By Topic

Antennas and Propagation, IEEE Transactions on

Issue 5 • Date September 1981

Filter Results

Displaying Results 1 - 25 of 30
  • [Front cover and table of contents]

    Publication Year: 1981 , Page(s): 0
    Save to Project icon | Request Permissions | PDF file iconPDF (192 KB)  
    Freely Available from IEEE
  • Comments on the Bojarski identity

    Publication Year: 1981 , Page(s): 825
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (95 KB)  

    First Page of the Article
    View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Correction to "A systematic design formulation for butler matrix applied FFT algorithm"

    Publication Year: 1981 , Page(s): 825
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (95 KB)  

    First Page of the Article
    View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • [Back cover]

    Publication Year: 1981 , Page(s): c4
    Save to Project icon | Request Permissions | PDF file iconPDF (319 KB)  
    Freely Available from IEEE
  • Inverse scattering of a layered and dispersionless dielectric half-space, part I: Reflection data from plane waves at normal incidence

    Publication Year: 1981 , Page(s): 726 - 732
    Cited by:  Papers (14)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (504 KB)  

    An inverse scattering theory and two inversion algorithms for the reconstruction of the dielectric profile of an inaccessible, layered, and dispersionless half-space are presented. The source and receiver are located at a distance above the inaccessible region. The source is an artificial electromagnetic source which is assumed to be capable of radiating plane waves at normal incidence for all the positive frequencies. In this case the receiver measures the reflection coefficient phase and amplitude for all the positive frequencies. Alternatively, the source is radiating an impulsive plane wave and the receiver measures the impulse response of the inaccessible region. From either of these data, the dielectric profile of the inaccessible region is constructed uniquely and exactly. Two numerical algorithms are developed and their performance is examined for the cases of precise and imprecise data. It is also shown that if the inaccessible half-space is made of an inhomogeneous layer of known thickness on top of a uniform half-space of known dielectric constant, then the average value of the refractive index profile of the inhomogeneous layer and the refractive index at the edges of the layer can be estimated from the minimum and maximum values of the reflection coefficient amplitude. Results are given for these estimates for five different inhomogeneous layers. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Radar imaging from a distorted array: The radio camera algorithm and experiments

    Publication Year: 1981 , Page(s): 740 - 748
    Cited by:  Papers (50)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (872 KB)  

    High angular resolution radar imaging may be achieved with a large-aperture antenna even if the aperture is distorted, provided that adaptive signal processing compensates for the distortion. The radio camera is an instrument designed for this purpose. Its algorithm for imaging ground-based targets is described and experimental results are given for a 3 cm wavelength demonstration system using a distorted 27-m random sparse array. The measured beamwidth of 1 mrad conformed to theory, confirming the validity of the technique. Extension of the algorithm to accommodate isolated targets such as aircraft and ships also is discussed. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Theoretical aspects of the physical realizability of broad-band equivalent circuits for energy collecting structures

    Publication Year: 1981 , Page(s): 697 - 707
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1040 KB)  

    The practical implementation of equivalent circuits that represent the energy delivered to an arbitrary load impedance by an antenna or a port on a scatterer is discussed. Particular attention is paid to the positive-real (PR) function issues associated with the equivalent admittance of the structure when evolved from the point of view of the singularity expansion method (SEM). A proof is given which establishes that the eigenadmittances (reciprocal eigenvalues) of a structure are positive-real functions. The connection between this fact and the positive realness of the admittance associated with individual current eigenmode contributions to total current is discussed. An ad hoc approach to approximating these admittances with simpler pole-pair positive-real admittances is given for high- Q structures. A brief survey of the applicable circuit synthesis algorithms and their features is provided. Some fundamental considerations in the implementation of the sources representing the energy coupled from the incident wave are presented. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • The Doppler effect for scattering by plane boundaries at normal incident

    Publication Year: 1981 , Page(s): 825
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (96 KB)  

    For original papers see ibid., vol.AP-28, p.791-95 (1980) and also ibid., vol.AP-29, p.639-37 (1981). In the analysis of the one-dimensional scattering problem involving a velocity dependent boundary, the simple example of the harmonically vibrating boundary has been considered in detail. It appears that the authors were unaware of existing work by the author of the present note, which includes the De Smedt construct employed by Van Bladel and De Zutter. In the interest of obviating future repetition and duplication, it seems worthwhile to call the attention of readers to earlier results and related studies View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Rough surface scattering using specular point theory

    Publication Year: 1981 , Page(s): 798 - 800
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (320 KB)  

    The expression for the average scattering cross section for a random surface is derived using the stationary phase approximation for the scattered field due to specular points on a finitely conducting rough surface. A previous error in the literature is corrected by showing that the proper result is proportional to the average value of the product of the number of specular points per unit area and the principal radii of curvature at the specular point, rather than the product of the average value of the number of specular points and the average value of the radii of curvature. When the correct expression for the average value of the product is inserted in the expression for the scattering cross section, the result is in total agreement with the answers obtained when the averaging and stationary phase processes are interchanged. This analysis explicitly accounts for shadowing. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Approximate boundary conditions

    Publication Year: 1981 , Page(s): 826 - 829
    Cited by:  Papers (55)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (400 KB)  

    Approximate boundary conditions are a means for simulating material and surface effects in scattering and propagation. A number of conditions are discussed, and criteria are given for their validity. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • The design of microstrip dipole arrays including mutual coupling, part II: Experiment

    Publication Year: 1981 , Page(s): 761 - 765
    Cited by:  Papers (18)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (424 KB)  

    Experiments are described from which determination can be made of the self and mutual impedance for microstrip dipoles and of the backscattering relation involving the radiating current. Functional representations of these sources of input data then permits the design of planar microstrip dipole arrays, including the effects of mutual coupling. The design, construction, and performance of a typical array are described. Agreement between theory and experiment is good. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • The design of microstrip dipole arrays including mutual coupling, part I: Theory

    Publication Year: 1981 , Page(s): 757 - 760
    Cited by:  Papers (23)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (328 KB)  

    A theory is developed to explain the behavior of planar arrays of microstrip dipoles. Relations are obtained involving the active input impedances of individual dipoles (thus recognizing the effects of mutual coupling) and the radiating currents in the dipoles resulting from a set of impressed voltages. These relations permit the establishment of a design procedure with the goals of an input impedance match and a desired radiation pattern. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Control of reflector antennas performance by rim loading

    Publication Year: 1981 , Page(s): 773 - 779
    Cited by:  Papers (9)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (624 KB)  

    An analysis of the behavior of reflector antennas loaded by a surface impedance along a peripherical rim is carried out in order to ascertain the possibility of improving their performance by such a loading technique. Both single and dual (Cassegrain) reflector antennas are considered. It is shown that an effective control of the radiated field can be achieved by the proper choice of the loading characteristics. In the case of Cassegrain antennas, subreflector loading is sufficient to enhance copolar or crosspolar overall performance. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Experimental performance of a thinned microwave imaging array

    Publication Year: 1981 , Page(s): 804 - 808
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (440 KB)  

    The performance of an experimental X -band "quad" array imaging system is reported. The configuration has a physical aperture of only 33 \lambda , with 204 radiating elements and constitutes a basis for low cost real-time imaging. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Current distribution on a receiving dipole antenna

    Publication Year: 1981 , Page(s): 817 - 822
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (336 KB)  

    The current distribution on a receiving dipole antenna is dependent on its feed-point load impedance. Calculations based on the modified King-Middleton approximation have been made of the distribution for antenna half lengths of 0.1, 0.2, 0.25, and 0.3 \lambda . Representative values of the antenna load impedance, resistive, capacitive, and inductive, are used to show their effects on the antenna current distribution. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • An adaptive low-angle tracking system

    Publication Year: 1981 , Page(s): 766 - 772
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (584 KB)  

    A system for source tracking down to a fraction of a beamwidth of a surface with unknown multipath reflecting properties is described. The system has three major features: 1) the multipath returns are decorrelated by frequency diversity; 2) an efficient broad-band multiple beam antenna design is employed such that the data are characterized by a highly symmetrical (Toeplitz) correlation matrix; 3) Burg's reflection coefficient technique is employed to obtain rapid convergence to the maximum entropy spectrum from which the target location is determined. Realistic simulations including imperfect decorrelation, antenna errors, and transient results show that the system can provide accurate low-angle estimates using a practical antenna and reasonable data-processing time. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A simplified expression of the dyadic Green's function for a conducting half-sheet

    Publication Year: 1981 , Page(s): 749 - 756
    Cited by:  Papers (5)  |  Patents (13)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (600 KB)  

    Simple analytical expressions of the dyadic Green's function for a conducting half-sheet have been derived. These expressions involve some finite integrals which can be easily calculated by a digital computer and are much simpler than those involving the vector mode function expansion. Input impedances of monopole antennas on and near an edge of a conducting half-sheet and the impedance of a notch antenna have been obtained, and the usefulness of these simplified expressions has been proved. The present results can be applied to check the limits of the applicability of the asymptotic theories, e.g., the geometrical theory of diffraction (GTD) and the uniform asymptotic theory of diffraction (UAT). View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • On the integral equation of piecewise linear antennas

    Publication Year: 1981 , Page(s): 787 - 792
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (424 KB)  

    An efficient computation technique for obtaining the current distribution on a piecewise linear antenna is presented. The generalized Hallen's type integral equation with closed form kernel is formulated and then solved numerically by the collocation method. Numerical and experimental results for the gull shape and the trapezoidal tooth wire antennas are included. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Analysis of an over-constrained adaptive array

    Publication Year: 1981 , Page(s): 802 - 804
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (280 KB)  

    In antenna arrays, the number of nulls that can be formed independently is equal to or less than the number of array elements minus one. Therefore, if the number of interferences exceeds the number of freedom for pattern synthesis in adaptive arrays, nulls in the radiation pattern can not be steered toward each interference direction. To clarify the behavior of the adaptive array in such an environment, an analysis is made for the case where two interferences are impinging on the two-element directionally constrained adaptive array. As a result, it is proved that the adaptive array acts to reduce the undesired noise power at the array output. However, improvement in output signal-to-noise ratio is insufficient because of the limitation in null formation. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • On the application of the GTD-MM technique and its limitations

    Publication Year: 1981 , Page(s): 780 - 786
    Cited by:  Papers (13)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (632 KB)  

    In 1975 two techniques were published that combined the method of moments (MM) and the geometrical theory of diffraction (GTD). One technique extended the moment method through the use of the GTD while the second used the moment method to solve for unknown diffraction coefficients, thereby extending the use of the GTD. It is the latter method that is considered in this paper and is referred to as the GTD-MM technique. One problem area that existed with the original GTD-MM work was associated with a field incident along or nearly along one wall of a wedge structure. An improved series representation for the diffracted current that is sufficient at all incidence angles is shown. The improved formulation is then applied to the problem of bistatic scattering by a three-sided pyramid. Radar cross section (RCS) results that compare very well with experimental measurements are obtained. This is believed to be the first use of the GTD-MM technique in treating a three-dimensional geometry. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Rayleigh scattering and power conservation

    Publication Year: 1981 , Page(s): 795 - 798
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (312 KB)  

    In the usual formulation of Rayleigh scattering in terms of the quasi-static dipole moments of the scatterer, the scattered field is evaluated exactly to the lowest order (k_{0}a)^{3} where a is a characteristic dimension of the scatterer. Although the scattered power may be found correctly to order (k_{0}a)^{6} in terms of the scattered field, power conservation does not hold. To achieve power conservation the scattered field must be determined exactly to order (k_{0}a)^{6} . It is shown that the term of order (k_{0}a)^{6} may be found by including radiation reaction as part of the polarizing field. The scattered power can then be found by using the forward scatter theorem (optical extinction theorem) and leads to power conservation correct to lowest order. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Variational principles and variational functions in electromagnetic scattering

    Publication Year: 1981 , Page(s): 811 - 815
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (384 KB)  

    Using the Lagrange multiplier technique, the variational principles for the scattering amplitude of scalar and electromagnetic waves due to reflecting surfaces are derived in a novel way. Formulation of a variational principle for a function provides an alternative approach for obtaining variational estimates of functionals. The method provides a general prescription for formulating variational principles. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • GTD analysis of the radiation patterns of a shaped subreflector

    Publication Year: 1981 , Page(s): 792 - 795
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (288 KB)  

    A technique of analyzing the principal plane radiation patterns of a subreflector shaped using the method enunciated by Collins [1] has been presented. The analysis is based on the uniform geometrical theory of diffraction (UGTD) [2], and a simplified procedure has been adopted in the determination of the principal plane radii of curvature of the subreflector. The numerical results obtained based on UGTD correlate well with those obtained using the method of physical optics (PO). View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Dielectric rod leaky-wave antennas for millimeter-wave applications

    Publication Year: 1981 , Page(s): 822 - 824
    Cited by:  Papers (21)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (248 KB)  

    Dielectric rod leaky-wave antennas have the property of being frequency scannable. Bounds are derived for the proper range of spacing of perturbations along the rod to avoid an intrusion upon a grating lobe when frequency scanning. In addition some experimental results are reported on sidelobe levels and polarizations in the far field for these antennas made from a material with \epsilon_{r}= 2.33 at 81.5 GHz. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A numerical study on realizable broad-band and equivalent admittances for dipole and loop antennas

    Publication Year: 1981 , Page(s): 707 - 717
    Cited by:  Papers (13)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (768 KB)  

    Some realizable broad-band equivalent circuits for straight-wire and wire-loop structures are developed. The realizability of the circuits is explored in terms of the positive-real (PR) function properties of the circuit admittances. The postulate of PR "terminal eigenadmittances" as couched by Pearson and Wilton [8] is generally supported in the numerical examples, but a potential counterexample-that of the quarter-driven wire-occurs as well. A "dominant pole-pair" approach leads to a quate satisfactory approximate synthesis for the structures studied here. The conduct of this approximate synthesis is described in the context of the Bott-Duffin synthesis procedure. The circuits developed are tested by comparing their computed transient response with the response of electrodynamic models for the same structures. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.

Aims & Scope

IEEE Transactions on Antennas and Propagation includes theoretical and experimental advances in antennas.

Full Aims & Scope

Meet Our Editors

Editor-in-Chief                                                 Kwok W. Leung