Showing papers on "Metamaterial antenna published in 2018"

Study on isolation improvement between closely-packed patch antenna arrays based on fractal metamaterial electromagnetic bandgap structures

Abstract: A decoupling metamaterial (MTM) configuration based on fractal electromagnetic-bandgap (EMBG) structure is shown to significantly enhance isolation between transmitting and receiving antenna elements in a closely-packed patch antenna array. The MTM-EMBG structure is cross-shaped assembly with fractal-shaped slots etched in each arm of the cross. The fractals are composed of four interconnected-`Y-shaped' slots that are separated with an inverted-`T-shaped' slot. The MTM-EMBG structure is placed between the individual patch antennas in a 2 × 2 antenna array. Measured results show the average inter-element isolation improvement in the frequency band of interest is 17, 37 and 17 dB between radiation elements #1 & #2, #1 & #3, and #1 & #4, respectively. With the proposed method there is no need for using metallic-via-holes. The proposed array covers the frequency range of 8-9.25 GHz for X-band applications, which corresponds to a fractional-bandwidth of 14.5%. With the proposed method the edge-to-edge gap between adjacent antenna elements can be reduced to 0.5λ 0 with no degradation in the antenna array's radiation gain pattern. Across the array's operating band, the measured gain varies between 4 and 7 dBi, and the radiation efficiency varies from 74.22 and 88.71%. The proposed method is applicable in the implementation of closely-packed patch antenna arrays used in SAR and MIMO systems.

Dual Band Metamaterial Antenna For LTE/Bluetooth/WiMAX System

Abstract: A compact metamaterial inspired antenna operate at LTE, Bluetooth and WiMAX frequency band is introduced in this paper. For the lower band, the design utilizes an outer square metallic strip forcing the patch to radiate as an equivalent magnetic-current loop. For the upper band, another magnetic current loop is created by adding metamaterial structure near the feed line on the patch. The metamaterial inspired antenna dimension of 42 × 32 mm2 compatible to wireless devices. Finite integration technique based CST Microwave Studio simulator has been used to design and numerical investigation as well as lumped circuit model of the metamaterial antenna is explained with proper mathematical derivation. The achieved measured dual band operation of the conventional antenna are sequentially, 0.561~0.578 GHz, 2.346~2.906 GHz, and 2.91~3.49 GHz, whereas the metamaterial inspired antenna shows dual-band operation from 0.60~0.64 GHz, 2.67~3.40 GHz and 3.61~3.67 GHz, respectively. Therefore, the metamaterial antenna is applicable for LTE and WiMAX applications. Besides, the measured metamaterial antenna gains of 0.15~3.81 dBi and 3.47~3.75 dBi, respectively for the frequency band of 2.67~3.40 GHz and 3.61~3.67 GHz.

Thin Hybrid Metamaterial Slab With Negative and Zero Permeability for High Efficiency and Low Electromagnetic Field in Wireless Power Transfer Systems

Abstract: Current wireless power transfer (WPT) systems have limited charging distance and high induced electromagnetic field (EMF) leakage. Thus, we first proposed a thin printed circuit board (PCB) type hybrid metamaterial slab (HMS) combining two kinds of metamaterial cell structures. The metamaterial cells in the center area of the HMS have zero relative permeability and straighten the magnetic field direction. The metamaterial cells located at the edges of the HMS have negative relative permeability and change the outgoing magnetic fields to opposite direction by magnetic boundary condition. Therefore, the magnetic field can be more confined between transmitter and receiver coils, enhancing the power transfer efficiency, while decreasing the EMF leakage in a WPT system. In this paper, we demonstrated that increased power transfer efficiency from 34.5% to 41.7% and reduced EMF leakage from −19.21 to −26.03 dBm in 6.78-MHz WPT system. Furthermore, we proposed new analysis method for relative permeability measurement of the metamaterial using a novel cubic structure with perfect electrical conductor and perfect magnetic conductor boundary.

A novel monofilar‐Archimedean metamaterial inspired leaky‐wave antenna for scanning application for passive radar systems

Abstract: A novel backfire-to-endfire leaky-wave antenna is presented with ability to scan from -25ο to +45ο. The antenna is based on metamaterial transmission-lines (MTM-TLs) and is implemented using Monofilar Archimedean spiral and rectangular slots, spiral inductors and metallic via-holes. The slots act as series left-handed capacitances, and the spirals with via-holes provide the shunt left-handed inductances to realize the metamaterial antenna. A prototype antenna was fabricated prototype on FR4 dielectric substrate, which has an electrical size of 0.0302λo×0.0357λo×0.0008λo, where λo is free space wavelength at 165 MHz. Measured bandwidth of the antenna is 710 MHz (165-875 MHz) corresponding to a fractional bandwidth of 136.5%. The main advantage of the antenna is its ability to scan over a wide angle from -25 degrees to +45 degrees with acceptable gain and radiation efficiency of 1.2 dBi and 50.1%, respectively, measured at 400 MHz. The wide scanning attributes of the antenna make it suitable for passive radar applications to scan across the VHF-UHF bands for FM-Radio, television, mobile phones and GPS applications.

Low-RCS Monopolar Patch Antenna Based on a Dual-Ring Metamaterial Absorber

Abstract: In this letter, a novel ring-type layout of metamaterial absorber (MA) is investigated for the first time. Three-layer MA unit cell is duplicated along the ring lattices to obtain the proposed dual-ring MA structure, which possesses desirable electromagnetic wave absorbing characteristics. A center-fed circular patch antenna (CPA) coupled with the dual-ring MA is presented to produce a monopole-like radiation pattern and reduce the in-band radar cross section (RCS). MA array acts as an absorber and a radiator simultaneously in this integrated antenna. Both the simulated and measured results demonstrate that compared with the CPA with an annular ring, the in-band RCS of the proposed antenna is dramatically reduced without degradation of antenna radiation performance.

Miniaturised planar-patch antenna based on metamaterial L-shaped unit-cells for broadband portable microwave devices and multiband wireless communication systems

Abstract: This study describes the design of a metamaterial planar antenna for multi-octave band operation. The metamaterial unit-cell comprises L-shaped slit which is etched inside a rectangular patch with a grounded inductive spiral. The slit essentially behaves as a series left-handed capacitance and the spiral as a shunt left-handed inductance. The antenna was modelled and optimised for impedance bandwidth, gain and efficiency performance using commercial three-dimensional full-wave electromagnetic simulation tools. The antenna has a measured impedance bandwidth of 6.02 GHz for S 11<−10 dB. This corresponds to a fractional bandwidth of 172.49%, which is higher than multiband planar antennas reported to date. The antenna has a maximum gain and efficiency performance of 3.7 dBi and 73%, respectively, at 3.25 GHz. The physical footprint of the antenna is comparable to other wideband planar antennas reported to date. The overall size of the antenna is 0.037λ 0 × 0.027λ 0 × 0.002λ 0 and 0.25λ 0 × 0.18λ 0 × 0.017λ 0, where λ 0 is free-space wavelength at 0.48 and 3.25 GHz, respectively.

Metamaterial-based circularly polarised antenna employing ENG-TL with enhanced bandwidth for WLAN applications

Abstract: This work explains the design and development of a low profile and compact single probe-fed metamaterial (MTM)-based circularly polarised (CP) antenna using the modified rectangular patch with two pairs of spiral strips and vias for 5.2/5.8 GHz WLAN applications. The intended CP antenna mainly consists of two pairs of radiators and each radiator is realised by using epsilon negative (ENG) transmission line (TL) to generate zeroth-order resonance. CP characteristics are achieved by placing two radiators for x -polarised wave are orthogonally aligned to the other two radiators for y -polarised wave. The antenna radiating element offers a compact size of 0.24λ 0 × 0.22λ 0 with a low profile of 0.04λ 0 at 5.5 GHz. To confirm the characteristics of the intended MTM CP antenna design, the designed antenna is fabricated and measured. Measurement results show that the antenna obtains -10 dB impedance bandwidth of 610 MHz (10.86%) which is 2.3 times larger than the standard microstrip patch antenna and axial ratio bandwidth of 140 MHz (2.54%) is obtained.

Composite right/left-handed based compact and high gain leaky-wave antenna using complementary spiral resonator on HMSIW for Ku band applications

Abstract: In this communication, a novel compact high gain composite right/left-handed (CRLH) based leaky-wave antenna (LWA) is presented at Ku band. A half-mode substrate-integrated waveguide incorporated with a suitably oriented complementary quad spiral resonator (CQSR) is used to achieve a CRLH LWA. The unit cell is realised by a CQSR in such a way that the orientation of spirals exhibits higher leakage loss having a minimum cross coupling between them. The antenna is capable of scanning backward to forward along with a broadside direction in visible space. The proposed configuration has a length of 4.85 λ 0 which can scan within the frequency range of 13.5-17.8 GHz having a beam scanning range of 86° (-66° to 20°) and a maximum gain of 16 dBi. The simulated reflection coefficient of the proposed antenna is below -10 dB throughout the working frequency range with a side-lobe level of below -10 dB. The designed prototype is more compact in nature having high gain, fair scanning range, and good cross-polarisation level along with simpler design methodology and tuning capability to enhance the gain as well as radiation efficiency maintaining a fixed size. The proposed antenna could be a promising candidate in Ku-band applications like fixed satellite services, and broadcast satellite services etc.

Extended Aperture Miniature Antenna Based on CRLH Metamaterials for Wireless Communication Systems Operating Over UHF to C-Band

Abstract: This paper presents a simple technique to extend the aperture of planar composite right/left-handed (CRLH) metamaterial antennas with minimal impact on the antenna’s dimensions Unlike most CRLH antenna structures the proposed antenna is via-free The proposed antenna is shown to operate over a wideband from UHF to C-band with good radiation characteristics The antenna configuration consists of a vertically stacked CRLH unit-cells comprising of a patch and meandered lines, where the patch is engraved with an S-shaped slot The design uses minimal ground plane area The meander line inductance is grounded using CPW ground which eliminates conventional CRLH TL metallic via into ground plane The antenna is feed through a coplanar waveguide (CPW) match stub that is electromagnetically coupled to the unit cells Antenna dimensions are 175×3215×16 mm3, which corresponds to 0204λ_0×0375λ_0×0018λ_0 where free-space wavelength (λ_0) is 35GHz Parametric study enabled the optimization of the antenna performance in terms of impedance bandwidth, radiation gain and radiation efficiency Measured results confirm the antenna can operate from 850 MHz to 790 GHz, which is equivalent to a fractional bandwidth of 16114% The antenna has a maximum gain and radiation efficiency of 512 dBi and ~80%, respectively, at 35GHz

Pattern controlled and frequency tunable microstrip antenna loaded with multiple split ring resonators

Abstract: We propose a reconfigurable design of a metamaterial-inspired microstrip patch antenna, capable of tuning the frequency spectrum and beam radiation. The metamaterial component is composed of a three-ring square split ring resonator (SRR) loaded in the antenna's substrate. Radiofrequency (RF) micro-electro-mechanical-system (MEMS) switches are added in the gap of the proposed SRR to achieve frequency and radiation tuning in the performance of the microstrip patch antenna. The proposed reconfigurable antenna can be tuned to different frequencies depending on the operation states (no switching, one switch on, two switches on, and three switches on) of the SRR RF MEMS switches. The beam radiation can also be changed by setting in the `on' state the SRR switches. Beam width and beam angle can be independently tuned depending on the four different switching states. The proposed pattern controlled and frequency tunable metamaterial antenna demonstrates efficient reconfigurable reflection coefficient, radiation pattern, and current density performance. The designed antenna will be applicable to C-band long-distance radio telecommunications.

Miniaturization of microstrip loop antenna for wireless applications based on metamaterial metasurface

Abstract: The metamaterial and fractal techniques are two main methods for antenna miniaturization and in this paper, we have modeled an especial shape of the antenna based on loop formation with metamaterial load for this aim. The metamaterial layer is made by multi parallel rings and the result shows that the final antenna size reduced drastically while the frequency shifts from 7 to 4 GHz. The antenna has Omni-directional pattern with the gain of 3.5 dBi, so the size is reduced around 40%for 4.5 GHz and another resonance is made at 2.5 GHz with a return lossless than −6 dB with more than 60% frequency shift. The reflection and transmission have been utilized for showing the left hand characteristic based on two port periodic simulations in HFSS full wave software. We show that how the metamaterial load can provide the circular polarization (CP) by controlling the current distribution. We also presented that by making slots we obtained the better Axial Ratio (AR) and miniaturized the antenna with reconfigurable qualification. As a result of fact, we show that by using metasurface we able to miniaturized the antenna and simultaneously achieved the circular polarization.

A compact metamaterial loaded monopole antenna with offset-fed microstrip line for wireless applications

Abstract: A compact metamaterial loaded monopole antenna with offset-fed microstrip line is proposed for Universal Mobile Telecommunication System (UMTS), Worldwide interoperability for Microwave Access (WiMAX), and Wireless Local Area Network (WLAN) wireless applications. The proposed antenna is printed on a 19.18 × 22.64 × 1.6 mm3 FR-4 substrate having a dielectric constant ( e r ) of 4.4. The antenna radiating element consists of split ring structure and CSRR for generating multiband characteristics, which is fed by offset microstrip line. A split in the outer vertical arm creates a lower order resonance at 2.1 GHz and the Complementary Split Ring Resonator (CSRR) in the monopole antenna is used to generate a new resonance frequency of 3.45 GHz. The precise equivalent circuit design equations are used to analyze the CSRR resonance frequency. Also, the band characteristics of a split ring structure and CSRR are enlightened in detail to verify the metamaterial property. Simulated results are verified with measured results. The measured azimuthal plane (H-Plane) exhibits omnidirectional radiation pattern and elevation plane (E-plane) represents a bidirectional radiation pattern.

High-Gain and High-Efficiency GRIN Metamaterial Lens Antenna With Uniform Amplitude and Phase Distributions on Aperture

Abstract: A gradient index (GRIN) metamaterial lens antenna with extremely high gain and high aperture efficiency is presented. The proposed antenna is much more advantageous in terms of gain and aperture efficiency without compromising in simplicity and stability. The gain and aperture efficiency are improved by using a new method to design the GRIN lens for a hybrid mode, which possesses both uniform amplitude and phase distributions on the aperture. At the center of frequency band (14.25 GHz), the proposed antenna achieves a gain of 26.6 dBi, which corresponds to aperture efficiency greater than 90%.

A Compact Ultrawideband Antenna Based on Hexagonal Split-Ring Resonator for pH Sensor Application.

Abstract: A compact ultrawideband (UWB) antenna based on a hexagonal split-ring resonator (HSRR) is presented in this paper for sensing the pH factor The modified HSRR is a new concept regarding the conventional square split-ring resonator (SSRR) Two HSRRs are interconnected with a strip line and a split in one HSRR is introduced to increase the electrical length and coupling effect The presented UWB antenna consists of three unit cells on top of the radiating patch element This combination of UWB antenna and HSRR gives double-negative characteristics which increase the sensitivity of the UWB antenna for the pH sensor The proposed ultrawideband antenna metamaterial sensor was designed and fabricated on FR-4 substrate The electrical length of the proposed metamaterial antenna sensor is 0238 × 0194 × 0016 λ, where λ is the lowest frequency of 3 GHz The fractional bandwidth and bandwidth dimension ratio were achieved with the metamaterial-inspired antenna as 14691% and 318305, respectively The operating frequency of this antenna sensor covers the bandwidth of 17 GHz, starting from 3 to 20 GHz with a realized gain of 388 dB The proposed HSRR-based ultrawideband antenna sensor is found to reach high gain and bandwidth while maintaining the smallest electrical size, a highly desired property for pH-sensing applications

Design of plasmonic rectangular ribbon antenna based on graphene for terahertz band communication

Abstract: This study proposes a new idea for designing antenna based on graphene for THz application in detailed analysis. Here, design of a novel graphene-based ribbon antenna is presented based on surface plasmon polariton (SPP) behavioural in graphene. Noble metals support and confine EM waves in infrared region. However, SPP wave propagation is supported by graphene in much lower frequencies of infrared region, in THz region. The conductivity of graphene and SPP waves behavioural in graphene sheet is analysed and studied for designing antenna based on new idea of ribbon antenna. The numerical simulations with COMSOL and CST are presented in proposed new idea structure of antenna. In order to achieve the desired tunable THz band communication, the parametric study method is used for the proposed graphene-based ribbon antenna to achieve higher efficiency.

Coplanar waveguide-fed rose-curve shape UWB monopole antenna with dual-notch characteristics

Abstract: In this study, a new design of a planar ultra-wideband (UWB) monopole antenna with a rose-curve contour shape is proposed. The rose-curve circumference of the monopole is expressed in polar coordinates as: r=r 0 +acos(nθ). This function enables a flexible and easy to control layout, which directly affects the antenna's response. The arguments of the function are specified based on a simple deterministic design rule and the outputs of a parametric study. The antenna covers the 3.1-11 GHz band and has an ultra-miniaturised size of 864 mm 3 when realised on a RT/Duroid 6010LM substrate of 0.635 mm thickness. To add dual-notch characteristics to the proposed antenna, a complementary dual-band split ring resonator inclusion is etched on the antenna's patch near the feeding line. The inclusion is designed to operate at the two Wi-Fi and ISM frequency bands, 3.5 and 5.8 GHz, respectively. These centre band frequencies are determined using a new hybrid method that utilises the resonant and non-resonant design approaches of metamaterial structures. Simulated and measured return loss values, radiation patterns and gain values for the proposed antennas (with and without notching) are in very good agreements, and demonstrate satisfactory performance.

Focused microwave power transmission system with high-efficiency rectifying surface

Abstract: A focused microwave power transmission (MPT) system with high-efficiency rectifying surface is proposed. This work has two main novel contributions: (i) most of wireless power transmission systems reported so far are non-focused. This study presents the first focused MPT system with circular polarisation; (ii) a novel high-efficiency rectifying surface using sub-wavelength resonant elements is developed. To design a focused transmitting array antenna with high power density at the receiving site and high beam collecting efficiency in the near field, a method based on the optimisation of a partial scattering matrix is employed. A left-handed circularly polarised microwave power rectifying surface consisting of 8 × 8 sub-wavelength resonant elements is designed and the measured conversion efficiency reaches 57.74%. To validate the concept, an experimental system including one focused transmitting array antenna and one 2 × 2 elements rectifying surface is implemented and measured, and the improvement of output direct current (DC) power and radiofrequency (RF)-to-DC conversion efficiency compared with non-focused condition is shown. The highest RF-to-DC efficiency of 66.5% is achieved in the focused mode, compared to that of 34.8% only in the non-focused mode as in traditional systems.

Miniaturisation of an electrically small metamaterial inspired antenna using additional conducting layer

Abstract: An electrically small antenna ensures easy integration with devices without compromising the form factor. The performance in terms of bandwidth, gain and so on for these antennas is extremely critical and is governed by fundamental limitations in size, i.e. Chu's limit. This study initially presents an analysis of these limits and corresponding performance parameters. Next, a compact dual-band antenna has been designed using an electric field driven LC (ELC) resonator and a coplanar ground plane which operates at GSM 1800 and Wi-MAX. This proposed antenna has a compact size of $0.31\lambda _0 \times 0.08\lambda _0 \times 0.01\lambda _0$0.31λ 0 ×0.08λ 0 ×0.01λ 0 in the first band which is resonant at 1.89 GHz. Finally, a conducting layer is placed below the ELC resonator and both are connected through a via. This provides stronger capacitive coupling between the radiator and the feeding arm and thus, results in miniaturisation of 76.9% in the area. The new antenna is electrically small and covers various cellular bands such as GSM 900, Bluetooth, Wi-Fi and Wi-MAX. Prototypes of both designs have been fabricated and experimentally tested in order to validate the simulation results.

A Compact Reconfigurable NRI-TL Metamaterial Phase Shifter for Antenna Applications

Abstract: This communication presents a compact reconfigurable phase shifter based on negative-refractive-index transmission-line (NRI-TL) metamaterial unit cells. Two interswitchable NRI-TL metamaterial unit cells are collocated within the same board area, and can be reconfigured based on the biasing polarity of embedded p-i-n diodes to provide two discrete phase states. The p-i-n diodes are located on the shunt branches of the metamaterial line in order to reduce losses in the direct signal path. Design limitations in terms of return loss and insertion loss are discussed in relation to the two phase states. A proof-of-concept module with a size of $17.8 \times 21.6~ \text {mm}^{2}$ is designed at 1 GHz, with measured insertion phases of −14.5° and +58.5° in the two phase states leading to a differential phase shift of 73°, while exhibiting insertion losses of 1.43 and 0.89 dB, respectively. The combined bandwidth for which the reflection coefficient in both states remains simultaneously below −10 dB is 0.46 GHz (46%), from 0.83 to 1.29 GHz.

Reconfigurable dual-band metamaterial antenna based on liquid crystals

Abstract: In this paper, a novel reconfigurable dual-band metamaterial antenna with a continuous beam that is electrically steered in backward to forward directions is first proposed by employing a liquid crystal (LC)-loaded tunable extended composite right-/left-handed (E-CRLH) transmission line (TL). The frequency-dependent property of the E-CRLH TL is analyzed and a compact unit cell based on the nematic LC is proposed to realize the tunable dual band characteristics. The phase constant of the proposed unit cell can be dynamically continuously tuned from negative to positive values in two operating bands by changing the bias voltage of the loaded LC material. A resulting dual band fixed-frequency beam steering property has been predicted by numerical simulations and experimentally verified. The measured results show that the fabricated reconfigurable antenna features an electrically controlled continuous beam steering from backward −16° to forward +13° at 7.2 GHz and backward −9° to forward +17° at 9.4 GHz, respectively. This electrically controlled beam steering range turns out to be competitive with the previously reported single band reconfigurable antennas. Besides, the measured and simulated results of the proposed reconfigurable dual-band metamaterial antenna are in good agreement.

A Triangular Complementary Split Ring Resonator Based Compact Metamaterial Antenna for Multiband Operation

Abstract: In this paper, a triangular complementary split ring resonator (TCSRR) based compact metamaterial antenna for multiband operation is presented. TCSRR is used to achieve a compact antenna structure. The proposed antenna consists of a trapezoidal radiating patch with partial ground plane and loaded TCSRR. The trapezoidal radiating patch is responsible for lower and higher frequencies, wherein the two inner resonance frequencies are obtained by loading TCSRR structure. The negative permittivity characteristics of the TCSRR structure are demonstrated through waveguide setup method. The proposed antenna with compact size of 25 × 25 × 1.6 mm3 is developed and tested. The measured and simulated results are good in agreement with each other and it covers 2.4/5.2 GHz (WLAN), 2.5 GHz (WiMAX), 7.4 GHz (X-band downlink) and 8.2 GHz (ITU band) simultaneously. The proposed antenna design has good radiation pattern for both E-plane and H-plane in all the desired frequencies.

Nanoparticle using parallel split rings and implementation of chain for creating Fano resonance with polarization independence for energy harvesting in mid-infrared

Abstract: In optical devices, the polarization of the incident wave affects the Nano particle characteristics. Therefore, designing a polarization-independent device is significant in the process of designing optical structures. On the other hand, the concept of Fano resonance and dark mode has been utilized for achieving more energy enhancement. In this paper, we have developed a symmetrical Nano antenna by employing Fano resonance, which is independent of the incident wave polarization. The proposed Nano antenna is modified in mid infrared regime for biosensing and energy harvesting applications. The designed metamaterial antenna is made by Nano split ring resonators with etched capacitive gaps, which are utilized for concentrating energy. The introduced Nano antenna has a bright and dark mode with a weak enhancement of electric field. The effect of the incident wave polarization is investigated at wave incident angles between 0° and 45° to illustrate the independency of the polarization due to the symmetrical shape of the Nano antenna. In order to trigger the dark mode and enhance the electric field, a Nano chain is incorporated in the final structure. This arrangement has led to increasing of electric field drastically. Furthermore, the figure of merit has been calculated as an advantageous factor in sensing the surrounding materials with various refractive indices. Our findings illustrated that the chain arrangement has caused a peak in the linear form of the extinction cross section of the Nano antenna. This in turn has resulted in the appearance of Fano resonance with no impact on the resonance frequency that has been originally adjusted by capacitive gaps and inductive strips.

Metamaterial-inspired wideband biocompatible antenna for implantable applications

Abstract: A compact wideband coplanar waveguide (CPW)-fed antenna is designed for body implantable applications. The proposed antenna has an electrical dimension of only 0.42 λ × 0.42 λ × 0.0072 λ at 2.3 GHz resonating frequency. Fractional bandwidth of 93.5% (1.35-3.5 GHz) is achieved with the low-profile antenna. To understand the extent of miniaturisation and bandwidth enhancement of the antenna, the characteristic modal analysis is performed. The wideband feature is achieved with the application of asymmetric complementary split-ring resonator structure through multiple mode excitations. Additional miniaturisation and impedance matching are obtained with a pair of asymmetrical arc-shaped annular ring slots within the main radiator. The substrate and radiator have been realised using silicon and gold due to their inherent property of excellent bio-compatibility with the human body. Single layer, as well as multi-layers phantom model, was used to assess the performance of the antenna. Owing to the inherent wideband feature of the designed antenna, it is able to cover the desired band efficiently even after detuning in different phantom models. The designed antenna is tested in vitro with the development of proper muscle mimicking liquid and the measured results are found to be in good agreement with the simulated ones.

Side lobe level reduction and gain enhancement of a pyramidal horn antenna in the presence of metasurfaces

Abstract: In this study, the design method and experimental presentation of low-refractive-index metasurfaces have been reported. These metasurfaces are employed in the interior E-plane walls of a pyramidal horn antenna. The target is a linearly polarised horn antenna with low side lobe levels (SLLs) and symmetric radiation patterns in the K u band (13-18 GHz) for satellite communications. Particle swarm optimisation algorithm has been applied to the design procedure to achieve low-loss dispersion-engineered metasurfaces with desirable surface impedance characteristics. The metasurfaces were fabricated using precise low-cost printed-circuit board technique. There was perfect agreement between the measurement and simulation results. The fabricated horn showed low SLLs and an increase in the gain across the entire bandwidth. The SLLs are reduced by 14-29 dB in the E-planes and the gain is improved by 1.2-2.3 dB compared with a corresponding conventional horn. The far field radiation patterns of the metahorn verify the metasurface design approach. Furthermore, this method assures a lighter horn with an easier manufacturing technique in comparison with the other conventional horns, such as corrugated horns.

Frequency tunable graphene metamaterial reflectarray for terahertz applications

Abstract: A graphene-based metamaterial (GMM) reflectarray antenna with frequency tunable radiation characteristics has been investigated in this study. The unit-cell element consists of graphene split-ring-resonator (SRR) with two gaps printed on a grounded SiO2 substrate. The electrical properties of the metamaterial unit-cell have been determined at different graphene chemical potentials and different SRR gaps using the waveguide simulator. The metamaterial unit-cell element introduces negative ɛ r and μ r over a wide frequency band starting from 390 to 550 GHz. A reflectarray unit-cell element based on the GMM is designed at different frequencies. The phase compensation of the reflected waves is achieved by changing the SRR gap width. Reflection coefficient phase variations for 0°–301° with a variable slope are obtained for different graphene conductivities. Three different 13 × 13 GMM reflectarrays are designed and analysed at different graphene chemical potentials. A maximum gain of 22.6, 19, and 21.5 dB with side lobe level (SLL) is 11.31/9.15, 10.98/5.31, and 7.31/8.45 dB in an E/H-plane for the reflectarray arrangements (I), (II) and (III), respectively. An averaging phase curve is calculated to construct a single structure GMM reflectarray with frequency tunable radiation characteristics. A maximum gain of 21.8 ± 1 dB with improved SLL of 13 dB was achieved.

Miniaturised triple-band antenna loaded with complementary concentric closed ring resonators with asymmetric coplanar waveguide-fed based on epsilon negative transmission line

Abstract: This study presents an open-ended triple-band miniaturised metamaterial (MTM) inspired antenna based on the epsilon negative-transmission line (ENG-TL) The zeroth-order resonance (ZOR) and first-order resonance (FOR) characteristics are implemented using the ENG-TL theory The proposed MTM antenna consists of rectangular and square-shaped complementary concentric closed ring resonator (CCCRR) in the left and right half of the asymmetric coplanar waveguide (CPW) ground plane, respectively The CCCRR generates an extra coupling capacitance and inductance, which help for improving the gain at ZOR mode and better impedance matching at higher-order mode The resonance characteristic of the antenna is controlled by the shunt elements due to its open-ended boundary condition The proposed triple-band MTM antenna offers measured -10 dB impedance bandwidths of 854% (112-122 GHz), 1025% (222-246 GHz) and 3575% (294-422 GHz) All these three bands show good impedance matching with appropriate gain and high radiation efficiency and also having an omnidirectional pattern in the xz- plane and dipolar type pattern in the yz -plane The designed antenna shows an overall dimension of 011 λ 0 × 011 λ 0 × 0006 λ 0 at ZOR frequency (116 GHz)

The Metamaterial Antenna: A Novel Miniaturized Dual-Band Coplanar Waveguide-Fed Antenna with Backed Ground Plane

Abstract: A miniaturized dual-band coplanar waveguide (CPW)-fed metamaterial (MTM) antenna is presented and developed in this article. The antenna is an asymmetric structure composed of two identical elements and one backed ground plane. Each element consists of an interdigital capacitor (IDC) connected with a radial stub by means of a thin strip. These stubs act as virtual ground planes because they offer high capacitance at higher frequencies. The proposed antenna shows a compact nature with an overall electrical size of 0.145 l0 t 0.20 l0 t 0.018 l0 and a radiating element size of 0.043 l0 t 0.073 l0 t 0.018 l0 at f 0

Embroidered Metamaterial Antenna for Optimized Performance on Wearable Applications

Abstract: © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim In this work, an embroidered metamaterial monopole antenna based on a split ring resonator electromagnetic bandgap shielding structure is designed, simulated, and tested. This work investigates the impact of different types of embroidering metamaterial patterns on the antenna performance, shielding effect in terms of human safety through specific absorption rate analysis and degree of material wearability, in comparison with the standard antenna topologies. The proposed antenna design presents a full compact embroidered metamaterial device manufactured in felt textile substrate and requires a 85 × 70 mm2area, operating at 2.45 GHz. On-voxel analysis reveals that specific absorption standards are satisfied for both public and occupational sector with a significant safety margin whereas the antenna performance in terms of gain and directivity are significantly optimized with regard to standard wearable materials.