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Volume 143
Issue 4
IEE Proceedings - Microwaves, Antennas and Propagation
Volume 143, Issue 4, August 1996
Volumes & issues:
Volume 143, Issue 4
August 1996
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- Author(s): T.S. Bird
- Source: IEE Proceedings - Microwaves, Antennas and Propagation, Volume 143, Issue 4, p. 265 –271
- DOI: 10.1049/ip-map:19960443
- Type: Article
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p.
265
–271
(7)
A solution is given for the problem of cross-coupling between a pair of open-ended coaxial cables, excited in the TEM mode and terminating in a ground plane. New integral and series representations are derived for the mutual admittance of the TEM modes, and useful low-frequency and far-field approximations are found. Computed results are given for several examples of cables radiating into lossless dielectric media. Measured data is given for a pair of cables radiating in air and computed results agree very well over a wide frequency range. These results show the coupling coefficient increasing initially with frequency, in contrast to waveguide radiators where the coupling coefficient mainly decreases with frequency; the levels attained are significant, particularly above the cut-off of the TE11 mode. Cross-coupling is shown to be greatest when the inner-to-outer conductor ratio is about 0.53. The solution should be useful for analysing arrays of coaxial horns and obtaining the permittivity and permability of materials. - Author(s): K. Krishnamurthi and R.G. Harrison
- Source: IEE Proceedings - Microwaves, Antennas and Propagation, Volume 143, Issue 4, p. 272 –276
- DOI: 10.1049/ip-map:19960431
- Type: Article
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p.
272
–276
(5)
Heterostructure-barrier varactors (HBVs) reported previously had limited power output. By using a pseudomorphic In0.52Al0.48As/AlAs/In0.52Al0.48As barrier with good current blocking characteristics and stacking three MBE-grown varactor layers, we achieve a symmetric stacked varactor on InP with low leakage and high breakdown voltage (~14 V). Tripler experiments at Ka band using these varactors give 20 dBm output with 7 dB conversion loss using a waveguide multiplier, and 10.8 dBm with 11 dB conversion loss using a microstrip circuit. These are the first HBVs to demonstrate reduced device capacitance per unit area and freedom from resistive tripling effects. - Author(s): E. Michielssen ; A. Boag ; W.C. Chew
- Source: IEE Proceedings - Microwaves, Antennas and Propagation, Volume 143, Issue 4, p. 277 –283
- DOI: 10.1049/ip-map:19960400
- Type: Article
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p.
277
–283
(7)
A recursive algorithm is presented for analysing TM and TE plane-wave scattering from two-dimensional elongated objects. The computational complexity and the memory requirements of the algorithm are O(N log2N) and O(N log N), respectively. The algorithm is based on the concept of a reduced representation and fast computation of fields that are radiated by quasialigned sources. While many existing fast algorithms for analysing electromagnetic scattering problems rely on iterative strategies, the proposed algorithm provides a direct solution to the scattering problem. The algorithm has a variety of potential applications, including the analysis of scattering from truncated and quasiperiodic structures, winglike structures, phased-array antennas and rough surfaces. - Author(s): P.-S. Kildal and M.M. Davis
- Source: IEE Proceedings - Microwaves, Antennas and Propagation, Volume 143, Issue 4, p. 284 –292
- DOI: 10.1049/ip-map:19960388
- Type: Article
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p.
284
–292
(9)
Antennas are normally characterised in terms of their far field radiation patterns, directive gain and aperture efficiency. The paper describes how to characterise antennas that are focused in the near field, in terms of a focusing gain and a focusing efficiency. The paper also presents an algorithm from which the location of the near-field focus can be calculated directly from the aperture field of the antenna. The definitions and the algorithm are applied to an extensive numerical study of focusing of the beam of the Arecibo tri-reflector system at low altitudes. The focusing is obtained by displacing the feed, or the tertiary reflector, or both at the same time. Finally, an approximate formula is presented, from which results can be calculated easily at other frequencies and altitudes than those being computed. - Author(s): E. Baruch and Y. Leviatan
- Source: IEE Proceedings - Microwaves, Antennas and Propagation, Volume 143, Issue 4, p. 293 –297
- DOI: 10.1049/ip-map:19960401
- Type: Article
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p.
293
–297
(5)
A procedure for the design of a planar reflector antenna comprising a quasiperiodic metallic echelette grating is described. The reflector is designed so that the power radiated by the feed is deflected by the various portions of the reflector towards a desired direction. The possibility of steering the main beam by shifting the frequency with nearly no loss in gain is demonstrated. The sensitivity to cell fabrication errors and to improper feed location, which is essential information for the antenna designer, is examined. - Author(s): D. Morris
- Source: IEE Proceedings - Microwaves, Antennas and Propagation, Volume 143, Issue 4, p. 298 –303
- DOI: 10.1049/ip-map:19960446
- Type: Article
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p.
298
–303
(6)
It is shown how the principles of simulated annealing can be incorporated into the Misell algorithm for phase retrieval. Simulations of phase retrieval from the infocus and defocused radiation patterns of a reflector antenna show that the solution can be refined in this way. Locking at local minima can be avoided and the accuracy limits set by the measurement errors can be reached. The price paid for a reliable and significant improvement in accuracy is at least an order of magnitude increase in computing. - Author(s): P.N. Fletcher and M. Dean
- Source: IEE Proceedings - Microwaves, Antennas and Propagation, Volume 143, Issue 4, p. 304 –308
- DOI: 10.1049/ip-map:19960588
- Type: Article
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p.
304
–308
(5)
It is a difficult problem to synthesise beams with the desired characteristics (low sidelobe levels, narrow main beam) from small phased arrays with few elements. Mutual coupling between elements means that conventional tapering algorithms are corrupted. In the paper a technique is presented whereby weights are calculated by point matching measured element radiation patterns to an ideal sinc function. It is found that a very close approximation to an ideal sinc beam can be synthesised by point matching to the nulls and main beam peak value of the ideal. Moreover, an orthogonal set of sinc beams can be synthesised using this technique, which in turn are used to construct a low sidelobe beam using the main beam gain of orthogonal sinc beams as sampling points. This technique gives insight into the limits of how far sidelobe levels can be reduced in arrays with few elements. No knowledge of the coupling coefficients of the array is required. - Author(s): J. Cooper ; V. Hombach ; A. Schiavoni
- Source: IEE Proceedings - Microwaves, Antennas and Propagation, Volume 143, Issue 4, p. 309 –316
- DOI: 10.1049/ip-map:19960499
- Type: Article
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p.
309
–316
(8)
Simulations are made of lossy dielectric homogeneous and inhomogeneous spheres illuminated by plane-wave or by 0.4 λ-dipole radiation at 900 MHz. The electric and magnetic field components and specific absorption rate values for each case are determined using several computational electromagnetic codes and the different results compared and illustrated. Local differences in specific absorption rate values between the methods exist, but values averaged over 1 or 10 g are within 10% of each other. A knowledge of the spread in results from different methods is needed for biomedical applications of the numerical codes to more complex problems in mobile communication. - Author(s): D.Ž. Djurdjević and B.D. Popović
- Source: IEE Proceedings - Microwaves, Antennas and Propagation, Volume 143, Issue 4, p. 317 –322
- DOI: 10.1049/ip-map:19960498
- Type: Article
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p.
317
–322
(6)
An entire-domain method is proposed for the analysis of thin-wire antennas assembled from arbitrarily interconnected straight segments situated in imperfectly conducting layered media. Following the Sommerfeld formulation, novel recursive formulas for the Hertzian vector components for vertical and horizontal Hertzian dipole located in any layer are obtained. Such exact Sommerfeld solutions are incorporated into the Hallén integral equations which are numerically solved by polynomial approximation of current and point matching. The Sommerfeld integral terms are evaluated numerically with high accuracy. - Author(s): R.J. Norman ; P.L. Dyson ; J.A. Bennett
- Source: IEE Proceedings - Microwaves, Antennas and Propagation, Volume 143, Issue 4, p. 323 –327
- DOI: 10.1049/ip-map:19960395
- Type: Article
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p.
323
–327
(5)
A method is presented of fitting quasicubic segments (QCS) automatically to measured electron-density profiles of the ionosphere. Any number of layers and valleys which occur in the ionosphere may be represented by this model, where the parameters are found by fitting to actual data points. The approach is similar to that adopted for the quasiparabolic-segment (QPS) model which has been developed in recent years and applied to a variety of ionospheric-propagation studies. The new model has been developed as an improvement to the QPS model, particularly when power calculations are required. The QCS model, like the QPS model, has analytic solutions for a number of ray quantities in the ionosphere and so can be used to study the same range of propagation phenomena as can be studied using the QPS model. - Author(s): V.A. Kalinin and B.K.J.C. Nauwelaers
- Source: IEE Proceedings - Microwaves, Antennas and Propagation, Volume 143, Issue 4, p. 328 –334
- DOI: 10.1049/ip-map:19960386
- Type: Article
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p.
328
–334
(7)
A method of simulation for a wide range of planar microwave transmission lines and optical waveguides is developed. It is based on the electric field integral equation using a free space dyadic Green's function and solved by the method of moments. The method is applicable to any waveguiding structure that can be represented by a set of rectangular dielectric, metal and superconducting regions with a phase velocity of a mode less than the velocity of light in a vacuum. It allows the mode propagation constant to be found and the field distributions both in dielectric and conducting regions. Results of calculations for rectangular dielectric waveguide and parallel plate line demonstrate good agreement with data obtained by other methods. Results of a simulation of microstrip lines with combined metal and superconducting layers are also presented. - Author(s): S. Maci ; S. Raffaelli ; M. Leoncini ; L. Borselli ; P.-S. Kildal
- Source: IEE Proceedings - Microwaves, Antennas and Propagation, Volume 143, Issue 4, p. 335 –340
- DOI: 10.1049/ip-map:19960364
- Type: Article
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p.
335
–340
(6)
The properties of a monopole antenna on a circular, dielectric-loaded ground plane are analysed by using the finite-difference time-domain (FDTD) technique. The thickness of the dielectric slab has been chosen to maximise the decay of the space-wave contribution at grazing, thus reducing the space-wave diffraction at the truncation. This permits realisation of a low-side-/back-lobe antenna provided that the spurious diffraction of the dominant TM surface wave is properly blocked. The radiation pattern of the antenna is similar to that of a monopole on an artificially soft (corrugated) disc. The accuracy of the FDTD prediction is tested by comparisons with far-field measurements and a moment-method analysis. - Author(s): R. Stamper
- Source: IEE Proceedings - Microwaves, Antennas and Propagation, Volume 143, Issue 4, p. 341 –346
- DOI: 10.1049/ip-map:19960575
- Type: Article
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p.
341
–346
(6)
The paper presents an investigation into the use of artificial neural networks to predict the values of the IF2 and IG ionospheric indices. Since 1982, the World Data Centre C1 for Solar-Terrestrial Physics has produced predictions for these indices using an adaptation of the McNish-Lincoln technique for predicting sunspot numbers. It is demonstrated that significantly more accurate predictions are obtained using artificial neural networks, which form the basis of predictions which will in future be issued by the World Data Centre. - Author(s): M.E. Bialkowski ; S.T. Jellett ; R.S. Varnes
- Source: IEE Proceedings - Microwaves, Antennas and Propagation, Volume 143, Issue 4, p. 347 –352
- DOI: 10.1049/ip-map:19960396
- Type: Article
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p.
347
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(6)
The paper describes an L-band land-vehicle mobile satellite-communications system which is designed for the Australian continent. A 14-element cylindrical antenna array for use at the vehicle end of the link is presented. The array uses electronic steering in the azimuth to maintain a communications channel to the satellite. It incorporates novel, low-cost antenna elements which feature increased impedance and ellipticity bandwidth. Also included is a novel configuration of a switched radial divider/combiner which allows for the use of low-cost switching diodes. The indoor and outdoor test results for the subsystems and the entire antenna system are presented in the paper. - Author(s): B. Nelson and W.L. Stutzman
- Source: IEE Proceedings - Microwaves, Antennas and Propagation, Volume 143, Issue 4, p. 353 –357
- DOI: 10.1049/ip-map:19960587
- Type: Article
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p.
353
–357
(5)
One year of atmospheric propagation data were collected and analysed at Blacksburg, Virginia, USA, using the Olympus satellite 12.5, 20 and 30 GHz beacons. The results are in the form of statistics which communication system designers can use to quantify precipitation effects on Ka-band links. The paper presents the results for rain fade dynamics including fade slope statistics as well as a simple model for estimating fade slope statistics for any frequency in the range 10 to 30 GHz. - Author(s): F.A. Alhargan and S.R. Judah
- Source: IEE Proceedings - Microwaves, Antennas and Propagation, Volume 143, Issue 4, p. 358 –360
- DOI: 10.1049/ip-map:19960539
- Type: Article
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p.
358
–360
(3)
Confocal annular elliptic resonators (CAER) have some useful properties and are used in the design of patch antennas and multiport microstrip junctions. The paper presents charts for several modes of the CAER using a new normalisation technique, relating the wavenumbers of the annular ring to the annular ellipse and the ratio of the outer and inner eccentricities. This normalisation reveals a virtually linear behaviour, thus easing the evaluation of the resonant frequencies for a CAER with any given outer and inner eccentricity. Comparison between experimental and theoretical results show good agreement.
Cross-coupling between open-ended coaxial radiators
Millimetre-wave frequency tripling using stacked heterostructure-barrier varactors on InP
Scattering from elongated objects: direct solution in O(N log2N) operations
Characterisation of near-field focusing with application to low altitude beam focusing of the Arecibo tri-reflector system
Analysis of quasiperiodic reflector antenna
Simulated annealing applied to the Misell algorithm for phase retrieval
Derivation of orthogonal beams and their application to beamforming in small phased arrays
Comparison of computational electromagnetic codes applied to a sphere canonical problem
Entire-domain analysis of thin-wire antennas in layered media
Quasicubic-segmented ionospheric model
Free space dyadic Green's function applied to the full-wave numerical analysis of planar transmission lines and dielectric waveguides
Analysis of surface-wave excitation and radiation mechanisms of a monopole on a circular grounded dielectric slab with critical thickness
Improved prediction of IF2 and IG indices using neural networks
Electronically steered antenna system for the australian mobilesat
Fade slope on 10 to 30 GHz Earth-space communication links — measurements and modelling
Mode charts for confocal annular elliptic resonators
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