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Antennas and Propagation, IEEE Transactions on

Issue 11 • Date Nov. 2005

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Displaying Results 1 - 25 of 64
  • Table of contents

    Page(s): c1 - 3425
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  • IEEE Transactions on Antennas and Propagation publication information

    Page(s): c2
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  • Fundamental transmitting properties of carbon nanotube antennas

    Page(s): 3426 - 3435
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    Fundamental properties of dipole transmitting antennas formed by carbon nanotubes are investigated. Since carbon nanotubes can be grown to centimeter lengths, and since they can be metallic, the properties of carbon nanotubes as antenna elements are of fundamental interest. In this paper, dipole carbon nanotube antennas are investigated via a classical Hallen's-type integral equation, based on a quantum mechanical conductivity. The input impedance, current profile, and efficiency are presented, and the radiation pattern is discussed, as are possible applications. View full abstract»

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  • A wide-band, circularly polarized, magnetodielectric resonator antenna

    Page(s): 3436 - 3442
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    Previously insurmountable challenges posed by stringent requirements of simultaneous compact size, high bandwidth, high to moderate efficiency, and circular polarization operation at UHF have been surpassed by a unique design employing layered magnetodielectric materials. To achieve percentage bandwidth values in excess of 50% for an antenna with a maximum dimension of 0.15λ three approaches for bandwidth enhancement are combined in a proper fashion. A volumetric source, as opposed to printed planar or wire sources, inherently provides higher bandwidth and is used as the fundamental radiating element of the antenna. The radiating structure is made up of layered magnetodielectric material with proper design of permittivity and permeability values forming a magnetodielectric resonator antenna (MDRA). Noting that miniaturization and wave impedance in the MDRA are, respectively, proportional to the square-root of the product and ratio of the permeability and permittivity, moderate values of permittivity and permeability are used to enhance the bandwidth while achieving considerable miniaturization. The third method for bandwidth enhancement is based on the integration of a resonant feed and many parasitic elements into the MDRA structure. Square symmetry of the MDRA is used to obtain circular polarization operation. A prototype small UHF antenna operating over 240-420 MHz with a linear dimension smaller than 0.15λ at the lowest frequency is fabricated and tested; the results are summarized in this paper. View full abstract»

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  • Bandwidth-enhancing ultralow-profile compact patch antenna

    Page(s): 3443 - 3447
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    A novel method to extend the operation bandwidth and reduce the size of the ultralow-profile patch antenna is presented in this paper. The designed results indicate that two orthogonal modes of TM10 and TM01 can be excited simultaneously in the antenna, resonate at two close frequencies, and also are matched well. Thus, a bandwidth-enhancing characteristic is achieved. The size reduction is obtained due to utilizing the slot-loading technique. Because most patch currents of the two modes flow in the same direction, the similar radiation characteristics is observed at two resonance frequencies. The significantly high cross polarization makes the proposed antenna applicable for the wireless communication in multipath environment. View full abstract»

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  • Broad-band radial slot antenna fed by coplanar waveguide for dual-frequency operation

    Page(s): 3448 - 3452
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    A novel design of a broad-band radial slot antenna fed by a coplanar waveguide for dual-frequency operation is presented. Various frequency ratios, within the range of about 1.3 to 2.1, of the two operating frequencies can be obtained by varying the included angle between the radial slots and/or by varying the length of the central slot pair. The bandwidth of the lower operating band lies in the range of 2.4% to 9.7%, while that of the upper band is much wider and ranges from 17.4% to 23.2%. Radiation patterns at the two operating frequencies are broadside and bidirectional. Details of the antenna design and the experimental results are presented and discussed. View full abstract»

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  • Neurocomputational analysis of a multiband reconfigurable planar antenna

    Page(s): 3453 - 3458
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    Procedures using neural networks are developed for characterizing multiband reconfigurable antennas. A multilayer perceptron (MLP) is used to locate the operational frequency bands of the antenna at different reconfigured conditions. Another self-organizing map (SOM) neural network accomplishes the task of locating the switches to be turned ON for a desired frequency response. The developed formulation is tested on a laboratory prototype antenna. View full abstract»

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  • Parallel particle swarm optimization and finite- difference time-domain (PSO/FDTD) algorithm for multiband and wide-band patch antenna designs

    Page(s): 3459 - 3468
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    This paper presents a novel evolutionary optimization methodology for multiband and wide-band patch antenna designs. The particle swarm optimization (PSO) and the finite-difference time-domain (FDTD) are combined to achieve the optimum antenna satisfying a certain design criterion. The antenna geometric parameters are extracted to be optimized by PSO, and a fitness function is evaluated by FDTD simulations to represent the performance of each candidate design. The optimization process is implemented on parallel clusters to reduce the computational time introduced by full-wave analysis. Two examples are investigated in the paper: first, the design of rectangular patch antennas is presented as a test of the parallel PSO/FDTD algorithm. The optimizer is then applied to design E-shaped patch antennas. It is observed that by using different fitness functions, both dual-frequency and wide-band antennas with desired performance are obtained by the optimization. The optimized E-shaped patch antennas are analyzed, fabricated, and measured to validate the robustness of the algorithm. The measured less than - 18 dB return loss (for dual-frequency antenna) and 30.5% bandwidth (for wide-band antenna) exhibit the prospect of the parallel PSO/FDTD algorithm in practical patch antenna designs. View full abstract»

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  • Microstrip antennas with suppressed radiation in horizontal directions and reduced coupling

    Page(s): 3469 - 3476
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    Microstrip (patch) antennas usually strongly radiate in directions along the ground plane. This effect causes unwanted radiation patterns and increased coupling among array elements. Dielectric polarization currents are identified as physical sources of this radiation. A general technique is proposed to compensate these currents and suppress radiation in horizontal directions. View full abstract»

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  • Dual-band circularly polarized equilateral triangular-patch array antenna for mobile satellite communications

    Page(s): 3477 - 3485
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    The Japan Aerospace Exploration Agency will launch the Engineering Test Satellite VIII (ETS-VIII) in 2006 to support the next generation of mobile satellite communications covering the area of Japan (beam coverage El=38° to 58°). In this paper, a satellite-tracking left-handed circularly polarized triangular-patch array antenna is developed for ground applications. The targeted minimum gain of the antenna is set to 5 dBic at the central elevation angle (El=48°), in the Tokyo area, for applications using data transfer of around a hundred kbps. The antenna is composed of three equilateral triangular patches for both reception and transmission units operating at 2.50 and 2.65 GHz frequency bands, respectively. The antenna was simulated by method of moments (MoM) analysis, and measurement of the fabricated antenna was performed to confirm the simulation results. The measurement results show that the frequency characteristics and the 5-dBic gain coverage in the conical-cut plane of the fabricated antenna satisfy the specifications for ETS-VIII. A prototype of the proposed antenna system is employed in outdoor experiments using a pseudosatellite and shows good performance from El=38° to 58°. View full abstract»

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  • Reactance-domain ESPRIT algorithm for a hexagonally shaped seven-element ESPAR antenna

    Page(s): 3486 - 3495
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (896 KB) |  | HTML iconHTML  

    A direction-of-arrival (DoA) method that combines the reactance-domain (RD) technique and the ESPRIT algorithm is proposed for use with the 7-element electronically steerable parasitic array radiator (ESPAR) for the estimation of noncoherent sources. Simulations show that the method could resolve up to three incoming signals with an estimation performance that depends on the signal's angle of arrival. Moreover, the method is compared with the Cramer-Rao lower bound (CRB) and the MUSIC asymptotic error variance, both modified for the RD technique. Numerical comparison between this lower bound and the MUSIC algorithm confirmed that the proposed method can achieve the CRB and provide high-precision DoA estimation with a level of performance that is sufficient for many DoA finding applications. The proposed method could be demonstrated by means of experiments on DOA estimation conducted in an anechoic chamber. View full abstract»

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  • WLAN chip antenna mountable above the system ground plane of a mobile device

    Page(s): 3496 - 3499
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (376 KB) |  | HTML iconHTML  

    A novel wireless local-area network (WLAN) chip antenna suitable to be mounted above the system ground plane of a mobile device is presented. The antenna in the study is easily fabricated from folding a single metal plate onto a foam base, and mainly comprises a short-circuited radiating strip and an antenna ground. The antenna ground occupies the bottom surface and two adjacent side surfaces of the foam base. When the antenna is mounted at the corner of the system ground plane, this antenna ground structure is expected to effectively reduce the antenna's possible fringing electromagnetic fields inside the mobile device. In this case, when the associated element such as the radio-frequency shielding metal case is placed under the proposed antenna, small or negligible variations in the antenna performance are obtained. Design considerations of the proposed antenna for WLAN operation in the 2.4 GHz band are described, and results of the constructed prototypes are presented. View full abstract»

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  • Study of a printed circular disc monopole antenna for UWB systems

    Page(s): 3500 - 3504
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    This paper presents a study of a novel monopole antenna for ultrawide-band (UWB) applications. Printed on a dielectric substrate and fed by a 50 Ω microstrip line, a planar circular disc monopole has been demonstrated to provide an ultra wide 10 dB return loss bandwidth with satisfactory radiation properties. The parameters which affect the performance of the antenna in terms of its frequency domain characteristics are investigated. A good agreement is achieved between the simulation and the experiment. In addition, the time domain performance of the proposed antenna is also evaluated in simulations. View full abstract»

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  • 2-D periodic leaky-wave antennas-part I: metal patch design

    Page(s): 3505 - 3514
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    The far-field radiation characteristics of a two-dimensional (2-D) periodic leaky-wave antenna (LWA) constructed from a periodic array of metal patches on a grounded dielectric substrate is investigated. A simple dipole source is used as the excitation. Reciprocity together with a periodic spectral-domain method of moments is used to calculate the far-field pattern. Design rules for the scan angle, the substrate dielectric constant, and the periodicity are provided. Finally, a comparison of the 2-D periodic LWA and a dielectric-layer LWA is given to show the similar performance of the two antennas. View full abstract»

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  • 2-D periodic leaky-wave Antennas-part II: slot design

    Page(s): 3515 - 3524
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2024 KB) |  | HTML iconHTML  

    The far-field radiation patterns of a two-dimensional (2-D) periodic slot leaky-wave antenna (LWA) are studied. The antenna consists of a two-dimensional periodic array of slots in a conducting plane that is printed on top of a grounded dielectric slab. The antenna is excited by a simple source such as a dipole inside the slab. Reciprocity along with the spectral-domain method is used to calculate the far-field pattern, and the radiation characteristics of the structure are investigated. A comparison between the present periodic slot LWA and a 2-D periodic patch LWA discussed in Part I is given to show the advantages of the slot antenna for certain applications. The slot LWA can achieve high directivity patterns, and a circularly-polarized version of the antenna can achieve good circular-polarization at broadside. View full abstract»

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  • General formulas for 2-D leaky-wave antennas

    Page(s): 3525 - 3533
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (552 KB) |  | HTML iconHTML  

    General formulas for a two-dimensional (2-D) leaky-wave antenna (LWA) are obtained, which are applicable to any general class of 2-D leaky-wave antenna that consists of a partially reflecting surface that is mounted on top of a grounded substrate, and excited by a simple source. Closed-form expressions are obtained for the radiated fields, the field peak values in the E- and H-planes, the beamwidths in the E- and H-planes, and the pattern bandwidth. The formulas are obtained from a simple transverse equivalent network model of the structure. An accurate formula for the substrate thickness necessary to give a beam at any desired angle is also obtained. View full abstract»

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  • A dual planar reflectarray with synthesized phase and amplitude distribution

    Page(s): 3534 - 3539
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    A quasi-planar reflector arrangement for generating an arbitrary phase and amplitude distribution in the antenna aperture and thus a wide range of far field patterns is presented. A parallel pair of reflectarrays is used. One is implemented as a standard reflectarray using rectangular patches on a microwave substrate with metallized backside. The other reflectarray is provided with a polarizing grid, which acts as a ground plane for one polarization and is transparent for the orthogonal polarization. An offset rectangular feed horn is embedded in the lower reflectarray to illuminate the upper reflector. A design procedure for a linear polarized antenna with a sector beam in the azimuth and a narrow beam width in the elevation is presented and is verified with measurement results. View full abstract»

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  • Design realization and measurements of a high performance wide-band corrugated horn

    Page(s): 3540 - 3546
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    We report on the design and realization of horn antennas required to achieve high performances with respect both to the return loss and the cross polarization level over a wide band. View full abstract»

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  • An array-compensated spherical reflector antenna for a very large number of scanned beams

    Page(s): 3547 - 3555
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (816 KB) |  | HTML iconHTML  

    There are many stringent demands imposed on the applications of spaceborne antenna systems. One of the most challenging demands is the generation of multiple beams with the ability to scan a very large number of beamwidths. Since the parabolic reflectors have limitations in this application, a 35-m spherical reflector antenna is proposed for a geostationary radar antenna at Ka-band (35.6 GHz) due to its inherent capability of scanning the beams to very large number of beamwidths. The utility of using planar array feeds for correcting spherical phase aberrations is investigated to overcome the performance degradation effects. Two different methodologies are developed for the array excitation coefficients determination based on phase conjugate matching and the results are compared. Using the compensating feed array, the radiation characteristics of the compensated spherical reflector are simulated for no scan and large scan cases and the results are compared with the uncompensated case to show performance improvement. In order to demonstrate the technological readiness of the concept a 1.5-m breadboard model is designed to be built for experimental measurements. Some important mechanical design tolerances and realistic array feed topologies are investigated. The antenna concept developed in this paper is advocated to be used in the next generation of geostationary satellite antenna systems for remote sensing radar applications. View full abstract»

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  • Problem-matched basis functions for microstrip coupled slot arrays based on transmission line Green's functions (TLGF)

    Page(s): 3556 - 3567
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    Problem matched basis functions are proposed for the method of moments analysis of printed slot coupled microstrips. The appropriate equivalent currents of the integral equation kernel are represented in terms of two sets of entire domain basis functions. These functions synthesize on one hand the resonant behavior of slots, microstrips or dipoles and on the other hand the field in proximity of the feeding source and of the discontinuities. In order to define these basis functions, canonical geometries are identified, whose Green's functions have been found in semi-analytical form. The accuracy and the effectiveness of the method in terms of convergence rate and number of unknowns is demonstrated by comparison with a standard fine meshing full-wave analysis. The method is extremely convenient for large arrays, where the subwavelength details should be treated together with large global dimensions. Since the proposed solution is independent of the dimensions of these details, it provides dramatic reduction of the number of unknowns and improvement of condition number. View full abstract»

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  • Radiation properties of one-dimensional random-like antenna arrays based on Rudin-Shapiro sequences

    Page(s): 3568 - 3575
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    The development of exotic new materials, such as metamaterials, has created strong interest within the electromagnetics (EM) community for possible new phenomenologies and device applications, with particular attention to periodicity-induced phenomena, such as photonic bandgaps. Within this context, motivated by the fairly recent discovery in X-ray crystallography of "quasi-crystals", whose diffraction patterns display unusual characteristics that are associated with "aperiodic order", we have undertaken a systematic study of how these exotic effects manifest themselves in the radiation properties of aperiodically configured antenna arrays. The background for these studies, with promising example configurations, has been reported in a previous publication [V. Pierro et al., IEEE Trans. Antennas Propag., vol. 53, pp. 635-644, Feb. 2005]. In this paper, we pay attention to various configurations generated by Rudin-Shapiro (RS) sequences, which constitute one of the simplest conceivable examples of deterministic aperiodic geometries featuring random-like (dis)order. After presentation and review of relevant background material, the radiation properties of one-dimensional RS-based antenna arrays are analyzed, followed by illustrative numerical parametric studies to validate the theoretical models. Design parameters and potential practical applications are also given attention. View full abstract»

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  • An effective compensation method for the mutual coupling effect in phased arrays for magnetic resonance imaging

    Page(s): 3576 - 3583
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (344 KB) |  | HTML iconHTML  

    An effective compensation method to compensate for the mutual coupling effect in magnetic resonance imaging (MRI) phased arrays is introduced. This method uses the knowledge of the position of the signal source in MRI, i.e., the active slice, to define a new mutual impedance that accurately quantifies the coupled voltages and enables them to be removed from the terminal voltages almost completely. Numerical results using the method of moments show that the percentage errors in the compensated voltage are at least on the order of 10-5% and the isolations between two coils are more than 120 dB even at a low-field case of 0.5 T (f0=21.3 MHz). This method can be implemented by either software or hardware. View full abstract»

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  • A demonstration of the coupled oscillator based agile beam receiver concept

    Page(s): 3584 - 3588
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    The Cao-York concept of using a linear array of mutually injection locked oscillators to provide local oscillator signals for an agile beam receiver is demonstrated using a 15 circuit array of L-band voltage controlled oscillators coupled to nearest neighbors. The concept involves mixing each 1.265 GHz local oscillator (l-o) signal with a corresponding 1.950 GHz signal received by an element in an antenna aperture and combining the resulting 685 MHz intermediate frequency (i-f) signals. A normally incident wave is simulated using a power divider to provide 15 equal in-phase signals to the r-f ports of the mixers and the i-f combining is accomplished using a similar power divider in reverse. The "antenna beam" is steered through this "normally incident wave" by antisymmetrically detuning the end oscillators of the array and a plot of the i-f combiner output represents the receive beam shape. Finally, this system is used to demonstrate the Kott sidelobe suppression technique. View full abstract»

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  • Wide-band photonically phased array antenna using vector sum phase shifting approach

    Page(s): 3589 - 3596
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (616 KB) |  | HTML iconHTML  

    In this paper, a wide-band photonically phased array antenna is demonstrated. The array configuration consists of a 4 × 1 Vivaldi single-polarization antenna array and an independent photonic phasing system for each element. The phasing network of this array is implemented using two novel photonic phase shifters based on the vector summation approach. A vector sum phase shifter (VSPS), which exhibits a frequency-linear characteristic from dc to 15 GHz and can be continuously tuned from 0 to 100°, is presented. A second-order VSPS (SO-VSPS), a modification of the VSPS that is capable of 0-430° phasing range, is also demonstrated. This paper presents the operation and characterization of each component of the array, including the radiating elements and the various photonic phase shifters and, finally, a demonstration of the combined system. A discussion on the practicality of this system for airborne applications is presented, along with suggestions for simplification and improvement. View full abstract»

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  • Real frequency wide-band impedance matching with nonminimum reactance equalizers

    Page(s): 3597 - 3603
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    This paper describes two modifications to the real frequency technique of broadband impedance matching. A fundamental limitation of all broadband matching techniques is that the real and imaginary parts of the equalizer impedance must be related by the Hilbert transform. It is shown that additional degrees of freedom in the Hilbert transform, and thus a better match, can be obtained by employing equalizer impedances with nonminimum reactance and by optimizing the equalizer resistance outside the stated bandwidth. Examples will be presented for a thin wire dipole antenna. View full abstract»

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

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Editor-in-Chief                                                 Kwok W. Leung