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Antennas and Propagation, IEEE Transactions on

Issue 4 • Date April 2004

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Displaying Results 1 - 25 of 35
  • Table of contents

    Publication Year: 2004 , Page(s): c1 - 913
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  • IEEE Transactions on Antennas and Propagation publication information

    Publication Year: 2004 , Page(s): c2
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  • Complex-wall effect on propagation characteristics and MIMO capacities for an indoor wireless communication environment

    Publication Year: 2004 , Page(s): 914 - 922
    Cited by:  Papers (29)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (480 KB) |  | HTML iconHTML  

    The effects of complex wall structures on the characteristics of fading and the capacity of multi-input multi-output (MIMO) wireless communication systems for some typical indoor propagation environments are investigated. Two cases of wall structures are examined in this paper. In the first case, the walls are considered to be homogenous solid slabs, while, in the second case, the walls are assumed to be of complex structures. A two-dimensional finite difference time domain method is employed to calculate the electric field distributions, and then, the local mean power, the Rician K factor, and the MIMO capacity are calculated and analyzed. It is found that the patterns of the local mean power distributions are different for the two wall-structure cases. As for the small-scale fading, it is shown that the Rician K factors for the two cases may be different by 5 dB. The resulting values of MIMO capacities are also quite different and are less than the ideal cases, where the elements of the transfer (H) matrix are assumed to be zero-mean Gaussians with unit variance. We also investigate the cases where complex walls are replaced by effective slab walls. It is found that complex walls cannot be appropriately characterized by simple effective slab walls as considerable difference exists between the two cases. View full abstract»

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  • Impact of seasonal and diurnal variations on satellite system design in V band

    Publication Year: 2004 , Page(s): 923 - 932
    Cited by:  Papers (8)
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    In the framework of the ITALSAT campaign various European institutions carried out propagation measurements at V band. In this frequency band, signal reception in a satellite-to-Earth or Earth-to-satellite path may suffer severely from signal attenuation due to meteorological effects such as rain, snow, hail, fog, clouds, etc., where rain provides the most significant contribution. In this paper, a joint analysis of the ITALSAT propagation measurement campaigns at 39.6 GHz (precisely 39.592 GHz) carried out at both Oberpfaffenhofen, close to Munich, Germany, and Spino d'Adda, close to Milan, Italy, is presented. For both stations long-term attenuation statistics are available and reveal that signal attenuation due to meteorological effects depends very much on the season and on the time of the day. Signal attenuation can be compensated by an appropriate fade margin. In this paper, we show that the required fade margin to guarantee a target link availability has to be chosen very carefully, since it depends very much on the time interval upon which availability is defined. We consider complete years, ITU-R recommendations, all single months of the year, worst months, and spring, summer, fall, and winter. Furthermore, we evaluate diurnal variations for four time intervals: 00:00-06:00, 06:00-12:00, 12:00-18:00, and 18:00-24:00. View full abstract»

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  • Indoor signal focusing by means of Fresnel zone plate lens attached to building wall

    Publication Year: 2004 , Page(s): 933 - 940
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (336 KB) |  | HTML iconHTML  

    A simple inexpensive on-wall Fresnel zone plate (FZP) lens for indoor focusing of microwave signals is studied. It consists of concentric metal rings mounted on the outside of an exterior building wall. In our theoretical and empirical work the on-wall FZP lens is illuminated normally by a plane or spherical wave, of vertical or horizontal polarization, but other, more general incidence situations can be treated by similar means. The scalar quasi-optical focusing theory of the free-space zone plate has been modified and used for design and analysis of one-, two-, and three-ring on-wall FZP lenses. It is found that the presence of the wall does not change the FZP lens focusing efficiency significantly, but it has a strong axial defocusing effect. A 2-GHz FZP lens assembly consisting of three metal rings made out of thin antimosquito mesh has a focusing efficiency of about 15 dB (measured) and 14 dB (calculated), and axial defocusing of about 0.22 m. Some variations of on-wall/on-roof FZP lenses and their feasible applications in the microwave/millimeter-wave communication links are also discussed. View full abstract»

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  • Dyadic eigenfunctions and natural modes for hybrid waves in planar media

    Publication Year: 2004 , Page(s): 941 - 947
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (224 KB) |  | HTML iconHTML  

    A new formulation for studying electromagnetic wave propagation in an open, planarly layered medium is presented based on eigenfunctions of the Hertzian potential dyadic Green's function operator. Due to the complicated coupling of scalar components of potential at material interfaces, elevation of the usual vector eigenfunction problem to dyadic level is found to lead to a convenient, compact representation of wave propagation phenomena. Although we study the source-free problem here, the three columns of the eigenfunction dyadics represent (up to an excitation-dependent amplitude) the vector fields excited by a given three-dimensional source. The general theory of dyadic eigenfunctions is presented, including orthogonality and the possibility of associated functions (root functions) at modal degeneracies, and an example of propagation in a grounded dielectric slab environment is provided. View full abstract»

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  • Field of a rectangular loop

    Publication Year: 2004 , Page(s): 948 - 952
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (176 KB) |  | HTML iconHTML  

    Design advantages of square- and rectangular-loop antennas make these types of antennas attractive for use in mobile devices to improve their communication capabilities. However, modified characteristics of such antennas require additional analysis to evaluate interaction with antennas of other types and other components of mobile devices and human organisms. In this paper, the azimuth and radial field components of a rectangular-loop antenna in near and far fields are calculated and the results are compared to the elementary circular-loop antenna's field. It is demonstrated that loop dimensions and shape substantially affect its field magnitude, especially in the near field. View full abstract»

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  • The radiation properties of electrically small folded spherical helix antennas

    Publication Year: 2004 , Page(s): 953 - 960
    Cited by:  Papers (87)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (400 KB) |  | HTML iconHTML  

    The radiation properties of several electrically small, folded spherical helix antennas are presented. The primary variables considered in the design of these antennas are the number of helical turns and the number of helical arms. The principle design objectives are to achieve self resonance, a low quality factor (Q), and a practical radiation resistance for small values of ka. Designs are presented for ka less than 0.5, where the antennas are self resonant, exhibiting an efficiency in excess of 95%, a Q within 1.5 times the fundamental limit, and a radiation resistance near 50 Ω. The relationship between the number of helical turns, the number of helical arms, and achieving self resonance at low frequencies is discussed. View full abstract»

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  • Methods for modeling wire antennas loaded with shielded networks

    Publication Year: 2004 , Page(s): 961 - 968
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (304 KB) |  | HTML iconHTML  

    Wire antennas are often loaded with lumped circuits in order to control or alter one or more of the antenna's characteristics. Shielding these circuits forces the load to manifest itself to the antenna from a small aperture. This ensures that the laws of circuit theory may be used in an analysis to characterize the load, rather than Maxwell's equations, simplifying the computations. To this end, four configurations of lumped loads are used in place of the antenna's shielded networks in the analysis of the loaded wire. Two of the lumped load configurations are specific to an aperture-coupled shielded network presented in this paper. Two other configurations considered, however, are physically representative of a large class of wire antenna loads. Data obtained from analyses based upon the models introduced and from measurements are presented for comparison. View full abstract»

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  • Analysis of a tubular monopole loaded with a shielded helical coil

    Publication Year: 2004 , Page(s): 969 - 977
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (408 KB) |  | HTML iconHTML  

    An analysis of a shielded helical coil in a cylindrical tubular antenna is presented, based on a combination of aperture theory and a network model containing lumped RLC components, which is motivated by the desire to use this analysis in antenna-optimization routines. Measured input admittance data for an antenna loaded with a shielded helical coil are presented for comparison with computed data. Also, an experimental procedure by means of which one may measure the transverse electro-magnetic (TEM) input impedance of a coaxial guide loaded with helical coil is described. View full abstract»

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  • A CPW-fed dual-frequency monopole antenna

    Publication Year: 2004 , Page(s): 978 - 982
    Cited by:  Papers (63)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (536 KB) |  | HTML iconHTML  

    A new dual-frequency design of coplanar waveguide (CPW)-fed monopole antenna is proposed and experimentally studied. The proposed antenna utilizes the advantages of the CPW line to simplify the structure of the antenna into a single metallic level, thereby making easier the integration with the microwave integrated circuits. The two operating modes of the proposed antenna are associated with various lengths of two monopoles, in which the longer monopole works for the first resonant mode and the shorter monopole works for the second mode. Moreover, by increasing the width of the longer monopole, a broadband dual-frequency operation is demonstrated. Experimental results show that the impedance bandwidth, determined from 10-dB return loss, of the two operating frequencies can both be greater than 14%. Details of the experimental results are presented and discussed. View full abstract»

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  • Stacked H-shaped microstrip patch antenna

    Publication Year: 2004 , Page(s): 983 - 993
    Cited by:  Papers (18)  |  Patents (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (672 KB) |  | HTML iconHTML  

    A small H-shaped microstrip patch antenna (MPA) with enhanced bandwidth is presented. The H-shaped antenna is first studied by a transmission line model and then is fully analyzed with a MoM code. A stacked patch configuration is proposed to increase the narrow bandwidth, radiation efficiency and directivity. The stacked H-shaped MPA is studied using Chu's fundamental limit for electrically small antennas. View full abstract»

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  • Switchable circular disk antenna for RCS and mobile communications applications

    Publication Year: 2004 , Page(s): 994 - 998
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (224 KB) |  | HTML iconHTML  

    In this paper, we describe the operation of a low profile, 3 mm deep, circular disk antenna which requires a small ground plane, and incorporates a shorting bar which can be rotated. The position of the shorting bar determines the return loss and radiation characteristics of the antenna element. In one mode at 2.34 GHz the antenna exhibits a return loss of better than -25 dB, 5 dBi gain, and a conical/monopole beam pattern suitable for radar tracking/mobile communications applications. When the short circuit is positioned at 90 degrees the return loss at 3.52 GHz becomes -18 dB, 7 dBi gain, and the antenna exhibits normal linear polarized broadside cosine radiation characteristics. In addition when the short circuit is positioned at zero degrees at 3.52 GHz the antenna gives -1 dB return loss and by reciprocity will act as a reflector to incoming energy. Theoretical results are provided in support of the experimental results observed and are used to explain the operating mechanisms of the antenna. View full abstract»

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  • Design and analysis of a reconfigurable dual-beam grating antenna for low-cost millimeter-wave beam-steering

    Publication Year: 2004 , Page(s): 999 - 1006
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (368 KB) |  | HTML iconHTML  

    This paper presents a reconfigurable dual-beam grating antenna for low-cost millimeter-wave beam steering. Experimental results indicate that this multibeam approach provides over ±50° beam steering at fixed frequencies across the entire 35 to 40 GHz band, with excellent radiation patterns maintained across the scans. An approximate analysis developed for the reconfigurable antenna closely predicts the observed scan angles and main beam radiation patterns across the complete range of scan states. These results should have numerous applications in millimeter-wave beam-steering technology. View full abstract»

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  • Investigation of Simulated annealing, ant-colony optimization, and genetic algorithms for self-structuring antennas

    Publication Year: 2004 , Page(s): 1007 - 1014
    Cited by:  Papers (52)  |  Patents (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (376 KB) |  | HTML iconHTML  

    A self-structuring antenna (SSA) is capable of arranging itself into a large number of configurations. Because the properties of the configurations are generally unknown at the onset of operation, efficient search algorithms are required to find suitable configurations for a given set of environmental and operational conditions. This paper investigates the use of ant-colony optimization, simulated annealing, and genetic algorithms for finding suitable antenna states. The implementation of each algorithm for SSA searches is described, and the performance of each algorithm is compared to a random search. View full abstract»

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  • Optimization technique for linearly polarized radial-line slot-array antennas using the multiple sweep method of moments

    Publication Year: 2004 , Page(s): 1015 - 1023
    Cited by:  Papers (15)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (432 KB) |  | HTML iconHTML  

    This paper presents an effective full-wave procedure to optimize linearly polarized radial-line slot-array antennas. The procedure is based on a recursive method for solving large matrix equations known as the multiple sweep method of moments. As a result of this paper, new design suggestions have been introduced which greatly contribute to the performance improvement of this type of antennas. These elements are the arrangement of the slots in concentric ellipses instead of circles and a slight but crucial modification on the usual collocation of the reflection-canceling slots. View full abstract»

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  • Efficiency calculation of feed structures and optimum number of antenna elements in a subarray for highest G/T

    Publication Year: 2004 , Page(s): 1024 - 1029
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (200 KB) |  | HTML iconHTML  

    For an antenna array, different feed structure topologies may yield the same radiation characteristics. However, different topologies may result in different efficiency and noise performance. In this paper, parallel arm antenna arrays are analyzed for efficiency and noise temperature using the noise equivalent line length method (NELL) with the number of antenna elements in a subarray as a parameter. It is shown that efficiency of an antenna array feed structure as well as its noise temperature can be calculated using the NELL method. The comparison of the two parameters, efficiency and noise temperature, yield the optimum number of antenna elements in a subarray of a parallel arm antenna array for the highest G/T ratio. View full abstract»

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  • Transverse slot antenna array in the broad wall of a rectangular waveguide partially filled with a dielectric slab

    Publication Year: 2004 , Page(s): 1030 - 1038
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (712 KB) |  | HTML iconHTML  

    A compact and wide-band transverse slot antenna array in the broad wall of a rectangular waveguide partially filled with an H-plane -dielectric slab is presented in this paper. By partially filling an H-plane dielectric slab in the waveguide, the inter-element spacing between slots is reduced to be about 0.8 free-space wavelengths to avoid grating lobes. In addition, the partially filled material provides extra flexibility to adjust the slot impedance as desired within a relatively wide frequency range. A new feeding network is designed for this antenna array, which can prevent the shift in the pointing angle of the array's main radiation beam with the change of frequency. Experimental data for a 2×4 antenna array operating at X-band show that stable radiation pattern over a wide frequency range can be obtained. The measured gain is 16.9 dB at 10 GHz and the fluctuation is less than 2 dB over a frequency band of 1.5 GHz. The slot array's 10-dB return loss bandwidth is 13% and the cross-polarization level is better than -25 dB. View full abstract»

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  • A frequency-controlled beam-steering array with mixing frequency compensation for multichannel applications

    Publication Year: 2004 , Page(s): 1039 - 1048
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (648 KB) |  | HTML iconHTML  

    A frequency-controlled beam-steering planar array with mixing frequency compensation is presented for cost-effective multichannel phased array applications. The new feed networks for frequency compensation not only operate in wide band but also ensure radio-frequency (RF) amplitude imbalance cancellation and progressive phase distribution. The parallel equal power dividers installed in both LO and intermediate-frequency (IF) feed networks provide uniform amplitude and phase distribution, while the fixed delay lines installed in the LO feed network exhibit precise phase progression, compared to a series feed structure. The LO power imbalance caused by the unequal delay line loss between elements is corrected by pumping each mixer into the LO saturation region, leading to linear IF-RF response. Thus, sidelobe degradation and pattern distortion caused by the RF amplitude imbalance, as well as the beam-steering error and beam squint caused by the phase errors of the delay lines, are removed. The proposed feed networks combined with quasi-Yagi antenna arrays and microwave monolithic integrated circuit mixers realize a broad bandwidth of more than 3 GHz in K band for multichannel wireless applications. The K band transmitter/receiver pair proposed in this paper successfully demonstrates two-channel simultaneous RF transmission and single channel 50-Mb/s data communication with 40° scanning. This simple, compact, yet cost-effective planar array ensures multichannel broadband wireless communications with beam-steering capability. View full abstract»

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  • Electromagnetic transmission through multiple circular apertures in a thick conducting plane

    Publication Year: 2004 , Page(s): 1049 - 1055
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (304 KB) |  | HTML iconHTML  

    The boundary-value problem of electromagnetic wave scattering from multiple circular apertures in a thick conducting plane is rigorously solved. The eigenfunction expansion, integral transform, and superposition principle are utilized to represent the scattered field in the discrete and continuous modes. The boundary conditions are enforced to obtain a set of simultaneous equations for the discrete modal coefficients. The transmission coefficient is represented in a fast convergent series. Computation is performed to illustrate the behavior of transmission and coupling through multiple circular apertures in terms of the aperture geometry. View full abstract»

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  • Diffuse specular sea scatter in the near field

    Publication Year: 2004 , Page(s): 1056 - 1061
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    The far-field theory of Beckmann and Spizzichino (1963) is modified to produce a theory for diffuse scatter in the near field which can be applied to the analysis of multipath effects over a rough sea. View full abstract»

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  • On the determination of resonant modes of dielectric objects using surface Integral equations

    Publication Year: 2004 , Page(s): 1062 - 1069
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (496 KB) |  | HTML iconHTML  

    Although surface integral equations have been extensively used for solving the scattering problem of arbitrarily shaped dielectric objects, when applied to the resonance problem, there are still some issues not fully addressed by the literature. In this paper, the method of moments with Rao-Wilton-Glisson basis functions is applied to the electric field integral equation (EFIE) for solving the resonance problem of dielectric objects. The resonant frequency is obtained by searching for the minimum of the reciprocal of the condition number of the impedance matrix in the complex frequency plane, and the modal field distribution is obtained through singular value decomposition (SVD). The determinant of the impedance matrix is not used since it is difficult to find its roots. For the exterior EFIE, the original basis functions are used as testing functions; for the interior EFIE, the basis functions rotated by 90° are used as testing functions. To obtain an accurate modal field solution, the impedance matrix needs to be reduced by half before SVD is applied to it. Numerical results are given and compared with those obtained by using the volume integral equation. View full abstract»

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  • Diffraction of plane waves by a finite array of dielectric-loaded cavity-backed slots on a common ground plane for oblique incidence and arbitrary polarization

    Publication Year: 2004 , Page(s): 1070 - 1079
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (552 KB)  

    Plane-wave diffraction by a finite array of two-dimensional dielectric-loaded cavity-backed slots on a common ground plane is investigated for oblique incidence and arbitrary polarization. The governing system of coupled singular integral/integrodifferential equations is discretized using moment-method-oriented direct singular integral equation methods. Treating all singular integrals analytically via rapidly converging algorithms leads to numerically stable and efficient analytical expressions for all matrix elements. As a result, no numerical integration is required to compute these elements. Several numerical examples are presented to validate the algorithm and illustrate its convergence characteristics. Results are also presented that reveal the possibility of controlling the absorption efficiency by suitably selecting several geometrical and physical parameters of the structure. View full abstract»

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  • New method for the efficient summation of double infinite series arising from the spectral domain analysis of frequency selective surfaces

    Publication Year: 2004 , Page(s): 1080 - 1094
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (640 KB) |  | HTML iconHTML  

    When the method of moments (MoM) in the spectral domain is applied to the analysis of frequency selective surfaces, the entries of the MoM matrix are slowly convergent double infinite series. In this paper, a two-step acceleration technique is developed which makes it possible the fast and accurate computation of these double series in the particular case where subsectional rooftops are used as basis functions. The technique is based on a combination of the use of Kummer's transformation, the use of Poisson's transformation, and the determination of judicious Chebyshev polynomial interpolations of some of the spectral discrete functions involved in the infinite series. The results obtained show that when all the double series of the MoM matrix are to be computed with an accuracy of three significant figures, the new acceleration technique turns out to be about one thousand times faster than brute-force computation, and a few times faster than the acceleration technique based on fast Fourier transform. View full abstract»

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  • Comparison of the dispersion properties of higher order FDTD schemes and equivalent-sized MRTD schemes

    Publication Year: 2004 , Page(s): 1095 - 1104
    Cited by:  Papers (24)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (376 KB)  

    The dispersion errors of higher order finite-difference time-domain (HO-FDTD) algorithms are compared to those of multiresolution time-domain (MRTD) algorithms that have equivalent spatial stencil sizes. Both scaling-function-based MRTD (S-MRTD) and wavelet-function-based MRTD (W-MRTD) schemes are considered. In particular, the MRTD schemes considered include the Coifman scaling functions and the Cohen-Daubechies-Feauveau (CDF) biorthogonal scaling and wavelet functions. In general, the HO-FDTD schemes are more accurate than their MRTD counterparts. 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