Abdel-Razik Sebak

A Printed Monopole Antenna With Two Steps and a Circular Slot for UWB Applications

This letter presents a printed monopole antenna with two steps and a circular slot for ultrawide band (UWB) applications. The proposed antenna is fabricated and tested. The proposed antenna has a wide frequency bandwidth of 8.4 GHz starting from 3 GHz up to 11.4 GHz for a return loss (S_11) of less than - 10dB and gain flatness over the frequency range. Measured results show also that the proposed antenna features satisfactory radiation characteristics within the achieved impedance bandwidth. By introducing a simple and proper narrow slot in the radiating element, frequency-notched characteristics can be obtained and a good band-notched performance in the 56 GHz band can be achieved.

Compact Multiband Planar Antenna for 2.4/3.5/5.2/5.8-GHz Wireless Applications

A low-profile planar monopole antenna is proposed to operate within WLAN and WiMAX frequency bands. The antenna is composed of three radiating elements together with an additional strip to control the antenna performance. An electromagnetic (EM) model of the proposed antenna is developed in CST Microwave Studio for numerical analysis and optimization. The principle of operation and parametric study on the antenna performance are provided. Two dual-band and triple-band antennas are fabricated, and experimental results are presented.

Analysis and design of a cylindrical EBG-based directive antenna

In this paper, a cylindrical electromagnetic bandgap (CEBG) structure composed of infinite metallic wires is analyzed, designed and used as a model to develop a new reconfigurable directive antenna. This structure is circularly and radially periodic, and it is excited at its center using an omnidirectional source. The analysis is based on calculating the transmission and reflection coefficients of a single cylindrical frequency selective surface (FSS) and then, considering only the fundamental mode interaction, deducing the frequency response of the CEBG structure composed of multiple cylindrical FSSs. For this structure, new analytical formulas are derived, and their accuracy is assessed compared to those obtained by the finite-difference time-domain method. As in rectangularly periodic structure case, the frequency response of the CEBG structure exhibits pass-bands and bandgaps, and it is possible to obtain directive beams by introducing defects in the periodic structure. Using this concept, a new antenna was developed to obtain a controllable directive beam. An antenna prototype, without control, was designed, fabricated, and tested. An excellent agreement was obtained between theory and experiment for both return loss and radiation patterns.

High-Gain Hybrid Dielectric Resonator Antenna for Millimeter-Wave Applications: Design and Implementation

A new low-cost and high-gain microstrip/dielectric resonator hybrid antenna is described for short-range millimeter-wave communication systems operating in the 57-65 GHz frequency band. The impedance bandwidth (VSWR < 2) of the proposed antenna is wide enough to entirely cover this portion of unlicensed spectrum (ap 5%). Furthermore, the measured high gain (11.9 plusmn 0.9 dB) is fairly constant across the operating band. A study of the electric and magnetic fields inside the hybrid structure concludes that the excitation of a higher-order mode inside the dielectric resonator (namely the HEM15delta hybrid mode) is responsible for the improved gain since the electrical size of the antenna is increased. In order to validate the proposed design, theoretical calculations and measurements from a fabricated prototype are provided.

Broadband L-shaped dielectric resonator antenna

In this letter, a broadband inverted L-shaped dielectric resonator antenna (DRA) is proposed. The DRA with the two equiangular-triangle across sections is built on a ground plane and excited by a coaxial probe to provide broadside radiation patterns. The simulated and measured results verify that the proposed antenna offers a bandwidth of 38% (from 1.71 to 2.51 GHz) and stable broadside radiation patterns. The proposed antenna is suitable for multiband wireless communication applications as digital communication systems (DCS; 1710-1880 MHz), personal communication systems (PCS; 1850-1990 MHz), universal mobile telecommunication systems (UMTS; 1920-2170 MHz), and wireless local area networks (WLANs; 2.4-2.485 GHz).

Novel photonically-controlled reflectarray antenna

A novel method for generating a reconfigurable reflectarray based on the creation of photoinduced plasma inside the semiconductor substrate of a reflectarray is presented in this paper. A reflectarray antenna prototype is fabricated and measured to demonstrate the validity of the design methodology. Measurements were carried out to characterize the bandwidth and the gain of the antenna in both the OFF and ON states of an optical flash lamp that was used to induce photoconductivity inside the silicon substrate.

Carbon Nanotube Composites for Wideband Millimeter-Wave Antenna Applications

In this paper, we explore using carbon nanotube (CNT) composite material for wideband millimeter-wave antenna applications. An accurate electromagnetic model of the composite antenna is developed using Microwave Studio for numerical analysis. Good agreement between computed and measured results is shown for both copper and CNT antennas, and their performance is compared. The CNT antenna shows stable gain and radiation patterns over the 24 to 34 GHz frequency range. The dispersion characteristics of the CNT antenna show its suitability for wideband communication systems. Using a quarter-wave matched T-junction as feed network, a two-element CNT antenna array is realized and the performance is compared with a copper antenna. The housing effect on the performance of the CNT antenna is shown to be much lower than for the copper antenna.

Multi-Band Miniaturized Antenna Loaded by ZOR and CSRR Metamaterial Structures With Monopolar Radiation Pattern

Miniaturized low-profile monopole antennas loaded by metamaterial (MTM) structures are presented. The antenna is loaded by zeroth-order resonator (ZOR) and complimentary split-ring resonator (CSSR) units, resonating over three frequency bands so that they can be tuned by changing the geometrical parameters of the MTM structures. Surface current distribution and equivalent circuit models are provided to describe the principle of operation. The experimental results are presented to validate the numerical results. Showing the monopole-shape radiation pattern characteristics at all resonant frequencies, the proposed MTM antennas are suitable for vehicular wireless applications.

Millimeter-Wave Compact EBG Structure for Mutual Coupling Reduction Applications

A new millimeter-wave (MMW), electromagnetic band-gap (EBG) structure is presented. The proposed EBG structure without the use of metallic vias or vertical components is formed by etching two slots and adding two connecting bridges to a conventional uniplanar EBG unit-cell. The transmission characteristics of the proposed EBG structure are measured. Results show that the proposed EBG structure has a wide bandgap around the 60 GHz band. The size of the proposed EBG unit-cell is 78% less than a conventional uniplanar EBG, and 72% less than a uniplanar-compact EBG (UC-EBG) operating at the same frequency band. Moreover, and despite the fabrication limitations at the 60 GHz band, the proposed EBG unit-cell provides at least 12% more size reduction than any other planar EBG structures at microwave frequencies. Its enhanced performance and applicability to reduce mutual coupling in antenna arrays are then investigated. Results show a drastic decrease in the mutual coupling level. This EBG structure can find its applications in MMW wireless communication systems.

Full-Composite Fractal Antenna Using Carbon Nanotubes for Multiband Wireless Applications

In this letter, single-wall carbon nanotube (CNT) composite materials are explored for the design of multiband antennas. An accurate electromagnetic (EM) model of the modified Sierpinski fractal composite antenna is developed using Microwave Studio for numerical analysis. For antenna fabrication, we printed CNT on both sides of a substrate and then cut out the desired antenna pattern using a high-precision milling machine. The CNT material was hardened by resin infiltration in order to be processed on the milling machine. The CNT antenna shows satisfactory gain and radiation patterns for UHF-RFID (900 MHz), Bluetooth (2.4 GHz), and WLAN (5.5 GHz) applications. Good agreement between computed and measured results is observed.