Karim Y. Kabalan

The Analysis of a Reconfigurable Antenna With a Rotating Feed Using Graph Models

This letter investigates a new reconfigurable antenna technique based on the rotation of a slot. The surface currents are redistributed for each slot position. The antenna is simulated, fabricated, and tested. The return loss frequency tuning matches the simulated data. The antenna radiation pattern remains unchanged for different slot positions. Finally, the process for automatic rotation and control of the slot is investigated using graph models.

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.

Characteristic modes for slots in a conducting plane, TE case

Consider an infinitely long slot in a perfectly conducting plane in an unbounded medium illuminated by a uniform transverse electric (TE) (to the slot axis) plane wave. The theory of characteristic modes for apertures is applied to solve the problem. For a narrow slot, analytic expressions for the first two characteristic currents and the equivalent magnetic current are given. As computed by the method of moments, numerical results for the characteristic currents and fields, the equivalent magnetic current, and the transmitted field pattern are presented for the slot whose width is one wavelength.

New Multi-Band Microstrip Antenna Design for Wireless Communications

This paper presents a new approach for the design of a multi-wideband microstrip-patch antenna. The radiating elements in this antenna are composed of rectangular slots following a Chebyshev distribution of order 10 around a center rectangular slot, and an additional triangular slot. These slots are engraved in the rectangular and triangular patch, joined together in one structure, and fed by one probe feed. A sample antenna was analyzed, simulated, fabricated, and tested. There was good agreement between the computed and test results. The new antenna can be used for several applications, especially in the GSM domain, and for Wi-Fi, Bluetooth, and several other applications, as detailed in this paper.

Characteristic modes of a slot in a conducting cylinder and their use for penetration and scattering, TE case

A characteristic mode theory for slots in a circular conducting cylinder is given for calculating the characteristic magnetic currents, the equivalent magnetic current, the radiation patterns, and the fields everywhere (especially in the aperture region) of an infinitely long thin perfectly conducting cylinder with an infinitely long slot. The characteristic modes are obtained from the solution of an eigenvalue equation representing the continuity of the tangential component of the magnetic field in the slot. >

A spreadsheet simulation of logic networks

The authors present a method for simulating logic networks using spreadsheets. This method may be used to simulate combinational, sequential, synchronous and asynchronous networks. The characteristics of the method make it significant as an important tool in the analysis, design and test logic networks in education environments. >

Characteristic mode analysis of a slot in a conducting plane separating different media

The authors analyze a slot in a conducting plane separating different media when the slot is illuminated by a transverse electric and a transverse magnetic plane wave. The general characteristic mode theory for different media is used for the solution of this problem. The characteristic modes, which are computed using the method of moments, provide numerical results for the characteristic currents, the equivalent magnetic currents, and the field pattern for a slot whose width is a function of the wavelength. Analytical expressions for the narrow slot are also given. >

Characteristic modes of a rectangular aperture in a perfectly conducting plane

The objective of the paper is the analysis of a rectangular aperture in a perfectly conducting plane using the characteristic mode theory. The problem is first formulated as an operator equation involving the continuity of the tangential components of the magnetic field in the aperture region. The operator equation is used, with the help of the moment method, to determine the eigenvalues, eigencurrents, and the characteristic magnetic currents of the aperture. When these modes are determined, the equivalent magnetic current and other parameters of interest can then be obtained. >

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.

Blind spectrum sensing using symmetry property of cyclic autocorrelation function: from theory to practice

Spectrum sensing has been identified as the key step of the cognition cycle and the most important function for the establishment of cognitive radio. In this paper, a blind cyclostationary feature detector, which is based on the symmetry property of cyclic autocorrelation function (SP-CAF), is implemented and tested using universal software radio peripheral platform and GNU Radio open-source software development toolkit. Performance of the SP-CAF is compared to the classical energy detector via various tests conducted in real scenarios where both detection algorithms are employed to blindly sense the spectrum for opportunistic access. This study shows that the blind cyclostationary feature detector outperforms the classical energy detector while guaranteeing acceptable complexity and low sensing time. Moreover, different experimental results indicate that the blind sensing detector can achieve high detection probability at a low false alarm probability under real channel conditions and low signal-to-noise ratio.