Papers by Najib Fadlallah
In this paper, an electrical model is developed to represent the input admittance of an antenna a... more In this paper, an electrical model is developed to represent the input admittance of an antenna array with a finite number of elements. This model consists of an RLC bock component to represent the input admittance of each elementary antenna element and a capacity component to represent different degrees of antenna coupling effects. The equations based on cavity model are developed to represent physical meaning of each model. Numerical results show that good accuracy for the simulation results can be obtained by using this electrical model to the results obtained by using HFSS. As the array is large and sparse, a very small amount of computation can yield good accuracy. This model is shown not only to be numerically efficient compared to the full wave analysis using the moment method, but also to give physical insight into the antenna array mutual coupling mechanism. Furthermore, this model has no limitation on antenna array geometry and excitation.
This paper presents a novel technique to achieve a broad impedance bandwidth required to pursue t... more This paper presents a novel technique to achieve a broad impedance bandwidth required to pursue the development in the field of wireless communication by proposing a design of a reconfigurable broadband stacked patch antenna, based on liquid crystal and aperture coupled feeding with two square patch elements. The MDA-00-3506 liquid crystal (LC) is used as a dielectric. The antenna operates at millimeter wave from 24.4 GHz to 32.8 GHz with a bandwidth of 7.8 GHz. The maximum achievable antenna gain is 7 dB.
International Journal of Communication Networks and Information Security, 2009
In this paper, we propose two electrical models of carpet and gasket Sierpenski patch antenna. In... more In this paper, we propose two electrical models of carpet and gasket Sierpenski patch antenna. In our approach, we replace the antenna structure by its equivalent rectangular patch. Then, we build the electrical model in which we extract the resonant circuit RLC parameters. Return losses of the models are compared to physical patch for frequency band [1GHz, 3GHz]. Simulation results given by our approach, show that the antenna and its model have the same resonant frequency at 2.45GHz but with a little difference in Bandwidth.
Wireless Engineering and Technology
The advanced design of a 10 × 1 linear antenna array system with the capa-bility of frequency tun... more The advanced design of a 10 × 1 linear antenna array system with the capa-bility of frequency tunability using GT3-23001 liquid crystal (LC) is pro-posed. The design for this reconfigurable wideband antenna array for 5G ap-plications at Ka-band millimeter-wave (mmw) consists of a double layer of stacked patch antenna with aperture coupled feeding. The bias voltage over LC varies from 0 V to 10.6 V to achieve a frequency tunability of 1.18 GHz. The array operates from 25.3 GHz to 33.8 GHz with a peak gain of 19.2 dB and a beamwidth of 5.2° at 30 GHz. The proposed reconfigurable antenna ar-ray represents a real and efficient solution for the recent and future mmw 5G networks. The proposed antenna is suitable for 5G base stations in stadiums, malls and convention centers. It is proper for satellite communications and radars at mmw.
2019 IEEE Conference on Antenna Measurements & Applications (CAMA)
This paper presents a novel technique to achieve a broad impedance bandwidth required to pursue t... more This paper presents a novel technique to achieve a broad impedance bandwidth required to pursue the development in the field of wireless communication by proposing a design of a reconfigurable broadband stacked patch antenna, based on liquid crystal and aperture coupled feeding with two square patch elements. The MDA-00-3506 liquid crystal (LC) is used as a dielectric. The antenna operates at millimeter wave from 24.4 GHz to 32.8 GHz with a bandwidth of 7.8 GHz. The maximum achievable antenna gain is 7 dB.
2017 International Conference on Control, Automation and Diagnosis (ICCAD)
In this paper, we study an electromagnetic optimization technique using Taguchi's method and ... more In this paper, we study an electromagnetic optimization technique using Taguchi's method and apply it to concentric ring antenna array design. Taguchi's method was developped on the basis of the orthogonal array (OA) concept, which offers systematic and efficient characteristics. The newly proposed idea is the implementation of Taguchi optimization method for Concentric Circular Antenna Array (CCAA). The optimization procedure is then used to provide an optimum set of weights for different CCAAs. Obtained results show that the desired radiation pattern with optimum sidelobe level (SLL) reduction is successfully achieved. The numerically simulated patterns are obtained and compared with those of concentric circular isotropic arrays (12, 18, 24, 30 and 36 elements). Compared to traditional optimization techniques and well-known algorithms (Evolutionary Programming (EP) algorithm and Firefly Algorithm (FA)), Taguchi's method is easy to implement and efficient to reach the optimum solutions.
In this paper, we present a neural network approach to the problem of cylindrical antenna array s... more In this paper, we present a neural network approach to the problem of cylindrical antenna array synthesis. In modern satellite mobile communications systems and global positioning systems, both desired and interfering signals change their directions continuously. Therefore, a fast tracking system is needed to constantly track the users and then adapt the radiation pattern of the antenna with direct multiple narrow beams to desired users and nulls interfering sources. This paper proposes a neural network architecture that consists of 2 sub-systems, each one composed of 8 patches and 9 sub-neural networks, to solve the synthesis of a cylindrical antenna array. The network’s training database contains a finite number of samples of cylindrical targets at certain angles. A part of the database is used to train the network and the rest is used to test its performance for target identification and classification. Used neural networks are multi-layered perceptron (MLP) with a back-propagati...
2019 2nd IEEE Middle East and North Africa COMMunications Conference (MENACOMM), 2019
In this paper, an improved design is presented to achieve a compact reconfigurable wideband anten... more In this paper, an improved design is presented to achieve a compact reconfigurable wideband antenna based on GT3-23001 liquid crystal (LC) for millimeter wave (mmw) 5G networks. The proposed design consists of two stacked patch antenna using aperture coupled feeding. The GT3-23001 LC is an anisotropic dielectric material used as substrate and it has a variable permittivity that can be controlled by a biasing voltage. The dimensions of the designed stacked patch antenna are (5.34 × 5.34 × 2.06) in mm. The proposed antenna is suitable for radar, satellite communications and for 5G applications, such as theatres, shopping malls, convention centers and stadiums. It operates at millimeter wave from 25.4 to 33.5 GHz with a bandwidth of 8.16 GHz and a maximum antenna gain of 6.75 dB is achieved.
This paper presents the design of a low cost Electromagnetic Band Gap (EBG) antenna with high gai... more This paper presents the design of a low cost Electromagnetic Band Gap (EBG) antenna with high gain and mono-band characteristics covering the up/downlink GSM (890–960 MHz). These properties are performed using Plexiglas layers suspended over a ground plane. The principle of Fabry-Perot cavity is used to obtain the high gain performance.
International Journal of Communication Networks and Information Security, 2010
This paper covers the design and optimisation of fractal antennas for RFID application at microwa... more This paper covers the design and optimisation of fractal antennas for RFID application at microwave frequencies. Basing on the Sierpenski gasket antenna and slot technique we propose a novel structure of Sierpenski fractal antenna which is named Sierpenski Slot antenna. The propose structure present a reduction of size by more than 52% which is very important in the case of TAG RFID antenna.
Proceedings of the Twentieth National Radio Science Conference (NRSC'2003) (IEEE Cat. No.03EX665), 2003
ABSTRACT This paper describes a wideband resonant patch antenna for GSM system applications. A th... more ABSTRACT This paper describes a wideband resonant patch antenna for GSM system applications. A thick substrate is used to increase the bandwidth of such antenna. A new design method is suggested to solve the problem due to the inductance created by the probe feed. The 3D FDTD is used for the simulation of the antenna. A wide impedance matching bandwidth of 8% was reached. A good agreement is obtained between theoretical and practical results.
Journal of Engineering and Technology Research, 2011
In this paper, an electrical model is developed to represent the input admittance of an antenna a... more In this paper, an electrical model is developed to represent the input admittance of an antenna array with a finite number of elements. This model consists of an RLC bock component to represent the input admittance of each elementary antenna element and a capacity component to represent different degrees of antenna coupling effects. The equations based on cavity model are developed to represent physical meaning of each model. Numerical results show that good accuracy for the simulation results can be obtained by using this electrical model to the results obtained by using HFSS. As the array is large and sparse, a very small amount of computation can yield good accuracy. This model is shown not only to be numerically efficient compared to the full wave analysis using the moment method, but also to give physical insight into the antenna array mutual coupling mechanism. Furthermore, this model has no limitation on antenna array geometry and excitation.
2009 16th IEEE International Conference on Electronics, Circuits and Systems - (ICECS 2009), 2009
ABSTRACT An adaptive antenna system consists of a combination of multiple antenna elements with a... more ABSTRACT An adaptive antenna system consists of a combination of multiple antenna elements with a signal-processing capability to optimize its radiation and/or reception pattern automatically in response to the signal environment. In a telecommunication system, adaptive antenna system is the port through which radio frequency (RF) energy is coupled from the transmitter to the environment and, in reverse, to the receiver from the environment. In this paper, an efficient method for the pattern synthesis of the linear antenna arrays with the prescribed nulling and steering lobe is presented. The proposed method is based on LMS algorithm. This paper proposes the novel architecture for implementing a least mean square (LMS) algorithm, using an 8 quasi-Yagi array with its feeding system.
2007 IEEE Radar Conference, 2007
Patch antennas plane networks have been used largely in communication systems. Their capability t... more Patch antennas plane networks have been used largely in communication systems. Their capability to change radiation pattern electronically, multi-beam capacity and high spatial resolution has made them attractive for mobile communication applications. The work presented in this paper refers to the synthesis of periodic patch antennas plane networks supplied with coaxial lines. The method of synthesis used for this type of networks let's possible an optimal approach for the desired radiation pattern specified by a gauge sensible for source excitation and space distribution of the radiant sources. The development of the synthesis is based on the neural networks technique.
2009 16th IEEE International Conference on Electronics, Circuits and Systems - (ICECS 2009), 2009
This paper describes a new approach to cylindrical antenna controlled by the excitation (amplitud... more This paper describes a new approach to cylindrical antenna controlled by the excitation (amplitude and phase) to synthesize directive lobe and multilobe patterns, and create adaptive nulls in interference direction and large lobe pattern. The proposed method is based on iterative minimization of a function that incorporates constraints imposed in each direction with respect to excitation (amplitude and phase). To verify the performances of the proposed technique, an 16-element cylindrical antenna has been simulated for various types of beam configurations.
Ce memoire s'inscrit dans le cadre d'un projet CEDRE (Collaboration entre l'universit... more Ce memoire s'inscrit dans le cadre d'un projet CEDRE (Collaboration entre l'universite de Limoges et l'universite Libanaise) sur le theme des antennes intelligentes dans les radio- communications mobiles. Le travail a consiste en une contribution a l'optimisation du lobe de rayonnement pour une antenne intelligente. Deux approches complementaires ont ete developpees pour implementer la technique de formage du lobe, une basee sur un algorithme d'optimisation qui calcule les phases des excitations en fonction des specifications desires (lobe pointe, multi- lobes, creation des zeros) et l'autre utilisant les resultats de la premiere technique pour implementer un modele avec des reseaux de neurones. La premiere methode a un inconvenient concernant le temps de calcul (quelques seconds), la deuxieme est quasiment une application en temps reel. La prise en compte de l'effet de couplage sur le rayonnement a ete implementee directement dans la technique de synthese, et une validation pratique de cet effet a ete realisee. De nombreuses mesures d'une antenne reseau 8 elements, excites seulement en phase, ont permis de valider nos outils developpes.
International Journal of …, 2009
In this paper, we propose two electrical models of carpet and gasket Sierpenski patch antenna. In... more In this paper, we propose two electrical models of carpet and gasket Sierpenski patch antenna. In our approach, we replace the antenna structure by its equivalent rectangular patch. Then, we build the electrical model in which we extract the resonant circuit RLC parameters. Return losses of the models are compared to physical patch for frequency band [1GHz, 3GHz]. Simulation results given by our approach, show that the antenna and its model have the same resonant frequency at 2.45GHz but with a little difference in Bandwidth.
IET Microwaves, Antennas & Propagation, 2008
An efficient phase-only control method is presented to synthesise directive lobe and multilobe pa... more An efficient phase-only control method is presented to synthesise directive lobe and multilobe patterns, and create adaptive nulls in interference direction. The proposed method is based on iterative minimisation of a function that incorporates constraints imposed in each direction with respect to excitation phases. To verify the performances of the proposed technique, an eight-element array has been realised and tested for various types of beam configurations.
IET Microwaves, Antennas & Propagation, 2009
A new approach to adaptive phase-only nulling with phased arrays is described. An efficient metho... more A new approach to adaptive phase-only nulling with phased arrays is described. An efficient method is presented to synthesise directive beam and multi-beam patterns and create adaptive nulls in interference direction. The proposed method is based on iterative minimisation of a function that incorporates constraints imposed in each direction with respect to excitation phases and neural network technique. Various results are presented to show the advantages and limitations of this approach. The back-propagation algorithm proves to be better than previous phase-only adaptive algorithms. To verify the performances of the proposed technique, an eight-element array has been realised and tested for various types of beam configurations.
International Journal of …, 2010
This paper covers the design and optimisation of fractal antennas for RFID application at microwa... more This paper covers the design and optimisation of fractal antennas for RFID application at microwave frequencies. Basing on the Sierpenski gasket antenna and slot technique we propose a novel structure of Sierpenski fractal antenna which is named Sierpenski Slot antenna. The propose structure present a reduction of size by more than 52% which is very important in the case of TAG RFID antenna.
Uploads
Papers by Najib Fadlallah