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Antennas and Propagation Magazine, IEEE

Issue 6 • Date Dec. 1997

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  • 50 years of radio-scintillation observations

    Publication Year: 1997 , Page(s): 7 - 12
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (728 KB)  

    The author attempts a brief summary of the history of ionospheric fading from sources beyond the upper atmosphere. The concentration is on the early studies of scintillation. The first sources used as transmitters were radio stars with varying diameters. With the advent of satellite transmissions at altitudes varying from 300 km to several Earth radii, fading was studied as a function of various regions of the globe. In years of high solar flux, transionospheric propagation through polar and equatorial regions has experience deep fading at frequencies ranging from 54 MHz to 4 GHz. Fading of radio signals from satellites still plays a role in evaluating operational and proposed system effectiveness. The relevance of these studies to Global Positioning System reception and users of proposed systems at L band is discussed. View full abstract»

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  • Open Electromagnetic waveguides [Reviews and Abstracts]

    Publication Year: 1997 , Page(s): 66 - 67
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    Freely Available from IEEE
  • Antenna Engineering Using Physical Optics

    Publication Year: 1997 , Page(s): 67 - 68
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (292 KB)  

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  • EMC Analysis Methods And Computational Models

    Publication Year: 1997 , Page(s): 68 - 70
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    First Page of the Article
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  • Amplitude aperture-distribution control in displaced-axis two-reflector antennas

    Publication Year: 1997 , Page(s): 58 - 63
    Cited by:  Papers (1)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (556 KB)  

    A design method for improving the efficiency and reduction of sidelobes in displaced-axis two-reflector antennas is presented. The method is based on an analysis of the geometrical-optics field transformation in the displaced-axis two-reflector arrangement. The principal difference of the displaced-axis antenna from the Cassegrain/Gregory two-reflector antenna is pointed out. While decreasing the level of illumination of the subreflector edge in the Cassegrain/Gregory antenna leads to decreasing the sidelobe levels, and, respectively, the efficiency of the antenna system, in the displaced-axis antenna, decreasing the level of illumination of the subreflector leads to an increased level of sidelobes and an essentially nonuniform amplitude distribution in the aperture. The aperture-amplitude-distribution dependence of the illumination level of the subreflector edge in displaced-axis antennas is much stronger than in Cassegrain/Gregory antennas View full abstract»

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  • Dual-frequency patch antennas

    Publication Year: 1997 , Page(s): 13 - 20
    Cited by:  Papers (84)  |  Patents (39)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1052 KB)  

    Dual-frequency patch antennas may provide an alternative to large-bandwidth planar antennas, in applications in which large bandwidth is really needed for operating at two separate transmit-receive bands. When the two operating frequencies are far apart, a dual-frequency patch structure can be conceived to avoid the use of separate antennas. In this paper, a critical overview of possible solutions for dual-frequency patch antennas is presented, and future perspectives are outlined. Geometries are discussed in particular View full abstract»

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  • CADDRAD: a physical optics radar/radome analysis code for arbitrary 3D geometries

    Publication Year: 1997 , Page(s): 73 - 79
    Cited by:  Papers (20)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1000 KB)  

    CADDRAD is a radar/radome analysis code meant to aid in the design of modern radar radomes on aircraft. Arbitrary radome shapes may be input in a standard format used by computer-aided-design software. Multi-layered radomes, with thickness tapers in all layers, may be used. The radar may be either electronically or mechanically scanned. The underlying theory implemented in the code is discussed. Comparisons are shown between measurements and predictions of reflection lobes, beam peak loss, and boresight error View full abstract»

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  • The complementary operators method in FDTD simulations

    Publication Year: 1997 , Page(s): 33 - 45
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1132 KB)  

    The complementary operators method (COM) was developed for the purpose of canceling the reflections that arise from the artificial boundaries that terminate the computational domain in FDTD simulations. This article presents a discussion and an evaluation of COM. The theoretical background is developed in the analytical and discretized domains. Five numerical experiments are presented to show the effectiveness and high efficiency of COM. Applications to antenna radiation and absorbing boundary conditions are discussed View full abstract»

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  • The analogy between the Butler matrix and the neural-network direction-finding array

    Publication Year: 1997 , Page(s): 27 - 32
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (576 KB)  

    The Butler matrix and the neural network have been compared to provide insights about the neural-network behavior for a direction-finding array. The goal of the paper has been tutorial, since the two systems are only really comparable in the very limited case considered: an ideal array with equal element spacings, no failures, and using the orthogonal beam locations as training points. Within the constraints of this specialized case, the comparison illustrates the role of pre- and post-processing, the function of the Gaussian radial basis function, and the considerations in determining the weights applied to the Gaussian or modified sine function node outputs. In addition, the comparison points out the basic similarity of the two procedures, and reveals some insights about the operation of a neural network from the perspective of antenna engineering View full abstract»

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  • Illustrating vector fields with the use of symbols

    Publication Year: 1997 , Page(s): 21 - 26
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (660 KB)  

    Three-dimensional vector fields in a waveguide can be graphically represented, on a printed page, by a set of symbols that indicate both the direction and the intensity of the field. These miniature symbols are placed at equidistant points across the plane of illustration. The representation can be created with personal computers, and is suitable for reproduction in scientific publications. The advantages of such representation is that it can be automatically generated by a simple computer program, and that it does not require the use of color prints 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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Mahta Moghaddam