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Antennas and Propagation Magazine, IEEE

Issue 4 • Date Aug. 2007

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Displaying Results 1 - 25 of 67
  • Front cover - IEEE Antennas and Propagation Magazine

    Page(s): 1
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  • Table of contents

    Page(s): 3
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  • Information for Contributors

    Page(s): 4
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  • Magazine Staff

    Page(s): 5 - 6
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  • AP-S Officers and Administrative Committee

    Page(s): 7
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  • Editor's Comments

    Page(s): 238 - 241
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  • President's Message

    Page(s): 8 - 9
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  • 2008 IEEE International Symposium on Antennas and Propagation - Call for papers

    Page(s): 10
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  • Instructions for AP-S and URSI Authors

    Page(s): 11
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  • The Incremental Far Field and Degrees of Freedom of the Sinusoidal Current Filament

    Page(s): 13 - 21
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (5786 KB) |  | HTML iconHTML  

    From where radiation originates for a specified current source or PEC boundary seems not to be as well-understood or agreed-upon as many other aspects of electromagnetics. Two propositions are explored in this article that relate to this issue. One is that if some incremental portion of a source distribution increases (changes) the total far field at any observation angle, then by definition radiation originates from that portion of the source distribution. The other is that the greater the number of degrees of freedom in a radiation pattern, the greater will be the proportion of the source distribution that actually radiates. These issues are explored here in terms of the radiation from a sinusoidal current filament. View full abstract»

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  • Investigations into Operation of Single- and Multi-Layer Configurations of Planar Inverted-F Antenna

    Page(s): 22 - 33
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (8420 KB) |  | HTML iconHTML  

    The paper presents a tradeoff analysis between single- and multi-layer (stacked) configurations of a planar inverted-F antenna (PFIA) of fixed overall height, with respect to achieving multi-band operation. The investigations focus on two bands, 800 to 1000 MHz and 1700 to 2600 MHz, which cover a frequency spectrum allocated to most of the present-day wireless systems operating below 2600 MHz. Folding and tapering of a conducting patch in the single-layer configuration, and increasing the number of conducting patches in the multi-layer layer (stacked) configuration, are used to achieve multi-band operation. The results obtained show that the stacked PIFA is able to generate many (four or more) bands within the investigated frequency spectrum. However, it faces difficulty in broadening them, as the coupling of upper plates to the ground is weakened by the presence of middle plates. At the same time, the tuning of one band adversely affects the other bands' performance. For the single-layer PIFA, the multi-band impedance characteristics are easier to adjust. A significant band widening can be obtained by proper arrangement of a conducting patch, and by introducing cuts or slits in the ground plane. In the designs presented, the antenna volume, measured by its outline, fell under 3 cm3. The resulting radiation efficiencies were 95% at the lower band (900 MHz), and 89% at the upper frequency range (2020 MHz). View full abstract»

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  • Particle-Swarm Optimization in Antenna Design: Optimization of Log-Periodic Dipole Arrays

    Page(s): 34 - 47
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (8855 KB) |  | HTML iconHTML  

    This paper presents a short tutorial and overview of optimization algorithms based on particle-swarm schemes, and their application to solving electromagnetic problems. As a practical example, a particle-swarm optimization (PSO) tool has been applied in conjunction with the Numerical Electromagnetics Code (NEC) to get the design curves of optimized log-periodic dipole arrays (LPDAs). The graphs show the performance of several radiation parameters (directive gain, front-to-back ratio, bandwidth, SWR, and half-power beamwidth in the E and H planes) as a function of typical design parameters of log-periodic dipole arrays (geometrical parameters and characteristics of the feed). Examples of optimized antennas are given, and their performance is compared to that of standard log-periodic dipole arrays. View full abstract»

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  • To All IEEE Life Members

    Page(s): 47
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (544 KB)  

    First Page of the Article
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  • Element Efficiency: A Unifying Concept for Array Antennas

    Page(s): 48 - 56
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (4759 KB) |  | HTML iconHTML  

    The antenna-element efficiency parameter quantifies the effect of mutual coupling in array antennas. In general arrays, this efficiency varies from element to element. The average value of these element efficiencies is a significant summary parameter, and plays a prominent role in circumscribing array performance. A useful formula gives the minimum number of antennas necessary to realize a prescribed peak gain envelope. The important special case of an array of identical elements situated in identical array environments is termed an idempotent array. In particular, an infinite idempotent array models a large planar array. There, the unique element efficiency has been directly related to the rms value of the conventional active reflection coefficient as it varies when the beam is (phased) electronically steered. The element-efficiency formulation also provides a framework for the rigorous derivation of important theoretical results in the theory of phased arrays. View full abstract»

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  • Low-Cost Broadband Circularly Polarized Printed Antennas and Array

    Page(s): 57 - 64
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (4723 KB) |  | HTML iconHTML  

    This paper presents the design, simulation, and measurements of two low-cost broadband circularly polarized (CP) printed antennas: an element and an array at 2 GHz. To realize the broadband circularly polarized antenna element, a circular microstrip patch is electromagnetically coupled by crossed slots cut in the ground plane, which is fed by an L-shaped microstrip feed. Two orthogonal modes in the patch are excited by using the crossed slots, and a single L-shaped feed provides a 90deg phase shift between two orthogonal slots. The antenna element achieves a 9.6% bandwidth for an axial ratio (AR) below 3 dB and a voltage standing wave ratio (VSWR) below 1.5. To further improve the performance, a sequentially rotated feed network is designed for a 2 times 2 array. The axial ratio value of the array is below 3 dB within a 27.2% bandwidth, from 1.75 GHz to 2.3 GHz. The return loss is above 10 dB within a 41% bandwidth, from 1.62 GHz to 2.45 GHz. Details of the proposed antenna element and the array design are described, and both the simulation and the experimental results are presented and discussed. View full abstract»

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  • The Development of a Cellular Phone Antenna with Small Irradiation of Human-Organism Tissues

    Page(s): 65 - 73
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    The method put forward here is to reduce undesirable irradiation using an auxiliary radiator of low power. Calculations show that an arrangement with an additional radiator reduces irradiation by a factor of three to four. The structure and magnitude of the field in the far zone preserve their quality of communication with the correspondents (base stations) in all directions. View full abstract»

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  • On Poynting's Theorem and Reciprocity Relations for Discontinuous Fields

    Page(s): 74 - 83
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    Poynting's theorem and reciprocity relations are investigated, based on the postulate that Maxwell's equations are always valid in the sense of distributions. Three special cases of practical importance in which the fields possess bounded discontinuities on simple (nonmaterial) and material interfaces between two different media are rigorously examined, incorporating the basic properties of the Heaviside unit step function and the Dirac delta distribution for multiple variables. View full abstract»

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  • Study of the Dynamics of Large Reflector Antennas with Accelerometers

    Page(s): 84 - 101
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (11566 KB) |  | HTML iconHTML  

    The Atacama Large Millimeter Array (ALMA) will consist of up to 64 state-of-the-art sub-mm telescopes, subject to stringent performance specifications that will push the boundaries of the technology, and makes testing of antenna performance a likewise challenging task. Two antenna prototypes were evaluated at the ALMA Test Facility at the Very Large Array site in New Mexico, USA. The dynamic behavior of the antennas under operational conditions was investigated with the help of an accelerometer system capable of measuring rigid-body motion of the elevation structure of the antenna, as well as a few low- order deformation modes. This resulted in dynamic performance numbers for pointing stability, reflector-surface stability, path-length stability, and structure flexure. Special emphasis was given to wind effects, one of the major factors affecting performance on timescales of seconds to tens of minutes. Although the accelerometers could not directly measure antenna performance on timescales longer than 10 seconds, it was possible to use them to derive antenna properties that allowed extrapolation of the wind-affected performance to timescales of 15 minutes and longer. This paper describes the accelerometer system, its capabilities and limitations, and presents the dynamic performance results of the two prototype antennas investigated. In addition to verification of the performance requirements, we investigated the vibration environment on the antennas, relevant for vibration-sensitive equipment for use on the ALMA antennas; the lowest eigenfrequencies for the antennas; and the sensitivity to vibration generated by similar antennas operating nearby. This work showed that seismic accelerometers can successfully be used for characterization of antenna dynamics, in particular when complemented with simultaneous wind measurements and measurements for static performance. The versatility of the accelerometers also makes them a valuable tool for troubleshooting of unforeseen- antenna features. View full abstract»

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  • AP-S Adcom Minutes

    Page(s): 102 - 109
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  • Chapter News

    Page(s): 110 - 113
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  • AP-S Distinguished Lecturer Program for 2006-2007

    Page(s): 114
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  • 2008 IEEE Antennas and Propagation Society - Membership application

    Page(s): 115
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  • Wheeler and Fano Impedance Matching [Antenna designer's notebook]

    Page(s): 116 - 119
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    A recent series of articles in this Magazine's Antenna Designer's Notebook column highlighted Fano's fundamental work on the limitations of the impedance matching of arbitrary impedances and its application to antenna design. Lopez, using Harold Wheeler's methodology, constructed a closed-form solution to the nonlinear simultaneous equations of Fano. This article presents the Wheeler methodology that was the basis for this work, and is still invaluable in the understanding of optimum impedance matching. View full abstract»

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  • In Memoriam: Edmond S. "Stan" Gillespie

    Page(s): 120 - 121
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Aims & Scope

The IEEE Antennas and Propagation Magazine covers all areas relating to antenna theory, design, and practice.

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Editor-in-Chief
W. Ross Stone