By Topic

Antennas and Propagation, IEEE Transactions on

Issue 11  Part 1 • Date Nov. 2007

Filter Results

Displaying Results 1 - 25 of 31
  • Table of contents

    Page(s): C1 - 2941
    Save to Project icon | Request Permissions | PDF file iconPDF (41 KB)  
    Freely Available from IEEE
  • IEEE Transactions on Antennas and Propagation publication information

    Page(s): C2
    Save to Project icon | Request Permissions | PDF file iconPDF (40 KB)  
    Freely Available from IEEE
  • Guest Editorial for the Special Issue on Optical and THz Antenna Technology

    Page(s): 2942 - 2943
    Save to Project icon | Request Permissions | PDF file iconPDF (385 KB)  
    Freely Available from IEEE
  • Standoff Detection of Weapons and Contraband in the 100 GHz to 1 THz Region

    Page(s): 2944 - 2956
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (4486 KB) |  | HTML iconHTML  

    The techniques and technologies currently being investigated to detect weapons and contraband concealed on persons under clothing are reviewed. The basic phenomenology of the atmosphere and materials that must be understood in order to realize such a system are discussed. The component issues and architectural designs needed to realize systems are outlined. Some conclusions with respect to further technology developments are presented. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • THz Instruments for Space

    Page(s): 2957 - 2965
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (338 KB) |  | HTML iconHTML  

    Terahertz technology has been driven largely by applications in astronomy and space science. For more than three decades cosmochemists, molecular spectroscopists, astrophysicists, and Earth and planetary scientists have used submillimeter-wave or terahertz sensors to identify, catalog and map lightweight gases, atoms and molecules in Earth and planetary atmospheres, in regions of interstellar dust and star formation, and in new and old galaxies, back to the earliest days of the universe, from both ground based and more recently, orbital platforms. The past ten years have witnessed the launch and successful deployment of three satellite instruments with spectral line heterodyne receivers above 300 GHz (SWAS, Odin, and MIRO) and a fourth platform, Aura MLS, that reaches to 2520 GHz, crossing the terahertz threshold from the microwave side for the first time. The former Soviet Union launched the first bolometric detectors for the submillimeter way back in 1974 and operated the first space based submillimeter wave telescope on the Salyut 6 station for four months in 1978. In addition, continuum, Fourier transform and spectrophotometer instruments on IRAS, ISO, COBE, the recent Spitzer Space Telescope and Japan's Akari satellite have all encroached into the submillimeter from the infrared using direct detection bolometers or photoconductors. At least two more major satellites carrying submillimeter wave instruments are nearing completion, Herschel and Planck, and many more are on the drawing boards in international and national space organizations such as NASA, ESA, DLR, CNES, and JAXA. This paper reviews some of the programs that have been proposed, completed and are still envisioned for space applications in the submillimeter and terahertz spectral range. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • The ALMA Front End Optics—System Aspects and European Measurement Results

    Page(s): 2966 - 2973
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2118 KB) |  | HTML iconHTML  

    The Atacama large millimeter/submillimeter array (ALMA) is a radio telescope array with 50 Cassegrain style antennas that is currently being built in the Atacama desert in Chile. The telescopes are designed for a frequency range from 30 to 960 GHz with two orthogonal linear polarizations. Due to the extremely wide range, ten receivers are needed to cover the band, the divisions coinciding with the atmospheric windows. All receivers are built into a common cryostat on separate cartridges. The front end optics include the optical elements between the mixers and the secondary reflector. There are three different generic optical layouts. The two lower frequency bands use lenses that double as vacuum breaks. The next two frequency bands use ambient-temperature mirror systema and the upper six frequency bands have their complete optics cooled to cryogenic temperatures. In addition to the very demanding performance requirements, the optics design needs to take into account the constructional and operational aspects. As a large number of front ends will be built, the design must be robust with respect to mechanical and alignment tolerances. The exchange of receivers must be easy and should require as few alignments as possible. During operation, no mechanical adjustments are allowed. Measurement results are shown for the ALMA baseline bands. These measurements were made for single cartridges with the IRAM near-field measurement system and at SRON. The results of these measurements validate the design approach. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A 250 GHz Subharmonic Mixer Design Using EBG Technology

    Page(s): 2974 - 2982
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (937 KB) |  | HTML iconHTML  

    The design, manufacture and characterization of a sub-harmonic mixer operating in the millimeter wavelength range is described. The mixer combines for the first time electromagnetic band gap (EBG) technology (which improves the radiation features of the dipole antenna used to couple radiation to the mixer), with conventional local oscillator (LO) waveguide circuitry. The mixer is designed to operate in an RF frequency band around 250 GHz when supplied with a LO frequency between 115 and 135 GHz. The fixed IF frequency spans 2.5-3.5 GHz. Performance predictions were made using a combination of the finite elements (FE) method to compute the embedding impedance of the diodes and the harmonic balance analysis (HBA) to predict the noise temperature. A prototype mixer has been fabricated and tested. Best mixer performance (double side band (DSB) mixer noise temperature and conversion loss of 3000 K and 11.5 dB, respectively) was measured with a LO power level of about 5 mW. Good agreement is observed with the predicted performance. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Design and Demonstration of an Infrared Meanderline Phase Retarder

    Page(s): 2983 - 2988
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (974 KB) |  | HTML iconHTML  

    We compare design and measurements for a single-layer meanderline quarter-wave phase retarder, operating across the wavelength range from 8 to 12 micrometers (25 to 37.5 THz) in the infrared. The structure was fabricated using direct-write electron-beam lithography. With measured frequency-dependent material properties incorporated into a periodic-moment-method model, reasonable agreement is obtained for the spectral dependence of axial ratio and phase delay. As expected from theory, the single-layer meanderline design has relatively low throughput (23%), but with extension to multiple-layer designs, the meanderline approach offers significant potential benefits as compared to conventional birefringent crystalline waveplates in terms of spectral bandwidth, angular bandwidth, and cost. Simple changes in the lithographic geometry will allow designs to be developed for specific phase retardations over specified frequency ranges in the infrared, terahertz, or millimeter-wave bands, where custom-designed waveplates are not commercially available. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Phase Characterization of Reflectarray Elements at Infrared

    Page(s): 2989 - 2993
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (957 KB) |  | HTML iconHTML  

    The feasibility of a square-patch reflectarray element design is demonstrated at a frequency of 28.3 THz in the infrared (10.6 micrometer free-space wavelength) for the first time. Fabrication of arrays of various patch sizes was performed using electron-beam lithography, and the reflected phase as a function of patch size was characterized using an infrared interferometer. A numerical model for the design of these reflectarray elements was developed incorporating measured values of frequency-dependent material properties, and a comparison of computed and measured phase shows close agreement. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Substrate Integrated Image Guide Array Antenna for the Upper Millimeter-Wave Spectrum

    Page(s): 2994 - 3001
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (596 KB) |  | HTML iconHTML  

    A compact linear array antenna fed by substrate integrated image guide (SIIG) at 94 GHz is presented. The SIIG is a low-loss dielectric waveguide which is synthesized directly on a high dielectric constant substrate or semiconductor wafer. Such a low-cost approach of integration allows for the development of directive low profile antennas for future commercial millimeter-wave products. Special attention was directed towards the radiation elements that are fabricated in printed circuit technique on top of the SIIG. Their novel design provides a wide tuning range for the radiation coefficient and excellent linear polarization purity. In addition, an optimized reflection compensation technique effectively reduces the overall return loss and permits frequency scanning through broadside direction without suffering from a stop band due to distributed Bragg reflection. Published theory concerning the scan range of this class of frequency-scannable array antennas is extended in this work. Detailed design guidelines are given along with simulation and measurement results of a prototype. The 2 cm long implementation produced a fan beam with 11 dB gain. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Scattering Analysis for the Modeling of THz Communication Systems

    Page(s): 3002 - 3009
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1064 KB) |  | HTML iconHTML  

    Modeling propagation channels for future pico-cellular indoor THz communication systems requires the knowledge of the reflective properties of building materials. The reflectivity of smooth, optically thick materials can be modeled with Fresnel equations. In case of materials with a rough surface, diffuse scattering reduces the power reflected in the specular direction. Kirchhoff scattering theory can be employed to derive modified Fresnel equations which account for these losses by introducing a Rayleigh roughness factor calculated from the measured surface height distribution of the sample under observation. Using the resulting, analytically derived reflection coefficient based on material parameter and surface measurements in propagation models enables the simulation of arbitrary configurations. We present a set of calculated and measured reflection coefficients for a selection of common indoor building materials which are in good agreement, thus verifying our modeling approach. Furthermore, we illustrate by ray-tracing simulations the effect of wall and ceiling roughness on propagation in future indoor scenarios. Both, absolute power levels and propagation patterns are shown to be strongly influenced by scattering. In some cases, reflected transmissions with longer propagation paths can be more efficient than the shorter ones in terms of incurred losses. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A Monopole Antenna at Optical Frequencies: Single-Molecule Near-Field Measurements

    Page(s): 3010 - 3017
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2276 KB) |  | HTML iconHTML  

    We present a monopole antenna for optical frequencies (~600 THz) and discuss near-field measurements with single fluorescent molecules as a technique to characterize such antennas. The similarities and differences between near-field antenna measurements at optical and radio frequencies are discussed in detail. Two typical antenna properties, polarization selectivity and resonances, are studied for the optical monopole by direct near-field measurements and finite integration technique calculations. The antenna is driven by the local field of a sub-wavelength aperture. This gives rise to a dependence of the antenna response on the orientation of the local field vector, in an analogous way to the polarization selectivity of linear wire antennas. The antenna resonances are studied by varying the antenna length. Typical monopole resonances are demonstrated. The finite conductivity of metals at optical frequencies (in combination with the antenna radius) causes the wavelength of the surface charge density oscillation (surface plasmon polariton) along the antenna to be shortened in comparison to the free space wavelength. As a result, resonances for the optical monopole antenna occur at much shorter relative lengths than for conventional radio monopole antennas View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Core-Shell Nanowire Optical Antennas Fed by Slab Waveguides

    Page(s): 3018 - 3026
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (674 KB) |  | HTML iconHTML  

    A method of realizing nanoantenna systems at optical frequencies is suggested wherein a plasmonic nanowire is placed near a slab waveguide operating near the plasmonic resonant frequency of the nanowire. The polarizability of a nano-sized concentric cylindrical structure with the core made of an ordinary dielectrics and the shell made of a plasmonic material is calculated using Mie scattering theory. When such a core-shell nanowire is placed near a slab waveguide, the transverse magnetic (TM) surface wave guided by the waveguide can interact with the nanowire, and thus part of its energy is scattered into the open space. By reciprocity, under TM wave incidence, the induced dipole on the nanowire will launch a guided mode in the slab waveguide, thus converting part of the incident energy into the guided mode energy. A rigorous analytical treatment of the problem using the Green function of a dipole near a planar slab waveguide is developed, and the properties of such an optical antenna system are studied in detail. The finite element method is also utilized to demonstrate the idea directly. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Enhanced Directivity From Subwavelength Infrared/Optical Nano-Antennas Loaded With Plasmonic Materials or Metamaterials

    Page(s): 3027 - 3039
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3636 KB) |  | HTML iconHTML  

    Here, we explore theoretically the concept of enhanced directivity from electrically small subwavelength radiators containing negative-parameter materials, such as plasmonic materials with negative permittivity at THz, infrared and optical frequencies. In particular, we study higher order plasmonic resonances of a subwavelength core-shell spherical nano-antenna, and we analyze the near-zone field distributions and far-field radiation patterns of such a structure when it is excited by a small dipole source, demonstrating analytically and numerically the possibility of having highly directive patterns from a nano-structure with electrically small dimensions. Radiation characteristics and intrinsic limitations on performance are analyzed in detail, and a potential application of this novel technique for super-resolution detection of the displacement of a nano-object is also pointed out. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Measurement of Lightwave Antennas: Difficulties and Peculiarities in Comparison With Radio-Wave Antennas

    Page(s): 3040 - 3045
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (538 KB) |  | HTML iconHTML  

    A technique is described for measuring the far-field radiation pattern, gain, and the transmissivity of each portion of an aperture of lightwave (optical) antennas. First, the compatibility of lightwave antennas to a system is mentioned. Then, the principles and setup for each measurement term are presented. A comparison with radio-wave antennas is also given. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Lightwave Antenna With A Small Aperture Manufactured Using MEMS Processing Technology

    Page(s): 3046 - 3051
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (882 KB) |  | HTML iconHTML  

    High-performance antennas at lightwave frequency require optimal curved surfaces and high mechanical precision in order to realize high aperture efficiencies. We have developed a novel micro lightwave antenna by employing the micro electromechanical system processing technology. We describe a transparent antenna that has a multilevel step structure with a diameter of 4 millimeters. The ideal curve of the antenna surface is discretized by steps of constant height. The characteristics of the fabricated antenna have been measured; its gain is 84.1 dBi, which is 0.83 dB less than that of a reference antenna with a uniform field distribution. The aperture efficiency is 82.6%. The power radiation pattern is measured through the Fourier transform lens method and is in good agreement with the simulation result. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Development of Chiral Negative Refractive Index Metamaterials for the Terahertz Frequency Regime

    Page(s): 3052 - 3062
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1238 KB) |  | HTML iconHTML  

    A novel negative refractive index (NRI) chiral meta-material (MTM), based on the Y structure, has been designed and tested in the microwave and terahertz frequencies. In addition to providing magnetoelectric coupling, this MTM has a negative index of refraction passband that can be tuned in both the frequency of operation and bandwidth with lower losses compared to other known chiral structures. Group theory was used to analyze the magnetoelectric coupling of the Y-shaped structure and circuit analysis was used to aid in the design of the NRI material and full-wave finite difference time domain (FDTD) simulations were conducted to determine the transmission characteristics of the material. Wedge-and prism-shaped models comprised of the designed structures were simulated to validate the NRI behavior and were then compared to experimental results in the microwave regime. Furthermore, the Y-shaped design was fabricated in the THz regime and the co-and cross-polarized transmission coefficients were determined from experiments and were compared to numerical results. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Modeling the Optical Interaction Between a Carbon Nanotube and a Plasmon Resonant Sphere

    Page(s): 3063 - 3069
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (465 KB) |  | HTML iconHTML  

    A model is presented for the electromagnetic interaction between a carbon nanotube and an electrically-small sphere, such as a plasmonic metal particle. The sphere is characterized by its dipole moment, which is coupled to an integral equation for the nanotube. The model can be easily adapted to other systems consisting of electrically-small objects coupled to larger objects requiring a full-wave treatment. It is found that the presence of a non-plasmonic electrically-small sphere has a small effect on observed system properties, but that a plasmonic nanosphere in close proximity to a carbon nanotube leads to pronounced coupling, and may be useful as a way to excite carbon nanotube antennas. Furthermore, backscattering from a plasmonic nanosphere-carbon nanotube system is dominated by the nanosphere response. An approximate analytical solution is provided for the current induced on a nanotube in the presence of a plasmonic nanosphere. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Finite-Difference Time-Domain Study of Guided Modes in Nano-Plasmonic Waveguides

    Page(s): 3070 - 3077
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1262 KB) |  | HTML iconHTML  

    A conformal dispersive finite-difference time-domain (FDTD) method is developed for the study of one-dimensional (1-D) plasmonic waveguides formed by an array of periodic infinite-long silver cylinders at optical frequencies. The curved surfaces of circular and elliptical inclusions are modelled in orthogonal FDTD grid using effective permittivities (EPs) and the material frequency dispersion is taken into account using an auxiliary differential equation (ADE) method. The proposed FDTD method does not introduce numerical instability but it requires a fourth-order discretisation procedure. To the authors' knowledge, it is the first time that the modelling of curved structures using a conformal scheme is combined with the dispersive FDTD method. The dispersion diagrams obtained using EPs and staircase approximations are compared with those from the frequency domain embedding method. It is shown that the dispersion diagram can be modified by adding additional elements or changing geometry of inclusions. Numerical simulations of plasmonic waveguides formed by seven elements show that row(s) of silver nanoscale cylinders can guide the propagation of light due to the coupling of surface plasmons. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Bandwidth Enhancement of a Coupled Meander-Line-Feed High Gain Whip Antenna

    Page(s): 3078 - 3082
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2260 KB) |  | HTML iconHTML  

    High gain whip antenna fed by a meander-line with a coupled tuning stub for bandwidth enhancement is proposed and experimentally investigated. Both impedance and radiation characteristics of this antenna are studied. Experimental results indicate that a 1:2 VSWR bandwidth of 700 MHz is achieved at operating frequencies around 2.4 GHz, which is nearly nine times that of a conventional 5/8-wavelength whip antenna. Finite-difference time-domain simulation is used for optimization of the antenna and the results agree well with the measurement. The gain variations are less than 1.5 dBi in the resonant band. The experimental results of the constructed prototype are presented. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Compact Elliptical Monopole Antenna With Impedance Bandwidth in Excess of 21:1

    Page(s): 3082 - 3085
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (308 KB) |  | HTML iconHTML  

    A compact CPW-fed monopole antenna composed of an elliptical monopole patch and a coplanar trapeziform ground plane is introduced. The simulated and experimental results demonstrate that this antenna achieves a ratio impedance bandwidth of 21.6:1 for VSWR les 2, and exhibits a nearly omnidirectional radiation pattern, while its area is only about 0.19 lambda1 times 0.16 lambda1 where lambda1 is the wavelength of the lowest operating frequency. By comparing with various designs, it is shown that its bandwidth broadening comes from three factors: the optimum elliptical monopole shape, a trapeziform ground plane and a tapered CPW feeder. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • The Dipole Radiating Integrated Module: Experimental Results

    Page(s): 3085 - 3087
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (390 KB) |  | HTML iconHTML  

    A novel printed circuit realization of a dipole radiating integrated module (RIM) is combined with the method of moments. Practical application is illustrated through the optimization of a dipole RIM input VSWR. Experimental results are presented for 2.8 GHz microstrip radiating element capable of performing a turnstile antenna as well as a phased array. The peak cross-polarization level in the upper hemisphere is at least 12 dB below the peak co-polarization level. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Single Feed Low Profile Omnidirectional Antenna with Slant 45° Linear Polarization

    Page(s): 3087 - 3090
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1226 KB) |  | HTML iconHTML  

    It is shown that a side-fed bifilar helix antenna with a single feed, can generate a slant 45 linearly polarized omnidirectional toroidal pattern. The antenna has a low profile and does not require a ground plane. The bifilar helix antenna provides slant 45 polarization over a solid angle of almost steradians as compared to a crossed dipole which generates a tilted 45 linearly polarized pattern only over a solid angle of steradians. The computed results are validated by experimental data. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A Novel Broadband Printed Dipole Antenna With Low Cross-Polarization

    Page(s): 3091 - 3093
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (161 KB) |  | HTML iconHTML  

    A novel broadband printed dipole antenna with low cross-polarization is presented. The printed dipole employs a double-layered structure where the E-field component perpendicular to the dipole arms is minimized, thus low cross-polarization is obtained. Measurement results show that the printed dipole antenna achieves a bandwidth up to 50% while reducing the cross-polarization level to less than -30 dB within the frequency band. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A Magnetic Frill Source Model for Time-Domain Integral-Equation Based Solvers

    Page(s): 3093 - 3098
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (715 KB) |  | HTML iconHTML  

    A magnetic frill source model developed for time-domain integral-equation-based solvers for accurate characterization of coaxially driven structures is presented. The MFS model is developed by representing the coax as a magnetic frill current, and the evaluation of the expressions for fields radiated by this current does not call for numerical differentiation of any kind. Also, the expression for the axial component of the electric field only calls for one-dimensional numerical integration. For model validation and demonstration of efficacy, the developed source model is incorporated into a marching-on-in-time (MOT) scheme for broadband characterization of coaxially-driven antenna structures comprised of arbitrarily shaped perfect electrically conducting surfaces and thin wires. The numerical results obtained from the MOT scheme incorporated with the developed source model are compared with values obtained by measurement, and with the traditionally used delta gap source model. Compared to the delta gap source model, the magnetic frill source model provides a relatively accurate characterization of the antenna structures over a wide band of frequency. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.

Aims & Scope

IEEE Transactions on Antennas and Propagation includes theoretical and experimental advances in antennas.

Full Aims & Scope

Meet Our Editors

Editor-in-Chief                                                 Kwok W. Leung