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IEE Proceedings H (Microwaves, Antennas and Propagation)

Volume 136, Issue 3, June 1989

Volumes & issues:

Volume 136, Issue 3

June 1989

Scattering by a perfectly conducting strip loaded with a dielectric cylinder (TM case)
  • Author(s): A.Z. Elsherbeni  and  M. Hamid
  • Source: IEE Proceedings H (Microwaves, Antennas and Propagation), Volume 136, Issue 3, p. 185 –190
  • DOI:  10.1049/ip-h-2.1989.0035
  • Type: Article
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  • p. 185 –190 (6)
    A rigorous analysis of the problem of scattering from an incident E-polarised wave on a dielectric-loaded perfectly conducting strip is presented for a line source and plane wave excitations. The vector Green's theorem is used to derive an integral equation for the unknown electric and magnetic field components. The singular component of the magnetic field is then cancelled out by properly choosing the auxiliary fields and boundary conditions. The unknown expansion coefficients of the scattered electric field are determined by numerically solving an infinite set of simultaneous linear equations after truncation. The accuracy of the proposed solution is verified for the loaded and unloaded strip by comparing the resulting values of the scattered field with those based on the method of moments. For the loaded strip, the dependence of the scattered field as well as the scattering cross-sections on the strip width, dielectric constant and angle of incident wave is investigated and presented for plane wave incidence.
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Analysis of asymmetric TEM cell and its optimum design of electric field distribution
Propagation and radiation from partly filled elliptical waveguide
Near-field measurements on plane-polar facility
  • Author(s): J.C. Bennett  and  K.S. Farhat
  • Source: IEE Proceedings H (Microwaves, Antennas and Propagation), Volume 136, Issue 3, p. 202 –208
  • DOI:  10.1049/ip-h-2.1989.0038
  • Type: Article
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  • p. 202 –208 (7)
    Among the geometries used for acquiring the near-fields of microwave antennas, the plane-polar geometry is the most recent. This contribution describes far-field predictions obtained on a recently built plane-polar facility. The procedure for the transformation of the near-field to the far-field uses a fast algorithm for the calculation of the radiation integral and is presented in the form of a cross correlation which is carried out using the fast Fourier transform. Predictions of the far-field patterns of two antennas are shown. A numerical algorithm for the interpolation of the near-field from the plane-polar grid to the cartesian grid is derived and the interpolated data is used to predict the far-field patterns of the two antennas. A direct result of the interpolation to a cartesian grid is the adaptability of the near-field to processing for antenna metrology, enabling the surface diagnosis of antennas under test from measured plane-polar data. A technique for phase drift compensation is presented and verified. The phase drift compensation procedure is particularly suited for the plane-polar geometry.
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EM wave scattering from statistically inhomogeneous and periodic random rough surfaces
  • Author(s): D.P. Chrissoulidis
  • Source: IEE Proceedings H (Microwaves, Antennas and Propagation), Volume 136, Issue 3, p. 209 –214
  • DOI:  10.1049/ip-h-2.1989.0039
  • Type: Article
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  • p. 209 –214 (6)
    First-order scatter from statistically inhomogeneous and periodic random rough surfaces is treated by the boundary perturbation technique. The single array of rough strips on a perfectly conducting plane and the complementary arrays of rough strips are examined. Using a sampling approach, it is proved that scatter is produced through a multiple Bragg resonance mechanism. The scattering behaviour of the single array of rough strips is investigated numerically. Scatter for the corresponding surface which is covered throughout by roughness is used as reference. The numerical results indicate that the incidence/scattering directions are related to the orientation of the strips while the sensing radio wavelength is related to the strips width and period. Possible applications for this class of scatterers are discussed.
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Technical memorandum: Design of E-plane filters made easy
Matching using double slug transformer and correction to transistor gain
  • Author(s): J.R.G. Twisleton
  • Source: IEE Proceedings H (Microwaves, Antennas and Propagation), Volume 136, Issue 3, p. 219 –224
  • DOI:  10.1049/ip-h-2.1989.0041
  • Type: Article
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  • p. 219 –224 (6)
    Matching using a coaxial double slug transformer particularly in relation to measurements on microwave transistors at 0.5–2 GHz, is described. The limits arising from tuner loss and the correction to transistor gain which needs to be applied are determined analytically. The correction is compared with that deduced from reflection measurements, good agreement being obtained. The use of parallel plate line is investigated and from its Q-factor is shown to be a possible lower loss alternative to coaxial line in this application, provided that small radiation effects can be suppressed.
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Electromagnetic diffraction by two perfectly conducting wedges with dented edges loaded with a dielectric cylinder
  • Author(s): A.Z. Elsherbeni  and  H.A. Auda
  • Source: IEE Proceedings H (Microwaves, Antennas and Propagation), Volume 136, Issue 3, p. 225 –234
  • DOI:  10.1049/ip-h-2.1989.0042
  • Type: Article
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  • p. 225 –234 (10)
    A rigorous field analysis of the problem of two identical perfectly conducting parallel wedges with dented edges loaded with a dielectric cylinder, and excited by an electric or magnetic line current in the upper sector, is given in this paper. The dielectric medium is assumed to be linear, homogeneous, isotropic and free from losses, whereas the mediums of the upper and lower sectors are free space. A field equivalence theorem is used to derive, for each excitation, a system of coupled integral equations for the equivalent magnetic currents on the dielectric interfaces, which is later solved using Galerkin's method. The fields and powers transmitted into the lower sector, hence the transmission coefficients, for both polarisations are subsequently determined in terms of the equivalent magnetic currents on the lower dielectric interface. The analysis is then specialised to the problem of a slit loaded with a dielectric cylinder, as well as to the case of plane wave excitation. Sample numerical results for the dielectric-loaded double dented wedge and slit problems in the case of plane wave excitation are also given.
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Aperture impedance of flared horns
  • Author(s): J.W. Silvestro  and  R.E. Collin
  • Source: IEE Proceedings H (Microwaves, Antennas and Propagation), Volume 136, Issue 3, p. 235 –240
  • DOI:  10.1049/ip-h-2.1989.0043
  • Type: Article
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  • p. 235 –240 (6)
    The method of moments is often used when solving for the mutual coupling in arrays of aperture antennas. For elements that are waveguides or gradually flared horns the aperture fields can be approximated by a finite sum of waveguide modal functions. To solve for the flared horn case an approximation for the aperture impedances of the modes in the horn is needed. The WKB approach can be used to find these impedances, but this technique has an important limitation. It is known to fail in the vicinity of it's turning points. The turning point is the cutoff point of the mode being considered. To overcome this limitation a different technique, the spherical mode approach, is discussed. This approach has no cutoff problems and works well for conical and pyramidal horns. Comparisons between the impedances and the resulting dominant mode reflection coefficient found using the two techniques are presented to illustrate this point.
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Reflection coefficient at the feed of a radome-covered reflector antenna: a geometrical optics approach
Generalised Villeneuve n̅ distribution
  • Author(s): D.A. McNamara
  • Source: IEE Proceedings H (Microwaves, Antennas and Propagation), Volume 136, Issue 3, p. 245 –249
  • DOI:  10.1049/ip-h-2.1989.0045
  • Type: Article
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  • p. 245 –249 (5)
    In this paper, a generalised Villeneuve type linear array distribution is developed, which permits the direct synthesis of discrete array distributions for high efficiency sum patterns of arbitrary sidelobe level and envelope taper. With the Dolph–Chebyshev distribution as the parent space factor, and the correct perturbation of these space factor zeros, the excitation efficiency and beamwidths are kept as close to their optimum values as is possible under the given sidelobe ratio and envelope taper conditions. The method is the discrete analogue of the generalised Taylor n̅-distribution, used for continuous line source synthesis. Examples are given to illustrate the principal features of the distribution.
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Intrinsic mode theory of conical corrugated horns
  • Author(s): J.M. Arnold  and  A. Dendane
  • Source: IEE Proceedings H (Microwaves, Antennas and Propagation), Volume 136, Issue 3, p. 250 –256
  • DOI:  10.1049/ip-h-2.1989.0046
  • Type: Article
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  • p. 250 –256 (7)
    The application of the concept of intrinsic modes to the theory of propagation in conical corrugated horns is developed. An intrinsic mode is an exact solution of source-free Maxwell equations which satisfies the boundary conditions to a prescribed order of accuracy as the flare angle α becomes small. There exists an infinite number of intrinsic modes for a given structure and each one corresponds with a fixed local normal mode at every cross-section, to which it approximates asymptotically as α → 0. An intrinsic mode is given by a Fourier-like spectral integral which is uniformly valid, including the regions where the corresponding local normal mode is evanescent or in transition from propagating to evanescent. This spectral integral can be generated from knowledge of only one local normal mode at each cross-section, and numerical calculations show that the intrinsic mode based on the HE11 local normal mode is sufficient for many applications, including the calculation of crosspolar radiation.
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Technical memorandum: Edge mode effect in the operations of waveguide twin-slab ferrite phase shifter
  • Author(s): J. Helszajn
  • Source: IEE Proceedings H (Microwaves, Antennas and Propagation), Volume 136, Issue 3, p. 257 –260
  • DOI:  10.1049/ip-h-2.1989.0047
  • Type: Article
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  • p. 257 –260 (4)
    The distributions of the electric and magnetic fields and power of the classic rectangular waveguide twin-slab ferrite phase shifter, with one region magnetised along the positive y-direction and the other along the negative y-d irection, are re-examined in the paper. It indicates that this type of device may quite often be phenomenologically described by a nonreciprocal edge-mode effect, rather than, as is customary, in terms of circular variables. This model may be of value in the design of practical wideband devices. The presence of counter-rotating magnetic fields at the two open faces of the ferrite region is also of note. The use of unequal oppositely magnetised sections is a possibility that has not received any attention so far.
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Technical memorandum: Analysis of circular microstrip antennas with superstrate
Theoretical and experimental investigations of two-dimensional waveguide-excited short backfire antenna structure
Uniqueness of numerical solutions to electric-, magnetic- and combined-field integral equations for open-ended circular waveguides
  • Author(s): J.R. Parkinson  and  M.J. Mehler
  • Source: IEE Proceedings H (Microwaves, Antennas and Propagation), Volume 136, Issue 3, p. 269 –275
  • DOI:  10.1049/ip-h-2.1989.0050
  • Type: Article
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  • p. 269 –275 (7)
    The moment method is used to solve the electric-, magnetic- and combined-field integral equation, to determine the current distribution on a semi-infinite, open-ended, circular waveguide. A standard triangle-function expansion is used to represent the exterior waveguide wall currents. The approximate nature of this current distribution is shown to lead to difficulties with the uniqueness of both the solutions associated with the electric- and magnetic-field integral equations. By examining the degree to which the boundary conditions are satisfied, the combined-field integral equation is shown to yield superior results.
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Lens antennas with amplitude shaping or sine condition
  • Author(s): Samira Bishay ; S. Cornbleet ; J. Hilton
  • Source: IEE Proceedings H (Microwaves, Antennas and Propagation), Volume 136, Issue 3, p. 276 –279
  • DOI:  10.1049/ip-h-2.1989.0051
  • Type: Article
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  • p. 276 –279 (4)
    The paper demonstrates the method of generic curve series to obtain the profiles of dielectric antennas, with design conditions either for the specification of the aperture-amplitude distribution from a given source distribution, or for agreement with the Abbe sine condition. The method has already proved successful in the design of dual reflector antennas, and the extension to refractive media is shown to be straightforward. The method basically involves obtaining two equivalent expressions for a fundamental parameter from the usual optical equations and internal geometry of the lens, and obtaining agreement between them by a computational optimisation procedure using the series of curves. The parameter used in the paper is the internal segment of the ray within the lens. The method applies equally well to lenses with other a priori conditions such as afocal linear magnification or off-axis bifocality.
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Erratum: Input impedance of rectangular microstrip antennas

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