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Antennas and Propagation, IEEE Transactions on

Issue 8 • Date Aug 1991

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Displaying Results 1 - 25 of 32
  • Ultra-wide-band transient electromagnetic scattering laboratory

    Publication Year: 1991 , Page(s): 1230 - 1234
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (484 KB)  

    A unique free-field transient scattering facility is described which employs a dual-channel ultra-wide-band impulsive source. A brief historical review is presented, and the theory and operational characteristics of the laboratory are discussed. Technical implementations which have yielded significant improvement in effective bandwidth and signal-to-noise ratio (SNR) are described. High-quality experimental validations are shown, and consideration is given to future enhancements View full abstract»

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  • Wide-band, wide-angle microstrip stacked-patch-element phased arrays

    Publication Year: 1991 , Page(s): 1062 - 1070
    Cited by:  Papers (9)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (608 KB)  

    The feasibility of a probe-fed, microstrip-stacked-patch element for wideband phased arrays scanned from broadside to about 45° in two planes is established through computer simulation. The implementation of a systematic interactive design procedure of such phased array elements is described. The authors describe the array model, present the main steps in the analysis of scan and frequency gain performance, and consider various aspects of convergence acceleration. An iterative stacked-phased-array-element design procedure is developed. The method is facilitated by identification of the individual uncoupled resonant configurations of the stagger-tuned patch system. The authors present samples of numerical results for active resistance and reflection coefficient for single probe excitation, and some useful transmission line relations View full abstract»

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  • Theoretical design and predictions of volute antenna performance

    Publication Year: 1991 , Page(s): 1227 - 1230
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (344 KB)  

    To provide generic design guidelines for volute antenna elements over a wide range of parameters, a theoretical formulation and algorithm for computing the antenna radiation field have been developed. The procedure relies on the vector combination of the radiation fields of the helical wires and the end connecting wires with a continuous sinusoidal current distribution along each wire of the volute. The antenna patterns of circularly polarized fields, directivity, 3-dB beamwidth, axial ratio, front-to-back power ratio, etc. can all be calculated from a given set of volute parameters. A practical design example utilizing this procedure is presented View full abstract»

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  • Wiener-Hopf type analysis of dielectric-coated dipole antenna in relatively dense medium

    Publication Year: 1991 , Page(s): 1057 - 1061
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (372 KB)  

    The problem of dielectric-coated dipole antennas in a relatively dense medium is solved using the Wiener-Hopf technique. The analysis is done for a perfectly conducting dipole antenna coated by a low-loss dielectric and embedded in a lossy medium of a wavenumber larger than that of the lossy coating. Analytic expression are derived for the input admittance and the current distribution along the dipole which is excited at the center across a nonzero width feed gap. Results are compared with available literature data for different antenna lengths embedded in an ambient medium with a loss tangent of σ/ω∈. The numerical work involves only the determination of certain integrals using standard integration routines View full abstract»

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  • Adiabatic and intrinsic modes for wave propagation in guiding environments with longitudinal and transverse variation: formulation and canonical test

    Publication Year: 1991 , Page(s): 1130 - 1136
    Cited by:  Papers (14)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (672 KB)  

    For an application of the present formalism to continuously refracting media, see ibid., vol.39, no.8, p.1137-42 (1991). Adiabatic modes (AMs) fail in cutoff regions and can be made uniform by intrinsic modes (IMs), which are synthesized by a spectral continuum of AMs. Extending previous studies, the AM-IM format is applied here to longitudinally varying guiding environments wherein transverse confinement is due to a transversely graded trapping index of refraction instead of, or in addition to, the presence of boundaries or interfaces. After the general formulation of the problem, which involves the choice of best coordinate system, the solution strategy is applied to a simple test case, a conventional wedge waveguide treated in (nonseparable) rectangular and in (separable) cylindrical coordinates, in order to assess the numerical accuracy of the AM-IM formalism, and of various approximate versions of it View full abstract»

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  • A complete error model for free space polarimetric measurements

    Publication Year: 1991 , Page(s): 1105 - 1111
    Cited by:  Papers (20)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (680 KB)  

    The authors present a complete 12-term error model for the systematic errors in polarimetric radar and antenna free space measurements for test range and laboratory use. Errors are induced by the frequency response, the channel imbalance, the coupling between the transmit channels, the coupling between the receive channels, the coupling from transmit to receive and by the residual reflections of the environment. The errors are contained in three 2×2 matrices, the isolation matrix, the transmit matrix and the receive matrix. A full polarimetric calibration with the empty room, a sphere, a vertical dihedral corner and a 45° dihedral corner is proposed. The physical understanding is supported by a cubic signal graph for the error terms View full abstract»

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  • Mutual impedance of parallel and perpendicular coplanar surface monopoles

    Publication Year: 1991 , Page(s): 1251 - 1256
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (420 KB)  

    One dimensional integral formulas are derived for mutual impedance of arbitrary size, coplanar, parallel, and perpendicular surface monopoles. The integrals in formulas are expressed as exponential integrals where possible. The mutual impedance expression for parallel monopoles is a summation of exponential integrals and one-dimensional integrals. For perpendicular monopoles, the mutual impedance is in closed form, containing exponential integrals only. The final expressions are in a form suitable for numerical computation. Since the expressions contain at most one-dimensional integrals, they can be utilized to reduce the matrix filling time in the moment method formulations, especially when inhomogeneous sectioning is preferred. Additionally, they can be used in rectangular surface patch modeling of conducting surfaces with edges which are at an angle to the surface patches, providing the angle is small. To this end, the expressions were utilized in the moment method analysis of linearly tapered slot antennas. Very good accuracy was obtained with a reduction in computer time View full abstract»

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  • Wave scattering from slit coupled cylindrical cavities with interior loading. II. Resonant mode expansion

    Publication Year: 1991 , Page(s): 1085 - 1097
    Cited by:  Papers (13)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1028 KB)  

    For pt.I, see ibid., vol.39, no.8, p.1071-84 (1991). The authors consider self-consistent ray-mode parametrization of scattering from a narrow-slit-coupled smoothly convex perfectly conducting interior boundary. The regime at which the operating frequency is near an internal resonance is discussed. The field is expressed as a resonant mode expansion with slit-coupled loading of interior phenomena by exterior ones. A systematic multiple parameter perturbation analysis accounts for the effects of the slit, and of geometrical asymmetries with respect to the slit, in terms of effects pertaining to closed and slitted concentric circular cylinder configurations. Made evident, in particular, is the splitting of the resonant frequencies and mode fields due to asymmetric deviation from the concentric prototype. The analytical predictions are tested on numerical reference data generated by R. W. Ziolkowski and J. B. Grant (1989) for bistatic plane wave scattering when the configuration consists of circular concentric and eccentric boundaries View full abstract»

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  • Adiabatic and intrinsic modes for wave propagation in guiding environments with longitudinal and transverse variation: continuously refracting media

    Publication Year: 1991 , Page(s): 1137 - 1142
    Cited by:  Papers (13)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (508 KB)  

    The adiabatic and intrinsic mode formalism for nonuniform propagation environments, developed and tested in a companion paper (ibid., vol.39, no.8, p.1130-36, 1991), is applied to continuously refracting media. The first example involves a guiding refractive index profile with transverse and longitudinal, but coordinate separable, variation that may be regarded as a prototype for this class of waveguides. A second example involves a nonseparable profile with a guiding-to-antiguiding transition that converts an initially well trapped mode into a radiated beam. Both examples demonstrate the problems encountered in achieving a good parametrization for tracking mode-like wave phenomena under rather general conditions View full abstract»

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  • The admittance of a monopole antenna fed through a ground plane by a coaxial line

    Publication Year: 1991 , Page(s): 1243 - 1247
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (384 KB)  

    A solid circular cylindrical monopole fed through a perfectly conducting ground plane by a coaxial line is rigorously analyzed by applying full wave field theory using the conservation of complex power technique. The model of this analysis is the structure of a coaxial line feeding a larger coaxial waveguide terminated in a ground plane. As the outer radius of the coaxial waveguide is increased, the transverse electromagnetic (TEM) mode admittance of a cylindrical monopole radiating over a ground plane is estimated using a variable bound approach. Numerical results for a thin monopole are established and compared with R.W.P. King's (1971) results for the tubular one. Results for a thick monopole fed by its coaxial line having the dielectric constant εr are also given View full abstract»

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  • Design method of Yagi-Uda two-stacked circular loop array antennas

    Publication Year: 1991 , Page(s): 1112 - 1118
    Cited by:  Papers (1)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (504 KB)  

    A design method which works as a single balanced feed antenna is presented for the Yagi-Uda two-stacked circular-loop array antenna. The antenna is analyzed with a theoretical model consisting of loop elements and feeder sections. The results are compared with experiments. By using the computed and measured antenna currents, the gain enhancement of the antenna is confirmed to be due to both the stacked-loop-array and endfire-array effects. A method of compensation for the reflection loss and a design procedure are discussed in detail. A graphical method is given to estimate the optimum size of the antenna without detailed numerical calculations, and the performance of the designed antenna is demonstrated by experiments. Experimental results are presented for several antennas arranged with different numbers of loops in the endfire and broadside directions View full abstract»

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  • Electromagnetic field behavior near homogeneous anisotropic wedges

    Publication Year: 1991 , Page(s): 1143 - 1151
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (784 KB)  

    The behavior of electromagnetic fields in the vicinity of homogeneous anisotropic wedges is investigated. An extensive analytical treatment is presented for the fields near the tip of the wedge in the static limit. This can be carried out by first allowing the propagation parameter to vanish and then by solving the resulting Laplace-type equation to determine the local distribution of the electric and magnetic fields, which can be found from two transcendental equations. The roots of these equations govern the radial dependence of the field close to the tip and, hence, a graphical representation of their solutions is introduced to illustrate the circumstances under which the fields exhibit singular behavior. Numerical case-studies are presented along with the results obtained by using the static approximation to the dynamic problem. The near fields are calculated so that their radial dependence in the azimuthal plane can be compared to that extracted from the static power law View full abstract»

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  • A novel approach of resolution enhancement with application in array processing of single snapshot

    Publication Year: 1991 , Page(s): 1125 - 1129
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (312 KB)  

    An approach based on spatial filter preprocessing is developed to enhance the resolution of current spectrum estimation algorithms and is applied to sensor array processing in the single snapshot case. The effective signal-to-noise ratio (SNR) and the accuracy of autocorrelation estimation are significantly improved through the use of this approach. Simulation results are presented to illustrate the improved performance achieved by the new approach relative to that obtained with some other algorithms View full abstract»

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  • End-loaded crossed-slot radiating elements

    Publication Year: 1991 , Page(s): 1237 - 1240
    Cited by:  Papers (9)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (420 KB)  

    Three cavity-backed crossed-slot antenna configurations are described that offer simple design, easy frequency tuning, light weight, low loss, and low cost. These antennas are designed for mobile satellite vehicle phased-array applications. The slots in these antennas are end-loaded. The end loading makes the slots effectively longer, and hence reduces their resonant frequency. Therefore, relatively small radiating elements can be achieved for large-angle-scanning phased-array antennas. These antennas have good RF characteristics and provide a relatively wide bandwidth without needing external tuning circuits for impedance matching. Measurements for the return loss and the far-field pattern of these antennas are presented View full abstract»

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  • Compact duplexer-polarizer with semicircular waveguide [antenna feed]

    Publication Year: 1991 , Page(s): 1222 - 1224
    Cited by:  Papers (21)  |  Patents (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (296 KB)  

    A light, compact, and high-performance duplexer-polarizer able to generate circularly polarized waves in a circular waveguide is discussed. Two prototypes were built. The standing-wave-ratio (SWR) and ellipticity performances are extremely good (less than 0.15 dB ellipticity over 15% bandwidth). The experimental development was facilitated by the computation of the dispersion curves and of the transverse field distribution associated with the two fundamental guided modes propagating in the different sections of a septum waveguide View full abstract»

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  • Radio wave propagation over finite size plateau

    Publication Year: 1991 , Page(s): 1152 - 1157
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (320 KB)  

    The problem of radio wave propagation over a perfectly conducting, infinitely wide rectangular plateau of finite length has previously been solved. (see Electron. Lett., vol.25, p.707-9, 1989). This solution is now extended to deal with a perfectly conducting, rectangular plateau of finite size along all three coordinate axes. When the infinite width is reduced to a finite size the additional diffraction round the two sides of the plateau will produce a more complicated expression for the overall attenuation. The authors quantify the new attenuation and derive an approximate analytic expression for the attenuation function in closed form. Experimental confirmation of the calculated result both as a function of distance along the propagation path and as a function of transverse displacement of the plateau perpendicular to the propagation path is presented View full abstract»

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  • A serrated edge Gregorian subreflector for dual chamber compact range systems

    Publication Year: 1991 , Page(s): 1258 - 1261
    Cited by:  Papers (1)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (320 KB)  

    The performance of a Gregorian subreflector compact range system is studied. The compact range system uses a cosine blended rolled edge main reflector. Thus, the main reflector edge diffraction in the potential target zone of the compact system is very small. However, it was found that the diffraction from the edges of the subreflector degrades the incident fields on the main reflector, which subsequently leads to undesired stray fields in the target zone. To reduce the subreflector edge diffraction incident on the main reflector, serrations were added to the subreflector. It is shown that by using the serrated edge reflector, one can reduce the subreflector edge diffraction incident on the main reflector, which subsequently lowers the undesired stray fields in the target zone View full abstract»

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  • Correction factor for multiple knife-edge diffraction

    Publication Year: 1991 , Page(s): 1256 - 1258
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (208 KB)  

    The approximation of J. Deygout (1966) recommended the use of a nomograph proposed by G. Millington et al. (1962) to correct the excess of path loss observed when hills having the same individual loss were close to each other. To help realize that the method is not so pessimistic as believed, a simple mathematical expression is given to replace the use of that nomograph. The author shows how the results compare with those obtained by G. Millington and those obtained by C.L. Giovaneli (1984). Extrapolating from those two cases, it is concluded that J. Deygout's simplified approach, when fully applied, is not pessimistic but rather slightly optimistic. In fact, after hundreds of measurements over obstructed paths in hilly or mountainous terrains with ultra high frequencies, it was found that the mean error between evaluations and measurements is less than 1 dB, with 4-5 dB of standard deviation View full abstract»

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  • A fast null steering algorithm for linearly constrained adaptive arrays

    Publication Year: 1991 , Page(s): 1098 - 1104
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (468 KB)  

    A fast null steering algorithm for adaptive arrays with a look direction constraint is investigated. In this algorithm, the least mean square (LMS) algorithm is used to adaptively adjust the positions of the array response zeros one after another in a time-multiplexed manner to track unknown jammers. To ensure that the look direction response and the other zeros remain unchanged when a particular null is being updated, the element signals are suitably transformed before the LMS updating. Despite this signal transformation, the new algorithm has almost the same implementation complexity as when the LMS algorithm is employed directly, as only one zero is being adaptively updated at any instant. However, with each null being independently steered, the convergence behavior of the new algorithm is significantly faster and is almost independent of the external noise environment View full abstract»

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  • Determination of a natural basis function set on thick, structured slabs using Prony's method

    Publication Year: 1991 , Page(s): 1240 - 1243
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (376 KB)  

    The calculation of currents on a thick structured slab such as a thick slab of honeycomb is discussed. Unfortunately, for certain applications, the slab can be of the order of several wavelengths, so that the straightforward application of the method of moments using subdomain basis functions is too expensive. The authors discuss how to apply Prony's method to the currents calculated for a thin, structured slab to obtain a natural set of basis functions to represent the currents in the interior of a thick slab. Prony's method represents the currents as a series of complex exponential functions. The thick slab problem is then solved by the method of moments using subdomain basis functions near the slab interfaces and one or two of the complex exponentials as basis functions within the slab View full abstract»

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  • Wave scattering from slit coupled cylindrical cavities with interior loading. I. Formulation by ray-mode parametrization

    Publication Year: 1991 , Page(s): 1071 - 1084
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1084 KB)  

    The authors consider an observable-based parametrization of wave scattering for a class of two-dimensional slit-coupled cavity configurations with interior loading. In view of the structural features, the parametrization is chosen in terms of internal guided modes and external ray fields, coupled self-consistently through a narrow slit. Reduced formulations which are applicable when the interior is, or is not, near a resonance are described. These reduced formulations involve, respectively, anomalous and regular modifications of conventional geometrical theory of diffraction to account for high- Q resonant coupling. The problems of interest involve plane wave scattering from structures with exterior-interior coupling View full abstract»

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  • Sidelobe performance in quadratic phase conformal arrays

    Publication Year: 1991 , Page(s): 1234 - 1237
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (320 KB)  

    Sidelobe performance in an array with a quadratic phase distribution is related to the array curvature. Conditions are derived that ensure well-behaved sidelobes for quadratic phase conformal arrays. A similar condition is derived for parabolic shaped arrays and results are given to illustrate the validity of the derived requirement for well-behaved sidelobes for both parabolic and circular arrays. In addition, the sidelobe performance of a nonuniformly spaced linear array is related to the curvature of an equivalent conformal array View full abstract»

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  • Maximum likelihood estimation of direction-of-arrival and detection for broad-band sources via dynamic programming

    Publication Year: 1991 , Page(s): 1213 - 1221
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (672 KB)  

    An analysis is presented to estimate the number of broadband sources by sensor arrays and to compute the maximum likelihood estimator (MLE) of their direction-of-arrival (DOA) based on the dynamic programming algorithm. The approach is devised in the frequency domain. With proper selection of the number of elements, the distance between elements, and the step size, the global maximum for the log-likelihood function can be obtained. Otherwise, the global maximum is not guaranteed. Simulation results for broadband sources that demonstrate the performance of the proposed method are presented and compared with that of the MUSIC algorithm which employs coherent signal-subspace processing View full abstract»

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  • Effect of parasitic element on the characteristics of microstrip antenna

    Publication Year: 1991 , Page(s): 1247 - 1251
    Cited by:  Papers (15)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (372 KB)  

    The variations in the sizes and position of a parasitic element with the input impedance and bandwidth of a rectangular microstrip antenna are investigated by the method of moments. An integral equation for the unknown patch current densities is formulated in the spectral domain. The Galerkin procedure is employed to solve for the unknowns. It is found that the input impedance varies significantly with the size and position of the parasitic patch. The result is important for bandwidth enhancement and impedance matching of the microstrip antenna View full abstract»

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  • FDTD analysis of electromagnetic wave radiation from systems containing horn antennas

    Publication Year: 1991 , Page(s): 1203 - 1212
    Cited by:  Papers (25)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (772 KB)  

    The application of the finite-difference time-domain (FDTD) method to various radiating structures is considered. These structures include two- and three-dimensional waveguides, flared horns, a two-dimensional parabolic reflector, and a two-dimensional hyperthermia application. Numerical results for the horns, waveguides, and parabolic reflectors are compared with results from using the method of moments (MM). The results for the hyperthermia application are shown as extensions of the previously validated models. This new application of the FDTD method is shown to be useful when other numerical or analytic methods cannot be applied 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