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Microwaves, Optics and Antennas, IEE Proceedings H

Issue 6 • Date December 1984

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Displaying Results 1 - 20 of 20
  • Editorial

    Publication Year: 1984
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (94 KB)  

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  • Accurate transmission-line model for the rectangular microstrip antenna

    Publication Year: 1984 , Page(s): 334 - 340
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (717 KB)  

    An accurate and numerically efficient model for the rectangular microstrip antenna is presented. It concerns a transmission-line model which features the following three major improvements with respect to earlier such models: the mutual radiative coupling (both real and imaginary parts) between the equivalent slots is fully taken into account; the influence of the side slots on the radiation conductance is taken into account implicitly; simple analytic expressions are introduced for all relevant model parameters. By way of illustration, the new model is applied to antennas with a single microstrip feed line. Excellent agreement is shown with available experimental and theoretical results for the input impedance of a rectangular antenna. The improvements with respect to previous transmission-line models are illustrated for a square antenna. View full abstract»

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  • Millimetre-wave hybrid dielectric-microstrip antenna array

    Publication Year: 1984 , Page(s): 341 - 350
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1193 KB)  

    The new concept of using dielectric guides as a replacement for microstrip lines in linear microstrip arrays is conceived as a means of reducing the antenna dissipative loss, while retaining many of the attractive manufacturing and operational advantages of printed arrays. This hybrid microstrip-dielectric array takes the form of an insular guide to which the microstrip elements are to be coupled. Precise field representations for the insular guide enable design data for dissipative losses and element coupling to be analysed, principally for the Ey11 and Ex21 insular guide modes. For ease of manufacture and good coupling control, the microstrip elements take the form of proximity coupled resonant patch antennas, and measurements at both millimetre wavelengths and on microwave scaled models substantiate analytical results throughout. A 40-element travelling-wave hybrid array is designed illustrating the reduction in dissipative losses, the sensitivity to dimensional tolerances and the compatibility of the hybrid antenna concept with dielectric, as opposed to conventional metal, waveguide transmitter/receiver circuits. View full abstract»

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  • New procedure for near-field measurements of microwave antennas without anechoic environments

    Publication Year: 1984 , Page(s): 351 - 358
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1095 KB)  

    A new approach to the problem of environmental effects in microwave antenna pattern measurements is proposed. The method exploits the ability of a scanning probe to synthesise a high-quality, spatially selective wavefront which effectively avoids the illumination of unwanted scatterers. The development of a specialised planar array function is described, and the wavefront produced is demonstrated to be of high quality over the region of interest. An algorithm is presented to enable the procedure to be used for near-field/far-field transformation, and experimental results are provided as validation of the process. View full abstract»

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  • Parabolic torus transreflector antenna

    Publication Year: 1984 , Page(s): 359 - 364
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (749 KB)  

    The parabolic torus transreflector antenna is a circularly symmetric antenna which can be scanned through 360° by rotation of its feed alone. The reflector consists of a radome carrying 45° angled wires so that 45° polarised radiation is reflected on one side and transmitted by the other. A theoretical model has been developed to predict the radiation properties of this antenna for various feed configurations. An experimental torus has been constructed and tested, showing good agreement between theory and experiment. Good radiation patterns (sidelobes ¿ ¿ 20 dB) are obtained with limited aperture efficiency (about 25% of the horizontal aperture). The theory shows how the phase aberrations and amplitude distortions in the radiating aperture, due to the antenna geometry, limit the sidelobe performance for wider aperture illuminations with a single horn feed. A linear array feed, designed to correct phase aberrations in one plane, is found to offer only a partial improvement if the full vertical aperture is required. It is concluded that greater aperture efficiency (¿45%), with sidelobes ¿ ¿ 20 dB, requires either a torus with a restricted vertical aperture, (¿5 ¿0), or a planar array feed. View full abstract»

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  • Systematic design of a dual offset reflector antenna with an elliptical aperture

    Publication Year: 1984 , Page(s): 365 - 370
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (538 KB)  

    The systematic design of an optically shaped dual offset reflector antenna, capable of illuminating a given elliptical aperture over which the phase is uniform and the power is arbitrarily prescribed when fed by a scalar horn, is described in the paper. A conformal mapping transforms the ellipse to a circle, allowing the present problem to be solved by an existing method. Designs based upon Cassegrainian and Gregorian systems are derived. View full abstract»

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  • Compact gain measurements on reflector antennas

    Publication Year: 1984 , Page(s): 371 - 378
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (988 KB)  

    The paper describes an extremely compact method of making gain measurements on parabolic reflector antennas. The concept involves making return-loss measurements on the antenna when it is located in front of a plane reflecting screen mounted parallel to the antenna aperture. This compact configuration is convenient for laboratory measurements or factory testing and has been used on reflectors of up to 12 ft (3.66 m) in diameter (in the latter case, employing a water bath to represent the plane flat reflecting surface). The return-loss measurements provide information on the various loss mechanisms which degrade the normal operation of an antenna, and the paper provides a detailed experimental and theoretical study of such losses and their relation to the measurement system. The results show an accuracy of the order of 0.1 dB for gain measurement, aided by the fact that the system corresponds to a 2-way (transmit-and-receive) measurement on the antenna. The paper discusses various ways of using the measurement for comparative and absolute determination of antenna gain. View full abstract»

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  • Monofilar conical-helix antenna with low pitch angle

    Publication Year: 1984 , Page(s): 379 - 382
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (462 KB)  

    The radiation characteristics of a monofilar conical-helix antenna are investigated on the basis of the theoretical current distribution. It is shown that the current distribution may be divided into two regions, and that a decaying current from the feed point to a point of the first minimum is the major contributor to the radiation. It is also found that the wideband usage requires the arm length to include the region up to the second minimum at the lowest operating frequency. Experimental data concerning the input impedance and radiation characteristics are presented to verify the numerical results. View full abstract»

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  • Diffraction coefficients for a curved edge with soft and hard boundary conditions

    Publication Year: 1984 , Page(s): 383 - 389
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (798 KB)  

    Diffraction of high-frequency electromagnetic fields are very important from both the theoretical and engineering points of view. Generally, asymptotic methods are preferred for the solution of diffraction problems because rigorous analysis is generally impossible. In the paper the diffraction of whispering gallery modes by the edge of a conducting spherical reflector with soft and hard boundary conditions are considered separately, where the incident modes are assumed to be present in the concave side of the reflector. The analysis has been done for the special case (ka) ¿ 1 by using the locality principle of the GTD (geometrical theory of diffraction). The results are expressed in the GTD form and various coefficients for the determination of edge-excited rays and surface ray fields are extracted. It is concluded that these coefficients can be used for the determination of diffracted rays and surface ray fields excited by apertures on arbitrarily curved surfaces. These coefficients are not valid in the transition regions, but they reveal the effect of surface curvature on diffraction phenomenon. View full abstract»

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  • Meniscus-lens-corrected corrugated horn: a compact feed for a Cassegrain antenna

    Publication Year: 1984 , Page(s): 390 - 394
    Cited by:  Papers (5)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (624 KB)  

    The physical size of a corrugated conical horn feed having narrow beamwidth can be reduced considerably by correcting the spherical phase front in the aperture using a meniscus lens. Measured and calculated radiation characteristics of such lens-corrected scalar horns are presented. It is shown that the horns can provide efficient aperture illuminations when used as feeds for conventional Cassegrain antennas, for example radiotelescopes. Further, it is shown that the high crosspolarisation, which is normally present in lens horn designs, can be reduced to that of the horn itself by corrugating the lens surfaces with holes. Improved design formulas for such holes are given. View full abstract»

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  • Fast algorithm for optimal weight computation in linear array pattern synthesis having null constraints

    Publication Year: 1984 , Page(s): 395 - 396
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (218 KB)  

    A fast algorithm is given for computing the optimal weight vector in antenna array pattern synthesis having a set of null constraints. The algorithm requires only a UDUT decomposition of an m + 1 ¿¿ m + 1 real positive definite matrix and the computation of the first row of the inverse of a triangular matrix of the same dimension, where m is the number of null constraints. View full abstract»

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  • Circular waveguide bifurcation for asymmetric modes

    Publication Year: 1984 , Page(s): 397 - 404
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (746 KB)  

    An analytical solution for a circular waveguide bifurcation with incident TE11- and TM11-modes is presented using the residue calculus method. It is shown how the coupling between the TE1n- and TM1n-modes can be taken into account by expressing the coupling factor as a contour integral, which is the key step enabling the residue calculus method to be applied. Graphical results for the scattering matrix parameters of the junction are given for a range of waveguide radii of interest in the design of dual-mode coaxial prime focus feeds for paraboloidal antennas. View full abstract»

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  • Dual-mode coaxial feed with low crosspolarisation

    Publication Year: 1984 , Page(s): 405 - 410
    Cited by:  Papers (4)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (680 KB)  

    Design data for optimised TE11-TM11 dual-mode coaxial prime focus feeds is presented. The optimised feeds have a crosspolarisation below ¿¿30 dB, an input reflection coefficient below 0.1 and very little phase error in their radiation patterns, over a 5% bandwidth. Experimental patterns are also given that show that the theoretically derived design data can be relied upon. The optimised feeds are useful for paraboloidal reflectors with focal-length/diameter ratios in the range 0.3 to 0.5, and will give overall efficiencies as high as 70% or more with sidelobes below ¿¿30dB. View full abstract»

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  • Erratum: Design and performance of a low crosstalk directional coupler switch

    Publication Year: 1984
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (68 KB)  

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  • New power-density calculation method by three-dimensional finite elements

    Publication Year: 1984 , Page(s): 411 - 419
    Cited by:  Papers (4)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1241 KB)  

    A new method to calculate the absorbed power density in closed microwave systems is presented. The method, which is based on the use of a dual variational principle and three-dimensional finite elements, extracts more information from the field solution than a previously published method. The calculation of the total incident and reflected power in a microwave cavity is discussed. View full abstract»

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  • Book review: Shaped Reflector Antenna Design

    Publication Year: 1984
    Save to Project icon | PDF file iconPDF (171 KB)  
    Freely Available from IEEE
  • Mode charts of magnetised and demagnetised planar hexagonal resonators on ferrite substrates using finite elements

    Publication Year: 1984 , Page(s): 420 - 422
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (302 KB)  

    The mode charts of demagnetised and magnetised planar hexagonal resonators on ferrite or garnet substrates are of some interest in the theory of filter and circulator hardware. The paper employs the finite-element approach to derive the relationship between the magnetised mode chart and the magnetic and dielectric variables of the substrate for this resonator. Some experimental results are also given on the first two split modes in such a resonator. View full abstract»

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  • Wide-gap re-entrant cavity resonators for 900-1500 MHz

    Publication Year: 1984 , Page(s): 423 - 425
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (337 KB)  

    An approximate model for high Qfactor wide-gap re-entrant cavity resonators is presented which is suitable for evaluating the performance of units capable of operation in the 900 MHz and 1500 MHz bands. The model is used to estimate the unloaded Q-factor and temperature stability. Theory and practice are compared. View full abstract»

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  • Comment: Mutual coupling compensation for small, circularly symmetric planar antenna arrays

    Publication Year: 1984
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  • Reply: Mutual coupling compensation for small, circularly symmetric planar antenna arrays

    Publication Year: 1984
    Save to Project icon | PDF file iconPDF (127 KB)  
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