite array of 3 3 ring unit cell has been designed on both sides of a dielectric substrate to form the MTM superstrate. The gain enhancement is obtained using the zero‐index property of the metamaterial. The broadside gain enhancement for the proposed antenna is 7.4 dB more in comparison to that of the reference slot antenna. The proposed MTM superstrate loaded antenna provides a minimum overall thickness in the context of using ZIM superstrate for gain enhancement of antennas reported in earlier literatures. The overall thickness of the MTM loaded antenna is 0.13λ₀, where λ₀ is the free‐space wavelength at the resonance frequency of the antenna. Also, a high efficiency of about 93.2% is obtained in this case. The loading of the MTM superstrate produces a minimal effect on the cross polarization performance of the proposed slot antenna.     

A novel miniaturized metamaterial lens antenna

This article develops a flat, miniaturized lens based on metamaterial for antenna gain improvement. The overall size of the lens is 1.9λ₀ × 1.9λ₀ × 0.05λ₀ . The distance between the metamaterial lens and the antenna is only about 0.4λ₀ . The prototype lens antenna is fabricated and the measured results are in agreement with the simulated results. It shows that the proposed lens provides significant gain enhancement by 2 to 3.5 dB between 1.3 and 1.45 GHz, which effectively demonstrate a high directivity, miniaturized, and compact metamaterial lens antenna.     

A wearable flexible microstrip antenna based on the floating‐ground backplane

In the present study, a wearable coplanar waveguide fed flexible microstrip antenna is proposed, which is based on the floating‐ground backplane. When the antenna is placed on a high‐loss human body, the antenna maintains reasonable impedance matching and exhibits a peak gain of 5.6 dBi. Moreover, the performance of the antenna under different bending radii and crumpling conditions is also analyzed. The simulation and experimental results show that the bending and crumpling have little effect on the impedance bandwidth and radiation pattern of the proposed antenna. Accordingly, it is concluded that the proposed antenna has great robustness. Furthermore, it is found that the proposed floating‐ground backplane structure significantly reduces the backward radiation of the planar antenna and enables the antenna to obtain a very low specific absorption rate (SAR) and increase the antenna gain. It should be indicated that antennas with great robustness, very low SAR, and small size are ideal candidates for wearable applications.     

Miniaturized UWB multi-resonance patch antenna loaded with novel modified H-shape SRR metamaterial for microspacecraft applications

We present the design and analysis of a novel modified H-shaped split ring resonator (SRR) metamaterial. It has negative permeability and permittivity characteristics with multi-band resonance for the X, Ku, and Ka frequency bands. Different configurations of the patch antenna have been analyzed with different orientations and positions of the metamaterial. Optimized performance was achieved with the new shape of the metamaterial antenna with an appreciable 9 dB gain, 77 GHz bandwidth, 100% radiation efficiency, and 65% reduction in active area. The second-order fractal metamaterial antenna achieves high miniaturization on the order of 1/21. This is truly a boon in the communications world, as a sharp beam with smaller physical dimensions is urgently required.     

Genetic algorithm design for nonperiodic planar graphene leaky-wave antennas in THz

The aim of this paper is proposing a new fast designing method for planar graphene leaky-wave antennas without periodical changes. Thus, Floquet theory cannot be used for designing, an optimization in numerical EM solver is needed. Since leaky-wave antennas are electrically long, their simulation using commercial EM simulators needs a large number of meshes, also the optimization of the large number of parameters (slot lengths and their distances) needs huge amount of memory and computation time. To resolve this problem, the method of Moments, implemented in MATLAB, which has been accelerated by applying some techniques, has been used in the design procedure. The antenna comprises a slotted graphene micro ribbon with a specific pattern, which is placed on two dielectric substrates and a PEC reflector. Graphene is used in the proposed LWA, instead of the electric conductor, because of its wonderful properties. The suitable pattern of slots on the graphene microstrip, is obtained using optimization by MATLAB Genetic algorithm tool. The usefulness and performance of the proposed designing approach, is verified in one example. It has been shown that the presented antenna, compared with one of the new successful similar antennas, has a better gain, radiation efficiency, and a wider range of beam scanning.     

Effect of h‐BN nanoceramic substrate on the performance of microstrip patch antenna in S‐band applications

The modern portable communication devices demand compact antenna with superior performance and reduced size and weight. The design and development of such antennas for broadband applications is a challenge for the researchers. In this paper, a microstrip patch antenna with h BN nanoceramic‐based substrate for S‐band application has been proposed and analyzed its performance experimentally. The proposed antenna has been fabricated using powder metallurgy and etching process. The performance of the fabricated antenna has been analyzed in terms of its characteristics such as return loss, gain, and radiation efficiency. Return loss of the proposed antenna is obtained as ?43 dB at resonance frequency. Proposed antenna using h‐BN nanoceramic substrate achieves peak gain of 8 dB and acceptable radiation efficiency in S‐band.     

Optimization‐Driven Antenna Design Framework With Multiple Performance Constraints

This work proposes an optimization‐driven framework that allows for antenna design with multiple constraints and tradeoff investigation between various objectives. In particular, it allows for antenna size reduction while maintaining other figures of merit (in terms of both electrical and field properties). We demonstrate our framework with UWB antennas size reduction taking into account matching, gain, efficiency, and radiation pattern stability constraints. Furthermore, we compare design tradeoffs between the minimum attainable antenna size and its electrical and field properties using seven design scenarios. The best possible tradeoffs are obtained using rigorous numerical optimization of all geometry parameters of the structure at hand. Two examples of UWB monopole antennas are provided to illustrate that the qualitative performance tradeoffs are very much dependent on a particular antenna topology and material properties of the substrate. Numerical results are supported by experimental validation.