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Antennas and Propagation, IEEE Transactions on

Issue 10 • Date Oct. 2005

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Displaying Results 1 - 25 of 51
  • Table of contents

    Publication Year: 2005 , Page(s): c1 - 3117
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  • IEEE Transactions on Antennas and Propagation publication information

    Publication Year: 2005 , Page(s): c2
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  • Parallel GA-based approach for microwave imaging applications

    Publication Year: 2005 , Page(s): 3118 - 3127
    Cited by:  Papers (36)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (880 KB) |  | HTML iconHTML  

    Genetic algorithms (GAs) are well-known optimization strategies able to deal with nonlinear functions as those arising in inverse scattering problems. However, they are computationally expensive, thus offering poor performances in terms of general efficiency when compared with inversion techniques based on deterministic optimization methods. In this paper, a parallel implementation of an inverse scattering procedure based on a suitable hybrid genetic algorithm is presented. The proposed strategy is aimed at reducing the overall clock time in order to make the approach competitive with gradient-based methods in terms of runtime, but preserving the capabilities of escaping from local minima. This result is achieved by exploiting the natural parallelism of evolutionary techniques and the searching capabilities of the hybrid approach . The effectiveness of the proposed implementation is demonstrated by considering a selected numerical benchmark related to two-dimensional scattering geometries. View full abstract»

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  • Using NU-SSGA to reduce the searching time in inverse problem of a buried metallic object

    Publication Year: 2005 , Page(s): 3128 - 3134
    Cited by:  Papers (21)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (504 KB) |  | HTML iconHTML  

    We describe an inverse scattering problem with the aim of reducing the computation time for recovering the details of a perfectly conducting cylindrical object buried in a half-space. First, we use Fourier-series or cubic-spline methods to describe the shape and reformulate the inverse problem into an optimization one. Then we solved it by the improved steady-state genetic algorithm (SSGA) and simple genetic algorithm (SGA) respectively and compare the cost time in finding out the global extreme solution of the objective function. It is found the searching ability of SSGA is much powerful than that of the SGA. Even when the initial guess is far away from the exact one, the cost time for converging to a global extreme solution using by SSGA is much less than that by SGA. Numerical results are given to show that the inverse problem by using SSGA is much better than SGA in time costing. View full abstract»

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  • Global convergence of phase retrieval by quadratic approach

    Publication Year: 2005 , Page(s): 3135 - 3141
    Cited by:  Papers (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (464 KB) |  | HTML iconHTML  

    The reliability of two different implementations of a quadratic phase retrieval approach to the problem of determining the far field of a radiating system from only square amplitude information on the near field zone is studied. The first implementation exploits square amplitude data over two scanning surfaces. The second one exploits the square amplitude of the voltages received by two different probes moving over a single scanning surface. It is pointed out how the diversity between the two scanning surface data or the two probes gives rise to "cancellation effects" which help in avoiding the local minima problem. Numerical examples are shown to discuss the global convergence properties of the two algorithms. View full abstract»

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  • Testing of a 1.5-m reflector antenna at 322 GHz in a CATR based on a hologram

    Publication Year: 2005 , Page(s): 3142 - 3150
    Cited by:  Papers (14)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2296 KB) |  | HTML iconHTML  

    Hologram-based compact antenna test range (CATR) is a potential method for testing large antennas at submillimeter wavelengths. This paper describes testing of a 1.5-m single offset parabolic reflector antenna with a 3-m-diameter hologram-based CATR. This is the first time such a measurement is carried out at submillimeter wavelengths. The antenna tests were done in a CATR that was specifically designed and constructed for these tests. The measured radiation pattern at the frequency of 322 GHz is presented. The measured pattern corresponds reasonably well to the simulated pattern of the antenna. The effect of the quiet-zone field nonidealities on the measurement results and the reasons for the discrepancies in the measured antenna beam are discussed. View full abstract»

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  • Hologram-based compact range for submillimeter-wave antenna testing

    Publication Year: 2005 , Page(s): 3151 - 3159
    Cited by:  Papers (14)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2096 KB)  

    A hologram-based compact antenna test range (CATR) is being developed to overcome challenges met in antenna testing at submillimeter wavelengths. For the first time, this type of CATR has been built for testing of a large reflector antenna at submillimeter wavelengths. The CATR is based on a 3-m computer-generated hologram as the focusing element. This paper discusses the design and the construction of the CATR, and the verification of the CATR operation with quiet-zone tests done for the CATR prior to the antenna testing. Assembly of the CATR, testing of the 1.5-m reflector antenna at 322 GHz, and the disassembly were all done within two months in 2003. The quiet-zone field measurement results are analyzed in this paper. The CATR was concluded to be qualified for antenna testing. The antenna testing is described in a separate paper. View full abstract»

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  • A feed scanning based APC technique for compact antenna test ranges

    Publication Year: 2005 , Page(s): 3160 - 3165
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (616 KB) |  | HTML iconHTML  

    The measurement accuracy of a compact antenna test range (CATR) depends on the level of spurious signals. To improve the measurement accuracy, several error compensation methods have been developed, but most of them are not feasible at submillimeter wavelengths. This paper introduces an error compensation technique for compact antenna test ranges, which is especially suitable at submillimeter wavelengths. The method is based on antenna pattern comparison (APC). In the original APC technique the antenna pattern is recorded several times at different positions of the quiet-zone field, and the corrected pattern is obtained by averaging the measured patterns. In the proposed method, the lightweight transmitter is moved instead of moving the heavy combination of the antenna under test (AUT) and the rotation stage. The feasibility of the method is studied and the method is tested with measurements in a hologram based compact antenna test range at 310 GHz. The accuracy provided by the proposed method is compared to the accuracy provided by the conventional APC. The accuracies provided by both methods are practically equal. View full abstract»

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  • In situ characterization of building materials for propagation modeling: frequency and time responses

    Publication Year: 2005 , Page(s): 3166 - 3173
    Cited by:  Papers (13)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (728 KB) |  | HTML iconHTML  

    We propose original data processing methods for the dielectric characterization of frequency-dependent reflection coefficients of construction materials considering a very wide frequency band. Two types of approaches have been developed to obtain, from spectral measurements, estimates of the equivalent complex permittivity versus frequency or reconstruction of the impulse response. In particular, high-resolution (HR) algorithms based on the matrix pencil method have been used in an original way to identify wave multipath inside a sample. Both approaches have been used for the characterization of different types of building materials. A database of dielectric responses of materials is under construction in order to provide the deterministic propagation simulator with the characteristics of building materials. View full abstract»

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  • A Kirchhoff Integral approach to estimating propagation in an environment with nonhomogeneous atmosphere and complex boundaries

    Publication Year: 2005 , Page(s): 3174 - 3179
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (760 KB) |  | HTML iconHTML  

    For terrestrial radio wave propagation, it has been previously demonstrated that second order effects, such as diffraction, can be estimated through a combination of geometric optics and Kirchhoff style integral relations. In the present paper, it is shown that the approach can also yield accurate estimates when refractive effects, such as atmospheric ducting, are present. View full abstract»

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  • Numerical evaluation of singular and near-singular potential Integrals

    Publication Year: 2005 , Page(s): 3180 - 3190
    Cited by:  Papers (97)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1032 KB) |  | HTML iconHTML  

    A simple and efficient numerical procedure using a singularity cancellation scheme is presented for evaluating singular and near-singular potential integrals with 1/R singularities. The procedure not only has several advantages over singularity subtraction methods, but also improves on some aspects of other singularity cancellation methods such as polar and Duffy transformations. A theoretical analysis is presented for triangles, quadrilaterals, tetrahedrons, bricks, and prisms, and numerical results are presented for triangles and prisms. View full abstract»

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  • Electromagnetic field generated by a horizontal electric dipole near the surface of a planar perfect conductor coated with a uniaxial layer

    Publication Year: 2005 , Page(s): 3191 - 3200
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (424 KB) |  | HTML iconHTML  

    In this paper, simple explicit formulas are derived for six components of the electromagnetic field in air from a horizontal electric dipole over a planar perfect conductor coated with a uniaxially anisotropic layer. The total field consists of the direct field, the ideal reflected field or field of an ideal image, the lateral-wave field, and the trapped-surface-wave field. The computations and discussions show that the trapped surface waves including the electric-type and magnetic-type trapped surface waves cannot be neglected when the dipole and the observer are on or close to the surface of the uniaxially anisotropic layer. Both trapped surface waves of electric type and magnetic type attenuate exponentially in the zˆ direction. The wave numbers in the ρˆ direction of electric-type trapped surface wave, which are between k0 and kL, are different from those of the magnetic-type trapped surface wave, which are between k0 and kT. The electric-type trapped surface wave can be excited efficiently when the thickness l of the uniaxially anisotropic layer satisfies the condition 0<(kT/kL) (kL2-k02)12/·l<π and the magnetic-type trapped surface wave can be excited when the thickness l of the dielectric layer satisfies the condition (π/2)<(kT2-k02)12/·l<π. When the thickness l of the uniaxially anisotropic layer satisfies nπ<(kT/kL) (kL2-k02)12/·l<(n+1)π, there are n+1 modes of the electric-type trapped surface waves to propagate along the uniaxial surface, and when the thickness l of the uniaxially anisotropic layer satisfies (n-(1/2))π<(kT2-k02)12/·l<(n+(1/2))π, there are n modes of magnetic-type trapped waves to propagate along the uniaxial surface. When the conditions k0ρ≫1 and z+d≪ρ are satisfied, both the electric-type and magnetic-type lateral waves with the wave numbers being k0 are excited. View full abstract»

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  • Practical limitations of subwavelength resolution using negative-refractive-index transmission-line lenses

    Publication Year: 2005 , Page(s): 3201 - 3209
    Cited by:  Papers (21)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (648 KB) |  | HTML iconHTML  

    Previously, we have demonstrated both analytically and experimentally subwavelength imaging using a negative-refractive-index lens made of a periodically L, C loaded transmission line (TL) network. This loaded transmission line network has been referred to as the dual TL lens. Here, we consider the limitations on subwavelength imaging imposed by impedance mismatches and the component losses of a practical dual TL lens. Simple expressions for estimating the resolving capability of a dual TL lens are given. It is found that the resolution enhancement of the dual lens is proportional to the quality factor of the series loading capacitors divided by the electrical thickness of the lens. The effective material parameters of the dual TL lens are also derived so that these expressions can be directly related to those of previous studies considering uniform and isotropic left-handed lenses. Finally, the resolving capability of an experimental lens that achieves subwavelength imaging is theoretically predicted. These theoretical predictions are then directly compared to previously reported experimental results. View full abstract»

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  • Planar circularly symmetric EBG structures for reducing surface waves in printed antennas

    Publication Year: 2005 , Page(s): 3210 - 3218
    Cited by:  Papers (51)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1080 KB) |  | HTML iconHTML  

    This paper discusses the design and analysis of planar circularly symmetric (PCS) electromagnetic band gap (EBG) structures for reducing the surface waves excited by printed antennas on dense dielectric substrates. The key advantage of the circularly symmetric geometries is that a surface wave generated by a source located at its center experiences the same band gap effect in all radial directions. To obtain simple design rules of the PCS-EBGs for the optimization of the bandwidth, an equivalence is established between 2-D-EBGs and PCS-EBGs. Integrated planar printed antennas with bandwidths up to 20% are designed, manufactured and tested. View full abstract»

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  • Efficient full-wave modeling of patch antenna arrays with new single-layer capacitive feed probes

    Publication Year: 2005 , Page(s): 3219 - 3228
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (648 KB) |  | HTML iconHTML  

    This paper introduces a new variation on the capacitive feed probe for patch antennas on thick substrates. It consists of a small circular probe-fed capacitor patch that is situated next to the resonant patch. This configuration can bring about significant savings in terms of manufacturing cost, but also lends itself to a very efficient full-wave analysis. As such, the main focus of this paper is a spectral-domain moment-method formulation, which was specifically developed for the analysis of large, but finite, arrays of these antenna elements. Entire-domain and subdomain basis functions are combined in an efficient way to minimize the computational requirements, most notably computer memory. It is shown that, for general antenna array configurations, memory savings of more than 1000 times can be achieved when compared with typical commercial software packages where only subdomain basis functions are used. A number of numerical and experimental results are also included in order to verify the spectral-domain moment-method formulation and to illustrate various applications of the new antenna element. View full abstract»

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  • Comparison of models for the probe inductance for a parallel-plate waveguide and a microstrip patch

    Publication Year: 2005 , Page(s): 3229 - 3235
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (576 KB) |  | HTML iconHTML  

    Four different models for the probe inductance of a circular probe in an infinite parallel plate waveguide are studied. These models include a uniform-current model, a cosine-current model, a gap-voltage source model, and a coaxial-frill model. These different models treat the vertical variation of the fields within the substrate and the field of the coaxial feed with varying degrees of rigor. Numerical high frequency structure simulator data are also compared with the results of these models in order to draw reliable conclusions about the accuracy of these models as a function of the substrate thickness. A simple computer-aided design formula for the probe inductance of a coaxial feed probe for a rectangular microstrip patch antenna is also introduced. View full abstract»

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  • Bandwidth limitations of impedance matched ideal dipoles

    Publication Year: 2005 , Page(s): 3236 - 3239
    Cited by:  Papers (19)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (336 KB) |  | HTML iconHTML  

    Using circuit theory and Chu's network representations of the wave impedance of the lowest spherical multipole field, the Ideal dipole, an explicit expression is derived for the upper limit for the impedance bandwidth obtainable for an ideal, lossless, linearly polarized antenna. The expression embodies the network character of an ideal antenna and its role in the guidance of energy between the feed point and the free-space interface, making it more appropriate as a reference than the theoretical radiation quality factor (Q). Moreover, practical antennas do not always manifest a clear single-pole behavior, undermining the basic assumption of a reciprocal relation between Q and the bandwidth. View full abstract»

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  • The leaky lens: a broad-band fixed-beam leaky-wave antenna

    Publication Year: 2005 , Page(s): 3240 - 3246
    Cited by:  Papers (14)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (857 KB) |  | HTML iconHTML  

    A novel type of leaky-wave antenna is presented. Differently from previously reported leaky-wave antennas, it is characterized by a constant beam direction over a very wide range of frequencies. The radiation originates at a slot etched at the interface between air and a dense dielectric, which is shaped to form a cylinder of elliptical cross sections of decreasing dimensions. Two prototypes have been designed, manufactured, and tested. The measurements are in very good agreement with the expectations, demonstrating the potentials of the leaky lens concept to realize integrated transmitters or receivers that are extremely broadband and directive. View full abstract»

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  • Effect of defocus on the prompt response of a reflector IRA

    Publication Year: 2005 , Page(s): 3247 - 3254
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (760 KB) |  | HTML iconHTML  

    Impulse radiating antennas (IRAs) are an emerging class of antenna that are designed to radiate extremely short electromagnetic pulses with multiple decades of instantaneous bandwidth. The most common IRAs are made with a transverse electromagnetic (TEM) transmission line feeding a paraboloidal reflector. The IRA is usually constructed so that the electrical feed point of the TEM transmission line coincides with the focal point of the paraboloid. The paraboloidal reflector converts the spherical wave emanating from the feed point into a plane wave (i.e., a spherical wave centered at -∞). In many practical cases, the feed point and focal points are not exactly aligned, producing some defocus of the reflector. In this paper, we model the case of hyperbolic defocus because of its analytic form and compare this model with experimental measurements. A hyperboloidal reflector fed from one focus converts the expanding spherical wave into a second expanding wave which appears to emanate from the second focal point of the hyperboloid (which is behind the reflector). Hyperboloidal defocus is roughly equivalent to moving the electrical feed closer to the reflector than the optical focal point. Previous theoretical results from in-focus IRAs predicted that the E- and H-plane temporal responses should be symmetric with respect to the temporal center of the response. The results shown here demonstrate that the defocusing causes these responses to become asymmetric. The new results are in better agreement with experimental measurements of IRAs and provide a physical explanation for experimental results that differ from the original theory. View full abstract»

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  • Analysis of radiation from a horn with a superquadric aperture

    Publication Year: 2005 , Page(s): 3255 - 3261
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (432 KB) |  | HTML iconHTML  

    This paper presents an analysis of radiation from a horn with a superquadric aperture, modeled using a cascade of superquadric waveguides. Electromagnetic fields within each waveguide are expressed in terms of a set of orthogonal modes derived from polynomial functions based on a Cartesian coordinate system. The scattering matrix at the horn aperture is obtained by calculating the scattering matrix at each of the waveguide junctions using mode matching, and cascading them appropriately. Radiation patterns corresponding to both x- and y-polarizations of the input excitation are then obtained by integrating the aperture field. The computed numerical results are validated by comparing them with the corresponding results obtained from measurements. View full abstract»

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  • A simple and robust adaptive parasitic antenna

    Publication Year: 2005 , Page(s): 3262 - 3272
    Cited by:  Papers (21)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (776 KB) |  | HTML iconHTML  

    A novel Uda-Yagi adaptive antenna is numerically and experimentally investigated. The antenna consists of an active element and a relatively large number of parasitic elements closed on two different loads selectable by simple electronic switches. The use of fuzzy-logic based cost function and self-adaptive biological beamforming algorithms allows to obtain quite good performances both in terms of signal to interference plus noise ratio and voltage standing wave ratio. The antenna is simple, low cost, and is robust with respect to mechanical and electrical tolerances and with respect to failures of some passive elements. Experimental results on two different prototypes confirm the good performances of the proposed antenna. View full abstract»

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  • Design of a multiband CPW-fed monopole antenna using a particle swarm optimization approach

    Publication Year: 2005 , Page(s): 3273 - 3279
    Cited by:  Papers (41)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (424 KB) |  | HTML iconHTML  

    A novel coplanar waveguide fed planar monopole antenna for multiband operation is presented in this paper. By embedding appropriate slits into the 50 Ω feeding line, good impedance matching for multiresonant mode is obtained. The evolutionary design process of using a particle swarm optimization (PSO) algorithm in conjunction with the method of moments is employed to effectively obtain the geometry parameters of the antenna for optimum multiband performance. Prototypes of the obtained optimized design have been constructed and experimentally studied. The measured results explore good multiband operation with 10 dB impedance bandwidths of 55%, 8.5%, and 4.4% at bands of 2.51, 3.98, and 5.24 GHz, respectively, which cover the personal communication system and 2.4/5.2 GHz wireless local-area network operating bands, and show good agreement with the numerical prediction. Good monopole-like radiation patterns and antenna gains over the operating bands have also been observed. Effects of the patch size on the antenna performance and implementation of the physical PSO for the optimized configuration are all examined and discussed in detail. View full abstract»

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  • Broad-band fragmented aperture phased array element design using genetic algorithms

    Publication Year: 2005 , Page(s): 3280 - 3287
    Cited by:  Papers (21)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (896 KB) |  | HTML iconHTML  

    In this paper, a synthesis procedure to design thin broad-band fragmented aperture array elements is described. The arrays are assumed to be infinite periodic and the elements consist of a conducting pattern etched on a dielectric backed by a groundplane. A genetic algorithm (GA) is used to design the conducting pattern, relative permittivity, and thickness of the dielectric substrate with respect to array scan and bandwidth performance. The fitness function in the GA is evaluated using a finite-difference time-domain code with periodic boundary conditions. For a substrate thicker than about 0.1 λLL= wavelength at the lowest frequency in the frequency band investigated), it was found that a bandwidth of at least one octave can be obtained for arrays scanned within 45° from broadside. View full abstract»

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  • Circularly polarized array antenna with corporate-feed network and series-feed elements

    Publication Year: 2005 , Page(s): 3288 - 3292
    Cited by:  Papers (12)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (864 KB) |  | HTML iconHTML  

    In this paper, corporate-feed circularly polarized microstrip array antennas are studied. The antenna element is a series-feed slot-coupled structure. Series feeding causes sequential rotation effect at the element level. Antenna elements are then used to form the subarray by applying sequential rotation to their feeding. Arrays having 4, 16, and 64 elements were made. The maximum achieved gains are 15.3, 21, and 25.4 dBic, respectively. All arrays have less than 15 dB return loss and 3 dB axial ratio from 10 to 13 GHz. The patterns are all quite symmetrical. View full abstract»

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  • A numerical technique for calculating mutual impedance and element patterns of antenna arrays based on the characteristics of an isolated element

    Publication Year: 2005 , Page(s): 3293 - 3299
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (488 KB) |  | HTML iconHTML  

    A numerical technique for calculating mutual impedance and element patterns of antenna arrays based on the characteristics of an isolated element is presented. The basis for this technique is the theory of minimum-scattering (MS) antennas and, in particular, the interpretation of the mutual impedance between two canonical minimum-scattering (CMS) antennas as the first term in a perturbation series of the mutual impedance of arbitrary antennas. For the computation of the mutual impedance via the CMS approximation this pattern must be continued analytically into the complex domain. However, numerical codes provide radiation patterns only for real observation angles. To overcome this problem, the numerically calculated patterns are expanded in terms of spherical modes and the computation over complex angles is carried out analytically. Numerical results for collinear and linear arrays of parallel electric dipole antennas and rectangular probe-fed patch antennas are presented and a comparison is made with direct calculations using the WIPL-D code. Results presented show the good agreement between the CMS approximation and the WIPL-D code. 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