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Fundamental properties of carbon nanotube antenna are firstly investigated to predict the antenna bundle response. The carbon nanotube effects are mathematically introduced via a quantum mechanical conductivity. This paper presents a new formulation based on integral equations system to study the coupled carbon nanotube antennas. The proposed integ...
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In this paper, a systematic synthesis approach is proposed for achieving negative group delay responses using lossy coupling matrix. It is mathematically proved that, for a passive and reciprocal network, loss is the necessary condition to realize a negative group delay. Also, the optimum strategy is to place zeros and poles of the transfer functio...
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... Nevertheless, the two main difficulties to tackle for array antenna devices are: (1) the size which must be moderated to satisfy the consumer telecommunication market; (2) coupling problems that affect performance of the spacing between elements, this coupling phenomenon depends principally on the separation distance between the antenna elements and on the number of array elements [13,14]. So that to solve this coupling problem, we must ensure a distance between the antenna array elements upper than ∕2 [15,16]. In the present work, in order to install a large number of antenna elements in a physically reduced space, and to benefit from the coupling effect on frequency reconfigurability [17], we will consider a coupling distance less than ∕2 . ...
... However, the current density decreases sharply beyond this limit, and from δx ≅ 0.5 this density stabilizes at almost zero values, which means that the second antenna becomes decoupled. It can then be concluded that the critical distance cited above δx c corresponds to 2 according to the literature [15,16]. ...
Technology is advancing daily, and it has impacted almost every aspect of our lives. We show that growth in the number of miniaturized communications systems that are covering different wireless services can achieve a wide frequency range. The present work aims to propose a new rigorous formulation to model a reconfigurable array system used for different wireless applications. The studied structure consists of a reconfigurable antenna array composed of parallel microstrip antennas excited by localized voltage sources and commanded by located PIN diodes. Diodes are used to adjust the length of the radiating element in order to shift the resonant frequency. The proposed formulation consists to combine the moment method and generalized equivalent circuit’s method (MoM-GEC) to model the antenna array. The PIN diode is considered in the mathematical formulation by an impedance surface model. The input impedance, the reflection parameter (S11\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${S}_{11}$$\end{document}) and the current distribution density obtained with this method are presented and discussed. The results were in close agreement with those obtained by software simulation. The obtained results offer the possibility to generate various modes governed by a decision tree. Thus, these modes are related to different resonant frequencies suitable for RFID, WiMax and WLAN applications with a large bandwidth reaching 526 MHz.
... The field optics is the basic of a principle of optical antenna, the first use of colloidal gold nanoparticles for optical radiation on a classical surface was appear in 1928 by Synge. [29] In 1985 Wessel utilized gold nanoantenna, Fischer et al. in 1995 was confirmed SPs by a gold-coated [30]. In 1997, bow-tie kind nanoantennas have been proposed as optical probes for the near-field [31]. ...
p>In this study, we focus on plasmonic nanoantenna structures for the U shaped. We will do our simulations with FDTD method (finite difference time domain) by considering commercial software Lumerical. We use U-shaped and play with the geometrical parameters such as length (L), width (W), high (H), to enhance the transmission of light. In addition to this, we will consider the different methods and substrates. U-shaped designed structure by using gold and MgF2 materials and studied how to enhance nanoantenna coefficients to get the highest electric field improvement factor and support multi-spectral resonances, that can be tuned from visible to near-IR wavelengths. For the optimum coefficients, the proposed U-shaped nanoantenna reached the optimal transmission and multi-resonant for different geometrical size. In results shows that in this model are wideband range of wavelengths and optimal transmission and all physical boundary conditions are chosen as perfectly matched layer (PML) to avoid undesired reflections, when we change the size of U-shaped with different materials is used and gets more proposes in the biosensors, biomedical and laser optical communication and for nanoantennas can also be deposited on layered substrates to enable solar cells and energy harvesting applications .And we can see that there are two resonances at (𝝺<sub>1 </sub>and 𝝺<sub>2</sub>) wavelength range (500-950) nm, the first one has a transmission 0.73 at wavelength 700nm; and the other one has a transmission 0.88 at wavelength 845nm from this designed. We will investigate the structure of nanoantenna to be used as biosensors.
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... The integration of separated clusters happen when the concentration of nanotubes approaches a certain critical value. As a result in the system spreading (infinite) cluster is formed, which leads to appearance of the electric contacts between external electrodes in such a compound [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. Experimental studies [1] have shown that the conductivity in nanotube polymeric and ceramic matrix materials follows a percolation-like behavior. ...
... The quality of the spectroscopic signal of molecules absorption that is called surface enhanced Raman scattering (SERS) [9]. During the last decade, different models of plasmonic antennas with different shapes and arrangements are presented in nano scale for bio-sensing and spectroscopy application such as monopole (nano rods) [10], dipole [11], bowtie [12], triangular [13], disk [14], loop [15] for basic model. In new research complicated structures such as a U shape [16], SRR (split ring resonator) [17], slot [18], Yagi [19] and other types are noticed for DNA detection [20] and infrared sensor [21]. ...
... This formulation allowed a rigorously investigation of the antennas interaction for any coupling distance. [14] The majority of mentioned studies were developed in the frequency domain. ...
... This impedance surface can be investigated using the CNT dynamic conductivity. For a small radius of CNT, the surface conductivity per unit length is given by [14]: ...
... is the kinetic inductance. [11][12][13][14] In this formulation, the scattered fields are expressed in terms of the vector Hertz which is defined by: ...
Transient electromagnetic analysis of carbon nanotubes (CNT) dipoles is presented. The thin wire approximation and the scattering theory are employed to formulate the problem. Therefore, an accurate system of coupled time domain electric field integral equations (TD-EFIE) is developed in order to predict the responses of the CNT dipoles excited by transient electromagnetic waves. To obtain stable and accurate solutions based on proposed system, the marching-on in degree method is applied with piecewise functions as space basis and weighted Laguerre Polynomials as temporal basis. Numerical results involving transient currents on each CNT dipole are presented. The electromagnetic coupling analysis between the CNT dipoles is conducted depending on the separate distances and the number of the CNT dipoles. Hence, the physical coupling effects are proved.
The integration of extra wireless services in the limited size of mobile devices is a very challenging task. In this context, the antenna array presents the best choice to meet these requirements. This research demonstrates a reconfigurable antenna array system proposed for future 5G applications. The characteristics of the proposed structure are examined while using electromagnetic modeling. The mathematical formulation reposes on combining the moment method and generalized equivalent circuit’s methods (MoM-GEC), and the deduced electromagnetic equations allow the computation of the input impedance Zin, the reflection parameter S11 and the current and electric field distributions. Software simulations prove good agreement with MoM-GEC results. The obtained results offer the possibility to generate various modes governed by a decision tree. Thus, these modes are related to different resonant frequencies suitable for 5G mobile communications with a large bandwidth reaching 560 MHz.
Due to the recent groundbreaking developments of nanotechnologies, it became possible to create intrinsically quantum systems able to serve as high‐directional antennas in terahertz, infrared, and optical ranges. In fact, the quantum antennas, as devices shaping light on the level of single quanta, have already become key elements in nanooptics and nanoelectronics. The quantum antennas are actively researched for possible implementations in quantum communications, quantum imaging and sensing, and energy harvesting. However, the design and optimization of these emitting/receiving devices are still rather undeveloped in comparison with the well‐known methods for conventional radio‐frequency antennas. This review provides a discussion of the recent achievements in the concept of the quantum antenna as an open quantum system emitting via interaction with a photonic reservoir. The review is focused on bridging the gap between quantum antennas and their macroscopic classical analogues. Furthermore, the way of quantum‐antenna implementation is discussed for different configurations, based on such materials as plasmonic metals, carbon nanotubes, and semiconductor quantum dots.
A theorical and modulation study of a dipole antenna located in rectangular waveguide is presented. The aim is to determine the nature and dimensions which allow us to attain the simulations in free space. We compare the behavior of a dipole antenna modeled by MOM-GEC with those obtained in free space. A method of moment (MoM) approach combined to the generalized equivalent circuit (GEC) modeling is applied to compute the input impedance of a dipole antenna resonating at 9GHz. A parametric study is conducted to investigate the wall effects of the waveguide on the antenna performances. Also we study the convergence of the input impedance as a function of test function number. The current and the electric field distribution are simulated. The current values with integral method (MOM) are compared with the computed values obtained from numerical methods such as the combined MOM-GEC The simulated values agree with values obtained from numerical methods.
The resonance characteristics of dipole antennas based on armchair carbon nanotube are numerically investigated. The analysis takes into account the interaction of electrons with acoustic phonons which leads to the dependence of the electron relaxation time on the radius of the nanotube. The input impedance of the nanoantena as a function of the frequency of an incident electromagnetic field in the GHz range is obtained by the numerical solution of the Hallén’s integral equation. The dynamic quantum mechanical conductivity of armchair carbon nanotubes is used including the explicit dependence of the relaxation frequency on the radius. In this way, it is adequately described the resonant activity of the nanoantenna depending on the radius and length of the carbon nanotube. Current distributions are presented.
A theoretical and modulation study of a dipole antenna located in a rectangular waveguide is presented. The aim is to determine the nature and dimensions which allow us to attain the simulations in free space. We compare the behavior of a dipole antenna modeled by MOM-GEC with those obtained in free space. A method of moment
(MoM) approach combined to the generalized equivalent circuit (GEC) modeling is applied to compute the input impedance of a dipole antenna resonating at 1.8GHz. A parametric study is conducted to investigate the wall effects on the antenna performances. Also, we study the convergence of the input impedance as a function of test function number. The current values with integral method (MOM) are compared with the computed values obtained from numerical methods such as the combined MOM-GEC. The simulated values agree with values obtained from numerical methods.
