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.     

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.     

Design of a novel compact modified‐circular printed antenna for high data rate wireless sensor networks

This paper presents a novel compact circular patch Ultrawideband (UWB) antenna for sensor node applications. The microstrip‐fed low‐profile antenna comprises an elliptical ring slot, two crescent‐shaped slots and two dumbbell‐shaped slots in feedline. The antenna miniaturization is achieved by a novel combination of an elliptical ring slot, two crescent‐shaped slots in circular patch. The proposed prototype has been fabricated on inexpensive FR4 substrate and the relative permittivity is (ε_r = 4.3) with 1.6 mm thickness. The overall size of the proposed miniaturized antenna is about (0.1 λ_r × 0.15 λ_r), where λ_r is the resonating wavelength of the lowest UWB frequency (ie, 3.1 GHz). The measured radiation performances of the proposed antenna are nearly an omnidirectional pattern in H‐plane and bidirectional pattern in E‐plane for all the frequencies in the whole UWB band. The development process of the antenna, radiation properties and group delay is completely analyzed and discussed.     

RFID tag antenna for ultra and super high frequency band applications

A novel dual‐band antenna for radio frequency identification tag is proposed for ultra high frequency (UHF: 915 MHz) and super high frequency (SHF: 2450 MHz) bands. The proposed tag antenna is a single sided dual‐antenna structure, designed on the grounded (metallic) dielectric substrate. The proposed tag antenna can be used on any kind of surfaces including metals without severe performance degradation due to its metallic ground plane. At UHF band, proposed tag antenna works as dual‐antenna structure. In the dual‐antenna structure, one antenna works for receiving and another for backscattering. Due to separate backscatterer, the maximum differential radar cross section improved and results in the enhancement of the maximum read range. Whereas at SHF band, proposed antenna works as conventional single antenna structure and during operations it switches between receiving and backscattering modes. The proposed antenna consists of a meandered line antenna and a rectangular patch antenna loaded with an F‐shaped and an inverted L‐shaped slots. The S‐parameters are measured by means of differential probe technique. Simulated and measured results are observed in good agreement. The read range is observed about 5 and 6 m at 915 and 2450 MHz, respectively. © 2016 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:640–650, 2016.     

A dual‐band half‐mode substrate integrated waveguide‐based antenna for WLAN/WBAN applications

A dual‐band half‐mode substrate integrated waveguide (HMSIW) based cavity‐backed antenna is proposed for WLAN/WBAN applications at 5/5.8 GHz, respectively. A semi‐hexagonal slot is introduced on the top plane of the cavity primarily for radiation. This slot offers miniaturization for both the TM₂₁₀ and TM₀₂₀ modes. Later on, two rectangular slits are loaded on the open edge of the patch, to provide miniaturization and tuning mainly for the higher frequency band. The performance of the proposed antenna is investigated in free space and in proximity of the pork tissues. In free space conditions, the measured ?10 dB fractional bandwidths are 3% and 3.1% along with peak gains of 6.25 and 6 dBi for the frequency bands at 5 and 5.8 GHz, respectively. In proximity of the pork tissues, the measured fractional bandwidth is 3.2% along with the efficiency of 81.5% at 5.8 GHz. The specific absorption rate (SAR) is 0.48 mW/g averaged over 1 g of tissues with 100 mW input power.     

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.     

Miniaturized dual‐band slot antenna design for GPS,amateur radio and WLAN applications

In this article, miniaturization of dual‐band slot antenna design for GPS, WLAN and amateur radio applications is presented. The proposed dual‐band miniaturized antenna is achieved using slits, rectangular split ring and metallic strips fed by 50 Ω microstrip feed. The first resonant frequency is achieved by loading reference antenna with eight slits that is antenna 1 and the second resonant frequency is achieved by loading with one center slits and rectangular split ring that is antenna 2. Dual‐band antenna is achieved by loading reference slot antenna with nine slits and rectangular split ring which resonates at frequency of 1.52 and 3.03 GHz respectively. As a result, it is achieved 53.79% reduction in first band resonant frequency with 76.07% improvement in ?10 dB bandwidth and 7.90% reduction in second band resonant frequency compared to reference slot antenna. Further, this dual‐band antenna is miniaturized by metallic strips which are placed on the bottom of the substrate. This results in 61.39% reduction in first band resonant frequency with 32.07% improvement in ?10 dB bandwidth and 26.13% reduction in second band resonant frequency in comparison with reference slot antenna topology.     

Bandwidth and gain improvements of low‐profile H‐shaped microstrip patch antenna under quadruple‐mode resonance

A wideband low profile H‐shaped microstrip patch antenna (MPA) with reallocated quadruple‐mode resonance is presented for indoor wireless communication application. In this paper, the TM₂₀ (mode 1), TM₀₂ (mode 2), TM₂₂ (mode 3), and additionally notch mode 4 of the proposed MPA are simultaneously employed. First, the rectangular radiating patch is reshaped as an H‐shaped radiator so as to separate a pair of degenerate modes (mode 1 and mode 2). Then, a pair of linear notches is cut on the diagonal of the patch to excite an additional notch resonance (mode 4). Finally, in order to improve the frequency of mode 1, four shorting pins are placed at the four corners of the H‐shaped patch. Therefore, the bandwidth of the antenna is dramatically increased up by utilizing four resonant modes (modes 1, 2, 3, and 4). A prototype of H‐shaped patch antenna with notches and shorting pins is manufactured and measured. The results show that the antenna achieves a broad bandwidth of about 31.7% (2.31‐3.18 GHz), and its profile is only 0.036 wavelength of center frequency. It is particularly noticed that a relative high gain of around 9.8 dBi is successfully acquired, while keeping relative stable dual‐beam radiation patterns.     

Circularly polarized planar monopole antenna for ultrawideband applications

A broadband circularly polarized (CP) planar monopole antenna is proposed here for ultrawideband (UWB) communication. The antenna is composed of a modified annular ring patch fed by a tapered microstrip line and a rectangular semiground plane on the opposite side of the substrate. Capability of generating wide axial ratio bandwidth (ARBW) is another feature of the proposed antenna. Wide ARBW is achieved by introducing a rectangular slot and a stub in the ground plane. The CP antenna has an impressive ARBW of 5.52 GHz (81.42%, 4.02‐9.54 GHz) within the UWB frequency range (3.1‐10.6 GHz). Measured 10‐dB return loss bandwidth of the proposed antenna is 120.86% centered at 7.48 GHz (2.96‐12 GHz). The proposed antenna is well used for wireless local area network (5.2 and 5.8 GHz), Worldwide Interoperability for Microwave Access (5.5 GHz), and other wireless systems in C band as well as CP‐UWB antenna communication.     

Modeling and design of printed antennas using neural networks

A single neural network is developed to model the resonant frequency of rectangular patch printed on uniaxially anisotropic substrate with air gap using effective parameters in conjunction with spectral dyadic Green's function. Also, the strength of ANN models in antenna design is demonstrated by considering two case studies: the design of circular patch antenna and planar inverted‐F antenna. Results show good agreement with literature. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011.     

Dual‐band dual‐polarized compact planar monopole antenna for wide axial ratio bandwidth application

In this article, a geometrically simple, microstrip line‐fed planar monopole structure with slanting edge ground plane is designed to realize the dual‐band dual‐polarized operation. The proposed antenna consists of a rotated U‐shaped patch and an electromagnetically coupled L‐shaped parasitic radiating element. Owing to the combination of microstrip line‐fed radiating patch and a slanting‐edge rectangular ground plane on the opposite side of the substrate, the proposed dual‐band antenna can generate broad axial ratio bandwidth (ARBW) in the upper frequency band. The overall dimension of the prototype is only 32 × 32 × 1.6 mm³. The measured results validate that the proposed antenna has two operational frequency bands, 29.84% (1.54‐2.08 GHz) for linearly polarized radiation and 71.85% (3.96‐8.4 GHz) for circularly polarized radiation. Measured result shows that 3‐dB ARBW of the proposed antenna is 73.54% (3.80‐8.22 GHz) in the higher frequency band. It shows that the higher frequency band exhibits a left‐hand circularly polarized radiation in the boresight direction.     

Both transversal negative permeability and backward‐wave propagation in X‐Band waveguide with double‐side SRR metamaterials

In this article X‐band rectangular waveguides partially filled with the double‐side single ring resonator (DSRR) array are investigated for miniaturization, stop‐band, and multi‐band filters applications. Several rectangular waveguides loaded with the DSRR array in 2–10 GHz frequency band have been studied and optimized. We observe both the transversal negative permeability presented above the cutoff frequency and the backward‐wave located below the cutoff frequency with the DSRR array in X‐band waveguide. Both simulation and measurement results of DSRR array are with good agreement. The DSRR array provides better performance of the transversal negative permeability and the backward‐wave than the split‐ring resonator array. The physical explanation of backward‐wave is presented. The power loss distributions are clearly presented for the negative permeability attenuation and the backward‐wave propagation. © 2016 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:240–246, 2016.     

Bacterial foraging optimization technique to calculate resonant frequency of rectangular microstrip antenna

Resonant frequency of rectangular microstrip antenna having various substrate thicknesses are generally calculated using the standard expressions presented in literatures. But these equations suffer from errors when compared with the experimental values due to Quasi‐TEM propagation in the microstrip structure and fringing field. A number of researchers used soft computing approach such as neural networks and genetic algorithm on those equations to minimize the error for better accuracy. Bacterial foraging, an evolutionary optimization technique conceived in recent times, has many advantages over genetic algorithm and is yet to be applied on the design of microstrip patch antenna. In this article, a novel technique is developed to apply bacterial foraging optimization technique in conjunction with the expressions developed to calculate accurately the resonant frequency of rectangular microstrip antenna of any dimension and of any substrate thickness. Further, bacterial foraging is applied to the calculatation of the feed point of microstrip antenna. The technique developed in this article can be a generalized soft computing tool to calculate resonant frequency of rectangular microstrip antenna. Similarly, the idea of the article can be used for calculating the various parameters of microstrip antennas of different structure and geometry. © 2008 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2008.     

A dipole‐type millimeter‐wave antenna with directional radiation characteristics

A dipole‐type millimeter‐wave (mm‐wave) antenna with directional radiation characteristics is presented. A radiating patch structure composed of a dipole‐type radiation patch and a rectangular‐shaped parasitic patch are initially investigated to achieve a wider bandwidth. To further improve the operating bandwidth and to realize a directional radiation characteristic, this radiating patch structure is top‐loaded above a conducting cavity‐backed ground structure, which has a low profile (thickness of 3 mm). The measured results show that the proposed mm‐wave antenna can achieve a wide 10‐dB bandwidth of 51.3% (29.6‐50.0 GHz) and stable gain across the desired frequency range. Furthermore, good directional characteristics over the entire mm‐wave frequency band with a compact antenna size of 0.64λ_40GHz × 0.91_λ40GHz × 0.43_λ40GHz are also realized. Hence, it is suitable for many small size wireless mm‐wave systems.     

Miniaturization of a patch antenna using circular reactive impedance substrate

In this article, to construct a reactive impedance substrate, unit ring is designed and proposed with radial and concentric mode analysis. A cylindrical substrate backed with a PEC plane and circular metallic elements on the top is used for achieving reactive surface impedance behavior. In this aspect, three unit rings structure with different ring elements are designed and simulated to realize the reflection phase characteristics. Afterwards, a probe‐fed circular patch antenna is miniaturized by stacking the three‐ring circular reactive impedance surface. The fundamental resonance frequency of the proposed antenna is reduced by about 30% with an improvement in impedance bandwidth by 121.6%. An improved front‐to‐back ratio as well as an acceptable co‐pol and cross‐pol isolation is exhibited in both E‐plane and H‐plane at the resonance frequency. In addition of miniaturization, dual band behavior has also been observed in the proposed design. Both resonance phenomena have been explained by circuit model representation and surface current distribution analysis. Improved radiation efficiency at 81.5% has been measured for the proposed antenna configuration.     

Cross‐polarization reduction of microstrip antenna using microwave absorbers

In this article, a metamaterial inspired microwave absorber is used to reduce the cross‐polarization (XP) level of the radiated wave in microstrip antenna (MSA). A microwave absorber unit‐cell has been analyzed and implemented to reduce the cross polarization (XP) level in a single element and a 2 × 2 microstrip patch array antennas. The antennas have been designed on a FR‐4 substrate of thickness 0.8 mm at 10.1 GHz center frequency. The 2 × 2 patch array antenna with and without the absorbers have been experimentally verified for the S11 parameter, the radiation pattern, and the XP suppression in H‐plane and a good comparison has been found.     

A metamaterial hepta‐band antenna for wireless applications with specific absorption rate reduction

Present article embodies the design and analysis of slotted circular shape metamaterial loaded multiband antenna for wireless applications with declination of SAR. The electrical dimension is 0.260 λ × 0.253 λ × 0.0059 λ (35 × 34 × 0.8 mm³) of proposed design, at lower frequency of 2.23 GHz. The antenna consists of circular shape rectangular slot as the radiation element loaded with metamaterial split ring resonator (SRR) and two parallel rectangular stubs, etched rectangular single complementary split‐ring resonator (CSRR) and reclined T‐shaped slot as ground plane. Antenna achieves hepta bands for wireless standards WLAN (2.4/5.0/5.8 GHz), WiMAX (3.5 GHz), radio frequency identification (RFID) services (3.0 GHz), Upper X band (11.8 GHz—for space communication) and Lower K_U band (13.1 GHz—for satellite communication systems operating band). Stable radiation patterns are observed for the operating bands with low cross polarization. The SRR is responsible for creating an additional resonating mode for wireless application as well as provide the declination in SAR about 13.3%. Experimental characteristic of antenna shows close agreement with those obtained by simulation of the proposed antenna.     

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.     

Metamaterial loads used in microstrip antenna for circular polarization: Review

The metamaterial elements and structures have been noticed for obtaining circular polarization (CP) while developing various procedures. In this paper, we have mentioned some of these cases and compared the metamaterial loads effect on antenna current distribution. We have classified them into four categories. The first case covers patch antenna based on composite right/left‐handed method, where the metamaterial has been used for changing the current distribution in the loop form. The second case has been achieved by radome and metasurface. In the third model, the interaction between feed and metamaterial load has been considered and the last case has been made by the metamaterial load with truncated structure. The metamaterial loading has been modeled based on Nicolson‐Ross or transmission/reflection techniques for extracting the permittivity and permeability. While the microstrip slot antennas are attractive for wider bandwidth, the truncated structure can change the current for achieving CP. Here, we have studied the antenna for wireless and WiMAX applications.