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Volume 144
Issue 2
IEE Proceedings - Microwaves, Antennas and Propagation
Volume 144, Issue 2, April 1997
Volumes & issues:
Volume 144, Issue 2
April 1997
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- Author(s): A. Helaly ; E.A. Soliman ; A.A. Megahed
- Source: IEE Proceedings - Microwaves, Antennas and Propagation, Volume 144, Issue 2, p. 61 –66
- DOI: 10.1049/ip-map:19971034
- Type: Article
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p.
61
–66
(6)
An analytical technique for obtaining a complete set of scattering coefficients for a stratified plasma cylinder is presented, referred to as the scattering matrix model (SMM). The plasma model chosen for the study is cold, steady-state, nonuniform, collisional and magnetised. The nonuniform cylinder is represented by a number of concentric cylindrical shells and each has a fixed electron density. The overall density profile follows any prescribed distribution function. The field in each layer is written in terms of an appropriate wave function weighted by unknown scattering coefficients. These coefficients are obtained by using successive application of boundary conditions. Another approximate analytical technique for solving such a problem is employed known as the impedance boundary conditions (IBC), which replaces the interior cylinder with an impedance surface. Results show that SMM and IBC give identical results as long as the application criteria of the IBC are satisfied. IBC has been found to be faster and requires relatively simpler formulation. The effect of varying the plasma parameters on the backscattering cross section is investigated. - Author(s): H. Legay and L. Shafai
- Source: IEE Proceedings - Microwaves, Antennas and Propagation, Volume 144, Issue 2, p. 67 –72
- DOI: 10.1049/ip-map:19971035
- Type: Article
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p.
67
–72
(6)
A new approach for designing two-dimensional series-fed arrays is proposed in which each radiating element is connected in series to its adjacent elements. The power is injected into the central element and as it travels outwards excites other array elements, resulting in a two-dimensional illumination of the array aperture. At the operating frequency, the interconnecting line segments and radiating patches are designed to be resonant. Thus, provided they are identical in size, their resonances interfere and generate a global resonance over the aperture that causes equal radiation from all the patches. Shaping the radiation pattern is also possible by modifying the patch dimensions at appropriate locations in the array. Consequently, the proposed two-dimensional arrays represent a class of resonant series-fed arrays that are straightforward to feed and useful for illuminating medium-size arrays. - Author(s): H. Esteban ; V.E. Boria ; M. Baquero ; M. Ferrando
- Source: IEE Proceedings - Microwaves, Antennas and Propagation, Volume 144, Issue 2, p. 73 –80
- DOI: 10.1049/ip-map:19970895
- Type: Article
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p.
73
–80
(8)
An iterative method for two-dimensional problems with multiple scatterers is presented. Spectral techniques are used to characterise a scatterer by its transfer function. To obtain this transfer function physical optics and the method of moments have been used. An iterative method analysing the existence of a new object at each new iteration is outlined. The method produces combined transfer functions that give the response of the multiple scattering problem to several incident fields. A useful alternative iteration for clumped groups of scatterers is also presented. Results for a parabolic reflector, a Cassegrain structure and a horn for TM incidence are analysed and comparison with theoretical data is discussed. Finally, the extension of the method for the TE case and for 3D problems is outlined. - Author(s): G. Pan and J. Tan
- Source: IEE Proceedings - Microwaves, Antennas and Propagation, Volume 144, Issue 2, p. 81 –90
- DOI: 10.1049/ip-map:19970507
- Type: Article
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p.
81
–90
(10)
A new functional for general anisotropic 2½D guided-wave structures is derived, based on a rigorous 3D analysis. An impedance boundary condition at the interface between the anisotropic material and the imperfect conducting ground plane is proposed. The computation domain includes the cross-section of the lossy conducting line where the size of the cross-section has the same order as the skin depth, and the standard impedance boundary condition is no longer held. The vector element analysis procedure, and the subspace iteration method, are then used to find the partial or total system modes. Numerical examples of anisotropic dielectric image waveguide, PFEE bilateral fin line, and two coupled asymmetrical dual lossy transmission lines with finite conductivity and finite thickness are presented. Good agreement with previous publications is observed. - Author(s): N.C. Rogers ; E.M. Warrington ; T.B. Jones
- Source: IEE Proceedings - Microwaves, Antennas and Propagation, Volume 144, Issue 2, p. 91 –96
- DOI: 10.1049/ip-map:19970663
- Type: Article
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p.
91
–96
(6)
Large electron density gradients in the ionosphere associated with the walls of the midlatitude trough produce tilted reflecting surfaces which lead to HF signals propagating over paths well displaced from the great circle. Measurements are presented of signals propagating over two paths along the midlatitude trough for which bearings deviations of up to 100° from the great-circle path, i.e. the expected direction of arrival, were frequently recorded. The times of occurrence and magnitude of these large deviations are consistent with the known features of the midlatitude ionospheric trough. Such large deviations of the measured bearing from the great-circle path, which far exceed the instrumental errors, have serious implications for the operation of position location systems operating within the HF band. - Author(s): D.-C. Chang ; C.-C. Yang ; S.-Y. Yang
- Source: IEE Proceedings - Microwaves, Antennas and Propagation, Volume 144, Issue 2, p. 97 –102
- DOI: 10.1049/ip-map:19970832
- Type: Article
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p.
97
–102
(6)
For many years, the compact range has successfully been used to evaluate antenna electromagnetic radiation and target scattering. Single offset paraboloidal reflectors, dual parabolic–cylindrical reflectors, and dual shaped reflectors exist for the compact-range reflector systems. A dual-reflector compact-range system with a spherical main reflector and a shaped subreflector is described with this this design, an arbitrary position of the feed is permissible for the anechoic-chamber size and existing chamber-fitting considerations. A spherical surface is adopted to reduce manufacturing cost. A Gregorian-type dual-reflector system with a 1.83 m-diameter truncated spherical main reflector has been evaluated and manufactured. The test results, for frequencies from 8 to 39.5 GHz, showed that the performance of quiet zone is within ±0.4 dB amplitude ripple and ±5° phase ripple over a 70% area of the main reflector projected in the quiet-zone direction. - Author(s): A.B. Gnilenko ; A.B. Yakovlev ; I.V. Petrusenko
- Source: IEE Proceedings - Microwaves, Antennas and Propagation, Volume 144, Issue 2, p. 103 –110
- DOI: 10.1049/ip-map:19971036
- Type: Article
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p.
103
–110
(8)
A new generalised approach for the full-wave analysis of shielded printed-circuit transmission lines with finite metallisation thickness is presented. A rigorous formulation for the electric field vector is employed, representing the hybrid electromagnetic field in layers of multidielectric media. The dyadic Green's function of the electric kind is derived as a kernel of the vector integral representations for the electric field. Based on the method of overlapping regions, the approach can be applied to the characterisation of a large class of planar waveguiding structures to yield a set of linear algebraic equations of the second kind with a compact matrix operator. Numerical examples are shown for single and coupled shielded planar transmission lines illustrating application of the method. The technique described allows obtaining accurate and mathematically correct solutions of planar waveguide eigenvalue problems. - Author(s): L. Zhou and L.E. Davis
- Source: IEE Proceedings - Microwaves, Antennas and Propagation, Volume 144, Issue 2, p. 111 –117
- DOI: 10.1049/ip-map:19971011
- Type: Article
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p.
111
–117
(7)
In the paper, a finite element method with edge elements for directly calculating the phase and attenuation constants of ferrite-loaded waveguides with longitudinally or transversely magnetised directions is presented. The magnetic losses of the ferrite are included in the form of a Landau–Lifshiz damping term. Dispersion characteristics with attenuation of a rectangular waveguide loaded with a ferrite slab are in very good agreement with the analytical results, which confirms the correctness of the method. The analysis for a coplanar waveguide with a ferrite layer is also carried out. The calculation shows that a larger differential phase shift and lower attenuation can be achieved with transverse magnetisation than with longitudinal magnetisation at higher frequencies. - Author(s): R. Pregla
- Source: IEE Proceedings - Microwaves, Antennas and Propagation, Volume 144, Issue 2, p. 119 –125
- DOI: 10.1049/ip-map:19971010
- Type: Article
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p.
119
–125
(7)
A general procedure for the analysis of concatenations of straight and curved waveguide sections based on the method of lines is described. Field and impedance transfer equations for curved waveguides are derived, which can easily be transformed to the case of straight waveguides. A special impedance/admittance transformation formula is reported for waveguide connections, even with steps. Numerical results for some examples are given and compared with results in the literature. - Author(s): S. Gupta ; A. Bhattacharya ; A. Chakraborty
- Source: IEE Proceedings - Microwaves, Antennas and Propagation, Volume 144, Issue 2, p. 126 –130
- DOI: 10.1049/ip-map:19971016
- Type: Article
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p.
126
–130
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The paper presents a moment method analysis of an open-ended waveguide radiator when a dielectric plug is pushed into the radiating end. It is demonstrated that such a structure behaves as a very good radiator of microwave energy over a band of frequencies. Experiments were carried out with polystyrene plugs, of different thicknesses, inserted at the end of a WR-90 X-band waveguide, and excellent agreement between theory and experiment has been achieved. The analysis also shows that the frequency band of best match can be varied over the frequency range by adjusting the thickness of the plug which is inserted at the radiating end. - Author(s): U.R. Kraft
- Source: IEE Proceedings - Microwaves, Antennas and Propagation, Volume 144, Issue 2, p. 131 –135
- DOI: 10.1049/ip-map:19971018
- Type: Article
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p.
131
–135
(5)
A small printed four-arm spiral antenna with lumped resistive loading is investigated to assess its suitability as a compact antenna element with pure circular polarisation. The results of numerical investigations based on a simplified thin-wire model are presented, which indicate XPD improvements of ≥ 14 dB in comparison to conventional spirals of the same size. The corresponding gain reductions are ~1 – 3 dB, which is at least equivalent to the performance of conventional cavity backed spirals. Furthermore, experimental results are discussed for a true microstrip spiral, which verify XPD improvements of 12 – 17 dB and show that XPD figures of 30 dB as well as a radiation pattern with acceptable symmetry can be obtained, even with simple nonoptimised feed networks. Areas for further improvements are identified and briefly discussed. - Author(s): T.M. Au ; K.F. Tong ; K.M. Luk
- Source: IEE Proceedings - Microwaves, Antennas and Propagation, Volume 144, Issue 2, p. 137 –140
- DOI: 10.1049/ip-map:19971017
- Type: Article
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p.
137
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The characteristics of aperture-coupled microstrip antennas with parasitic elements are studied. Four configurations for increasing the bandwidth of aperture-coupled microstrip antennas are described. Additional patches are gap-coupled to the nonradiating edges of the rectangular fed patch. The spectral domain Green function approach and the reciprocity method are used for the analysis. The SWR bandwidth and the E- and H-plane beamwidths can be improved by changing the sizes and the locations of the parasitic patches. Low backlobe radiation can be achieved by locating a plane reflector slightly below the microstrip feedline. The bandwidth of the microstrip subarray can also be enhanced with the addition of the plane reflector. The theory is confirmed by experimental data. - Author(s): J.L. Rodríguez ; F. Obelleiro ; A.G. Pino
- Source: IEE Proceedings - Microwaves, Antennas and Propagation, Volume 144, Issue 2, p. 141 –144
- DOI: 10.1049/ip-map:19970964
- Type: Article
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p.
141
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The analysis of high-frequency scattering from electrically large open cavities is addressed in the paper. A magnetic-field integral equation (MFIE) for the equivalent currents on the interior cavity walls is obtained and solved by two different algorithms based on high-frequency principles of physical optics (PO). Once the currents are known, the scattered fields are obtained by using aperture integration (AI) in the cavity mouth, or a reciprocity integral (RI) over a surface close to the termination. Numerical results are presented which demonstrate the convergence and accuracy of the proposed methods, by comparison with modal reference solution. - Author(s): S. Gevorgian ; T. Martinsson ; A. Deleniv ; E. Kollberg ; I. Vendik
- Source: IEE Proceedings - Microwaves, Antennas and Propagation, Volume 144, Issue 2, p. 145 –148
- DOI: 10.1049/ip-map:19970843
- Type: Article
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p.
145
–148
(4)
A conformal mapping based analytic formula is proposed for computation of the frequency dependent effective dielectric constant, ɛeff, of coplanar waveguides (CPW). This formula is correct in a wide frequency band and for wide range of CPW parameters, and models both negative and positive slopes in the frequency dependence of ɛeff. The results are especially useful for modeling microwave/millimetrewave and ultrahigh speed digital interconnects. - Author(s): M.E. Cooley ; J.F. Walker ; D.G. Gonzalez ; G.E. Pollon
- Source: IEE Proceedings - Microwaves, Antennas and Propagation, Volume 144, Issue 2, p. 149 –151
- DOI: 10.1049/ip-map:19970963
- Type: Article
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p.
149
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The paper describes a novel dipole reflectarray element with variable reflection phase. The element is described and array waveguide simulator measurement data demonstrating its phase shifting properties is presented. The element was developed originally as a mechanism for antenna pattern tuning of a fixed-beam crossed-dipole reflectarray. However, it might also be applied, using small electric motors, to achieve electronic scanning or active beam reshaping. These potential applications are discussed briefly.
Electromagnetic waves scattering by nonuniform plasma cylinder
Planar resonant series-fed arrays
Generalised iterative method for solving 2D multiscattering problems using spectral techniques
General edge element approach to lossy and dispersive structures in anisotropic media
Large HF bearing errors for propagation paths tangential to auroral oval
Dual-reflector system with a spherical main reflector and shaped subreflector for compact range
Generalised approach to modelling shielded printed-circuit transmission lines
Calculation of phase and attenuation constants for waveguides loaded with lossy ferrite with longitudinal or transverse magnetisation
Concatenations of waveguide sections
Analysis of an open-ended waveguide radiator with dielectric plug
Polarisation properties of small printed spiral antennas with four resistively loaded arms
Characteristics of aperture-coupled coplanar microstrip subarrays
Iterative solutions of MFIE for computing electromagnetic scattering of large open-ended cavities
Simple and accurate dispersion expression for the effective dielectric constant of coplanar waveguides
Novel reflectarray element with variable phase characteristics
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