Metamaterial-inspired Antenna Research Articles

WiFi Energy-Harvesting Antenna Inspired by the Resonant Magnetic Dipole Metamaterial.

WiFi energy harvesting is a promising solution for powering microsensors and microsystems through collecting electromagnetic (EM) energies that exist everywhere in modern daily lives. In order to harvest EM energy, we proposed a metamaterial-inspired antenna (MIA) based on the resonant magnetic dipole operating in the WiFi bands. The MIA consists of two metallic split-ring resonators (SRRs), separated by an FR4 dielectric layer, in the broadside coupled configuration. The incident EM waves excite surface currents in the coupled SRRs, and the energy is oscillating between them due to near-field coupling. By varying the vertical distance of the two SRRs, we may achieve impedance matching without complicated matching networks. Collected EM energy can be converted to DC voltages via a rectifier circuit at the output of the coupling coil. Measured results demonstrate that the designed MIA may resonate at 2.4 GHz with a deep-subwavelength form factor (14 mm×14 mm×1.6 mm). The WiFi energy-harvesting capability of the proposed MIA with an embedded one-stage Dickson voltage multiplier has also been evaluated. A rectified DC voltage is approximately 500 mV when the MIA is placed at a distance of 2 cm from the WiFi transmit antenna with a 9 dBm transmitting power. The proposed compact MIA in this paper is of great importance for powering future distributed microsystems.

Metamaterial-inspired quintuple band printed patch antenna for dense communication networks

A compact 15 mm × 15 mm multi-band metamaterial-inspiredprinted antenna, composed of a simple microstrip antenna and a metamaterial superstate, is developed to accommodate nowadays advanced wireless communication devices and networks, where multi-functional tasks are simultaneously performed in different frequency ranges efficiently. A quintuple homocentric circular split ring resonator is explicitly designed as a band enhancer metamaterial superstate. The metamaterial geometry and orientation associated with the antenna location and radiating are optimized for the greatest consequence, where the resonances electrically and magnetically couple with the antenna radiation, generating quintuple bands in the X band: 8–12 GHz. The main lobe directions indicate an excellent directional propagation. This metamaterial-inspired antenna was designed and fabricated using a low cost commercial FR4 substrate offering a good cost margin for potential mass production. Four of five bands have a gain greater than 6dBi, which can be improved by using low-loss substrate. The measured and simulated results are in good agreement.

Effect of Substrate Material on the Electromagnetic Properties of the Photolithography Printed Antenna

In this study, a rectangular microstrip feed antenna on a fire-retarded substrate is presented. The antenna is designed using Computer Simulation Tool (CST) software. Different materials are used for the substrate, and the electromagnetic properties of the proposed structure are analyzed for each material. The EM property variation for each material is comparatively presented. The proposed antenna has CSRR (Complementary Split-Ring Resonator) which is engraved on the radiating element, and the shape of the CSRR is the hexagon. The proposed metamaterial-inspired antenna exhibits multiband operation at 2.1 GHz, 2.6 GHz, 4.6 GHz, 5.5 GHz, 6.1 GHz, and 7.1 GHz. With the help of material analysis, the fire-retarded substrate is chosen for the design, its excellent EM properties, and cheap cost. The photolithography-based printed antenna is validated with the help of S11, VSWR, gain, directivity, surface current distribution, and radiation pattern. Simple, compact structure, good gain, stable radiation pattern, and excellent EM properties of the fire-retarded substrates make it suitable for the GHz application.

Performance Analysis of Metamaterial-Inspired Structure Loaded Antennas for Narrow Range Wireless Communication

Nowadays, the demand for low-cost, compact, and interference rejected antennas with ultrawideband capability has been increased. Metamaterial-inspired loaded structures have capability of providing exceptional solutions for narrow range wireless communication and low consuming power while transmitting and receiving the signal. It is a difficult task to construct ideal metamaterial-inspired antennas with a variety of features such as extremely large bandwidth, notching out undesirable bands, and frequency. Metamaterial-inspired structures such as SRR and CSRR, and triangle-shaped TCSRR are most commonly used structures to achieve optimized characteristics in ultrawideband antennas. In this paper, an extensive literature survey is accomplished to get conception about metamaterial-inspired patch antennas. This review paper elucidates variants of metamaterial-inspired structures/resonators utilized in order to acquire sundry applications such as WiMAX, WLAN, satellite communication, and radar. Various researchers have used different methodology to design, stimulate, and analyze the metamaterial-inspired structure loaded antennas. Also, the results of different metamaterial-inspired antennas such as bandwidth, gain, return loss, and resonant frequency have been also represented in this paper. This manuscript also gives brief introduction about the metamaterial, its types, and then its application in microstrip patch antenna over the last decade. This manuscript throws light over the various studies conducted in the field of metamaterial-inspired antenna in the past. It has been seen that with the inclusion of metamaterial in conventional antenna, various characteristics such as impedance bandwidth, reflection coefficient, gain, and directivity have been improved. Also, frequency rejection of narrow bands which exits in ultrawideband frequency range can be done by embedding metamaterial-inspired structures such as SRR and CSRR.

Low-Profile Multifunctional Pattern Reconfigurable Antenna Using Periodic Capacitor-Loaded Surface for 5G and Beyond

This article describes a novel low-profile multifunctional pattern reconfigurable antenna using the periodic capacitor-loaded surface for 5G and beyond applications. A miniaturized periodic surface structure is first proposed using the shunt-loaded capacitor, which is studied by equivalent circuit models. A quarter-wavelength T-shaped director slot is etched on the edge of the ground, which leads to a tilted radiation pattern. By switching the ON-/OFF-states of p-i-n diodes embedded in the director slots, the main direction of the beam of the proposed antenna can be tuned among +35°, 0°, and −35°. To verify the design concept, a multifunctional pattern reconfigurable metamaterial-inspired antenna with a low profile of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.05~\lambda _{0}$ </tex-math></inline-formula> is fabricated and measured. The measured overlapping bandwidth for the eight radiation modes is 3.10–3.85 GHz (21.6%), well covering the 5G-N78 band. The port isolation between the two polarizations in eight modes is higher than 20 dB. The proposed reconfigurable metamaterial-inspired antenna shows the merits of low profile, wide bandwidth, high port isolation, low cost, multifunctional pattern reconfigurable capability, and easy fabrication for 5G and other sub-6 GHz applications.

Miniaturized Multiband Metamaterial Antennas With Dual-Band Isolation Enhancement

We present electrically small, multi-band, metamaterial-inspired antennas with adequate radiation characteristics and isolation enhancement. The antenna element consists of a complementary split-ring resonator (CSRR) embedded in a small monopole that has a size of &#x03BB;/8 &#x00D7; &#x03BB;/10 at the lowest frequency band, while rectangular patches are placed underneath it to further improve the performance. The antenna operates at the 2.4-2.5/2.9-4.8/5.1-6.5 GHz frequency bands. Moreover, we propose a systematic, metamaterial-based approach in order to improve the isolation between two of these small, closely spaced antenna elements at the lowest and highest frequency bands. The proposed techniques reduce the coupling by up to 29 dB without increasing the size of the structure. In particular, the isolation enhancement at the highest frequency band of interest is remarkably wideband. The cable effect, which is a common concern during the measurements of small antennas, is examined as well. The proposed antennas are not only small but also densely packed and can be easily integrated with modern, compact communication devices with advanced functionality. Simulations along with experimental results validate the effectiveness of our design.

A Metamaterial Inspired Compact Miniaturized Triple-band Near Field Resonant Parasitic Antenna for WLAN/WiMAX Applications

This paper presents a metamaterial-inspired triple-band antenna specified for WLAN and WiMAX applications with a compact size of 24mm × 18mm × 1mm (at 2.4 GHz). It consists of a dual-band left-handed metamaterial (LHM) unit surrounded by a G-style monopole antenna. The LHM is first designed and analyzed with equivalent circuits and simulations. A loop antenna based on the LHM unit is designed and simulated to investigate the radiating performance of the LHM unit structure. We also ran simulations for the G-style monopole. Later, the LHM unit is employed as a near-field resonant parasitic (NFRP) element that surrounded by the G-style monopole. A prototype of this antenna is fabricated. Simulations and measurements were carried out and the results match well, identifying good omni-directional radiating performance. Radiation comparisons with the loop antenna and the G-style monopole indicate that due to NFRP, the G-style monopole’s pass bands are shifted to lower frequencies to satisfy 2.45 GHz and 5.5 GHz bands requirements, meanwhile the LHM unit structure operates a third pass band of 3.5 GHz. The compact size and good radiation properties of the antenna render it suitable for WLAN/WiMAX applications.

Metamaterial-Inspired Antennas: A Review of the State of the Art and Future Design Challenges

Metamaterials are artificial structures with the ability of exhibiting unusual and exotic electromagnetic properties such as the realisation of negative permittivity and permeability. Due to their unique characteristics, metamaterials have drawn broad interest and are considered to be a promising solution for improving the performance and overcoming the limitations of microwave components and especially antennas. This paper presents a detailed review of the most recent advancements associated with the design of metamaterial-based antennas. A brief introduction to the theory of metamaterials is provided in order to gain an insight into their working principle. Furthermore, the current state-of-the-art regarding antenna miniaturisation, gain and isolation enhancement with metamaterials is investigated. Emphasis is primarily placed on practical metamaterial antenna applications that outperform conventional methods and are anticipated to play an active role in future wireless communications. The paper also presents and discusses various design challenges that demand further research and development efforts.

A Method for Optimising Superdirectivity of Coupled Meta-Atoms via Planar Directivity Evaluation

We propose a simple and rapid way of optimising directivity in metamaterial-inspired endfire antenna arrays with strong inter-element coupling. We introduce, in addition to the traditional 3D directivity, also its planar equivalents defined as the ratio of the power density in the desired endfire direction to the average power density calculated either in the horizontal (azimuthal) or vertical (elevation) plane. Using dimers of magnetically coupled split-ring resonators with only one element driven by an external source, we derive conditions that must be satisfied in order to realise superdirective current distributions. The superdirective conditions link the quality factor of the resonators and their coupling constant to the array size and the operating frequency. We demonstrate that a rapid measurement in the azimuthal plane can be used as a reliable indicator for whether the superdirective conditions for the 3D directivity are satisfied. Analytical calculations are verified by CST simulations in the MHz frequency range for meta-atoms of circular and square shape. Our method can be extended to arrays comprising larger number of meta-atoms of various shape and would enable rapid prototyping of 3D-printed meta-atoms with desired radiation properties.

Metamaterial-Inspired Antenna Array for Application in Microwave Breast Imaging Systems for Tumor Detection

This paper presents a study of a planar antenna-array inspired by the metamaterial concept where the resonant elements have sub-wavelength dimensions for application in microwave medical imaging systems for detecting tumors in biological tissues. The proposed antenna consists of square-shaped concentric-rings which are connected to a central patch through a common feedline. The array structure comprises several antennas that are arranged to surround the sample breast model. One antenna at a time in the array is used in transmission-mode while others are in receive-mode. The antenna array operates over 2–12 GHz amply covering the frequency range of existing microwave imaging systems. Measured results show that compared to a standard patch antenna array the proposed array with identical dimensions exhibits an average radiation gain and efficiency improvement of 4.8 dBi and 18%, respectively. The average reflection-coefficient of the array over its operating range is better than S11 ≤ −20 dB making it highly receptive to weak signals and minimizing the distortion encountered with the transmission of short duration pulse-trains. Moreover, the proposed antenna-array exhibits high-isolation on average of 30dB between radiators. This means that antennas in the array (i) can be closely spaced to accommodate more radiators to achieve higher-resolution imaging scans, and (ii) the imagining scans can be done over a wider frequency range to ascertain better contrast in electrical parameters between malignant tumor-tissue and the surrounding normal breast-tissue to facilitate the detection of breast-tumor. It is found that short wavelength gives better resolution. In this experimental study a standard biomedical breast model that mimics a real-human breast in terms of dielectric and optical properties was used to demonstrate the viability of the proposed antenna over a standard patch antenna in the detection and the localization of tumor. These results are encouraging for clinical trials and further refinement of the antenna-array.

Metamaterial‐inspired miniaturized antenna loaded with IDC and meander line inductor using partial ground plane

In this article, a novel omnidirectional compact dual band metamaterial-inspired antenna with CPW feed has been proposed for application of GSM 1800 (1.71-1.785 GHz/1.805-1.879 GHz), GSM 1900 (1.85-1.91 GHz/1.93-1.99 GHz), UMTS (1.92-2.17 GHz), WLAN/Wi Fi (4.9, 5, 5.9 GHz), HiperLAN1 (5.15-5.3 GHz), and HiperLAN2 (5.47-5.72 GHz) using a combination of meander line inductor and interdigital capacitor (IDC). The antenna consists of complimentary right/left handed (CRLH) transmission line on both sides of patch to excite zeroth order mode (n = 0). The rectangular slotted stubs act as a virtual ground for the structure using a short circuit condition at the end of the IDC. The zeroth order resonance (ZOR) frequency is mainly controlled by IDC and partially with the meander line inductor. The designed antenna operates from 1.72 to 2.22 GHz and 4.25 to 5.88 GHz with radiating size of 0.56λo × 0.35λo (32 × 20 mm2), where λo is the free-space wavelength at ZOR frequency of 5.27 GHz. The proposed antenna offers measured impedance bandwidth (|S11| <−10 dB) of 25.3 and 18.7% at 1.95 and 5.28 GHz and covers the targeted frequency bands. The proposed structure offers omnidirectional radiation patterns are congruous throughout the working band.

Thin-Layer Dielectric and Left-Handed Metamaterial Stacked Compact Triband Antenna for 2 GHz to 4 GHz Wireless Networks

As technology progresses, new approaches for the development of antenna systems must be developed. This study reveals a concept for a left-handed metamaterial-inspired compact triband antenna for use in wireless fidelity (WiFi), wireless local area networks (WLANs), and World Interoperability for Microwave Access (WiMAX) applications. The Microwave Studio computer technology simulation package was used to design and perform a numerical investigation on the metamaterial-inspired antenna on a thin layer of FR-4 dielectric material. The overall size of the antenna is 25 mm × 18 mm, and it is compatible with existing wireless devices. Results were measured in the frequency bands for wireless fidelity (2.41 GHz to 2.48 GHz), wireless local area networks (2.40 GHz to 2.49 GHz and 3.65 GHz to 3.69 GHz), and world interoperability for microwave access (3.30 GHz to 3.80 GHz). The measured average gain was 1.87 dBi, whereas the simulated gain was 1.93 dBi, associated with omnidirectional radiation patterns. The timing performance was analyzed, revealing fidelity factors for the face to face, side by side X, and side by side Y orientation of 0.76, 0.84, and 0.81, respectively. Finally, the operation bandwidth, antenna gain, omnidirectional radiation pattern, and fidelity factors of the timing performance reveal that the designed miniatured metamaterial antenna can be used in WiFi, WLAN, and WiMAX applications.

Improved Signal-to-Noise Ratio, Bandwidth-Enhanced Electrically Small Antenna Augmented With Internal Non-Foster Elements

Non-Foster technology facilitates the ability to surpass the Chu bandwidth limit associated with electrically small antennas (ESAs). Nonetheless, in addition to challenging stability issues, the enhanced performance can come at the cost of increased noise and resistance losses generated by the active circuit. Consequently, low total efficiency and degraded signal-to-noise ratio (SNR) values can arise. Stability and SNR have dominated most reports to date; little has been discussed with regard to the underlying innovative physics of non-Foster augmented radiators. In this communication, we propose a broad bandwidth non-Foster ESA, emphasizing those aspects. By embedding a non-Foster element into the near-field resonant parasitic element of a metamaterial-inspired antenna, its electrically small size is maintained. On the other hand, a 5-times enhancement of its −10 dB fractional bandwidth (15 times its −3 dB bandwidth) is measured, significantly surpassing its passive Chu limit. Under a good matching, the measurements demonstrate that this non-Foster ESA achieves a 1.05 dBi peak gain and realizes average 5.0 dB SNR and 17 dB gain improvements over its passive counterpart.

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

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 0.238 × 0.194 × 0.016 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 146.91% and 3183.05, 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 3.88 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.

Study of metamaterial surface wave antenna based on split ring resonator

In this paper, a new metamaterial-inspired high frequency surface wave antenna is designed. An artificial magnetic conductor surface is introduced into the near field region of a vertical meander monopole antenna to improve its electromagnetic performances, where a split ring resonator-cell is selected as an artificial magnetic conductor. The return loss, the radiation pattern, the electric field distribution and efficiency are evaluated through the finite element method (FEM simulations). The designed antenna has advantages of low cost, small size, and light weight.

SRR-LOADED METAMATERIAL-INSPIRED ELECTRICALLY-SMALL MONOPOLE ANTENNA

SRR-LOADED METAMATERIAL-INSPIRED ELECTRICALLY-SMALL MONOPOLE ANTENNA

The directivity of a compact antenna: an unforgettable figure of merit

When an electrically small antenna is conceived, designed, simulated, and tested, the main emphasis is usually placed immediately on its impedance bandwidth and radiation efficiency. All too often it is assumed that its directivity will only be that of a Hertzian dipole and, hence, its directivity becomes a minor consideration. This is particularly true if such a compact antenna radiates in the presence of a large ground plane. Attention is typically focused on the radiator and its size, while the ground plane is forgotten. This has become a too frequent occurrence when antennas, such as patch antennas that have been augmented with metamaterial structures, are explored. In this paper, it is demonstrated that while the ground plane has little impact on the resonance frequency and impedance bandwidth of patch antennas or metamaterial-inspired three-dimensional magnetic EZ antennas, it has a huge impact on their directivity performance. Moreover, it is demonstrated that with both a metamaterial-inspired two-element array and a related Huygens dipole antenna, one can achieve broadside-radiating electrically small systems that have high directivities. Several common and original designs are used to highlight these issues and to emphasize why a fundamental figure of merit such as directivity should never be overlooked.

Electrically Small, Broadside Radiating Huygens Source Antenna Augmented With Internal Non-Foster Elements to Increase Its Bandwidth

A broadside radiating, linearly polarized, electrically small Huygens source antenna system that has a large impedance bandwidth is reported. The bandwidth performance is facilitated by embedding non-Foster components into the near-field resonant parasitic elements of this metamaterial-inspired antenna. High-quality and stable radiation performance characteristics are achieved over the entire operational bandwidth. When the ideal non-Foster components are introduced, the simulated impedance bandwidth witnesses approximately a 17-fold enhancement over the passive case. Within this –10-dB bandwidth, its maximum realized gain, radiation efficiency, and front-to-back ratio (FTBR) are, respectively, 4.00 dB, 88%, and 26.95 dB. When the anticipated actual negative impedance convertor circuits are incorporated, the impedance bandwidth still sustains more than a 10-fold enhancement. The peak realized gain, radiation efficiency, and FTBR values are, respectively, 3.74 dB, 80%, and 28.01 dB, which are very comparable to the ideal values.

Compact and broadband antenna using double-negative transmission line metamaterial

In this manuscript, double-negative transmission line (TL) metamaterial-inspired antenna has been proposed with compactness and improved bandwidth. This antenna is made of double-negative meander lines, microstrip feed and partial ground. Double-negative TL metamaterials show negative permittivity and permeability simultaneously and play important role for antenna miniaturization and the impedance bandwidth improved. The antenna provides 600 MHz bandwidth (−10 dB) with 23.81% fractional bandwidth. The antenna radiating element size is 0.07λ × 0.07λ at 2.51 GHz frequency with 3.72 dBi maximum gain where the electrical dimension is 0.30λ × 0.30λ.

A compact CPW-fed wideband metamaterial-inspired antenna for GSM, WLAN/Wi-Fi, and WiMAX applications

A compact coplanar waveguide (CPW)-fed wideband metamaterial-inspired antenna is designed and developed in this paper. The proposed structure is an asymmetric structure in which three rectangular stubs are employed between signal patch and CPW ground plane. It is demonstrated that these stubs provides lumped parameters of conventional epsilon-negative transmission line (ENG-TL). As an advantage of these stubs proposed antenna operates on 1.67–2.76 GHz with −10 dB impedance bandwidth of 49.2%. The proposed antenna having small electrical size of 0.17λ0 × 0.35λ0 × 0.01λ0 at fo = 2.21 GHz. The simulated average gain and radiation efficiency of the proposed antenna is 1.61 dB and 96.33% respectively throughout the bandwidth. Properties such as smaller electrical size, simpler design, consistent radiation characteristics, and ease of fabrication are making this antenna suitable for GSM, WLAN/Wi-Fi, Bluetooth, and WiMAX applications.