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Antennas and Propagation, IEEE Transactions on

Issue 2 • Date March 1979

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Displaying Results 1 - 25 of 36
  • [Front cover and table of contents]

    Publication Year: 1979 , Page(s): 0
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    Freely Available from IEEE
  • From the Editor

    Publication Year: 1979 , Page(s): 129
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    Freely Available from IEEE
  • Comments on "Reduction of mutual coupling between active monopoles: Application to superdirective receiving arrays" and related publications

    Publication Year: 1979 , Page(s): 273 - 276
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    For original paper see ibid., vol.AP-25, p.737 (1977) View full abstract»

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  • Correction to "On the calculation of the ground wave attenuation factor at low frequencies"

    Publication Year: 1979 , Page(s): 286
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    First Page of the Article
    View full abstract»

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  • Calculation of far-scattered fields by the method of stationary phase

    Publication Year: 1979 , Page(s): 199 - 202
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (376 KB)  

    The scattering problems for a nonconvex body can be analyzed by the physical-optics approximation. The method of stationary phase is a technique for evaluating the diffraction integral in the short-wavelength region. In case of the nonconvex body there exist several stationary points including the complex ones in the reduced phase integral. The radar cross section of the nonconvex body varies with frequency as a result of the interference of the scattered waves from each stationary point. For a moderately high frequency the solutions by the method of stationary phase agree with those obtained using the mode-matching method. View full abstract»

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  • Depolarization and scattering of electromagnetic waves by irregular boundaries for arbitrary incident and scatter angles full-wave solutions

    Publication Year: 1979 , Page(s): 214 - 225
    Cited by:  Papers (15)
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    Explicit expressions are presented for the radiation fields scattered by rough surfaces. Both electric and magnetic dipole sources are assumed, thus excitations of both vertically and horizontally polarized waves are considered. The solutions are based on a full-wave approach which employs complete field expansions and exact boundary conditions at the irregular boundary. The scattering and depolarization coefficients axe derived for arbitrary incident and scatter angles. When the observation point is at the source these scattering coefficients are related to the backscatter cross section per unit area. Solutions based on the approximate impedance boundary condition are also given, and the suitability of these approximations are examined. The solutions are presented in a form that is suitable for use by engineers who may not be familiar with the analytical techniques and they may be readily compared with earlier solutions to the problem. The full-wave solutions are shown to satisfy the reciprocity relationships in electromagnetic theory, and they can be applied directly to problems of scattering and depolarization by periodic and random rough surfaces. View full abstract»

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  • Diffusive electromagnetic penetration into metallic-enclosures

    Publication Year: 1979 , Page(s): 194 - 198
    Cited by:  Papers (9)
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    The physics of shielding by a metallic enclosure is discussed. Simple engineering formulas in the frequency and time domains are deduced from a rigorous formulation to calculate the cavity fields for certain canonical enclosure shapes. These simple formulas are generalized so as to be applicable to enclosures of arbitrary shape. The great difference in shielding effectiveness between enclosures and planar slabs is pointed out. View full abstract»

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  • Optimum frequencies of a passive microwave radiometer for tropospheric path-length correction

    Publication Year: 1979 , Page(s): 233 - 239
    Cited by:  Papers (17)
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    Radio-astronomical observations require accurate calibration of tropospheric path length. Such calibration can be achieved by microwave radiometers operating near the 22-GHz water vapor line. However, the performances of current passive microwave radiometers are meteorology-profile dependent. This is shown due mainly to incorrect frequency combinations and to saturation of brightness temperatures. By properly selecting an optimum frequency pair and removing the saturation effect, the dependency is alleviated and can be further adjusted by surface measurements alone. Hence, a universal calibration equation is applicable to all environmental conditions. Optimum frequency pairs are systematically searched. Simulation analysis indicates that calibration for the tropospheric water-vapor path-length error is better than 0.3 cm at zenith and better than 2 cm for an elevation angle as low as 10\deg . View full abstract»

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  • Monopole antenna at center of circular ground plane: Input impedance and radiation pattern

    Publication Year: 1979 , Page(s): 151 - 153
    Cited by:  Papers (11)
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    Computer solutions of monopole antennas at the center of circular ground planes have previously been applied to the calculation of their input impedance through the use of magnetic edge currents. An alternative approach based on approximate physical currents is shown to give good agreement for both radiation patterns and input impedances. View full abstract»

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  • The singularity expansion method applied to perpendicular crossed wires over a perfectly conducting ground plane

    Publication Year: 1979 , Page(s): 248 - 252
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    The singularity expansion method (SEM) has been applied to determine natural resonances of a set of perpendicular crossed wires over a perfectly conducting ground plane. The variation of the natural resonances and the mode and coupling vectors have been studied as parameters of the system varied. View full abstract»

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  • Determination of conductivity profiles by time-domain reflectometry

    Publication Year: 1979 , Page(s): 244 - 248
    Cited by:  Papers (18)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (392 KB)  

    A new numerical method for the reconstitution of the inhomogeneous media conductivity is described. The conducting medium is nonmagnetic, and its relative permittivity equals one. Its frequency-independent conductivity varies normally to its interface. The medium is normally illuminated by a transverse electromagnetic (TEM) plane wave of causal time dependence. The reconstruction process is a direct approach to the inverse problem. It is based on a space time discretization of an exact integral equation. The conductivity profile is determined step-by-step without approximations other than numerical. Some examples are given to illustrate the most interesting properties of the method; special attention is given to the simulation of experimental errors. View full abstract»

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  • Theory and experiment on microstrip antennas

    Publication Year: 1979 , Page(s): 137 - 145
    Cited by:  Papers (284)  |  Patents (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (648 KB)  

    A simple theory based on the cavity model is developed to analyze microstrip antennas. Formulas for numerous canonical shapes are given. In general the theoretically predicted radiation patterns and impedance loci closely agree with those measured for many antennas of various shapes and dimensions investigated thus far. In fact, this theory enables the computation of both patterns and impedance loci with little effort. The input admittance locus generally follows a circle of nearly constant conductance, but its center is shifted to the inductive region in the Smith chart plot. Peculiar properties for the case with degenerate or slightly degenerate eigenvalues are discussed. An accurate formula for determining the resonant frequency of a rectangular microstrip antenna is also given. View full abstract»

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  • GTD analysis of the radiation patterns of wide-flare corrugated conical and E-plane sectoral horns

    Publication Year: 1979 , Page(s): 276 - 279
    Cited by:  Papers (1)
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    The E -plane radiation patterns of wide-flare corrugated conical and E -plane sectoral horns ( 2\alpha _{0} < 150\deg ) excited in the dominant mode are obtained employing the theory of Kouyoumjian and Pathak [12] and the slope diffraction technique [11]. Besides the other parameters of the horn, the finite thickness of the corrugated edge has been taken into account with a view to improve the accuracy of the pattern computation. The analysis presented enables one to predict accurately radiation patterns over the main beam, near and far sidelobes, and the back lobes of the horns. Validity of the analysis is established by satisfactory agreement between the calculated and measured E -plane patterns of a few typical experimental wide-flare corrugated conical and E -plane sectoral horns. View full abstract»

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  • Direct three-dimensional image reconstruction

    Publication Year: 1979 , Page(s): 239 - 241
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (304 KB)  

    The problem of radar target-shape estimation for perfectly conducting complex objects is formulated as an image-reconstruction problem. A convolve-and-backproject algorithm is derived when the measurements are taken by radars located in three-dimensional space around the object region. The algorithm can be used directly in that there are no restrictions on the sensor placement; the sensors are not required to lie in a plane, for example, as is often assumed in many applications. Two possible convolving functions with desirable implementation characteristics are described. The algorithm is applicable to the general problem of reconstructing the density function of three-dimensional objects and applies to the radar shape-estimation problem as a special case. View full abstract»

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  • Reciprocity identity for periodic surface scattering

    Publication Year: 1979 , Page(s): 252 - 254
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    The Lorentz reciprocity theorem is used to derive an identity which is helpful in examining the accuracy of solutions to periodic metal-surface scattering problems. The identity checks the amplitude and phase of individual propagating space harmonics while the more familiar criterion of energy conservation checks the total accumulated power. View full abstract»

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  • Finite-element computation of scattering by inhomogeneous penetrable bodies of revolution

    Publication Year: 1979 , Page(s): 202 - 214
    Cited by:  Papers (56)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1192 KB)  

    This investigation is concerned with the numerical solution of time-harmonic electromagnetic scattering by axisymmetric penetrable bodies having arbitrary cross-sectional profiles and even continuously inhomogeneous consistency. The initiation of this effort involved the discovery and development of the coupled azimuthal potential (CAP) formulation, which is valid in generally lossy isotropic inhomogeneous rotationally symmetric media. Electromagnetic fields in such regions can be represented, using the CAP formulation, in terms of two continuous potentials which satisfy a self-adjoint system of partial differential equations or, equivalently, a variational criterion. Using an optimized variational finite-element algorithm in conjunction with a triregional unimoment method, a versatile computer program is described that provides scattering solutions for each of multiple incident fields impinging upon an arbitrarily shaped inhomogeneous penetrable body of revolution. An extensive evaluation of the accuracy and convergence of the algorithm is presented, which includes comparison of scattering computations and experimental measurements at X -band for several solid and hollow plexiglas bodies of revolution with maximum interior dimensions of over 4 wavelengths. View full abstract»

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  • A note concerning the evaluation of the Sommerfeld integral

    Publication Year: 1979 , Page(s): 254 - 256
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    Van der Pol's approximate representation of the Sommerfeld integral is rederived to show that the approximation is valid regardless of the distance between image and point of observation. The only constraint is that the absolute value of the square of the refractive index is great compared to one. View full abstract»

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  • Frequency scanning microstrip antennas

    Publication Year: 1979 , Page(s): 146 - 150
    Cited by:  Papers (18)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (432 KB)  

    The principles of using radiating microstrip resonators as elements in a frequency scanning antenna array are described. The resonators are cascade-coupled. This gives a scan of the main lobe due to the phase-shift in the resonator in addition to that created by the transmission line phase-shift. Experimental results in X -band, in good agreement with the theory, show that it is possible to scan the main lobe an angle of \pm30\deg by a variation of the frequency \pm300 MHz, and where the 3 dB beamwidth is less than 10\deg . The directivity was 14.7 dB, while the gain was 8.1 dB. The efficiency might be improved by a trade-off between the efficiency and the scanning angle, or by using a better amplitude distribution. View full abstract»

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  • Linear antenna arrays with broad nulls with applications to adaptive arrays

    Publication Year: 1979 , Page(s): 185 - 190
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (496 KB)  

    The problem of designing a class of linear antenna arrays with broad nulls against interfering signals of variable direction of arrival is considered. The problem is formulated in an appropriate signal space selected for an efficient representation of array signals of specified angular occupancy. The array-weight vector is then chosen to be orthogonal to this space. The approach is seen to yield a min-max array in a sense to be defined in this paper. The application of such arrays to maintain the beamshape of an adaptive antenna array is also illustrated. View full abstract»

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  • Reconstruction of permittivity profiles from a spectral analysis of the reflection coefficient

    Publication Year: 1979 , Page(s): 241 - 244
    Cited by:  Papers (21)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (384 KB)  

    A spectral-domain approach to the inverse problem is considered. The permittivity profile of an inhomogeneous lossless dielectric slab is reconstructed from multifrequency measurements of the reflection coefficient. Simple and easy to use analytical relations are obtained. A simple experimental setup has been used, and the results obtained are in good agreement with those predicted by the theory. View full abstract»

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  • Dielectric-lined waveguide feed

    Publication Year: 1979 , Page(s): 279 - 282
    Cited by:  Papers (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (336 KB)  

    Theoretical radiation patterns are predicted and compared with those obtained experimentally. The measured peak cross-polarization level is less than -29 dB at 9 GHz. It is shown that aperture efficiencies of the order of 91-96 percent may be obtained. View full abstract»

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  • Echo width of foam supports used in scattering measurements

    Publication Year: 1979 , Page(s): 191 - 193
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (360 KB)  

    Theoretically and experimentally determined echo widths of dielectric cylinders having circular, triangular, and quadratic cross sections have been compared. The cylinders were made of foam material having a relative dielectric constant of about 1.035. The purpose of the investigation was to find a cross section with a small echo width. The result can be used in selecting a proper support for test objects in backscattering measurement studies. View full abstract»

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  • A model for calculating the radiation field of microstrip antennas

    Publication Year: 1979 , Page(s): 267 - 270
    Cited by:  Papers (16)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (320 KB)  

    Starting from the equivalence principle, an aperture model is developed for calculating the radiation field of microstrip antennas. In this communication the model is applied to the rectangular microstrip resonator antenna. Antenna characteristics, like patterns and radiation resistance, are computed and compared with experimental results. The model and the calculations include the higher order modes as well as the fundamental mode of the resonator antenna. View full abstract»

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  • Analysis of a dual-frequency array technique

    Publication Year: 1979 , Page(s): 130 - 136
    Cited by:  Papers (3)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (680 KB)  

    This paper describes the radiating properties of a new element for a dual-frequency phased array that operates over two frequency bands separated by about an octave. The analysis considers the array element excited by two waveguides for high-frequency operation, and includes an evaluation of the element radiation properties at both frequency bands. The analysis of radiation is carried out for the case of H -plane scan, which is expected to be the most severe test of the element's scanning behavior. Computed results indicate that the structure radiates efficiently within the two bands and operates free from anomalous behavior over substantial scan angles. These results demonstrate the feasibility and practicality of the basic concept. View full abstract»

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  • High-frequency fields excited by a line source located on a concave cylindrical impedance surface

    Publication Year: 1979 , Page(s): 172 - 179
    Cited by:  Papers (12)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (640 KB)  

    A previous study of high-frequency currents induced by a line source on a perfectly conducting concave cylindrical surface is extended to the case of nonvanishing surface impedance Z_{s} . Alternative field representations are formulated and evaluated asymptotically as combinations of ray-optical, whispering gallery (WG) mode, surface wave, continuous spectrum, and canonical integral contributions. Numerical calculations provide an insight into the accuracy and utility of the various formulations. Sufficiently far from the source point, a combination of ray optical fields and tightly bound WG modes was previously found to be a most appealing form when Z_{s} = 0 . As the surface impedance becomes more dissipative, the WG modes axe weakened by attenuation and eventually render the ray optical fields adequate by themselves. A representation in terms of rays and a canonical integral is found to be useful for all parameter ranges. The canonical integral has been evaluated numerically and tabulated. View full abstract»

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Aims & Scope

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

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Editor-in-Chief                                                 Kwok W. Leung