Taoufik Aguili

ANALYSIS OF MULTILAYERED CYLINDRICAL STRUCTURES USING A FULL WAVE METHOD

In this paper, Wave Concept Iterative Procedure (WCIP) is used to investigate scattering by multilayered cylindrical structures in free space and to calculate the diffracted far field by adopting a cylindrical coordinate formulation. The WCIP principle consists of alternating waves between the modal and space domains. Its iterative resolution process is always convergent in lossless media case. The proposed technique used for determining the electric far field diffracted by a multilayered cylindrical structure is validated and confronted to literature results.

Lightpath rerouting scheme for dynamic traffic in WDM all-optical networks

This paper considers rerouting and minimization of incurred disruption due to rerouting in all-optical wavelength division multiplexed (WDM) network with dynamic (random) traffic arrivals and departures. One limitation of such a network is the wavelength continuity constraint imposed by the all-optical cross-connect switches which do not allow a circuit to be placed on a non wavelength-continuous route. Rerouting is proposed to rearrange certain existing lightpaths to create a wavelength-continuous route in order to accommodate a new connection request. Recently, a wavelength rerouting scheme called “Parallel Move-To-Vacant Wavelength Retuning (MTV-WR)” with many attractive features such as shorter disruption period and simple switching control has been proposed. In this paper, we propose a new lightpath rerouting scheme based on the “Parallel MTV-WR” rerouting scheme minimizing the rejection ratio whilst keeping a little service disruption period due to rerouting. We assume that a new random lightpath demand (RLD) arrives at time t and that its routing phase fails to set up it. To establish the new RLD the proposed algorithm tries to reroute one or several RLDs by only changing the used wavelength whilst keeping the same physical path in order to reduce the disruption period. If it fails, it tries to reroute a minimum number of active RLDs by changing the physical path and then possibly the used wavelengths. Simulation results show that our proposed algorithm computes a better rejection ratio than the rerouting algorithms previously presented in the literature while keeping a minimum number of rerouted lightpaths and a very small service disruption period.

Studying of surface impedance behavior of RIS against incidence and polarization for miniaturized antenna

In this paper, we present a formulation based on surface impedance concept to model reactive impedance surface (RIS) applying the MoM-GEC method (MoM combined to generalized equivalent circuit). The study of the whole periodic infinite RIS is reduced to the unit cell modeling. We are interested especially in demonstrate the RIS impedance behavior against incidence and both TE and TM polarizations. Also, the effect of substrate dielectric permittivity is achieved. Obtained results are given and discussed.

A new multi-scale framework for convolutive blind source separation

This paper presents a new multi-scale decomposition algorithm which enables the blind separation of convolutely mixed images. The proposed algorithm uses a wavelet-based transform, called Adaptive Quincunx Lifting Scheme (AQLS), coupled with a geometric demixing algorithm called Deds. The resulting deconvolution process is made up of three steps. In the first step, the convolutely mixed images are decomposed by AQLS. Then, Deds is applied to the more relevant component to unmix the transformed images. The unmixed images are, thereafter, reconstructed using the inverse of the AQLS transform. Experiments carried out on images from various origins show the superiority of the proposed method over many widely used blind deconvolution algorithms.

Application of Generalized Equivalent Circuits (GEC) method for Calculating of the diffraction by dielectric obstacles with finite thickness in metallic waveguide: Application to the characterization of vegetation leaves

In this paper, we develop an electromagnetic analysis of a rectangular waveguide loaded with a dielectric model that is composed of a leaf plant with a finite thickness. By applying the Generalized Equivalent Circuits (GEC), we can determine the wave diffraction according to the dielectric properties. To validate this work, our obtained results are compared with those previously published and measured. We have seen a good agreement is presented.

Transient response of coupled wire antennas using the electric field integral equation with Laguerre polynomials as temporal basis functions

Two time domain integral equations of coupled identical and symmetrically wire antennas are presented. The equations are solved efficiently by method of moments particularly Galerkins method. The time domain unknown coefficients of the electric currents are approximated using a set of orthonormal basis function that is derived from the Laguerre functions. Numerical results involving transient currents on each antenna are presented depending on separate distance between the two antennas.

A novel lightpath rerouting algorithm for dynamic traffic with transmission impairments consideration in WDM all-optical networks

In this paper, we propose a novel lightpath rerouting algorithm to optimize network resources allocation in WDM all-optical networks in order to set up an incoming lightpath demand to be blocked for lack of resources or due to the absence of a suitable path and a suitable wavelength that meet the minimum Quality of Transmission (QoT) requirements. Indeed, in such networks, transmitted optical signal has to traverse crossconnect switches, fiber segments and optical amplifiers. Thus, while propagating through the network, the signal may degrade in quality as it encounters crosstalk at the cross-connect switches and collects amplified spontaneous emission noise at the optical amplifiers. Since these impairments continue to degrade the signal quality as it progresses toward its destination, the received Bit Error Rate (BER) at the destination node might become unacceptably high. Rerouting aims at reassigning the wavelength and/or the path of one or several established connections in order to free enough wavelengths to satisfy the incoming demand. Rerouting refers implicitly to dynamic traffic. Simulation results show that our algorithm improves the rejection ratio and is less CPU time consuming than rerouting algorithms previously presented in the literature.

Transmission Control of Electromagnetic Waves by Using Quarter-Wave Plate and Half-Wave Plate All-Dielectric Metasurfaces Based on Elliptic Dielectric Resonators

We present the design of all-dielectric Quarter-Wave Plate (QWP) and Half-Wave Plate (HWP) metasurfaces based on elliptic dielectric resonators (EDRs) for the transmission control of electromagnetic waves over the frequency band 20–30 GHz. First, an extensive numerical analysis was realized by studying the effect of the resonators geometry (thickness and ellipticity) on the transmission of both - and -polarized waves. Then, based on the numerical analysis, we have realized and characterized experimentally both QWP and HWP all-dielectric metasurfaces.

Wave Concept Iterative Process Method for Electromagnetic or Photonic Jets: Numerical and Experimental Results

In this paper, we report the numerical and experimental observations of electromagnetic or photonic jets created by a planar metallic waveguide filled with dielectric and terminated by an elliptical tip. The theoretical framework of the study is based on the wave concept iterative process (WCIP) method formulated in the spatial domain. The analyzed structure is excited by the fundamental transverse electric mode of the waveguide. The accuracy and efficiency of our program are investigated; the results of the radiated power density show a good agreement compared with those given by finite element method (FEM) simulation. The tangential electric field is computed along the elliptical tip interface and in its vicinity, i.e., in the exterior area. The parameters of the electromagnetic jet phenomenon are investigated according to the geometrical and physical characteristics of the proposed structure. Our numerical simulations are in good agreement with the measurements, indicating that the electromagnetic jet can also be obtained in the microwave field.

A New Hybrid Rerouting Scheme in WDM All-Optical Networks Under Dynamic Traffic

In WDM all-optical networks, the wavelength continuity constraint along with the wavelength clash constraint, lead to poorer network performances when dealing with the lightpath provisioning problem. The impact of these constraints is especially severe when traffic demands are unpredictable and characterized by random arrivals and departures. To improve the network utilization efficiency, either wavelength conversion or lightpath rerouting can be used. Since, in the foreseeable future, wavelength conversion is expected to remain an expensive technology, traffic rerouting is an attractive alternative solution to improve the network throughput conditioned by the aforementioned constraints. In this paper we propose to employ hybrid rerouting, to improve the network utilization efficiency considering a dynamic traffic model. Hybrid lightpath rerouting combines passive rerouting and active rerouting. Our proposed algorithm, namely, Sequential Routing with Hybrid Lightpath Rerouting algorithm (SeqRwHLR) establishes the traffic demands sequentially, that is demand by demand at arrival dates. When an incoming traffic demand cannot be set up in the absence of path-free wavelengths between its source and destination nodes, the SeqRwHLR algorithm performs passive rerouting procedure aiming hopefully at freeing a path-free wavelength to service the new traffic demand. Furthermore, our proposed algorithm dynamically reroutes some already established lightpaths from longer paths to vacant shorter ones so as to reduce the network resources consumption. This should hopefully lead to a better performances. The performances of the proposed algorithm are demonstrated to be promising through simulation results.