Lotfi Osman

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.

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.

An efficient hexagonal switched beam antenna structure based on Fabry-Perot cavity leaky-wave antenna

A novel design of switched beam antenna (SBA) system based on Fabry-Perot cavity leaky-wave antenna (FPC LWA) is designed and fabricated for base station operating in the unlicensed ISM central frequency band at 5.8 GHz of the wireless local area network (WLAN) standard. The proposed SBA is designed with hexagonal shape of FPC LWA Arrays in order to get 360° of coverage. The single element of FPC LWA array is composed of a patch antenna and covered by a Partially Reflective Surface (PRS), which is composed of a Metal Strip Grating and printed on a high permittivity Superstrate. First, the Transmission Line Model of FPC LWA is introduced to analyse and calculate the far-field components in E- and H planes by using the Transverse Equivalent Network. This approach is then compared with other full wave’s commercial software such as Ansoft HFSS and CST Microwave Studio. Second, a parametric study is performed to evaluate the effect of the angle formed by the two successive FPC LWA on the radiation efficiency of the activate sector. To examine the performance of the proposed SBA, experimental prototype was fabricated and measured. As a result, multiple orthogonal beams (six beams) of 10 dBi of gain with low Side Lobes Level and 360° of coverage are produced. This SBA structure is suitable for WLAN communication systems.

Efficient 2.45 GHz CPW patch antenna including harmonic rejecting device for wireless power transmission

An efficient coplanar waveguide CPW T-matched slot-loop patch antenna has been designed at 2.45 GHz. DGS is implemented to obtain the 3rd harmonic rejection while the second harmonic resonance is obtained by varying the T match length. The proposed antenna is well suitable for wireless power transmission because no input low pass filter and no via-hole connections are required, resulting in a simpler structure. An electromagnetic simulation has been used to optimize the antenna. The simulated antenna exhibits 4.4 dB gain at 2.45 GHz operating frequency. The return losses at the 2nd and 3rd harmonic frequencies are −1.2dB and −1.6dB respectively.

High sectorization switched beams for WLAN applications

In this paper, a high sectorization azimuthal plane technique based on hexagonal antenna array is presented. The sector of the antenna system is divided in three small sub-sectors by using a Reconfigurable Pattern Antenna (RPA). An active High Impedance Surface (HIS) is employed to steer the main beam using six PIN diodes as RF switch in each sector. As a result, the whole structure is able to cover all azimuth plane in 18 sectors with 9 dB gain. The proposed antenna can be used as base station for future Wireless Local Area Network (WLAN) applications.

Development of a novel wideband conical Dielectric Resonator Antenna

In this paper, we propose a dual layer conical Dielectric Resonator Antenna (DRA) excited by a slot. The inclination of the two environments with different dielectric constants relative to the slot can create a Circular Polarization (CP). Simulations performed under Ansoft HFSS software show that the proposed conical shaped DRA is circularly polarized and can reach a large bandwidth of 1.14 GHz with a gain of about 6.4 dB at the frequency of 5.8 GHz.

1D Switched Beam Fabry-Pérot Leaky Wave Antenna

A simple and efficient configuration of Switched Beam Antenna arrays based on 1D Fabry-Pérot Leaky Wave Antenna (FPLWA) is presented working at 5.8 GHz. The single 1D FPLWA is formed by a simple low gain patch antenna covered by a PRS screen formed by a Metal Strip Grating (MSG). Simulated results including return loss and switched beams are presented. multiple orthogonal beams (six beams) of 10dBi of gain with low Side Lobes Level (SLL) (of about -15 dB) and 360° of coverage are produced. This SBA structure is suitable for WLAN communication systems.

The Design of a 360°-Switched-Beam-Base Station Antenna

The concept of switched-beam antenna (SBA) systems covering an area of 360° for wireless base station applications is presented. First, a reconfigurable pattern antenna (RPA), which is composed of an omnidirectional slot-antenna array surrounded by an active cylindrical frequency selective surface (FSS), is studied. The behavior of FSS is controlled by PIN diodes which are able to divide the Azimuth plane into six sectors from one common source. Unfortunately for a sector antenna, a huge number of diodes are required which complicates the structure in terms of efficiency and complexity. However, a simple and an efficient SBA configuration based on a hexagonal Fabry-Pérot cavity leaky wave antenna (FPC LWA) arrays is proposed as a solution for RPA problems. A sector-directive beam is generated from a simple patch antenna embedded inside a resonant Fabry-Pérot cavity with specific dimensions which have an influence on beamwidth and radiation efficiency. To increase more sectorization level and channel’s capacity, the proposed sector in FPC LWA arrays can be divided into three subsectors by using an active highimpedance surface (HIS). As a conclusion, SBA based on FPC LWA is the most suitable solution for future wireless communications.

Design of electrically tunable phase shifter for antenna arrays operating in Ku-band

This paper deals with the modeling and simulation of a wideband analog phase shifter for Ku applications. The structure adopted is based on a 90° branch-line coupler loaded by varactor diodes used to provide a wide phase shift range. The main idea of this work is to integrate controlled phase shifters in the antenna array in order to control its main beam between different satellites. Several circuits have been tested and optimized using ADS software from Agilent Technologies to obtain a wide bandwidth and wide phase shift range with low insertion loss over the Ku band.

A novel miniaturized Circularly Polarized PIFA antenna for RFID readers

In this paper, a novel miniaturized Planar Inverted F Antenna (PIFA) for RFID readers with Circular Polarization (CP) is studied. The techniques of slots and miniaturization are applied in the designing of the antenna in order to decrease its size and its resonance frequency. The proposed structure is simulated under CST software and fabricated on a 0.4λ0×0.4λ0×0.06λ0. It operates in the European RFID UHF band. The measurement results obtained are very encouraging.