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Antennas and Propagation Magazine, IEEE

Issue 1 • Date Feb. 2014

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Displaying Results 1 - 25 of 63
  • [Front cover]

    Publication Year: 2014 , Page(s): c1
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  • [Front inside cover]

    Publication Year: 2014 , Page(s): c2
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  • Table of contents

    Publication Year: 2014 , Page(s): 3 - 5
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  • [Copyright notice]

    Publication Year: 2014 , Page(s): 5
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  • Information for contributors

    Publication Year: 2014 , Page(s): 6
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  • Magazine staff

    Publication Year: 2014 , Page(s): 7 - 10
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  • AP-S officers and Administrative Committee

    Publication Year: 2014 , Page(s): 11
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  • Editor's comments: 30 Years and Gone

    Publication Year: 2014 , Page(s): 12, 301 - 303
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  • President's message

    Publication Year: 2014 , Page(s): 12 - 13
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  • Changes of address or delivery problems

    Publication Year: 2014 , Page(s): 13
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  • Getting the magazine by air freight

    Publication Year: 2014 , Page(s): 13
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  • Revisiting the generation of cross-polarization in rectangular patch antennas: A near-field approach

    Publication Year: 2014 , Page(s): 14 - 38
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (7779 KB) |  | HTML iconHTML  

    In this work, the cross-polarized radiation from a rectangular patch antenna was studied as a consequence of the asymmetries (or disturbances) in the near field of the antenna. It was shown that the asymmetry of the probe location results in asymmetry in the near fields in the vicinity of the antenna, causing high cross-polarized radiation in the H plane of the antenna. These near-field disturbances show a varying trend with the variation of the frequency or dimensional parameters of the antenna, which ultimately affects the far-field cross-polarized radiation. Having developed the near-field model of the cross-polarized radiation, this approach is then applied to two important known configurations with low cross-polarized radiation, namely, differential feeding (for a single patch antenna) and rotational feeding (for an array antenna). The new approach presented here provides an insightful, visualization-based understanding of the cross-polarized radiation from a rectangular patch antenna. View full abstract»

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  • On reflector feeds with unidirectional axially symmetric radiation patterns: Their cross-polarization performance and efficiencies

    Publication Year: 2014 , Page(s): 39 - 61
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (15117 KB) |  | HTML iconHTML  

    The performance and radiation mechanisms of feed antennas with unidirectional axially symmetric radiation patterns are investigated in detail. Radiating circular apertures, electric-magnetic dipole pairs, and two-element elliptical dipole arrays are discussed. The performance metric considers both the maximum cross-polarization level and the efficiency performance when evaluated on a general reflector system with various focal-length-to-aperture-diameter (F/D) ratios. The axial symmetry and cross-polarization performance are strongly dependent on a complementary or higher-order mode being present. For the three classes of feeds investigated, equivalent performances can be achieved with the maximum cross-polarization levels below -40 dB, and the maximum asymmetry below 0.3 dB. Apertures perform the best in terms of symmetry, and electric-magnetic dipole pairs perform the worst. It is shown that for a two-element dipole array to achieve optimum performance, the dipoles need to be perfectly circular, and the dipole lengths need to be longer than a half-wavelength, to allow for a second-order current mode to coexist with the fundamental mode. View full abstract»

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  • Multimode beamforming networks for space applications

    Publication Year: 2014 , Page(s): 62 - 78
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (9160 KB) |  | HTML iconHTML  

    Increased demand for narrow multi-linguistic beams, and a reduction in the number of antennas for multi-spot systems, are revitalizing the need for lossless multimode networks at various frequencies. This paper reviews basic concepts, techniques, and technologies of multimode beamforming networks for satellite multiple beams and reconfigurable antennas. View full abstract»

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  • Advances in antenna designs for UHF RFID tags mountable on conductive items

    Publication Year: 2014 , Page(s): 79 - 103
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (5033 KB) |  | HTML iconHTML  

    The design of antennas for metal-mountable radio-frequency identification tags is driven by a unique set of challenges: cheap, small, low-profile, and conformal structures need to provide reliable operation when tags are mounted on conductive platforms of various shapes and sizes. During the past decade, a tremendous amount of research has been dedicated to meeting these stringent requirements. Currently, the tag-reading ranges of several meters are achieved with flexible-label types of tags. Moreover, a whole spectrum of tag-size performance ratios has been demonstrated through a variety of innovative antenna-design approaches. This article reviews and summarizes the progress made in antennas for metal-mountable tags, and presents future prospects. View full abstract»

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  • Microwave imaging using indirect holographic techniques

    Publication Year: 2014 , Page(s): 104 - 117
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3081 KB) |  | HTML iconHTML  

    This work describes how indirect holographic techniques, previously applied to the determination of antenna radiation patterns, can be adapted for the imaging of passive objects. It provides details of how complex scattered field values can be obtained in a simple and inexpensive manner from sampled scalar intensity measurements taken over a single scanning aperture. This work provides a brief outline of the basic theory of indirect microwave holography, and how the transformation of the holographic intensity pattern into the Fourier domain enables the isolation of the terms required for complex field reconstruction to be isolated from the remaining terms. The work is supported by a range of experimental results, illustrating the reconstructed complex fields for a number of simple test objects. Back-propagation techniques have also been included to reconstruct complex fields at the position of the scattering objects. View full abstract»

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  • Optical transfer function (OTF) of a Rotman lens antenna for imaging applications

    Publication Year: 2014 , Page(s): 118 - 129
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2251 KB) |  | HTML iconHTML  

    This paper presents a new approach to analyzing a Rotman lens for imaging applications. The optical transfer function (OTF) is used to analyze the imaging capability of a Rotman lens. The variations in optical transfer function and the image pattern were calculated with variations in the design parameters due to beam-port spacing, antenna spacing, array size, and so on. As a result, it was found that the cutoff frequency corresponds to the array size in λ , and the resolution is the inverse of the cutoff frequency. The beam-port spacing should be narrow enough to avoid aliasing. For a typical design in which the antenna spacing is λ/2 and the scanning angle is from -45° to 45°, the number of beam ports should be π/2 times greater than the number of array ports to avoid aliasing, and the antenna spacing should be less than 0.707λ to avoid grating lobes. For the first time, a Rotman lens has been analyzed in terms of the optical transfer function. As a result, important criteria for designing a Rotman lens are presented for imaging applications. This analysis will provide guidance to the design and estimation of a focal-plane antenna array, as well as a Rotman lens for imaging and sensing applications. View full abstract»

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  • A comparison of perturbation formulas for a square electromagnetic resonator

    Publication Year: 2014 , Page(s): 130 - 142
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2192 KB) |  | HTML iconHTML  

    Several perturbation formulas are available for the resonant frequency of an electromagnetic cavity subjected to shape and material perturbations. Each is based on a mathematical identity from vector calculus, a choice of trial fields, and the manner in which the boundary conditions are met. The limits of usefulness of a given perturbation formula depend on these factors. Slater proposed a perturbation formula for the resonant frequency of cavities that maintained currency for a long time. However, what remained obscure was that Dombrowski also proposed a perturbation formula, making a correction to that of Slater. A critical performance comparison of various perturbation formulas for a fixed geometry was not undertaken during the time they were proposed, for want of an exact solution to validate their accuracy. They were assessed only in some landmark or limiting cases. Today, several efficient numerical packages are available, and the need for perturbation formulas is rather grim or even completely obviated. If there is any interest in revisiting these formulas, it is all the more a matter of curiosity until there comes a revival in this area. The aim of this tutorial is then to apply about five different perturbation formulas to the same geometry (in the present case, a square cavity perturbed in shape); to obtain a closed-form expression for each; and to compare the limits of their accuracy. The performance of these formulas is rated with the help of commercially available HFSS software, using the eigenmode solver, both visually by plotting, and also using a power series. Along with these formulas, a new heuristic perturbation formula is proposed in this paper, which ranks number one among all of these in terms of accuracy as far as the present geometry is concerned. View full abstract»

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  • Advertisement

    Publication Year: 2014 , Page(s): 143
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  • Chapter news

    Publication Year: 2014 , Page(s): 144 - 151
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  • XVIIIth International Seminar/Workshop DIPED-2013

    Publication Year: 2014 , Page(s): 152 - 154
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    Publication Year: 2014 , Page(s): 155
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  • Comment on the definition of antenna half-power and impedance-matching bandwidths [antenna designer's notebook]

    Publication Year: 2014 , Page(s): 156 - 158
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    There are two antenna-bandwidth def nitions that are sometimes confused. These def nitions are for the antenna half-power bandwidth (HPBW) and the antenna impedance-matching bandwidth (IMBW). These are def ned below. View full abstract»

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  • Advertisement

    Publication Year: 2014 , Page(s): 159
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  • Three-dimensional position and orientation measurements using magneto-quasistatic fields and complex image theory [measurements corner]

    Publication Year: 2014 , Page(s): 160 - 173
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (13230 KB)  

    Traditional wireless position-location systems, operating using propagating waves, suffer reduced performance in non-line-of-sight (NLoS) applications. Traditional systems that use quasistatic fields have instead been limited to short ranges, progressive direction-finding applications, require RF fingerprinting, or do not provide complete immunity to dielectric obstacles (use of electric fields). These limitations impose severe restrictions in applications such as tracking an American football during game play, where position and orientation tracking may be required over long ranges, and when the line-of-sight (LoS) is blocked by groups of people. A technique using magneto-quasistatic fields and complex image theory was recently shown to circumvent these problems, and to enable accurate long-range one-dimensional and two-dimensional measurements. In this work, we present three-dimensional position and orientation measurements using the magneto-quasistatic system and complex image theory over an area of 27.43 m × 27.43 m. Inverting the theoretical expression for the voltage measured at the terminals of the receiving loops to determine three-dimensional position and orientation resulted in mean and median geometric position errors of 0.77 m and 0.71 m, respectively; inclination orientation mean and median errors of 9.67° and 8.24°, respectively; and azimuthal orientation mean and median errors of 2.84° and 2.25°, respectively. 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