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Antennas and Propagation Magazine, IEEE

Issue 4 • Date Aug. 2008

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Displaying Results 1 - 25 of 62
  • Front cover - IEEE Antennas and Propagation Magazine

    Page(s): c1
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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): 8 - 233
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  • President's message

    Page(s): 8 - 9
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  • Call for papers

    Page(s): 10
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  • 2009 IEEE Antennas and Propagation Society membership application

    Page(s): 11
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  • Solving large complex problems using a higher-order basis: parallel in-core and out-of-core integral-equation solvers

    Page(s): 13 - 30
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (11557 KB) |  | HTML iconHTML  

    The future of computational electromagnetics is changing drastically with the new generation of computer chips, which are multi-cored instead of single-cored. Previously, advancements in chip technology meant an increase in clock speed, which was typically a benefit that computational code users could enjoy. This is no longer the case. In the new roadmaps for chip manufacturers, speed has been sacrificed for improved power consumption, and the direction is multi-core processors. The burden now falls on the software programmer to revamp existing codes and add new functionality to enable computational codes to run efficiently on this new generation of multi-core processors. In this paper, a new roadmap for computational code designers is provided, demonstrating how to navigate along with the chip designers through the multi-core advancements in chip design. A new parallel code, using the method of moments (MoM) and higher-order functions for expansion and testing, and executed on a range of computer platforms, will illustrate this roadmap. The advantage of a higher-order basis over a subdomain basis is a reduction in the number of unknowns. This means that with the same computer resources, a larger problem can be solved using higher-order basis than using a subdomain basis. The matrix filling for MoM with subdomain basis must be programmed with multiple loops over the edges of the patches to account for the interactions. However, higher- order basis functions, such as polynomials, can be calculated more efficiently with fewer integrations, at least for the serial code. In terms of parallel integral-equation solvers, the differences between these categories of basis functions must be understood and accommodated. View full abstract»

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  • Reflectarray research at the communications research centre Canada

    Page(s): 31 - 52
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (14758 KB) |  | HTML iconHTML  

    It has been a decade since a research program began on reflectarray technology at the Communications Research Centre Canada (CRC). This endeavor has demonstrated the advantages and shortcomings of this technology, the issues that ought to be addressed, and future opportunities. This paper summarizes the outcome of this research in the context of projects that have been carried out, and the resulting insight into reflectarray technology. Design methodology, fabrication process, and measurements results will be briefly discussed for each particular development. View full abstract»

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  • A phase shifter with one tunable component for a reflectarray antenna

    Page(s): 53 - 65
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (7599 KB) |  | HTML iconHTML  

    The combination of a dipole and a tunable varactor forms a phase shifter with one tunable component that provides a phase shift over a wide range, from 0deg to nearly 360deg. The dipole, loaded with a tunable varactor, is used as a patch component of a low-profile reflectarray antenna. An economic assessment shows that the production price of the suggested phase shifter with one tunable component is more than 10 times smaller than the price of the traditional phase shifter, based on p-i-n diode components. The design of such a phase shifter is the goal of this paper. Simulations of the phase shift and loss of the reflected wave as a function of control voltage applied to the varactor were used, based on an analytical model verified by fullwave analysis. The results of simulations are in agreement with measurements. The fast and correct simulation of the reflection coefficient from the dipole loaded with the tunable varactor can be used for the design and optimization of a low profile steerable reflectarray antenna. View full abstract»

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  • Maximum electric and magnetic field strengths at a given distance from some ideal antennas

    Page(s): 66 - 71
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (4012 KB) |  | HTML iconHTML  

    This paper is about the computation of the maximum electric and magnetic field strengths at a given distance of an antenna, close to the antenna, the maximum being taken over all orientations. We provide closed-form expressions for the maximum field strengths produced in free space by three important ideal antennas: the electric Hertzian dipole, the magnetic Hertzian dipole, and the half-wave dipole. View full abstract»

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  • Prototype antenna elements for the next-generation TDRS enhanced multiple-access array

    Page(s): 72 - 83
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (8013 KB) |  | HTML iconHTML  

    This paper summarizes a study performed to produce prototype antenna elements for the next-generation enhanced Tracking and Data Relay Satellite Continuation (TDRS-C) multiple-access (MA) S-band phased-array antenna. Compared to the multiple-access antenna on the current class of TORS, the enhanced multiple-access antenna requires elements that achieve greater on-axis gain, simultaneous circular polarization capability, and increased beamwidth. To demonstrate that array elements could be realized meeting these requirements, designs that were successful in simulation were fabricated and tested. These included a helical antenna; a novel short backfire antenna, excited with a circular waveguide (cup waveguide) with integrated polarizer and orthomode transducer (OMT); and a corrugated-horn antenna with integrated polarizer and OMVT. The paper describes the design process for the novel elements, and compares measured and simulated results. It also compares the elements in terms of performance, size, and mass. View full abstract»

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  • Development of separated turnstile antenna for space applications

    Page(s): 84 - 93
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (5869 KB)  

    Dual-band operation and circular polarization are the main characteristics of the separated turnstile (ST) antenna that make it suitable for space applications. In this paper, we describe the design and optimization of a separated turnstile antenna to obtain a saddle-shaped pattern in the UHF band and an omnidirectional pattern in the VHF band, with simultaneous impedance matching in both bands. The antenna model and the effects of the body of the satellite and the solar panels were analyzed using the Moment Method. The effects of the physical parameters of the antenna on the radiation pattern, such as the length of the monopoles and their mounting angle, were investigated. A radio-frequency distribution unit - which included a diplexer, phase shifters, and a power divider/combiner for both bands - was also designed, analyzed, and measured. The test results agreed with the analysis results. The axial ratio and polarization efficiency of this antenna were calculated for incident waves with different polarizations. The antenna was fabricated and its radiation parameters were measured. The test results were compared with the analysis results to confirm the correctness of the design. View full abstract»

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  • Numerical analysis of dielectric lens antennas using a ray-tracing method and HFSS software

    Page(s): 94 - 101
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (4174 KB)  

    In this paper, we use for the first time the ray-tracing method combined with the HFSS software to analyze lens antennas. HFSS is a very popular commercial tool that can provide very accurate results for the simulation of antennas. However, because of limitations on computational resources, it is hard to apply to solving large electromagnetic problems. In this paper, HFSS is used to simulate the fields of the feed part of a lens antenna. The ray tracing method is adopted for the lens part. This treatment makes the combined method feasible for solving large lens antennas. In using the ray-tracing method, cubicspline interpolation is exploited to fit the face of the lens and to solve for the derivatives at each point on the curved surface. Newton's method is applied to find the intercept between the ray and the curved surface. The numerical method proposed in this paper is very suitable for the analysis of dielectric lens antennas with arbitrary feeds and lens shapes. The validity of the idea is demonstrated by comparing the simulation results of this new method with those from using CST (Computer Simulation Technology) software. Very good agreement is achieved. View full abstract»

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  • National Radio Science Meeting

    Page(s): 102
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  • Chapter news

    Page(s): 104 - 106
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  • Call for papers ANTEM/URSI 2009

    Page(s): 107
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  • The SUMMA Graduate Fellowships in Advanced Electromagnetics

    Page(s): 108
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  • AP-S Distinguished Lecturer Program

    Page(s): 109 - 110
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  • Revisiting medium-wave ground-system requirements

    Page(s): 111 - 114
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    The classic 1937 paper by Brown, Lewis, and Epstein [1] outlined the necessity for a proper ldquoimaging screenrdquo or ldquoground systemrdquo for efficient operation of a vertically polarized monopole antenna. While Brown et al. showed the effects of various configurations, they did not exhaustively examine the effects of successive reductions of the number of radials, particularly in systems with radial lengths less than 90". Furthermore, their measurements were made at 3 MHz, and were not corrected for the frequency scaling. Recent experimental work, undertaken for a US Department of the Navy laboratory to optimize the performance of temporary medium-wave antenna installations, showed that for surface-mounted radial systems with radials 90" or shorter, both radial length and the number of radials are significant. Property availability for siting of antennas at medium-wave frequencies often results in truncation or other restrictions on radial length. The results of this study provide a guide to the practical limits on such restrictions, as well as data on the resulting efficiency reductions. View full abstract»

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  • Report on the 2008 AP-S Symposium student paper contest

    Page(s): 116
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  • Announcement and call for papers

    Page(s): 117
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  • Practical uncertainty of pulse power measurements in Ka-band RCS instrumentation

    Page(s): 120 - 125
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    The output level of pulsed radar transmitter and receiver test sets can be defined with spectrum analyzers and diode detectors. Modern analyzers, which have 10 MHz or wider resolution bandwidths and cover appropriate input frequency ranges, can be used in the Ka- and V-band radar domains for pulse widths above about 200 ns. A practical uncertainty of 2 dB is obtainable. External mixers seem to show larger-level discrepancies, up to 5 dB, and may give only 20 dB of dynamic range. Their conversion loss may vary by 8 dB over just 500 MHz. Diodes work at higher power levels, but rise-time definitions are complicated. Above -15 dBm input levels, we can get uncertainties comparable to spectrum analyzers, but the true dynamic range can be just 15 dB, and temperature effects may hamper outdoor trials. Below 200 ns pulse widths, radar-receiver test-generator level calibration remains very challenging in the millimeter-wave bands due to inadequate sensitivity, regardless of the measuring instrumentation. View full abstract»

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Aims & Scope

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

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
W. Ross Stone