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Antennas and Propagation, IEEE Transactions on

Issue 12 • Date Dec. 2008

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Displaying Results 1 - 25 of 45
  • Table of contents

    Publication Year: 2008 , Page(s): C1 - 3605
    Save to Project icon | Request Permissions | PDF file iconPDF (44 KB)  
    Freely Available from IEEE
  • IEEE Transactions on Antennas and Propagation publication information

    Publication Year: 2008 , Page(s): C2
    Save to Project icon | Request Permissions | PDF file iconPDF (43 KB)  
    Freely Available from IEEE
  • 2008 Antennas and Propagation Society Awards Distinguished Achievement Award Recipient

    Publication Year: 2008 , Page(s): 3606 - 3610
    Save to Project icon | Request Permissions | PDF file iconPDF (1999 KB)  
    Freely Available from IEEE
  • Beam-Scanning Performance of Leaky-Wave Slot-Array Antenna on Variable Stub-Loaded Left-Handed Waveguide

    Publication Year: 2008 , Page(s): 3611 - 3618
    Cited by:  Papers (14)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1285 KB) |  | HTML iconHTML  

    Metamaterial is an artificial material in which the effective phase constant can be controlled by the internal physical periodic structure of the transmission line. Effective phase constant is designed to be of any value, which may be small, large, approximately zero, or negative, attained by changing the dimensions of the periodic structure. Miniaturization of the antenna and wide design flexibility of radiation patterns can be expected from the use of metamaterials. In this work, we developed a leaky-wave slot-array antenna on a variable stub-loaded left-handed waveguide. The radiation pattern of the fabricated antenna was measured and the characteristics of the left-handed transmission line were observed. Moreover, performance of beam-scanning by changing the length of the stubs on the waveguide was confirmed experimentally. View full abstract»

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  • Metamaterial-Based Dispersion Engineering to Achieve High Fidelity Output Pulses From a Log-Periodic Dipole Array

    Publication Year: 2008 , Page(s): 3619 - 3629
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1115 KB) |  | HTML iconHTML  

    A metamaterial-enabled approach is presented that allows one to engineer the dispersion of a log-periodic dipole array antenna (LPDA) to make it more suitable for wide bandwidth pulse transmission. By modifying the LPDA with electrically small transmission line metamaterial-based negative and positive phase shifters, the phase of each element of the LPDA are adjusted such that in the main beam direction, the phase shifts between each element approximates a linear phase variation. The performance characteristics of the resulting dispersion-engineered LPDA are obtained numerically with HFSS and MATLAB simulations. By measuring in the far field the fidelity between the actual transmitted pulse and the idealized output waveform, the required component values of the phase shifters are optimized. Significant improvements in the fidelity of the pulses transmitted are demonstrated with eight and ten element LPDAs. View full abstract»

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  • CPW-Fed Circular Fractal Slot Antenna Design for Dual-Band Applications

    Publication Year: 2008 , Page(s): 3630 - 3636
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1841 KB) |  | HTML iconHTML  

    Using configuration synthesis and design map, the CPW-fed circular fractal slot antennas are proposed for dual-band applications. In practice, the experimental results with broadband and dual-band responses (47.4% and 13.5% bandwidth) and available radiation gains (peak gain 3.58 and 7.28 dBi) at 0.98 and 1.84 GHz respectively for half-wavelength design are achieved firstly. Then, the other broadband and dual-band responses (75.9% and 16.1% bandwidth) and available radiation gains (peak gain 3.16 and 6.62 dBi) at 2.38 and 5.35 GHz for quarter-wavelength design are described herein. Contour distribution patterns are applied to figure out the omni-directional patterns. The demonstration among the design map and the EM characteristics of the antenna is presented by current distributions. View full abstract»

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  • A Compact Ultrawideband Antenna With 3.4/5.5 GHz Dual Band-Notched Characteristics

    Publication Year: 2008 , Page(s): 3637 - 3644
    Cited by:  Papers (114)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2590 KB) |  | HTML iconHTML  

    We propose a compact planar ultrawideband (UWB) antenna with 3.4/5.5 GHz dual band-notched characteristics. The antenna consists of a beveled rectangular metal patch and a 50 Omega coplanar waveguide (CPW) transmission line. By etching two nested C-shaped slots in the patch, band-rejected filtering properties in the WiMAX/WLAN bands are achieved. The proposed antenna is successfully simulated, designed, and measured showing broadband matched impedance, stable radiation patterns and constant gain. An equivalent circuit model of the proposed antenna is presented to discuss the mechanism of the dual band-notched UWB antenna. A UWB antenna and a single band-notched one are also provided for references. View full abstract»

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  • Wideband Dual-Polarized Microstrip Patch Excited by Hook Shaped Probes

    Publication Year: 2008 , Page(s): 3645 - 3649
    Cited by:  Papers (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (781 KB) |  | HTML iconHTML  

    A new design of a wideband dually-polarized shorted microstrip patch antenna coupled to hook shaped probes is presented. The antenna is designed to operate around 4 GHz. The mechanisms of the shorted microstrip patch antenna provide wider impedance bandwidth over 37%. The shorted patch is smaller than the full unshorted patch. A gain around a 9-10 dBi is achieved within the bandwidth. The present design provides about 40 dB isolation level between the two ports. A stable low cross polarization level of -20 dB is obtained. View full abstract»

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  • A Decoupling Technique for Increasing the Port Isolation Between Two Strongly Coupled Antennas

    Publication Year: 2008 , Page(s): 3650 - 3658
    Cited by:  Papers (79)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1319 KB) |  | HTML iconHTML  

    A compact decoupling network for enhancing the port isolation between two closely spaced antennas is proposed in this paper. In the network, we first connect two transmission lines (TLs) individually to the input ports of two strongly coupled antennas. The length of the TLs is designed so that the trans-admittance between ports changes from a complex one at the antenna inputs to a pure imaginary one. A shunt reactive component is then attached in between the TL ends to cancel the resultant imaginary trans-admittance. Finally, a simple lumped-element circuit is added to each port for input impedance matching. The even-odd mode analysis is adopted to investigate the currents excited on the antennas for predicting the radiation pattern of the two-element antenna array. Two examples of printed antennas at 2.45 GHz are tackled by using the proposed decoupling structure. The measurement results agree quite well with the simulation ones. High antenna isolation and good input return loss are simultaneously achieved in both cases, which demonstrates the feasibility of the structure. The decoupled antenna array in each example radiates, as prediction, toward different but complementary directions when the input power is fed in turn to the two input ports. The array efficiency is estimated better than 75% in each example. This pattern diversity effect is helpful for reducing the channel correlation in a multiple-input multiple-output (MIMO) communication system. View full abstract»

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  • Jumping Genes Multiobjective Optimization Scheme for Planar Monopole Ultrawideband Antenna

    Publication Year: 2008 , Page(s): 3659 - 3666
    Cited by:  Papers (18)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1307 KB) |  | HTML iconHTML  

    A planar ultrawideband (UWB) monopole antenna is proposed in this paper. It has a planar multiple-trapezoidal monopole with adjustable dimensions. The proposed antenna is incorporated with the rectangular/rounded-corner ground plane to further improve the monopole performances such as impedance bandwidth. The geometric complexity of the antenna configuration is not easily devisable when the UWB performance criteria such as low voltage standing wave ratio (VSWR), minimal antenna size, omni-directional and uniform radiation pattern, and relatively constant gain over the ultrawide frequency band are to be simultaneously met. In this paper, all of these requirements can now be easily accomplished by making use of the recently developed jumping genes (JGs) multiobjective optimization scheme. A vivid demonstration of this approach of UWB design is to select an antenna configuration from the thoroughly investigated results and come up with the ultimate recommendation of hardware prototype fabrication. This way not only confirms both the simulated and measured results are all in good agreement but also indicates that the proposed methodology is sound for the design of UWB antenna. View full abstract»

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  • A Low-Cost Ultra Low Profile Phased Array System for Mobile Satellite Reception Using Zero-Knowledge Beamforming Algorithm

    Publication Year: 2008 , Page(s): 3667 - 3679
    Cited by:  Papers (24)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2177 KB) |  | HTML iconHTML  

    In this paper, a stair-planar phased array antenna system for mobile broadcast satellite reception in Ku-band will be introduced. The height of the antenna is only 6 cm and the system has two-dimensional electronic scanning capability. The design procedures of low profile high gain microstrip sub-array antennas, low noise amplifiers, hybrid analog phase shifters, along with a novel fast electronic beamforming algorithm will be discussed in this paper. The mobile phased array antenna receives LHCP and RHCP signals simultaneously. For each polarization 496 microstrip elements have been used to provide a radiation gain of 31.5 dBi. This phased array system scans plusmn2.8deg in azimuth and plusmn20deg in elevation with less than 3 dB scanning loss. The main objective of this design is to develop a Ku-band phased array system with very low cost components and a minimum number of tracking sensors. A novel beamforming algorithm compensates for the fabrication inaccuracies of the microwave components and variations in their characteristics due to ambient changes. Neither a priori knowledge of the satellite's direction, nor the phase-voltage characteristic of the phase shifters are required in this algorithm which results in eliminating an expensive laborious calibration procedure. The real time field tests verify that the developed mobile antenna system can nullify the base vehicle yaw disturbances up to 60 deg/s and 85 deg/s 2. View full abstract»

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  • On the Geometry Synthesis of Arrays With a Given Excitation by the Orthogonal Method

    Publication Year: 2008 , Page(s): 3680 - 3688
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1278 KB) |  | HTML iconHTML  

    A geometry synthesis procedure for arrays by the help of the orthogonal method (OM) is given in the work at hand. We start from an initial array with a given excitation and we perturb the element positions by combining an iterative technique with the OM. The final position of the elements is found from the last iteration where the desired approximation of the pattern is obtained. It is noticed that our formulation does not give always a successful outcome, since the search can be trapped in a local minimum. Thus, the successful issue comes from a suitable selection of the initial array. Cases with uniformly excited arrays or arrays with less number of excitations than the number of the elements are studied. Several examples for different cases will be presented and will show the applicability of the method. View full abstract»

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  • RF MEMS Actuated Reconfigurable Reflectarray Patch-Slot Element

    Publication Year: 2008 , Page(s): 3689 - 3699
    Cited by:  Papers (43)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1830 KB) |  | HTML iconHTML  

    This paper describes the design of a reconfigurable reflectarray element using commercially available radio frequency micro-electromechanical system (RF MEMS) switches. The element consists of a microstrip patch on the top surface and a slot with an actuated variable length in the ground plane. RF MEMS switches are mounted on the slot to electronically vary the slot length by actuating the switches and thus obtaining the desired phase response. Waveguide measurements and high frequency structure simulator (HFSS) simulations are used to characterize the reflectarray element. The four MEMS switches element gives 10 independent states with a phase swing of 150 deg and a loss variation from 0.4 dB to 1.5 dB at 2 GHz (more switches can provide larger phase shift). The loss is mainly attributed to the dielectric loss and the conductor loss, which occur due to the relatively strong electric fields in the substrate region below the patch and the large currents on the top surface of the patch, respectively, close to the patch resonance. Detailed analysis is performed to characterize the effect of the switches by taking into consideration the switch model and wire bonding effects. View full abstract»

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  • Investigation of FSS-Backed Reflectarray Using Different Classes of Cell Elements

    Publication Year: 2008 , Page(s): 3700 - 3706
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (744 KB) |  | HTML iconHTML  

    A variety of cell elements are presented in this paper for the construction of frequency selective surface (FSS) backed reflectarrays. Among the cell elements are the conventional ring elements for FSS and slotted patch for the reflectarray. Different combinations of FSS cell elements and reflectarray cell elements are employed for the realization of FSS-backed reflectarrays and the criteria for the selection of the optimum structure are presented. Prototypes of these reflectarrays were fabricated and tested. The measurements demonstrated that for an optimum design, the gain of an FSS-backed reflectarray is about 1.0 dB lower than its counterpart backed by solid ground plane. Characterization of the out of band performance of these antennas demonstrated close to 1.0 dB insertion loss. View full abstract»

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  • Chebishev Bandpass Spatial Filter Composed of Strip Gratings

    Publication Year: 2008 , Page(s): 3707 - 3713
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (667 KB) |  | HTML iconHTML  

    A new filter composed of a cascade of strip gratings with a 3rd order Chebishev frequency response that operates within a prescribed frequency band, is presented in this paper. Theoretical development was undertaken to establish equivalence between electromagnetic characteristics of a frequency selective surface (FSS) configuration and equivalent model based on circuit parameters that are used in the realization of Chebishev frequency response. The FSSs replace the impedance inverter elements in circuit implementation of the filter and the spacing between FSSs, which are adjusted to obtain the desired electrical performance, correspond to resonant elements in the circuit implementation. Dielectric slabs similar to the ones that were employed in FSS stages were used as the spacers between the constituent FSS layers to increase the robustness and rigidity of the structure. The fabrication process is described in detail and methods are introduced to account for tolerances in the permittivity and etching process during the design stage. Close agreement between measurement results demonstrates the validity of the design procedure. View full abstract»

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  • The Modified Surface-Normal Vectors in the Physical Optics

    Publication Year: 2008 , Page(s): 3714 - 3722
    Cited by:  Papers (14)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1016 KB) |  | HTML iconHTML  

    Simple equivalent surface currents perturbed from the physical optics (PO) are proposed, which predict accurate scattering fields without using a special knowledge about the high frequency asymptotic theories such as the geometrical theory of diffraction (GTD). A novel and empirical concept named ldquomodified surface-normal vectorsrdquo is introduced in the classical definition of the PO current, which is defined in a way that the reflection law is satisfied at each point of interest in the integration region. This empirical and geometrical replacement of the surface-normal vectors drastically enhances the accuracy of the PO to a level of the GTD. View full abstract»

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  • Generalized Transition Matrix for Arbitrarily Shaped Scatterers or Scatterer Groups

    Publication Year: 2008 , Page(s): 3723 - 3732
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (631 KB) |  | HTML iconHTML  

    This paper presents a numerical method to evaluate the electromagnetic scattering characteristics of arbitrarily-shaped scatterers by using a generalized transition matrix. Each scatterer is regarded as a one-port device. By choosing a reference surface containing the scatterer, an associated generalized transition matrix is defined uniquely to describe the relationships between the rotated tangential incident field components and the rotated tangential scattered field components on the reference surface. The reference surface can be moved to a new surface with a regular shape, and the generalized transition matrix defined on the new reference surface can be obtained easily. The reference surface can be extended to contain a group of scatterers with arbitrary shapes and different materials. When the associated generalized transition matrix defined on a regularly-shaped reference surface is obtained, the scattered fields from that scatterer or scatterer group can be calculated simply by multiplying the rotated tangential incident fields on the reference surface with the generalized transition matrix, and not necessary to consider its internal structure again. Since the generalized transition matrix only concerns with the fields on the reference surface, it is valid for various incident fields with arbitrarily incidence angles. Two-dimensional examples are provided to verify the method. View full abstract»

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  • An Efficient Approach for the Computation of 2-D Green's Functions With 1-D and 2-D Periodicities in Homogeneous Media

    Publication Year: 2008 , Page(s): 3733 - 3742
    Cited by:  Papers (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (693 KB) |  | HTML iconHTML  

    This paper presents an algorithm for the acceleration of the series involved in the computation of 2-D homogeneous Green's functions with 1-D and 2-D periodicities. The algorithm is based on an original implementation of the spectral Kummer-Poisson's method, and it can be applied to the efficient computation of a wide class of infinite series. In the algorithm the number of asymptotic terms retained in Kummer's transformation is externally controlled so that any of the series that has to be accelerated is split into one series with exponential convergence and another series with algebraic convergence of arbitrarily large order. Numerical simulations have shown that there is an ldquooptimumrdquo number of asymptotic terms retained in Kummer's transformation for which the CPU time needed in the summation of the series is minimized. The CPU times required by Ewald's method for the evaluation of 2-D Green's functions with 1-D and 2-D periodicities have been compared with those required by the present algorithm, and the algorithm has been found to be between 1.2 and 3 times faster than Ewald's method when working in ldquooptimumrdquo operation conditions. View full abstract»

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  • Numerical Evaluation of High-Order Finite Element Time Domain Formulations in Electromagnetics

    Publication Year: 2008 , Page(s): 3743 - 3751
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (578 KB) |  | HTML iconHTML  

    This paper compares three full-wave finite-element time-domain (FETD) formulations. The first is based on the vector wave equation; the others on Maxwell's equations, viz. the EBHD formulation that discretizes E rarr, B rarr, H rarr and Drarr and the EB formulation that discretizes only E rarr and B rarr. The latter two formulations use a combination of 1- and 2-form discretization to avoid an auxiliary mesh. A novel method for making the EBHD formulation operational is presented. Conditions for finite-difference time-domain (FDTD)-like explicit operation are discussed. The formulations are compared numerically by solving a three-dimensional cavity and a rectangular waveguide using high-order field representations up to mixed fourth order. The error balance between time integration and field representation is investigated. Difficulties in making the EBHD formulation operational which have not previously been addressed in the literature are discussed and worked around. Novel numerical results show that the EBHD formulation has serious performance limitations. View full abstract»

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  • A Nondirective Plane Wave MLFMA Stable at Low Frequencies

    Publication Year: 2008 , Page(s): 3752 - 3767
    Cited by:  Papers (37)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (803 KB) |  | HTML iconHTML  

    A novel method, called the nondirective stable plane wave multilevel fast multipole algorithm (NSPWMLFMA), is presented to evaluate the low-frequency (LF) interactions that cannot be handled by the multilevel fast multipole algorithm (MLFMA). It is well known that the MLFMA cannot be used for LF interactions, since it suffers from numerical instability. Contrary to current techniques, the proposed technique is not based on the spectral representation of the Green function. Instead the addition theorem of the MLFMA is manipulated into a form that allows numerically stable translations along the z axis. The translation operator for these translations is derived in closed form. A QR-based method is devised to allow stable translations in all the other directions. Interpolations and anterpolations are also provided, allowing a full multilevel algorithm. Since the NSPWMLFMA is based on the same mathematical foundations as the MLFMA, it requires limited adaptations to existing MLFMA codes. The fact that a QR is needed limits this algorithm to LF interactions. However, a coupling with the MLFMA is straightforward, allowing the easy construction of a broadband algorithm. The DC limit of the algorithm is also presented and it is shown that the algorithm remains valid for static problems. Finally, it is shown that the error introduced in the different steps of the algorithm is controllable, and a single-level vectorial version of the algorithm is applied to a generic scattering application to demonstrate its validity. View full abstract»

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  • Singular Higher Order Divergence-Conforming Bases of Additive Kind and Moments Method Applications to 3D Sharp-Wedge Structures

    Publication Year: 2008 , Page(s): 3768 - 3788
    Cited by:  Papers (16)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3148 KB) |  | HTML iconHTML  

    We present new subsectional, singular divergence-conforming vector bases that incorporate the edge conditions for conducting wedges. The bases are of additive kind because obtained by incrementing the regular polynomial vector bases with other subsectional basis sets that model the singular behavior of the unknown vector field in the wedge neighborhood. Singular bases of this kind, complete to arbitrarily high order, are described in a unified and consistent manner for curved quadrilateral and triangular elements. The higher order basis functions are obtained as the product of lowest order functions and Silvester-Lagrange interpolatory polynomials with specially arranged arrays of interpolation points. The completeness properties are discussed and these bases are proved to be fully compatible with the standard, high-order regular vector bases used in adjacent elements. Our singular bases guarantee normal continuity along the edges of the elements allowing for the discontinuity of tangential components, adequate modelling of the divergence, and removal of spurious solutions. These singular high-order bases provide more accurate and efficient numerical solutions of surface integral problems. Several test-case problems are considered in the paper, thereby obtaining highly accurate numerical results for the current and charge density induced on 3D sharp-wedge structures. The results are compared with other solutions when available and confirm the faster convergence of these bases on wedge problems. View full abstract»

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  • Frequency Interpolation of the Electromagnetic Surface Currents Via Singular Value Decomposition. Application to High-Frequency Analysis

    Publication Year: 2008 , Page(s): 3789 - 3796
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (677 KB) |  | HTML iconHTML  

    The time-harmonic electromagnetic scattering from conducting surfaces is considered. In this context, a recently published model order reduction for frequency interpolation of the surface current via singular value decomposition (SVD) is analyzed and evaluated: the exact currents computed at Q frequencies are arranged columnwise in a matrix, the SVD of which provides an orthonormal basis; on account of the observed exponential decrease of the singular values of this matrix, it is assumed that the dimension of the basis required for an accurate interpolation is much smaller than the number of unknowns in the original formulation. We propose in this paper a formal framework that justifies this decrease of the singular values, as well as the corresponding behavior of the interpolation error made on the current. From considerations based on high-frequency electromagnetics, it is shown that this method can be interpreted in terms of sampling criteria for the current, that yield an a priori estimate for the minimum value of Q . Numerical examples illustrate the capacities of this technique for frequency interpolation and for high-frequency analysis of the currents. View full abstract»

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  • Compact Multiband Folded Loop Chip Antenna for Small-Size Mobile Phone

    Publication Year: 2008 , Page(s): 3797 - 3803
    Cited by:  Papers (32)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1207 KB) |  | HTML iconHTML  

    A multiband folded loop chip antenna with a very small volume of 1 cm3 (40 times 5times 5 mm3) is presented. The antenna has a simple metal pattern comprising a folded loop strip and a tuning pad, and is especially suited for application in small-size mobile phones (groundplane length 60 mm only) for multiband operation. The metal pattern is attached on the surfaces of a foam base, and the first three resonant loop modes (0.5-, 1.0-, and 1.5-wavelength modes) of the antenna can be excited with good impedance matching by simply adjusting proper dimensions of the tuning pad and its location along the folded loop strip. The excited 0.5-wavelength mode forms as the antenna's lower band at about 900 MHz for GSM operation, while the 1.0- and 1.5-wavelength modes are formed into a wide operating band at about 1900 MHz for the antenna's upper band to cover DCS/PCS/UMTS operation. Design considerations of the proposed folded loop chip antenna are described, and effects of the tuning pad on controlling the performances of the antenna are shown. View full abstract»

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  • Mode-Based Information Channels in Closely Coupled Dipole Pairs

    Publication Year: 2008 , Page(s): 3804 - 3811
    Cited by:  Papers (18)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (814 KB) |  | HTML iconHTML  

    Information channels supported by two orthogonal radiation modes in a pair of closely spaced dipole antennas are investigated. The radiation impedances of the two modes are closely related to the coupling behavior of the 2-element array as a function of the antenna spacing. Through a multiport impedance matching network, the common and difference modes of the coupled antenna system can be separated into different driving ports. Conjugate match can thus be independently performed for each port, resulting in a fully matched 2-element array. Such a 2-element array with closely spaced antennas can potentially offer a significant array gain or an ideal 2 times 2 multiple input multiple output channel capacity. Full-wave simulations of a pair of half-wave dipoles with 0.1 lambda spacing have demonstrated the feasibility of the approach for narrowband applications. By combining the common mode and difference mode, approximately 3 times of the gain of a single half-wave dipole can be achieved. Experimental validation with a test bed consisting of two lambda/4 monopoles and a rat-race coupler has been carried out. The concept may be extended onto closely coupled antenna systems with different numbers of elements. View full abstract»

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  • The Energy Absorbed in the Human Head Due to Ring-Type Jewelry and Face-Illuminating Mobile Phones Using a Dipole and a Realistic Source

    Publication Year: 2008 , Page(s): 3812 - 3817
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (795 KB) |  | HTML iconHTML  

    The effect of facial ring jewelry is investigated on the energy absorbed in the head when illuminated by communications-enabled personal data assistant (PDA)-type devices. We study the relative changes in specific absorption rates in the head due to perturbing metallic rings in proximity to the face illuminated by a 1.8 GHz dipole and a monopole on a conducting box. Simple and complex head models used in a validated finite-difference time-domain (FDTD) simulation are compared with measurements from an industry standard DASY4 SAR measurement system. Both simulation and measurement are referred to the IEEE specific anthropomorphic mannequin head. Results show that metallic rings may alter specific absorption rates (SAR) level distributions within the head. Results are given for several common ring sizes. View full abstract»

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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