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Antennas and Propagation, IEEE Transactions on

Issue 3 • Date May 1983

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Displaying Results 1 - 25 of 32
  • [Front cover and table of contents]

    Publication Year: 1983 , Page(s): 0
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    Freely Available from IEEE
  • Correction to "Multifocal three-dimensional bootlace lenses"

    Publication Year: 1983 , Page(s): 541
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  • Program for three-dimensional polar plots

    Publication Year: 1983 , Page(s): 542 - 544
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  • Experimental study of the characteristics of top-loaded microstrip monopoles

    Publication Year: 1983 , Page(s): 527 - 530
    Cited by:  Patents (1)
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    The characteristics of microstrip monopoles fed at the center with antiphase currents are investigated experimentally. First the impedance is measured as a function of frequency. It is found that the radiation resistance at the resonance near L \simeq 05 \lambda , is very low while the radiation resistance at the resonance near L \simeq \lambda is very high. For a given physical length of the monopole, the resonant frequency is dependent on the strip width and the substrate thickness. The effect of substrate thickness and strip width on the input impedance and bandwidth has also been studied. Finally the E -plane radiation pattern is found to contain two maxima, occurring at approximately \pm 40\deg from broadside. View full abstract»

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  • Propagation and radiation properties of corrugated cylindrical coaxial waveguides

    Publication Year: 1983 , Page(s): 477 - 483
    Cited by:  Papers (5)
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    A theoretical study is given for the behavior of cylindrical coaxial waveguides having reactive (corrugated) surfaces. After a general analysis assuming independent values for the surface reactances, the propagation and radiation properties for specific surfaces are considered. These include the case where 1) both surfaces are smooth-walled; 2) one surface is smooth-walled with the other corrugated; and 3) both surfaces are corrugated such that they have equal values for the surface reactance. View full abstract»

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  • Comparative analysis of a phase and an amplitude processor for amplitude monopulse systems

    Publication Year: 1983 , Page(s): 519 - 522
    Cited by:  Papers (2)
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    The theoretical performance of an amplitude monopulse processor is compared with that of a phase monopulse processor in the presence of thermal noise. Both processors use the sum and difference beam antenna model. Both processors exhibit a bias error at signal-to-noise ratios below 20 dB. The phase processor demonstrates a smaller standard deviation in the angle estimate for target angles in the vicinity of the monopulse boresight. View full abstract»

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  • Nonstationary probabilistic target and clutter scattering models

    Publication Year: 1983 , Page(s): 490 - 498
    Cited by:  Papers (24)
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    A probabilistic model for nonstationary and/or nonhomogeneous clutter and target scattering is proposed and developed. The first-order probability density of the scattered power is treated as the expected value of a conditional density that is a function of random parameters. The family of gamma densities is a general solution for the density function of the intensity reflected by objects comprised of several scatterers and is selected as the conditional density. In the general case, the gamma density is a function of two parameters: the mean and the inverse of the normalized variance. Assuming various distributions for a random mean, expressions for the first-order density of the scattered power are derived and used to explain previous experimental and theoretical results. An example of detection performance for nonstationary target fluctuation based on the developed model is also presented. View full abstract»

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  • Superresolution of multiple noise sources in antenna beam

    Publication Year: 1983 , Page(s): 456 - 462
    Cited by:  Papers (2)
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    The superresolution of external noise sources that lie within the beamwidth of an adaptive array antenna becomes increasingly more difficult as the number of sources and corresponding number of antenna subapertures are increased. This difficulty was demonstrated with a digital computer simulation of a particular array antenna that utilizes Gabriel's thermal noise algorithm to accomplish the superresolution processing. Two closely spaced sources are easily resolved when the antenna is divided into three subapertures. It is not as easy to resolve four sources when the antenna is divided into five subapertures, and it is especially difficult to resolve six sources when the antenna is divided into seven subapertures. When the sources are not completely resolvable, however, the two outermost sources in the cluster are accurately located in many instances, and at least precise bounds on the cluster are established. View full abstract»

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  • A spectral-iteration technique for analyzing scattering from arbitrary bodies, Part II: Conducting cylinders with H-wave incidence

    Publication Year: 1983 , Page(s): 535 - 537
    Cited by:  Papers (6)
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    The stacked two-dimensional spectral iteration technique (SIT) introduced in an accompanying paper is further developed and extended to the case of an H -polarized field incident on an arbitrary conducting cylinder. As before, the method takes advantage of the simplicity with which the relationships between planar sources and fields are expressed in the spectral domain. View full abstract»

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  • A spectral-iteration technique for analyzing scattering from arbitrary bodies, Part I: Cylindrical scatterers with E-wave incidence

    Publication Year: 1983 , Page(s): 499 - 506
    Cited by:  Papers (28)
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    In the past, methods for solving electromagnetic scattering problems in the frequency domain have been developed largely for the low-frequency (moment method) and high-frequency (asymptotic techniques) regimes. The intermediate frequency range has been analyzed by combinations of these two approaches or by separation of variables, when possible. This paper is devoted to the development of an independent approach, viz., the "stacked spectral-iteration technique," which is capable of handling arbitrary scatterers with dimensions ranging from small to moderately large. The method takes advantage of the simplicity with which the planar-source planar-field relationships are expressed in the spectral domain. The boundary conditions or constitutive relationships, on the other hand, are expressed most simply in the spatial domain. Alternating between the two domains is carried out with the aid of the fast Fourier transform (FFT) algorithm. The spectral-iteration technique (SIT) was applied in the past to thin planar structures which allow the analysis to be carried out on a plane. The generalization of the two-dimensional formulation to arbitrary three-dimensional bodies can be accomplished by sampling the current distribution on the scatterer over a number of parallel planes, and using the simple spectral-domain interaction relationships between the planes. This new approach involves no matrix inversion and is capable of analyzing scatterers whose sizes far exceed those treatable by the moment method. In addition to being arbitrarily shaped, the scatterer may be conducting, dielectric, or lossy dielectric. Thus, the SIT provides an efficient approach to filling the much-needed gap between low- and high-frequency conventional techniques, e.g., the moment method (MoM) and the geometrical theory of diffraction (GTD), and to extending the range of applicability to dielectric scatterers, with or without loss. Though the concepts presented herein are applicable to arbitrary three-dimensional scatterers, the problem of arbitrary cylinders with E -polarized excitation is addressed in this paper, while the H -case is treated in an accompanying work. The three-dimensional case is to be reported in a future communication which treats the problem of scattering- by a lossy inhomogeneons dielectric cylinder of finite length. View full abstract»

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  • Directivity optimization for Yagi-Uda arrays of shaped dipoles

    Publication Year: 1983 , Page(s): 522 - 525
    Cited by:  Papers (9)
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    A method is presented for the maximization of the directivity of Yagi-Uda arrays whose elements are not straight conductors. The optimum shapes as well as the positions of the array elements are determined, both of which depend on the radius of the conductors. The moment method is used in the optimization process. An example shows that an optimized Yagi-Uda array of three 1.5 \lambda elements can achieve a maximum directivity of 11.8 dB. View full abstract»

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  • Experimental study of the characteristics of coupled top-loaded microstrip monopoles

    Publication Year: 1983 , Page(s): 530 - 531
    Cited by:  Papers (7)
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    The characteristics of a two-element broadside array consisting of a top-loaded microstrip monopole fed at the center with antiphase currents and a parasitic microstrip element are investigated experimentally. The input impedance is measured as a function of frequency, with spacing between the elements and length of the parasitic element as parameters. Our results show that the coupled system has a dual frequency characteristics. It is also shown that a particular set of values of spacing and parasitic element length leads to a substantial increase in the bandwidth of the lower resonance. The radiation pattern of the array has also been measured. View full abstract»

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  • Theoretical analysis and some experiments on Vierergruppe Antenne (Two-dipole antennas)

    Publication Year: 1983 , Page(s): 413 - 418
    Cited by:  Papers (2)
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    A center-fed full-wave dipole antenna located one-quarter wavelength above a reflecting plate has a very low potential relative to the plate, at the center of each half-wave element. When metal support bars are attached between these center points and the reflector plate to support the antenna, the structure is called a "metal supported full-wave dipole antenna." An antenna made up of two such full-wave dipole antennas has four half-wavelength antenna elements and has been named "Vierergruppe Antenne." This antenna and the "Achterergruppe Antenne" were invented in Germany. Vierergruppe antenne (sometimes called two-dipole antennas) can be rugged because they are made entirely of metal and do not require insulator supports. They also have excellent electrical characteristics over a very wide frequency range, and are widely used by TV and FM broadcasting stations around the world. Since the full-wave dipole antenna element is composed of a conductor having a diameter as large as 1/20 of the operating wavelength, it is unsuitable to use conventional thin conductor theory to analyze the antenna behavior. In particular, the current at the end of the thick solid antenna element will not be zero, as in the case of the thin one. Flat end-face currents are determined by using a quasi-static approximation and the moment method of analysis. Accordingly the excellent characteristics of this antenna have been found theoretically and fully clarified in the quarter century since its invention. View full abstract»

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  • Maximum power penetration through an electrically small aperture

    Publication Year: 1983 , Page(s): 518 - 519
    Cited by:  Papers (1)
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    The maximum transmission cross section of an electrically small aperture reported by Harrington is derived from a power conservation law. View full abstract»

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  • Mutual coupling and radiation patterns of two slots asymmetrically located on a square plate

    Publication Year: 1983 , Page(s): 531 - 535
    Cited by:  Papers (2)
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    Two slot antennas mounted symmetrically on a square plate will radiate a symmetrical antenna pattern. When the slots are moved the pattern will be unsymmetrical. The degree of symmetry degradation of various locations of the slots and the mutual coupling between them is the subject of the investigation of this communication. The equivalent magnetic edge current is used to make calculations. View full abstract»

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  • Cylindrical and three-dimensional corner reflector antennas

    Publication Year: 1983 , Page(s): 451 - 455
    Cited by:  Papers (7)  |  Patents (3)
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    Two reflector antennas are proposed. The first is constructed by adding a cylindrical reflecting surface of suitable radius to the V -shaped corner reflector antenna. The feeding element is a half-wavelength dipole. The resulting cylindrical corner reflector provided a 2 dB increase in gain, minimum sidelobe level, low input reactance, and uncritical dependence of performance on frequency. The second antenna is constructed by adding a cylindrical surface to the three-dimensional corner reflector. This extension provided an increase in gain of at least 6.5 dB, an input resistance compatible with the commercially available 50- or 75-\Omega coaxial cables, low input reactance, and uncritical dependence of performance on frequency. A grid-type cylindrical corner reflector antenna, and a three-dimensional corner reflector antenna with a cylindrical subsurface of finite reflecting surfaces were designed, and the measured input impedances, gains, and field patterns showed excellent agreement with the theoretical results for both antennas. View full abstract»

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  • The singular integral problem in surfaces

    Publication Year: 1983 , Page(s): 507 - 509
    Cited by:  Papers (8)
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    The calculation of surface current distribution, given the geometry and source description, is a fundamental problem in antenna theory. In extending the harmonic analysis-integral equation method from one-dimensional to two-dimensional problems, a new way to deal with the singularity in the source-field relation is needed. Some results are given for surface current integrals which convert them to a convergent form. View full abstract»

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  • Creeping waves and resonances in transient scattering by smooth convex objects

    Publication Year: 1983 , Page(s): 426 - 437
    Cited by:  Papers (38)
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    Scattering by smooth convex objects, excited by a transient field with broad spectral content, has been analyzed either by ray formulations, which are useful at observation times descriptive of the early arrivals, or by the complex resonances of the singularity expansion method (SEM), which are most appropriate at intermediate and late observation times. Within the framework of SEM, efforts have recently been made to show that in a grouping of the resonances along "layers," rather than along the conventional "arcs" based on an angular harmonic field representation, the higher order resonances behave collectively like a wave traveling circumferentially around the object. This observation has provided the stimulus for the present investigation in which the relation between the wavefront arrivals (creeping waves) and the SEM resonances is placed on a rigorous basis. Using a perfectly conducting circular cylinder as a canonical model, this is done by direct application of the theory of characteristic Green's functions to construct alternative field solutions, and by collective summation of groups of wavefront arrivals or groups of resonances. The connection between creeping waves and resonances thus having been established, hybrid formulations are developed which combine the creeping waves and the SEM resonances within a single rigorous framework so as to maximize the utility of each over the entire range of observation times. These results are then generalized to smooth cylindrical objects with noncircular convex shape. View full abstract»

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  • Dielectric logging with downhole invasion effects

    Publication Year: 1983 , Page(s): 397 - 405
    Cited by:  Papers (2)
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    The transfer impedance between conducting coils is evaluated to estimate the downhole dielectric properties that can contribute to more effective exploration and production of gas/oil reservoirs. The earth formation with a borehole-mud filtrate invasion is simulated by concentric zones of variable dielectric properties to account for rocks saturated by different fluids. We have imposed analytical restrictions to allow only magnetic-dipole coupling between logging coils and to limit logging source frequencies from 10 to 30 MHz for typical coil spacings. Depending on the depth of invasion front, guided waves may exist in the invaded formation. When guided waves do not exist, rapidly converging branchcut integrations are used to evaluate the transfer impedance. When the invasion front begins to support guided waves the numerical convergence becomes somewhat slower using spatial-band-limited integrations. Both types of integration are used to produce inversion charts from which dielectric properties and invasion-front radii can be estimated from downhole-measurable transfer impedances. Ambiguity in parameter inversion is also demonstrated to provide insight for developing a future inverse process based on array processing of adequately sampled data. View full abstract»

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  • Time domain sensors for radiated impulsive measurements

    Publication Year: 1983 , Page(s): 438 - 444
    Cited by:  Papers (27)  |  Patents (3)
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    Discussion of various sensors and radiators commonly used for time domain antenna measurements is presented. The sensors and radiators discussed here are passive and analog devices which convert the electromagnetic quantity of interest to a voltage or current at their terminal ports. Moreover they are primary standards in the sense that their transfer functions can be calculated from their geometries and are flat (constant) across a wide frequency range. One of the major requirements for these sensors and radiators is that the electromagnetic far field, transmitted or received, is a replica or high fidelity derivative of the original pulse. Note that the transmitting transfer function of an antenna is proportional to the time derivative of the receiving transfer function of the same antenna, which follows from the reciprocity theorem. For electric field strength measurements, linear antennas loaded nonuniformly and continuously with resistance, or with both resistance and capacitance are discussed. Also, a conical antenna and an asymptotic conical antenna are discussed from the standpoint of improved characteristics. For an improved directivity, various types of transverse electromagnetic (TEM) horns are considered, e.g., a conducting TEM horn, and a resistively loaded TEM horn. View full abstract»

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  • Directivity of planar array feeds for satellite reflector applications

    Publication Year: 1983 , Page(s): 463 - 470
    Cited by:  Papers (29)
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    Array-fed reflector antennas are used extensively in today's contour and multiple beam satellite antennas. To determine the directivity of these antennas theoretically, the total radiated power of the array feed must be accurately computed. In this paper, a closed-form expression for the radiated power is obtained for arrays with the well-known (\cos \theta)q -type element patterns. The formulation is general, and takes into account polarization, nonsymmetric E - and H -plane element patterns, nonuniform element spacings and arbitrary complex excitation coefficients. Selective numerical data are presented to demonstrate the usefulness of this result. Comparisons are made with the available results obtained using direct numerical integration techniques, and with other available data based on less general formulations. Excellent agreement is observed for all cases. In particular, data are presented on the directivity of seven-element cluster feeds used in multiple beam designs, and an array feed for producing a contour beam covering the United States Eastern Time Zone (ETZ). View full abstract»

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  • The resonant cylindrical dielectric cavity antenna

    Publication Year: 1983 , Page(s): 406 - 412
    Cited by:  Papers (325)  |  Patents (28)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (528 KB)  

    An experimental investigation of the radiation and circuit properties of a resonant cylindrical dielectric cavity antenna has been undertaken. The radiation patterns and input impedance have been measured for structures of various geometrical aspect ratios, dielectric constants, and sizes of coaxial feed probes. A simple theory utilizing the magnetic wall boundary condition is shown to correlate well with measured results for radiation patterns and resonant frequencies. View full abstract»

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  • VHF propagation over hilly, forested terrain

    Publication Year: 1983 , Page(s): 483 - 489
    Cited by:  Papers (13)
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    Propagation measurements at low altitudes over hilly, forested terrain made with the objective of developing a computer-based propagation model capable of predicting path loss over similar terrain given the terrain profile between transmitter and receiver are reported. The measurements were made at a frequency of 110.6 MHz with the very high frequency omnidirectional range (VOR) station at Gardner, MA, as a transmitter. The received signals were measured at distances between 7 and 15 km by making vertical descents with a helicopter from altitudes of roughly 600 m down to 10 m above ground. Negligible specular ground reflection was observed from this terrain, and no reflection is included in the model. We found good agreement between the measurements and a multiple-diffraction model based on an extension of the Deygout approximation. Use of two knife edges was sufficient to characterize the terrain diffraction. Predictions of the Longley-Rice computer model are included for comparison. View full abstract»

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  • On the current distribution for open surfaces

    Publication Year: 1983 , Page(s): 515 - 518
    Cited by:  Papers (5)
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    The solution of electric and magnetic field type integral equations is investigated for a simple open surface, i.e., a thin plate. By combining the electric and magnetic field formulations, a set of coupled integral equations is obtained which can be solved for the currents on either side of the plate. Numerical results illustrate these currents for different size plates. View full abstract»

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  • A new MIC slot-line aerial

    Publication Year: 1983 , Page(s): 525 - 527
    Cited by:  Papers (16)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (288 KB)  

    The design and performance of a new microwave integrated circuit (MIC) slot-line antenna is presented. The new antenna has a narrower beam for the same order of gain as that of the conventional MIC dipole and resonator antennas. The antenna operates in X -band with a gain of 6 dB and a sidelobe level of 10 dB. It can be easily integrated with other MIC components. 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