Ali Gharsallah

A Dual Circularly Polarized 2.45-GHz Rectenna for Wireless Power Transmission

A 2.45-GHz rectifying antenna (rectenna) using a compact dual circularly polarized (DCP) patch antenna with an RF-dc power conversion part is presented. The DCP antenna is coupled to a microstrip line by an aperture in the ground plane and includes a bandpass filter for harmonic rejections. It exhibits a measured bandwidth of 2100 MHz (10 dB return loss) and a 705-MHz CP bandwidth (3 dB axial ratio). The maximum efficiency and dc voltage are respectively equal to 63% and 2.82 V over a resistive load of 1600 Ω for a power density of 0.525 mW/cm2.

Direction of Arrival Estimation Method Using a 2-L Shape Arrays Antenna

The paper presents a new algorithm for a 2-dimensionnal direction of arrival estimation. Based on the extended Kalman filter (EKF), we analyse a recursive procedure for 2-dimensional directions of arrival (DOA) estimation and we will employ the two-L-shape arrays. A new space-variable model which we call a spatial state equation is presented using array element locations and incident angles. In this paper we briefly recapitulate the most important features of the extended Kalman filter (EKF). The performance of the proposed approach is examined by a simulation study with three signals model. The simulation results show a good estimate performance.

Behavioral Modeling of MIMO Nonlinear Systems With Multivariable Polynomials

This paper proposes a novel behavioral model for multiple-input single-output (MISO) and multiple-input multiple-output (MIMO) nonlinear transmitters based on multivariable polynomials (MVPs). The main source of nonlinearity in these transmitters is the RF power amplifier, which is commonly modeled using polynomial models. The proposed MVP model is capable of handling the nonlinear effects of the RF transmitters, as well as the linear and nonlinear crosstalk between the input signals. At the same time, the developed model was optimized for computing efficiency without compromising its accuracy. The model was tested for MISO and MIMO wireless transmitters. The simulations and measurement results revealed that the proposed model gives excellent accuracy when modeling MIMO transmitters with different branch coupling factors.

2-L-Shape Two-Dimensional Arrival Angle Estimation with a Classical Subspace Algorithm

This paper proposes a computationally efficient method for a two-dimensional direction of arrival estimation of multiple narrowband sources. We apply the MUSIC method which requires eigenvalues decomposition to the cross spectral matrix. This paper employs two L-shape arrays that showed better performances than the one L-shape and the parallel shape arrays. In spite of its computational complexity, simulation results verify that the proposed subspace technique gives much better performance than the propagator method

Estimation of 2-D Direction of Arrival with an Extended Correlation Matrix

This paper presents a new subspace-based 2D direction of arrival (DOA) estimation algorithm for narrowband sources with high-resolution localization capabilities. DOA estimation is achieved by using the noise-subspace eigenvectors of a new extended correlation matrix (ECM). A 2-L shape antenna array is proposed. Unlike common planar and circular arrays, the novel antenna array with this special geometry requires no pair matching between the azimuth and elevation angle estimation also this key can remove the drawbacks of estimation-failure problems. The performance of the proposed approach is examined by a simulation study. The simulation results show a good estimate performance.

Beam-Switching Antenna With a New Reconfigurable Frequency Selective Surface

In this letter, a design of a beam-sweeping antenna using a new active frequency selective surface (FSS) is presented. The active FSS is composed of a steerable hybrid element that allows the control of radiation characteristics of the proposed antenna. The design is composed of an active cylindrical FSS structure containing PIN diodes and is divided into 10 equal columns. This design contains a simple dipole that is located in the center and surrounded by a cylindrical active FSS. The beam-sweeping of the antenna is produced by switching the PIN diodes between the on and off states. The antenna operates at 1.8 GHz and covers all azimuth angles in 10 steps with a maximum measured gain of 9.1 dBi. This beam-switching antenna can be used in the base stations of wireless communication systems.

Miniaturization of wearable electro-textile antennas using Minkowski fractal geometry

This paper deals with miniaturization of wearable electro-textile antennas by the use of Minkowski fractal geometries. Two electro-textile materials namely Flectron and Zelt are considered for the design of flexible microstrip antennas. In both cases, polyester fabric material has been employed as dielectric medium. In the basic design both the antennas are designed for WLAN applications. The Flectron antenna provides a gain of 6.54 dB with an impedance bandwidth of 132 MHz whereas, the Zelt antenna offers a gain of 7.4 dB and an impedance bandwidth of 104 MHz. By applying Minkowski fractal geometry to the antennas, miniaturization is achieved. In its first iteration, antenna designs are optimized and tuned to WiBro band and in the second iteration, antennas are further miniaturized in order to make them suitable for GSM 1900 applications. In these two bands, the gain and efficiency of both Flectron and Zelt antennas conform to their respective wireless standards. The simulation studies reveal that Zelt antenna yields better results compared to Flectron antenna.

Chipless RFID for space applications

Recent works reveal a great deal of interest in the subject of wireless passive sensor for space applications. In particular, wireless passive tags can be employed during in-flight operations as well as during ground test campaigns, thanks to their robustness in extreme environments since they do not contain batteries nor any active electronic circuits. Chipless backscatter-based radio frequency identification (RFID) could be a valid alternative to surface acoustic wave (SAW) imple-mentations, especially for short-range applications like sensor monitoring aboard of satellite systems. In this work we present chipless RFIDs based on resonant substrate integrated waveguide (SIW) cavities, showing both the experimental characterization and system simulations, proving the solution feasibility for their usage on space platforms.

Steering an adaptive antenna array by LMS algorithm

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.

Phased arrays in communication system based on Taguchi-neural networks

Phased antenna array design is one of the most important electromagnetic optimization problems. This research combined the Taguchi method and artificial intelligence methods, used them as the prediction tool in designing parameters for the communication system, and then constructed a set of the optimal parameter analysis flow and steps. In this paper, we present an application of artificial neural networks in the electromagnetic domain. We particularly look at the multilayer perceptron network, which has been the most used of artificial neural networks architectures both in the electromagnetic domain and in the Taguchi optimization technique and describes the Taguchi method to optimize the excitations elements of the linear array to produce a radiation pattern with minimum side lobe level and null placement control. This paper investigates how the implementation of the signal processing in hardware affects the performance of the adaptive array antenna. The investigation is confined to uplink or receive antenna array only. Results of a prototype of antenna array with feeding values designed using the proposed techniques are also presented. Copyright