Dual segment rectangular dielectric resonator antenna with metamaterial for improvement of bandwidth and gain

The simulation and experimental studies of an aperture‐coupled wideband dual segment rectangular dielectric resonator antenna with metamaterial for C‐band applications are presented in this paper. The antenna consists of Alumina (Al₂O₃) ceramic as upper segment and Teflon as lower segment. The combination of circular‐shaped coplanar split‐ring resonator and conducting strip has been used as metamaterial superstrate. With the use of metamaterial superstrate, the bandwidth of the antenna is increased by 48% through simulation and 22% experimentally. The broadside radiation pattern of the antenna is converted into directive radiation pattern with reduced beamwidth when metamaterial superstrate is used. The peak gain of the antenna is also enhanced by 33% through simulation and 31% experimentally with the use of metamaterial superstrate. © 2014 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:646–655, 2014.     

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.     

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...     

A novel frequency-selective metamaterial to improve helix antenna

A novel frequency-selective metamaterial with negative permittivity and permeability for improving directivity and gain of a helix antenna is presented in this paper.The proposed metamaterial is composed of two Z-shape resonators printed on opposite sides of a dielectric substrate.Two forms of multilayered cells are found to be suitable for antennas and waveguides applications.In addition,a new method of designing a metamaterial-based helix antenna is presented with high directivity and gain.A comparison on radiation properties is given between the conventional and the new metamaterial-based helix antennas.Two comparisons on radiation properties are performed:(1) the effect of proposed Z-structure on monopole,dipole,and helix antennas;(2) the effect of OE3,split-ring resonator (SRR),and proposed Z-structure unit cells on the performance of helix antennas.The results show improvement of parameters such as directivity,gain,and radiation power of the new metamaterial-based helix antenna.Therefore,the combination of Z-structure with the helix antenna shows the best performance.     

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.     

Wideband high aperture efficiency antennas with beam switching for mmWave 5G base stations

A compact metamaterial inspired sub‐wavelength unit cells are integrated into wideband Vivaldi antenna. A high gain Vivaldi antenna with 50% impedance bandwidth is proposed. The dimensions of the antenna are 1.55 λ₀ × 3.2 λ₀ at 28 GHz. Gain enhancement of 3‐dB achieved by placing metamaterial unit cells in the aperture of the antenna. These unit cells aid in phase correction of the antenna. The 1‐dB gain bandwidth of antenna is 42% with a peak gain of 12.5 dBi indicating high pattern integrity. Corrugations of varying length are introduced in the ground plane to improve front‐to‐back ratio without altering the input impedance bandwidth. The aperture efficiency of the metamaterial loaded Vivaldi antenna is 78% at 28 GHz. The proposed element is used in a stacked module to achieve wide angular coverage of 120°.     

High‐gain dual‐polarized antenna for ultrawideband applications

In this article, a high‐gain and dual‐polarized antenna with UWB operation is proposed. The antenna is composed of two tapered dipoles as radiating elements, which are arranged orthogonally and fed perpendicularly to achieve polarization diversity. A metallic cavity reflector is placed behind the radiator for high gain radiation entire the operating bandwidth. To validate the design method, an antenna prototype is designed, fabricated, and measured. The measured results demonstrate that the proposed design has good performance with |S₁₁| ≤ ?10 dB and isolation ≥20 dB over a frequency band 3.2‐8.8 GHz, equivalently to about 93.3%. In addition, unidirectional radiation pattern and broadside gain of from 8.1 to 11.8 dBi are obtained across the operating bandwidth.     

Novel Design of UWB Jeans Based Textile Antenna for Body-Centric Communications

This research presents an ultra-wideband (UWB) textile antenna design for body-centric applications. The antenna is printed on a 1 mm thick denim substrate with a 1.7 relative permittivity. The jeans substrate is sandwiched between a partial ground plane and a radiating patch with a Q-shaped slot. The slotted radiating patch is placed above the substrate and measures 27.8 mm × 23.8 mm. In free space, the antenna covers the ultra-wideband spectrum designated by the Federal Communication Commission (FCC). Various parameters of the antenna design were changed for further performance evaluation. Depending on the operating frequency, the antenna's realized gain varied from 2.7 to 5 dB. The antenna achieved high radiation efficiency with an omnidirectional radiation pattern. A parametric study was performed in research on varying antenna substrates and other components of the antenna. The three outermost layers of the human body are used to model a human phantom for on-body simulation. After that, the antenna was placed at five different distances from the phantom. The findings demonstrate that at close distances to the phantom, the antenna's gain and efficiency at lower frequencies are reduced. The antenna's radiation efficiency and gain were much higher at higher frequencies for distances greater than 6 mm. Compared to free space, the antenna's radiation pattern was more omnidirectional, especially at higher frequencies. This antenna is novel, compact and has an ultra wide bandwidth, a maximum of 94.60% radiation efficiency and a 5 dBi gain that will make it a good candidate for body-centric communications.     

Wide bandwidth microstrip antenna with defected patch surface for low cross polarization applications

A simple and single element wide slot dipole loaded shorted rectangular microstrip antenna has been proposed and investigated experimentally for broad impedance bandwidth and improved cross polarized (XP) radiation compared to maximum co‐polarized (CP) gain without changing the co‐polarized (CP) radiation pattern. Around 23‐35 dB isolation between CP and XP radiation along with 25% impedance bandwidth is achieved with the proposed structure. The measured gain of the antenna is around 6.2 dBi over the entire band. The present antenna is very simple and easy to manufacture. Unlike the other structures, the present one is free from back radiation in terms of XP fields. The design of the antenna structure is theoretically justified and rigorously analyzed. The present investigation provides an insightful, clear visualization‐based understanding of the concurrent improvement in both the impedance bandwidth and XP performance with the present structure.     

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°.     

Design and fabrication of a new high gain multilayer negative refractive index metamaterial antenna for X‐band applications

This article presents the design of a planar high gain and wideband antenna using a negative refractive index multilayer superstrate in the X‐band. This meta‐antenna is composed of a four‐layer superstrate placed on a conventional patch antenna. The structure resonates at a frequency of 9.4 GHz. Each layer of the metamaterial superstrate consists of a 7 × 7 array of electric‐field‐coupled resonators, with a negative refractive index of 8.66 to 11.83 GHz. The number of layers and the separation of superstrate layers are simulated and optimized. This metamaterial lens has significantly increased the gain of the patch antenna to 17.1 dBi. Measurements and simulation results proved about 10 dB improvement of the gain.     

High performance microstrip monopole antenna with loaded metamaterial wire medium superstrate

A novel design of printed monopole antenna loaded with wire medium is developed for radar applications. The advocated design aims to simultaneously enhance the gain and bandwidth of the proposed geometry. The proposed antenna is composed of a circular patch etched with double C‐shaped slots and the ground is defected to achieve wide bandwidth. Wire medium superstrate and a metal reflector are implemented to provide high gain. The promising tunable wire medium superstrate consists of a periodic array of parallel metallic wires arranged in a rectangular pattern that mimic the behavior of epsilon‐near‐to‐zero (ENZ) metamaterial. This medium is suspended at a distance of a quarter‐wavelength in air above the antenna to provide the optimum gain and reduce the side lobes level. Prototype of the optimized antenna is fabricated using Rogers's substrate to offer ?10 dB bandwidth over the entire frequency range (900 MHz to 2.85 GHz). Details of the design process are investigated through full wave electromagnetic simulations performed by CST software. Experimental results of the fabricated prototype are presented and also compared with simulation results where an appreciable agreement between them is demonstrated.     

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.     

Dual ISM band printed antenna with omnidirectional radiation pattern and better radiation efficiency

Designing a high gain planar antenna on the low‐cost FR4 substrate is one of the major challenging tasks for the researchers. The omnidirectional radiation pattern is desired for 360° coverage. Both of these requirements have been addressed in this article. This article presents a dual band printed antenna designed on an FR4 substrate of 1.6 mm thickness. The proposed antenna operates in the ISM band of 2.4 and 5.8 GHz for the application of dual‐band WLAN/WIFI. The proposed antenna consists of a circular patch and ring‐shaped ground plane. The overall dimension of the antenna is 66 × 66 × 1.6 mm³. Excellent impedance matching and radiation efficiency for both the bands have been achieved. The proposed antenna shows omnidirectional radiation pattern at 2.4 GHz ISM band and nearly omnidirectional pattern along with high gain of 4.7 dBi at 5.8 GHz ISM band.     

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 high‐gain dual‐band directional/omnidirectional reconfigurable antenna for WLAN systems

A high‐gain dual‐band antenna for the wireless local area network system is presented in this article. Two symmetrical linear arrays can be dynamically reconfigured that could switch radiation pattern with a switchable feed circuit between direction and omnidirection. The antenna can also be used for a pattern diversity antenna for the multiple‐input–multiple‐output communication systems. The design process for the antenna system is given, and the parameters and characteristics of the antennas are achieved by the method. Measured return losses, isolation, and radiation patterns are in good agreement with the simulated ones, which illustrates that the method is valid and the antenna system can be integrated with pattern reconfigurable and pattern diversity applications. © 2008 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2008.     

Gain enhanced multipattern reconfigurable antenna for vehicular communications

This article presents the design and implementation of a high‐gain tunable dual‐band pattern reconfigurable antenna for vehicular communications. The proposed antenna consists of a slotted patch loaded with a double‐side FSS acting as superstrate. The proposed slotted antenna operates at 2.45 and 3.5 GHz and the frequency tuning over the dual‐band is accomplished by employing a varactor diode for tuning the center frequency from 2.41 to 2.62 GHz and from 3.38 to 3.65 GHz at lower and upper frequency bands, respectively. To obtain pattern reconfiguration, the slotted patch is divided into four regions by using two diagonal lines of vias. By properly choosing the excitation port combinations, 14 different radiation patterns are realized with a maximum realized gain of 8.4 and 7.9 dB. Further enhancement of gain is achieved using frequency‐selective surface (FSS) screens which act as a partially reflecting surface. The unique feature of this design is to provide reflection coefficient with high reflectivity in two predetermined frequency ranges. The prototype antenna is fabricated and the measurement results are reported. The experimental results show that the prototype antenna with FSS offers tunable dual‐band with beam reconfigurable properties.     

A novel pattern‐reconfigurable grid array antenna

This article presents the design of a grid array antenna with pattern reconfigurable ability. Discussion of various factors that affect the radiation pattern is presented. Interdigital structure, which serves as short radiation line of grid array antenna is then introduced to reconfigure radiation pattern. Change of main beam direction is realized via state change of PIN diodes loaded in interdigital structure and variation of feed point. The scanning angle varies from ?33° to +38° and the average gain is about 10 dBi. The proposed antenna was fabricated and measured. Measured results show the proposed antenna possesses good beam‐scanning characteristics and has potential value in long‐distance power supply for various passive nodes.     

Pattern diversity of path loss compensated antennas for 5G base stations

In this article, a tapered slot antenna (TSA) operating from 27 to 29.8 GHz with an endfire gain of 9 dBi and high pattern integrity is presented. The gain specifications for path loss compensation on ground for a ceiling mounted millimeter wave base station is computed and the gain of the antenna elements with beam angled at ±45° was found to be 12 dBi. To enhance gain with minimal physical footprint, a combination of dielectric loading and electrical resonator metamaterial unit cells were integrated to the proposed TSA to achieve the expected gain enhancement of 3 dB across the band, operating in the same frequency band with aperture efficiency greater than 73% and a 1 dB gain bandwidth of 20.7%. A compact stacking topology for pattern diversity of all three antenna elements for path loss compensation is also investigated. The base station has a coverage of ±60° with uniform illumination and mutual coupling lesser than 35 dB. The detailed simulated and measured results are presented.     

A Wideband E‐plane Pattern Reconfigurable Antenna with Enhanced Gain

A novel method of steering antenna beam in its E‐plane is introduced and a design of wideband pattern reconfigurable antenna with enhanced gain is proposed in this paper. A bowtie antenna is used as the driven radiator, and two parasitic bowtie‐shaped microstrip stubs with two diodes are loaded beside each arm of the driven radiator. With the introducing of a low profile artificial magnetic conductor (AMC) beneath the bowtie radiator, unidirectional radiation pattern can be obtained. By altering the working states of the diodes, the main beam of the antenna can be switched in its E‐plane. The biasing circuit of the antenna is simple and easy to be implemented. The prototype of the antenna is fabricated, and good agreement can be observed between the simulated and measured results. Compared to other pattern reconfigurable antennas, the proposed antenna has advantages of a wide operating band, ability of beam switching in E‐plane, and high gain. These advantages makes it a good candidate for the wireless communication systems.