Ali Harmouch

Cylindrical Omnidirectional Slotted Waveguide Antenna with optimized directional characteristics

Antennas, nowadays, are used in many systems especially in wireless internet communications and military Radar applications where high power handling capability, high gain along with reliable mechanical characteristics is needed. However, these parameters are very hard to simultaneously optimize, there is always a trade-off in between. In this paper, a Cylindrical Omnidirectional Slotted Waveguide Antenna (COSWA) is presented. The purpose of this paper is to provide an optimized version of circular slotted waveguide antennas by simply selecting the optimum position, number, shape and size of the slots within the waveguide wall. Such configurations are suitable to be used in Wireless internet distributing systems, Military radar applications and even oil drilling devices. Simulation results along with Experimental validations will be conducted at 2.4 GHz frequency demonstrating high effectiveness in terms of directivity and high gain given a reduced cost, simplicity and size.

On miniaturization of efficient ultrawideband printed quazi-Yagi antenna array for indoor applications

This paper describes the design and analysis of a compact and efficient ultrawideband unidirectional printed antenna array for indoor applications.A12.2×6.3×1 cm antenna array is capable of covering an ultra-wide frequency band starting from LTE up to Wi-MAX with an average gain approaching 5 dBi over the entire bandwidth. In comparison with the already existing antenna systems in the wireless market for similar purposes, the proposed antenna has considerably better performance and supplementary compactness, which makes it competitive among other antenna models. Simulation results have also shown low cross polarization levels, where the sidelobe level was also minimized by introducing a special reflecting element in the designed model. Adopting the proposed antenna in indoor communication systems would surely enhance the quality of signal within the covered area as well as minimize the number of access points needed for a given network.

Impact of human hair configuration on the human head absorption rate

In this paper, electromagnetic cellular propagation modeling with the presence of a human head is presented, taking into account the nature of the human hair existing in the world. Numerical results obtained by the “Complete Technology” approach - offering Finite Integration Technique, Finite Element Method, Method of Moments, MLFMM, Transmission-line matrix and System Assembly and Modeling - are presented in CST Studio Suite simulations. As a cellular network, a typical IEEE human head has been used for this study featuring several ways of implementing hair on it and adding more layers to this hair. A patch directional antenna (also known as a rectangular micro strip antenna) that is resonant at 2.4 GHz is used for simulation. The main purpose of this study is to optimize the configuration of the human hair to get to a minimum SAR on the human body lying inside the tested area. Simulation results would provide a chart describing the best configuration of the human hair within environments which use cellular frequently.

A combination of transformation optics and surface impedance modulation to design compact retrodirective reflectors

This study proposes a new approach to flatten retrodirective corner reflectors. The proposed method enables compact reflectors via Transformation Optics (TO) combined with Surface Impedance Modulation (SIM). This combination permits to relax the constraints on the anisotropic material resulting from the TO. Phase gradient approach is generalized to be used within anisotropic media and is implemented with SIM. Different reflector setups are designed, simulated and compared for fop = 8GHz using ANSYS® HFSS® in order to validate the use of such a combination.

Study on the validity of the formalism of norton to describe the propagation of electromagnetic waves on the surface of the body

In this paper, we focus on the study of electromagnetic waves that allow the communication between two antennas located on the surface of the human body. The link between the antennas leads to the appearance of space wave, whose level increases with height above the skin, and a surface wave which, on the contrary, decreases with the altitude. We use the wave propagation model of Norton with the notion of Somerfield’s attenuation. We give the limits of validity of this formalism in the area containing mainly surface waves. To generate this type of waves, the excitation sources used are small elementary electric dipoles with normal polarization.

Double-plane pattern enhancement of rectangular slotted waveguide antennas using slotted concave surfaces

Conventional slotted waveguide antennas are well known and prominently used for many military and even marketable applications. This is due to their different advantageous electrical and mechanical characteristics. It is also well known that this type of antennas is a typical array of slots with which the width of the main beam can be controlled in only one plane by using a different number of elements in such antennas. Numerous research, discuss the capability of using an array of such antennas in order to narrow down the main beam in both planes and even achieve a scanning phased array. In this paper, a new and broader approach is presented concerning beam width control of the typical configuration of such antennas. This work presents the ability to control the main lobe in both planes using only one slotted waveguide to a certain extent. Different simulation results are considered at the 2.4 GHz frequency demonstrating improved effectiveness in terms of directivity and high gain as well as minimizing the side-lobe level and mechanically controlling the main lobe of the antenna.

Beamwidth control of sectional waveguide antennas using parabolic slotted surfaces

This research is concerned with controlling the radiation pattern of a sectional cylindrical slotted waveguide antenna (SCSWA) in both horizontal and vertical planes to make the antenna more directive. In order to cover an area several SCSWAs are used, so the beam should be narrow in the horizontal plane to avoid interference. To control the beam in the vertical plane, the number, the width, and the position of slots could be varied. In this research, the focus is on controlling the radiation pattern in the horizontal plane by changing the concavity of the surface where the slots are placed. A series of simulations were performed on the proposed antenna at a desired frequency of 2.4 GHz, the results showed good control over the antennas performance.

Multi-resonant compact patch antenna with fractal slots on the basis of smith chart configuration

This paper describes the design and analysis of a multi-resonant compact patch antenna with fractal slots on the basis of Smith Chart geometry for indoor communication systems. A 60mm × 60mm × 1mm single patch antenna with periodic fractals in the form of combined r and x circles is capable of resonating at some desired sub-bands starting from LTE to WI-MAX with good enough directional characteristics greater than 3 dB in average within the whole frequency band. The dielectric material used for the proposed Microstrip patch antenna is Rogers TMM4 with dielectric constant of 4.5 and the patch is made up of perfect electric conductor (PEC). The proposed fractal geometry possesses multiband behavior at 0.7 GHz, 1.15 GHz, 1.8 GHz, 2.4 GHz, 3.7 GHz, 5.2 GHz and 5.8 GHz. In comparison with the already existing antenna systems in the wireless market for similar purposes, the proposed antenna has considerably shown better performance and supplementary compactness which makes it competitive among other antenna models.

Compression technique for retrodirective reflectors using transformation optics

In this paper, the design of compressed retrodirective reflectors via transformation optics is addressed. The proposed method enables a compressed reflector to perform as a classical retrodirective corner reflector while having a much lower profile. Using a simple linear coordinate transformation, the lower profile can be achieved with a TO domain in the reflector consisting of anisotropic homogeneous media. The proposed design is validated at f0=8GHz by full wave electromagnetic simulations. Furthermore, using the Effective Medium Theory approach, the practical feasibility of the involved medium distribution is discussed and verified. The results of the investigations could be of interest in different radar, communication and identification applications.

Characterization and dosimetry of TEM cells for bioelectroma gnetic studies

In this paper, characterization and dosimetry for two Transverse Electromagnetic (TEM) cells by measurements and simulations at the frequency of 1800 MHz are presented. The characterization consists of assessing the S-parameter and the dosimetry consists of getting the Specific Absorption Rate (SAR) values for two TEM cells with 20 cm and 40 cm length. Two Petri dishes put inside the TEM cells and filled with a biological solution are used as a biological load. The transmission and reflection coefficients prove that the bandwidth for both TEM cells is more than 1 GHz. The average SAR values, normalized per input power, for the 20 cm and 40 cm TEM cells are 1 ± 0.5 W/kg/W and 0.29 ± 0.17 W/kg/W, respectively. These values are recorded for 2 mL of biological solution contained in the Petri dish.