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Antennas and Propagation Magazine, IEEE

Issue 4 • Date Aug. 1997

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  • Microstrip Antennas, [Book Review]

    Publication Year: 1997 , Page(s): 76 - 77
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    Freely Available from IEEE
  • Integrated Active Antennas and Spatial Power Combining, [Book Review]

    Publication Year: 1997 , Page(s): 77
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    Freely Available from IEEE
  • In Memoriam: Jim Brittingham

    Publication Year: 1997 , Page(s): 80
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    Freely Available from IEEE
  • Modern Radio Science, [Book Review]

    Publication Year: 1997 , Page(s): 77
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    Freely Available from IEEE
  • Comparison of three FMM techniques for solving hybrid FE-BI systems

    Publication Year: 1997 , Page(s): 47 - 60
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1192 KB)  

    By virtue of its low operation count, the application of the fast multipole method (FMM) results in a substantial speed-up of the boundary-integral (BI) portion of the hybrid finite-element/boundary-integral technique, independent of the shape of the BI contour. Previously, various versions of the fast multipole method have been proposed, each introducing a different approximation to the implementation of the boundary integral. The main goal of this paper is to provide a comparison of the various FMM approaches on the basis of implementation, CPU time, and accuracy. To gain an appreciation of the differences among the various FMM methodologies, a large portion of the paper is devoted to a discussion of the algorithms at a tutorial level. Flow charts and pseudo-code are also given, at sufficient detail to facilitate their implementation. We present quantitative CPU and memory requirements, using the scattering by a groove as the basis for comparison, and conclude that the FMM can accelerate the BI computation without any significant deterioration in accuracy. A simpler FMM-based algorithm results in a much smaller execution time but has a larger error. However, it turns out that a third algorithm, designated the “windowed” FMM, provides a very good compromise with respect to error and execution time. The paper concludes with the presentation of some three-dimensional applications for which a hybrid FE-BI technique, in conjunction with a fast-integral algorithm, is well suited View full abstract»

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  • Genetic algorithms in engineering electromagnetics

    Publication Year: 1997 , Page(s): 7 - 21
    Cited by:  Papers (210)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1860 KB)  

    This paper presents a tutorial and overview of genetic algorithms for electromagnetic optimization. Genetic-algorithm (GA) optimizers are robust, stochastic search methods modeled on the concepts of natural selection and evolution. The relationship between traditional optimization techniques and the GA is discussed. Step-by-step implementation aspects of the GA are detailed, through an example with the objective of providing useful guidelines for the potential user. Extensive use is made of sidebars and graphical presentation to facilitate understanding. The tutorial is followed by a discussion of several electromagnetic applications in which the GA has proven useful. The applications discussed include the design of lightweight, broadband microwave absorbers, the reduction of array sidelobes in thinned arrays, the design of shaped-beam antenna arrays, the extraction of natural resonance modes of radar targets from backscattered response data, and the design of broadband patch antennas. Genetic-algorithm optimization is shown to be suitable for optimizing a broad class of problems of interest to the electromagnetic community. A comprehensive list of key references, organized by application category, is also provided View full abstract»

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  • Asymmetrical vertical-dipole antennas for MF AM transmitting revised

    Publication Year: 1997 , Page(s): 69 - 73
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    A number of comments are included which will provide the reader with new insights about feeding antennas over soil and, generally, feeding antennas against limited ground planes. Trainotti (see ibid., vol.35, p.47-50, 1993, vol.38, p.75-82, 1996, and IEEE Trans. on Broadcasting, vol.37, no.3, p.106-14, 1991) has published a series of interesting papers that show by detailed numerical modeling and measurement) that an antenna system that employs a dipole-type vertical radiator can be used as a MF broadcast antenna, without the 120 buried-radial-wire ground system, which is traditionally used. Certainly this is true. The author's basic problem with the published work of Trainotti has to do with certain statements made that can be wrongly interpreted. The intention here is clarify his understanding of this antenna system. The comments from Trainotti are also included View full abstract»

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  • Estimating the attenuation due to combined atmospheric effects on modern Earth-space paths

    Publication Year: 1997 , Page(s): 26 - 34
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (996 KB)  

    With the emergence of new satellite-communications systems operating in the Ka band, the role of atmospheric effects on propagation paths has gained increased significance. The impairing factors of rain have always been considered when designing links at above 10 GHz. However, water vapor, clouds, and oxygen, which were previously considered “secondary affects”, are now appearing to play a statistically significant part in the overall degradation of signal strength. A method for statistically combining all attenuators to provide a composite attenuation is now presented View full abstract»

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  • On the role of fractional calculus in electromagnetic theory

    Publication Year: 1997 , Page(s): 35 - 46
    Cited by:  Papers (24)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1272 KB)  

    We have applied the concept of fractional derivatives/integrals in several specific electromagnetic problems, and have obtained promising results and ideas that demonstrate that these mathematical operators can be interesting and useful tools in electromagnetic theory. We give a brief review of the general principles, definitions, and several features of fractional derivatives/integrals, and then we review some of our ideas and findings in exploring potential applications of fractional calculus in some electromagnetic problems View full abstract»

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  • Visualization with OpenGL: 3D made easy

    Publication Year: 1997 , Page(s): 116 - 120
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (724 KB)  

    This article addresses a freely available application programming interface (API) for three-dimensional graphics, known as OpenGL. This API bridges the gap between piles of raw data and extremely complicated three-dimensional animation in a way that requires only a few hours to learn. It is can be used for EM field visualization. In this article, we try to take most of the “leg-work” out of learning OpenGL, by presenting a tutorial that will get you started in the right direction. Some other interesting OpenGL-related technologies are also mentioned View full abstract»

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

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Editor-in-Chief
Mahta Moghaddam