Bandwidth enhanced microstrip patch antenna using metamaterials

Small printed antennas suffer from low efficiency. Low profile efficient antennas are crucial in the development of commercial compact 5G communication and Internet of things (IOT) systems. The communication, IOT and biomedical industries have been in rapid growth in recent years. It is important to develop efficient high gain compact antennas for 5G communication and IOT systems. Metamaterials and fractal structures may be used to improve the efficiency of compact printed antennas. In this chapter metamaterial antennas will be presented. Metamaterial technology is used to design small wideband wearable antennas with high efficiency. Design considerations and the computed and measured results of printed metamaterial antennas with high efficiency are presented in this chapter. The proposed antenna may be used in communication and medical systems. The antennas’ S11 results for different positions on the human body are presented in this chapter. The gain and directivity of the patch antenna with split ring resonator (SRR) is higher by 2.5 dB than the patch antenna without SRR. The resonant frequency of the antenna with SRR on human body is shifted by 3%.

AbsIracf - Two-dimensional backward-wave meta-material based on evanescent parallel-plate waveguide filled with uniaxial magnetic tilling with negative transversal permeability is investigated experimentally. The prototype comprised a two-dimensional array of the double ring resonators sandwiched between two metallic plates and it was operating in 8 GHz frequency hand. The backward-wave propagation was verified by the measurement of negative lateral displacement of the beam impinging the meta-material slab at several different angles of incidence I. INTRODUCTION A material which supports propagation of the backward waves ('left-handed material' or 'backward-wave material') was predicted theoretically in sixties by Veselago (I) and realized experimentally for the first time by Smith at al. (2) in 2000. The rather simple type of one-dimensional backward-wave meta-material based on an evanescent waveguide loaded with the split ring resonators was presented in (3). Such a waveguide was interpreted as one-dimensional material with both negative permeability and negative permittivity (3). In (4,5), it was shown that the propagation below the cut-off frequency actually occurs due to uniaxial anisotropy of negative permeability of the meta-material based on the split ring resonators. The extension of this basic principle to two dimensions, similarly to the idea introduced in (6), is investigated experimentally in this paper. 11. THEORETICAL RESULTS Let us analyze the structure that comprises a slab of anisotropic uniaxial magnetic materials sandwiched within the two infinite parallel PEC plates (Fig.1). If the optical axis of the uniaxial material is perpendicular to the plates (the transversal direction), it is obvious that this structure is essentially isotropic in two dimensions. Thus, the electromagnetic energy will propagate in any direction parallel to the plates (the longitudinal direction) in the exactly the same way (the propagation for two perpendicular longitudinal directions is sketched in Fig. 5). For any particular longitudinal direction, one may think of this structure as a parallel plate waveguide. In the lossles case, the longitudinal propagation factor of such a waveguide is given by the simple set of equations (4,51: Here, k, stands for longitudinal propagation factor, ko is a free space propagation factor, g is relative permittivity and p,, and pi, stand for relative permeability in transversal and longitudinal directions of the waveguide, respectively. The symbol f stands for a frequency of the signal, whereas Lo and L are the cut-off frequency of an empty parallel-plate waveguide and the parallel-plate waveguide filled with a material, respectively. If the transversal permeability is negative &<0 ) and the longitudinal permeability is positive (ppO), one must choose the negative sign in front of the square root in (I) for frequencies below the cut-off. This yields the peculiar phenomenon of the backward-wave propagation. Hence, the structure actually behaves as two-dimensional backward-wave meta-material provided that the vector of the magnetic field is perpendicular to the walls (TE 01 mode). If one stacks more parallel plate waveguides in the transversal direction, it is possible to manufacture the two-dimensional 'backward-wave' material of arbitrary thickness, as proposed in (6). The backward-wave propagation below the cut-off frequency can he simply explained by two-dimensional transmission line equivalent circuit of the structure (Fig.2). The distributed series impedance (212) is associated with the transversal permeability. The distributed shunt admittance associated with the relative permittivity (Y,) and the admittance associated with the longitudinal permeability (Y,) form the tank circuit. In the case of the uniaxial material with positive permeability, the series admittance will he also positive. Below the cut-off, the tank circuit behaves as an inductance and, for any direction parallel to the plates, the whole structure behaves as a transmission line with the distributed series inductance and the distributed parallel inductance (L-L transmission line), This kind of transmission line does not support the propagating waves. If the transversal

&lt;p&gt;A high gain patch antenna inspired by 4 layers of negative refractive index (NRI) metamaterial superstrate is proposed to operate at downlink radio frequency (RF) band (935 MHz to 960 MHz of GSM 900). The metamaterial unit cell consists of a nested split ring resonator (SRR) and strip line laminated on other side of FR4 substrate. The effective permittivity and permeability of the proposed unit cell are designed synchronously to approach zero, which leads the NRI superstrate to have impedance match with zero and negative refractive index.The NRI superstrate is studied using Fabry-Perot (F-P) resonant cavity. The gain is improved by 82.48% at the air gap of 55 mm in the desired frequency band.Therefore, the gain of the antenna is effectively enhanced based on the negative refractive index metamaterial. The measured radiation pattern and S parameter results also showed that it has good agreement with the simulation results.&lt;/p&gt;

Tunable surface waves supported by graphene-covered left-handed material structures

This paper presents the design and analysis of a broad-band patch antenna using split ring metamaterial. The SRR metamaterial structures are embedded in a unique and novel way in the patch antenna, so that subwavelength modes get introduced in the patch cavity and a broad bandwidth antenna with good performance characteristics is obtained. A rectangular microstrip patch antenna is taken as a reference antenna, which resonates at a frequency of 5.2 GHz and has an impedance bandwidth of 70 MHz. To improve the bandwidth of the patch antenna, firstly the split ring resonator (SRR) is designed according to the reference patch antenna. The optimized SRR metamaterial is placed in between the patch and ground plane of the proposed antenna. The – 10 dB impedance bandwidth of the metamaterial-embedded proposed antenna is 1.63–4.88 GHz and has an average gain of 4.5 dB. The Prototype of the proposed antenna and reference antenna is fabricated and experimental results are obtained. Experimental and simulated results are in good agreement. The presented antenna can be used for LTE, GSM, WiMAX, Bluetooth, and other wireless applications.

This paper presents a new type of thin absorber exhibiting double negative metamaterial (MTM) characteristics. A MTM unit cell was constructed by a multiple split ring resonator (MSRR) and a meander-line arrangement. A MSRR structure exhibits negative permeability and a meander-line structure exhibits negative permittivity. Each unit cell is printed on the two side of a FR-4 substrate (relative dielectric constant = 4.4, thickness = 0.8 mm). The proposed one-layer absorber based on double negative MTM was shown to reach thickness of the order of λ 0 /250 at the aimed frequency of 1.55 GHz. In order to maximize the absorption per unit volume, ten unit cells disposed in an array configuration were considered. Simulated results show a high maximum absorption of 95% at 1.52 GHz. In the design of the double negative MTM unit cell, the complex permittivity and permeability of the cell were retrieved from scattering parameters.

We experimentally investigated the microwave reflection of the negative permeability material composed of periodical arrays of the copper split-ring resonators (SRRs).The negative dielectric materials are composed of periodical arrays of copper wires and left-handed materials(LHMs) in a planar slab waveguide, and the microwave is incident to the surface in different directions.We also investigated the negative refraction through a prism fabricated from the LHMs.The experimental results show that for the negative permeability materials,there is a reflection peak at the resonance frequencies of the SRRs, and the reflectivity of the negative dielectric material is closed to 0dB.A single smaller reflection peak occurs in the reflected curve of the LHMs,the reflectivity of which increases with the incident direction,that is,the reflection increases.The reflection peak has a shift with respect to the transmission peak. It is demonstrated that negative refractive index of -0.796 occurs in the LHMs at the frequency o 800MHz.

Electromagnetic metamaterials (MTM) are effectively homogenous structures that are artificially created and not found in nature. Extensive investigation and theoretical analyses by researchers show that this material or structure exhibits simultaneous negative permittivity and permeability phenomenon. Due to the special double negative electromagnetic properties the material was named “left-handed material”. In 1967, V.G. Veselago a physicist from the Lebedjev Physical Institute in Moscow first proposed this metamaterials, and later on Pendry and Smith demonstrated the special electromagnetic properties can be realised practically using split ring resonators and metal strip structures. According to their investigation the split ring resonator's (SRR) inherent capacitance and inductance interact to create the negative permittivity. Also the thin metal wire (TW) strip parallel arrangement through a dielectric substrate induces negative permeability within the substrate. The TW-SRR MTM structure is resonant at a particular frequency defined by the dimensions of the structure. It's known that the quality-factor (Q) of the resonant structure is inversely proportional to its bandwidth, and transmission-loss is inversely proportional to the quality-factor. This means a high-Q will have a reduced bandwidth and be responsible for higher a transmission loss. After taking these resonant structures restrictions into consideration, in 2002, Caloz, Eleftheriades investigated the viability of the non resonant transmission-line approach to realise the metamaterial structure. They demonstrated the same electromagnetic properties could be realised using a series capacitor and shunt inductor circuit arrangement using microstrip technology. In this planar configuration, low loss and broad bandwidth can be achieved by proper design of the structure, as well as achieving a good match to the external ports.

Composite structures based on metal open rings and thin wires are well established, for obtaining efficient negative index materials (NIM), acting as metamaterials in the long wavelength regime. The main losses are due both to metal absorption and to the inner electric resistance of metals; to overcome this latter loss we propose a new metal-semiconductor structure dimensioned by direct synthesis method, which offers an almost perfect Drude-like effective magnetic permeability. The choice of particular semiconductor components allows to get a negative resistance for the current induced by the electromagnetic field, which cancels that of the metal but puts a limit to the spectral response of the metamaterial. We consider some parasite effects, such as bianisotropy and incorrect values of structural parameters, to see limitations and features of this new NIM technology.

This article is focused on understanding of the effect of a low-pressure argon plasma on split ring resonator (SRR) metamaterial resonance. After an experimental characterization of SRR arrays that denies reaching critical density at 2.45 GHz, we present an alternative SRR, called sparse SRR, tunable in resonance frequency, that admits higher plasma density in its structure. This innovative structure is characterized with plasma to search for left-handed material signature. Several plasma effects such as gradients and sheaths are quantified. It is shown that plasma shifts the SRR resonance to higher frequencies. The amplitude of the resonance shift can not be estimated without taking into account the sheath thickness. Moreover, the plasma gradient causes the appearance of several distinguishable dips of resonances. These different effects are studied with simulations, highlighting the difficulty to create a left-handed material based on plasma-metamaterial.

In the quest for ever smaller, lighter weight, and conformal components and devices for radar and communication applications, researchers in the RF community have increasingly turned to artificially engineered, composite structures (or “metamaterials”) in order to exploit the extraordinary electromagnetic response these materials offer. One particularly promising class of metamaterials that has recently received a great deal of attention are “left-handed” or negative index materials. Because these metamaterials exhibit the unique ability to bend and focus light in ways no other conventional materials can, they hold great potential for enabling a number of innovative lens and antenna structures for a broad range of commercial and DoD relevant applications. Exploring the possible implementation of negative index materials for such applications will require significant enhancements in the properties of existing Negative Index Materials (NIM) (bandwidth, loss, operational frequency, etc.), as well as improved understanding of the physics of their electromagnetic transport properties. For this reason the Defense Advanced Research Project Agency (DARPA) has initiated a program that seeks to further develop and demonstrate NIM for future DoD missions including, but not limited to, the following: 1) lightweight, compact lenses with improved optics; 2) sub wavelength/high resolution imaging across the electromagnetic spectrum; 3) novel approaches to beam steering for radar, RF, and/or optical communications; and 4) novel approaches for integrating optics with semiconductor electronics. A brief overview of the salient properties of NIM will be presented as well as a general discussion of a few of their potential applications.

This paper describes the design of a subwavelength microwave imaging system using a negative index metamaterial (NIM) lens for nondestructive evaluation (NDE) applications. The imaging system consists of a split ring resonator (SRR)-wire based NIM lens, operating at 6.3 GHz, used in conjunction with a homodyne detection system. Simulation studies of the unit cell design are presented followed by experimental verification of left-handed focusing by the NIM lens with a focal spot of size 0.65λ. A subwavelength hole of diameter 0.25λ in a glass fiber reinforced polymer (GFRP) sample is imaged at a stand-off distance of 1.67λ using the proposed system. High SNR and preservation of polarity and phase information associated with synchronous detection provides a NIM lens imaging system that can be used in the field for rapid inspection at large standoff distances.

Inspired by the dendritic geometry in nature, we designed the single dissymmetrical hexagonal split ring resonators (SRRs). The SRRs were fabricated on one side of the dielectric substrate using shadow mask/etching technique. By experiments and computer simulations, we have researched the microwave transmission behavior of the SRRs in the frequency band of 7—12 GHz. The results show that, for an individual hexagonal SRR, the resonance frequency is affected by the size of the SRR; for two SRRs, there are two resonance peaks in the transmittion curve when they are close to each other. For three SRRs or the radialized rings, the resonance frequency of the structure with high-level branches shifts towards lower values compared with that with no branches. The simulations are in agreement with the experimental results.

A high gain Double Negative (DNG) metamaterial superstrate based Circularly Polarized (CP) microstrip patch antenna for Ka band satellite communication is represented in this article. The rectangular patch antenna is developed with shorting pins along the two orthogonal diagonals. Pairs of shorted pins are placed to generate two different modes for obtaining CP. A simple coaxial probe-feeding is used to excite the patch antenna at Ka band. A 4x4 array of rectangular-shaped slotted ring patches which exhibits the characteristics of negative dielectric permittivity and permeability at Ka band has been used as superstrate. The implementation of this DNG metamaterial-based superstrate enhances the right hand CP gain from 10.2 dB to 12.2 dB, which makes the overall antenna height to be 0.58 times of the free space wavelength (λ0). The proposed design shows minimum axial ratio of 1.42 dB near the magnetic resonance of 28.5 GHz which makes the structure suitable for satellite applications.

Photonic magnetic metamaterial basics