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Antennas and Propagation, IEEE Transactions on

Issue 11 • Date Nov 1988

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Displaying Results 1 - 25 of 28
  • An X-band experimental model of a millimeter-wave interinjection-locked phased array system

    Publication Year: 1988 , Page(s): 1641 - 1645
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (348 KB)  

    An interinjection-locked 10 GHz model of a millimeter-wave phased-array system has been built and tested. It has been successfully demonstrated that this novel technique can be used to control limited-scan phased-array antennas. A beam shift of ±5° has been achieved with only one phase shifter in a four-oscillator system. Adaptability to monolithic fabrication and a reduction in the number of phase shifters required make this method attractive for use at millimeter-wave frequencies View full abstract»

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  • Antenna array design for covariance-based direction-finding methods

    Publication Year: 1988 , Page(s): 1537 - 1544
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (740 KB)  

    Angle-of-arrival estimates based on the analysis of a spatial covariance matrix are particularly vulnerable to error in the presence of coherent signal interference. When this condition exists, the wave interference field is statistically nonstationary, and estimation techniques that are based upon an assumption of stationarity tend to produce poor results. A method is proposed for the design of antenna arrays that exploits the effects of time-averaging and spatial smoothing to approximate the condition of statistical stationarity and thereby enhance the performance of bearing estimation methods View full abstract»

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  • A quick way to approximate a Sommerfeld-Weyl-type integral [antenna far-field radiation]

    Publication Year: 1988 , Page(s): 1654 - 1657
    Cited by:  Papers (12)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (336 KB)  

    A method to evaluate the Sommerfeld-Weyl-type integral rapidly in the far field is reviewed. With such a method, one can perform `back-of-the-envelope' derivations for the far-field expressions of Sommerfeld-Weyl-type integrals. First, the stationary-phase point of the integrand is identified. Closed-form integrals are then identified that can be used to integrate the rapidly varying part of the integrand in closed form View full abstract»

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  • The application of a biquadratic programming method to phase only optimization of antenna arrays

    Publication Year: 1988 , Page(s): 1545 - 1550
    Cited by:  Papers (14)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (436 KB)  

    Antenna array optimization by a biquadratic programming method is formulated with variable-phase (analog and digital) and constant amplitude excitation. The method can optimize an antenna performance index expressible as a ratio of Hermitian quadratic forms. Power gain optimization and least-squares pattern synthesis with a specified gain are illustrated. Linear, planar, and circular arrays with dipole or circular loop elements are optimized, taking mutual coupling effects between antenna elements into account. The method shows much more rapid convergence characteristics than the Rosenbrock (1960) and Fletcher-Power (1963) methods View full abstract»

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  • Scattering from dipoles loaded with diodes

    Publication Year: 1988 , Page(s): 1649 - 1651
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (268 KB)  

    The problem of scattering from dipoles arbitrarily loaded with passive and active diodes is solved by the method of moments. Results are presented for the tumble average scattering radar cross section of dipoles loaded with p-i-n diodes and negative resistance diodes such as tunnel and Gunn diodes. Single as well as multiple loadings are considered View full abstract»

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  • Mutual coupling and sidelobe tapers in phase-only antenna synthesis for linear and planar arrays

    Publication Year: 1988 , Page(s): 1624 - 1629
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (508 KB)  

    A method of obtaining the lowest possible peak sidelobe levels, given a specified sidelobe envelope, by phase-only variation of the generator phases is presented. A generalization of earlier work by the authors, this technique involves the optimization of a piecewise differentiable objective function using the method of steepest descent to obtain desired generator phases, given prescribed excitation magnitudes. The method has been applied to both linear and planar arrays of radiators, with single-mode mutual coupling effects included to provide realistic data. Values for the various array performance indices are presented, and results indicate that introduction of sidelobe taper improves the array gain while raising the peak sidelobe level somewhat. Inclusion of mutual coupling effects alters the required phases for optimum patterns but does not significantly affect the performance indices of the array View full abstract»

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  • Characteristics of the equilateral triangular patch antenna

    Publication Year: 1988 , Page(s): 1510 - 1518
    Cited by:  Papers (28)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (556 KB)  

    The results of a comprehensive analysis of this antenna based on the cavity model with a coaxial feed source are given. The theoretical formulas are given, and the characteristics obtained from them are presented, including radiation patterns, percentages of power radiated, total Q-factors, input impedances, and their variations with feed position. A number of disagreements with previously published results are noted. The theoretical and experimental results are compared. The results of the comparison indicate that the equilateral triangular patch can be designed to function as a triple frequency antenna. A method for correcting for the nonperfect magnetic wall is suggested View full abstract»

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  • Analysis of electromagnetic scattering from dielectrically coated conducting cylinders using a multifilament current model

    Publication Year: 1988 , Page(s): 1602 - 1607
    Cited by:  Papers (12)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (480 KB)  

    A method of moments solution is presented for the problem of transverse magnetic scattering from dielectrically coated conducting cylinders. The solution uses fictitious filamentary electric sources of yet unknown currents to simulate both the field scattered by the cylinder and the field inside the dielectric coating. The simulated fields obey the boundary conditions, namely, the continuity of the tangential components of the electric and magnetic fields across the air-dielectric interface and the vanishing of the tangential component of the electric field at the perfect conductor, at selected sets of points on these respective surfaces. The result is a matrix equation that is readily solved for the unknown current. The currents can be used to determine approximate values for the fields and field-related parameters of interest. The procedure is simple to implement and is general in that cylinders of smooth but otherwise arbitrary shape and coating of arbitrary complex permittivity can be handled. Illustrative examples are considered and compared with available data, demonstrating the efficiency of the solution View full abstract»

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  • An anisotropic lens for transitioning plane waves between media of different permittivities

    Publication Year: 1988 , Page(s): 1571 - 1579
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (464 KB)  

    A particularly simple geometry is considered in which an inhomogeneous and anisotropic lens is specified for the transitioning of plane waves between media of different permittivities. The permittivities of the regions outside of the lens can be constant, but the permittivity of the lens region depends on position. Results are presented for a plane wave in the second medium propagating normally to the assumed plane boundary of that medium. The results for the case of normal incidence are then generalized to the case of nonnormal incidence. The conditions of transit time conservation and impedance matching are related to the Brewster angle View full abstract»

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  • The `clamshell problem'-interpolation of shaped reflectors and other smooth surfaces

    Publication Year: 1988 , Page(s): 1560 - 1565
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (492 KB)  

    An interpolation method for shaped reflector antennas and similar smooth surfaces is developed using cubic spline interpolants in a parametric representation. Ordinary one-dimensional splines are combined in tensor products to give a two-dimensional interpolant for each cartesian component of points of the surface. The two independent variables are the polar coordinates of rays traced from an aperture disk. This ray tracing maps a grid of lines from the aperture to the surface being interpolated and gives a general-purpose method for interpolating smooth surfaces. The polar coordinates are partitioned into uniform intervals, which simplifies the calculations. The interpolant is differentiated to provide partial derivatives of the surface coordinates, and these derivatives are combined to give surface normals and Jacobians. The bicubic spline is also integrated to give a general-purpose two-dimensional integration routine. The parametric form makes it easy to find a variety of cross sections, boundaries, inflection points, and other characteristics of the surface View full abstract»

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  • An experimental adaptive array to suppress weak interfering signals

    Publication Year: 1988 , Page(s): 1551 - 1559
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (712 KB)  

    An experimental adaptive antenna system to suppress weak interfering signals is described. It is a sidelobe canceller with two auxiliary elements. Modified feedback loops are used to control the array weights. The received signals are simulated in hardware for parameter control. Digital processing is used for algorithm implementation and performance evaluation. The experimental results are presented. They show that interfering signals as much as 10 dB below the thermal noise level in the main channel are suppressed by 20-30 dB. Such a system has potential application in suppressing the interference encountered in direct broadcast satellite communication systems View full abstract»

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  • Performance of probe-fed microstrip-patch element phased arrays

    Publication Year: 1988 , Page(s): 1501 - 1509
    Cited by:  Papers (30)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (632 KB)  

    The performance trends for large phased arrays with probe-fed microstrip-patch elements are discussed, with primary consideration given to single-probe (unbalanced) feed for rectangular grid arrays with rectangular patch geometry. The effects of substrate thickness and permittivity, patch dimensions, and element spacing are examined. Pronounced surface- and leaky-wave effects that tend to limit the scan volume are found. Interaction between the patch resonance at broadside scan and the leaky-wave resonances leads to an E-plane scan-bandwidth tradeoff. In the H-plane scan a transverse electric (TE)-type guided wave resonance is found that becomes pronounced when the H-plane dimension is a large fraction of the H-plane element spacing. This leads to a limitation of the H-plane patch dimension in the rectangular grid arrays. An element design procedure is proposed and illustrated for an element suitable for wide-angle scan over a ±5% frequency band View full abstract»

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  • A new prediction method for tropospheric scintillation on Earth-space paths

    Publication Year: 1988 , Page(s): 1608 - 1614
    Cited by:  Papers (40)  |  Patents (101)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (556 KB)  

    A method of predicting scintillation fading occurring on Earth-space paths is proposed that is based on the data obtained from a low-elevation 14/11 GHz wave propagation experiment at Yamaguchi, Japan. This model includes parameters representing meteorological conditions that have not been covered in existing models and can be applied to broad regions with varying climates. The prediction accuracy of the method is evaluated using experimental data collected at four sites in the western part of Japan, as well as data reported thus far on a worldwide basis. Although data used for evaluation are limited, the model shows good prediction accuracy for frequencies from 7 to 14 GHz and elevation angles from 4° to 30° View full abstract»

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  • Asymptotic behavior of the scattering solutions for a multilayered sphere

    Publication Year: 1988 , Page(s): 1594 - 1601
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (540 KB)  

    The asymptotic behavior of the scattering solutions for a point source radiating in the presence of a N-layered sphere is studied. A spectral integral representation is used to represent the potentials and the fields. The scattering solutions are approximated by the residue series arising from the poles of the integrand in the complex-order plane (v-plane). A diffraction factor D0 (vp) is used to determine the significance of each pole in the evaluation of the scattering solutions. Numerical results illustrate the dependence of D0p) on the geometric parameters and material properties. Results for multilayered cylinders are included for comparison View full abstract»

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  • Extended integral equation formulation for scattering problems from a cylindrical scatterer

    Publication Year: 1988 , Page(s): 1580 - 1586
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (520 KB)  

    An extended integral equation is developed for electromagnetic scattering from a perfectly conducting cylinder and a dielectric cylinder. The conventional surface integral equations cannot yield unique solutions when the wavenumber of the electromagnetic wave is equal to an eigenwavenumber of the system. Several methods to overcome this difficulty have been presented, but each method includes some drawbacks. A numerical method is proposed in which the boundary element method is applied to the extended integral equations with the observation points lying on a closed surface inside the scatterer. It is shown that the extended integral equations have unique solutions for any given wavenumber. As examples, plane wave scattering from a perfectly conducting elliptic cylinder, a dielectric elliptic cylinder, and a dielectric rectangular cylinder is numerically analyzed View full abstract»

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  • V-conical antenna

    Publication Year: 1988 , Page(s): 1519 - 1525
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (412 KB)  

    A new angular antenna called the V-conical antenna was investigated. The characteristics of the antenna are frequency-independent, and the electromagnetic fields are pure spherical waves (transverse electromagnetic mode) even in the near region. The theoretical analysis makes use of conformal mapping. Closed-form solutions for the fields, currents, and characteristic parameters are obtained. The formulas are simple and precise. An experimental study of the antenna was conducted under pulse excitation. The shape of the measured electric-field pulses is the same as that of the source pulse from a picosecond pulse generator. The measured field patterns are very close to those predicted by the theory. Such a structure with a tapered resistive termination is an ideal directional pulse antenna or electromagnetic pulse simulator View full abstract»

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  • Realizable feed-element patterns and optimum aperture efficiency in multibeam antenna systems

    Publication Year: 1988 , Page(s): 1637 - 1641
    Cited by:  Papers (12)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (464 KB)  

    The results of an earlier paper by Y. Rahmat-Samii et al. (ibid., vol.AP-29, pp.961-3, 1981), regarding realizable patterns from feed elements that are part of an array that feeds a reflector antenna, are extended. The earlier paper used a cosq θ model for the element radiation pattern, whereas here a parametric study is performed, using a model that assumes a central beam of cosq θ shape, with a constant sidelobe level outside the central beam. Realizable q-values are constrained by the maximum directivity based on feed element area. The optimum aperture efficiency (excluding array feed network losses) in an array-reflector system is evaluated as a function of element spacing using this model as well as the model of the earlier paper. Experimental data for tapered slot antenna arrays are in agreement with the conclusions based on the model View full abstract»

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  • Approximate analytic continuation of the Rayleigh series [radar cross-section]

    Publication Year: 1988 , Page(s): 1652 - 1654
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (252 KB)  

    Pade approximants are used to continue approximately the Rayleigh series for the radar cross section (RCS) of the sphere beyond its radius of convergence. Numerical studies show that accurate results for the RCS can be obtained to ka ~2.2 if many series terms are available. Since this is rarely, if ever, the case, it is further demonstrated that even with only four nonzero terms available the technique is accurate to ka ~1.1. This provides an indication of the number of series coefficients that must be calculated to use the Rayleigh series in the lower part of the resonance regime. An additional point that is demonstrated is the ability of the technique to provide highly accurate estimates of the radius of convergence of the series. A useful byproduct is the generation of an approximation for the scattering of the sphere, valid for all real values of ka, which has a maximum error of less than 3% View full abstract»

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  • Shaped-pattern synthesis using pure real distributions

    Publication Year: 1988 , Page(s): 1645 - 1649
    Cited by:  Papers (26)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (380 KB)  

    Shaped patterns can be produced by properly excited equispaced linear arrays. An earlier synthesis procedure, which accomplishes this with control ripple in the shaped region and controlled sidelobe levels elsewhere, results in array distributions that are generally complex. It is shown here that if the shaped pattern is symmetric and has 2M filled nulls, there are 2M complex symmetric distributions, and 2M pure real asymmetric distributions, and 22M-2M+1 complex asymmetric distributions that will produce the desired pattern. By adding 2M elements to the array, one can find a symmetric pure real distribution that will achieve the same result. A representative example illustrates the procedure. The results have application to standing-wave-fed planar arrays with quadrantal symmetry via use of the collapsed distribution principle View full abstract»

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  • A template for shaped-beam satellite antenna patterns

    Publication Year: 1988 , Page(s): 1633 - 1637
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (448 KB)  

    A modified template is proposed for shaped-beam satellite antenna patterns for use in orbit-planning studies of a fixed satellite service. Based on a previously discussed simple model, the template now includes the effects of beam scanning, aperture blockage, and surface errors. It is found to agree well with the measured data on current satellites and is a reasonable upper bound specification for future satellite antennas View full abstract»

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  • Spectral domain analysis of a coupled slot antenna

    Publication Year: 1988 , Page(s): 1620 - 1624
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (400 KB)  

    The characteristics of a coupled slot resonator suitable for novel design of an integrated planar antenna are analyzed. The analysis is based on the spectral domain immittance matrix approach, and all the wave phenomena associated with the structure are incorporated. The resonant frequencies in the even and odd resonance modes are evaluated from the numerical solution of the characteristic equation, and the radiation patterns are calculated. The numerical results are compared with experimental data with good agreement View full abstract»

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  • Comparison between computed and measured bandwidth of quarter-wave microstrip radiators

    Publication Year: 1988 , Page(s): 1615 - 1616
    Cited by:  Papers (33)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (132 KB)  

    A simple theory based on a cavity model is used to analyze a quarter-wavelength flat element, without a dielectric substrate, which is connected to the ground plane in one of its sides by a metallic wall. The bandwidth of the element is computed from this model. Very good agreement is obtained between the computed and the measured bandwidth for elements in the S-band View full abstract»

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  • Element gain pattern prediction for finite arrays of V-dipole antennas over ground plane

    Publication Year: 1988 , Page(s): 1629 - 1633
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (368 KB)  

    The element gain pattern for finite phased arrays of dual-polarized crossed V-dipole antennas over ground plane is addressed. The method of moments is used to predict the center-element gain pattern. An experimental, 19-element, passively terminated planar array is described, and center-element gain pattern measurements are presented. The theoretical results are in good agreement with measurements View full abstract»

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  • A design procedure for slot arrays fed by single-ridge waveguide

    Publication Year: 1988 , Page(s): 1531 - 1536
    Cited by:  Papers (20)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (348 KB)  

    R.S. Elliott's (1983) design procedure for arrays of longitudinal slots in one broad wall of each rectangular waveguide is extended to the case in which the waveguides have ridges in the opposite broad walls. External mutual coupling has been taken into account. A two-be-eight array was constructed and tested, and the results validate the theory. Ridging is significant because it permits E-plane scanning from broadside to endfire View full abstract»

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  • A conjugate gradient procedure for the analysis of planar conductors with alternating patch and aperture formulations [EM scattering]

    Publication Year: 1988 , Page(s): 1616 - 1620
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (424 KB)  

    The formulation of an electromagnetic scattering problem by an operator equation can be done in different ways leading to different rates of convergence when the conjugate gradient algorithm is used. The convergence can tend to slow down at certain stages, depending on the formulation used. Thus, whenever the error tends to level off in one formulation, it is advisable to switch to another one. To this end a procedure that alternates repeatedly between formulations is presented. It is shown to accelerate the convergence rate during the earlier stages of the iterative process, making it possible to arrive at a prescribed practical error criterion faster. A substantial saving in storage allocation is attained 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