Youssef Tawk

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Reconfigurable antennas, with the ability to radiate more than one pattern at different frequencies and polarizations, are necessary in modern telecommunication systems. The requirements for increased functionality (e.g., direction finding, beam steering, radar, control, and command) within a confined volume place a greater burden on today's transmitting(More)
This communication presents a new antenna system designed for cognitive radio applications. The antenna structure consists of a UWB antenna and a frequency reconfigurable antenna system. The UWB antenna scans the channel to discover “white space” frequency bands while tuning the reconfigurable section to communicate within these bands. The(More)
This paper discusses the fundamental principles of a cognitive-radio RF system. The key points required to achieve a true cognitive-radio device are outlined. The operation of a cognitive-radio system is mainly divided into two tasks. In the first task, a cognitive-radio device searches and identifies any part of the spectrum that is not occupied. The(More)
The advancement in wireless communications requires the integration of multiple radios into a single platform to maximize connectivity. In this paper, the design process of reconfigurable antennas is discussed. Reconfigurable antennas are proposed to cover different wireless services that operate over a wide frequency range. They show significant promise in(More)
This letter details a new reconfiguration technique for implementing frequency-tunable bandpass filters. This is achieved by changing the filter total capacitance via an integrated varactor within its structure. The reconfigurable bandpass filter is then incorporated within the feeding line of a printed antenna to form one structure. This combination allows(More)
This study presents new antenna schemes suitable for cognitive radio communications. The antenna structures consist of a ultra wide band (UWB) sensing antenna, and a frequency reconfigurable communicating antenna both incorporated into the same substrate. Two different techniques to achieve the required frequency agility are proposed. The first one is based(More)
This paper presents a new reconfigurable mircrostrip antenna design approach. The approach is based on replacing the patch in a microstrip antenna by many open ended microstrip lines intersecting with each other with optimized lengths, widths and spacings. The antenna, built one line at a time, is composed of 8 intersecting microstrip lines. A 50 Ω(More)
This letter presents a new antenna design suitable for cognitive radio communication. It consists of two structures incorporated together into the same substrate. The first structure is an ultrawideband (UWB) antenna covering the spectrum from 3.1-11 GHz for channel sensing. The second structure is a frequency reconfigurable triangular-shaped patch for(More)
This letter presents a novel frequency reconfigurable antenna design using photoconductive silicon elements as optical switches. By illuminating these silicon elements with light of suitable wavelength, their physical properties can be altered from that of a semiconductor to almost metal-like, which in turn alters the radiation properties of the antenna(More)
A cognitive radio front end using an optically pumped reconfigurable antenna system (OPRAS) is investigated. The scheme consists of a ultrawideband antenna and a reconfigurable narrowband antenna in close proximity to one another. The narrowband reconfigurability is achieved by a integrating laser diodes within the antenna structure to control the switching(More)