Mohammed Al-Husseini

A RECONFIGURABLE U-KOCH MICROSTRIP ANTENNA FOR WIRELESS APPLICATIONS

In this paper, a low-cost multiband printed-circuit-board (PCB) antenna that employs Koch fractal geometry and tunability is demonstrated. The antenna is fabricated on a 1.6mm-thick FR4- epoxy substrate with dimensions 4cm £ 4.5cm, is microstrip-line fed and has a partial ground plane ∞ushed with the feed line. The proposed antenna is simulated using the Finite-Element Method for three difierent switching cases and the return loss is measured for each case. It is shown that the antenna can cover the bands of several applications including 3G, WiFi, WiMAX as well as a portion of the UWB range. The radiation patterns are satisfactorily omnidirectional across the antennas operation bands.

A low-cost microstrip antenna for 3G/WLAN/WiMAX and UWB applications

This paper presents a low-cost ultra-wideband microstrip antenna for wireless communications. Printed on a 40×50×1.83 mm3 Isola Gigaver 210 substrate, the antenna features a microstrip feed line with two 45° bends and a tapered section for size reduction and matching, respectively. The ground plane is partial and comprises a rectangular part and a trapezoidal part. The patch is a half ellipse, where the cut is made along the minor axis. Several slots are incorporated into the patch. The placement and sizes of the slots are assisted by the knowledge of fractal geometries. The return loss, input impedance, gain, efficiency and radiation characteristics of the antenna are presented. It is shown that the antenna can operate in the bands used for UMTS, WLAN, WiMAX, and UWB applications.

RECONFIGURABLE FILTER ANTENNAS FOR PULSE ADAPTATION IN UWB COGNITIVE RADIO SYSTEMS

The design of fllter antennas with reconflgurable band stops is proposed. They are meant for employment in ultrawideband cognitive radio (UWB-CR) systems, where unlicensed users communi- cate using adaptive pulses that have nulls in the bands used by licensed users. Neural networks or circuits implementing the Parks-McClellan algorithm can generate such pulses. With fllter antennas, reconflg- urable bandstop fllters are flrst designed, to induce adaptive nulls in UWB pulses, and are then integrated in the feed line of a UWB an- tenna. The advantages of this combination are discussed. The fllters are based on split-ring resonators (SRRs) and complementary split-ring resonators (CSRRs). The relationship between the SRR and CSRR parameters and the stop band is also studied.

Implementation of a cognitive radio front-end using optically reconfigurable antennas

This paper presents a reconfigurable radio front-end antenna scheme suitable for cognitive radio communications. Our scheme comprises of an UWB antenna structure (antenna-1) and a reconfigurable antenna structure (antenna-2) incorporated together on the same substrate. The UWB antenna-1 is used for channel sensing while the reconfigurable antenna-2 is designed to frequency-hop between pre-determined communication channels. The reconfiguration of antenna-2 is achieved by using photoconductive switches which are selectively illuminated by laser light from a series of integrated laser diodes. A prototype was fabricated and tested to prove the applicability of our proposed radio front-end scheme.

Cognitive Radio Transceivers: RF, Spectrum Sensing, and Learning Algorithms Review

A cognitive transceiver is required to opportunistically use vacant spectrum resources licensed to primary users. Thus, it relies on a complete adaptive behavior composed of: reconfigurable radio frequency (RF) parts, enhanced spectrum sensing algorithms, and sophisticated machine learning techniques. In this paper, we present a review of the recent advances in CR transceivers hardware design and algorithms. For the RF part, three types of antennas are presented: UWB antennas, frequency-reconfigurable/tunable antennas, and UWB antennas with reconfigurable band notches. The main challenges faced by the design of the other RF blocks are also discussed. Sophisticated spectrum sensing algorithms that overcome main sensing challenges such as model uncertainty, hardware impairments, and wideband sensing are highlighted. The cognitive engine features are discussed. Moreover, we study unsupervised classification algorithms and a reinforcement learning (RL) algorithm that has been proposed to perform decision-making in CR networks.

Design based on complementary split-ring resonators of an antenna with controllable band notches for UWB cognitive radio applications

This paper presents a planar antenna for employment in overlay and underlay ultra-wideband cognitive radio (UWB-CR). The antenna can be operated as ultra-wideband, for underlay CR and for sensing in the overlay CR. When used in the overlay CR mode, the proposed antenna can selectively have one, two or three notches in the WLAN, WiMAX, and U-NII bands, to prevent interference to primary users operating in these bands. The band notches are induced using complementary split-ring resonators (CSRRs), and are controlled using three electronic switches mounted over the CSRRs.

Reconfigurable Microstrip Antennas for Cognitive Radio

According to the current spectrum allocation regulations, specific bands are assigned to particular services, and only licensed users are granted access to licensed bands. Cognitive radio (CR) is expected to revolutionize the way spectrum is allocated. In a CR network, the intelligent radio part allows unlicensed users (secondary users) to access spectrum bands licensed to primary users, while avoiding interference with them.

Design and ground plane consideration of a CPW-fed UWB antenna

In this paper, a novel ultrawideband (UWB) antenna with co-planar waveguide (CPW) feed is presented. The antenna is based on an egg-shaped conductor printed on a 30×40 mm2 FR4 substrate of 1.6-mm thickness. Two configurations of the antenna are studied. In the first, the ground plane features a large egg-shaped slot, and in the second, the ground plane is partial and rectangular in shape. The measured and computed return loss responses are given. Other characteristics of the antenna are computed using a finite-element-based EM solver. The radiation patterns, peak gain, and radiation efficiency of both configurations are presented and compared. The results show that the design based on the large slot yields better omnidirectional patterns and higher gains in the principal planes. The second design has slightly larger radiation efficiencies, and larger peak gains at high frequencies.

Antenna array design using spreadsheets

This paper presents a spreadsheet method for the design and analysis of antenna arrays. The method exploits the familiarity of modern spreadsheets programs to a wide variety of computer users and offers them a quick and user friendly means to design and study the characteristics and performance of several classes of linear arrays. It is useful for educational purposes since it does not require writing computer programs nor access to advanced antenna design packages. The procedure is briefly described, and examples illustrating its use with uniform, binomial, and Chebyshev arrays are presented. Linear and polar array factor plots are generated, and estimates of the directivity and the half-power beamwidth are also obtained.

Tunable Filter-Antennas for Cognitive Radio Applications

In this paper, frequency-tunable microstrip antennas, for cognitive radio applications, are proposed. The approach is based on electrically tuning the antennas operating frequency by integrating reconflgurable band pass fllters into wideband antenna structures. The design of an open loop resonator (OLR)-based bandstop fllter, and its transformation to a bandpass fllter, are investigated flrst. Then, the incorporation of the bandpass fllter, with a wideband antenna, is detailed. The same methodology is employed to design cognitive radio pattern and polarization diversity tunable fllter-antennas. A good agreement between the simulated and measured results for the difierent fabricated prototypes is attained.