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Microwaves, Antennas and Propagation, IEE Proceedings H

Issue 6 • Date December 1987

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Displaying Results 1 - 17 of 17
  • Dual-function multi-way uniform combline directional couplers for application to monopulse feed system

    Page(s): 481 - 487
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (714 KB)  

    A new technique of obtaining two distinct power splitting functions from a multi-way uniform combline directional coupler is introduced. The new directional coupler is called a `dual-function multi-way combline coupler¿¿. An experimental coupler has been fabricated using comblines in an open microstrip configuration for the frequency range 1.2 to 1.5 GHz. The measured results show good agreement with the theoretical predictions. A proposal is made for a possible application of the new dual-function coupler, which, in conjunction with a number of multi-way uniform and warped-mode combline directional couplers, would make a feed network for a multi-element monopulse antenna array. View full abstract»

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  • Mode nomenclature of circular gyromagnetic and anisotropic waveguides with magnetic and open walls

    Page(s): 488 - 496
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (847 KB)  

    The problem of propagation along a longitudinally magnetised gyromagnetic circular waveguide with a magnetic wall has not been fully treated in the literature. This waveguide, unlike the electric wall problem, for which only the phase constants are split, exhibits both split phase constants and cutoff numbers. It is also of note that, in keeping with the solution of the electric wall problem, a single continuous cutoff curve, belonging to one of the two factors of the characteristic equation, need not necessarily describe the same mode throughout its entire length. Such discontinuities are displayed whenever the order and polarity of the Bessel functions at the intersection of any two cutoff curves coincide. Some calculations on the open anisotropic waveguide are also included for completeness. View full abstract»

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  • Resonant frequencies of whispering-gallery dielectric resonator modes

    Page(s): 497 - 501
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (482 KB)  

    Whispering-gallery dielectric resonator modes have shown their usefulness in millimetre wave integrated circuits. In the paper, a method for the determination of the resonant frequencies of the whispering-gallery modes of cylindrical dielectric resonators is presented. Theoretical and experimental results are given. A comparison with other methods is also made. View full abstract»

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  • A generalised network formulation for a class of waveguide coupling problems

    Page(s): 502 - 508
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (610 KB)  

    The paper considers the general problem of a waveguide coupled to an arbitrary region via a rectangular aperture of arbitrary dimensions in the thick common broad wall. An equivalence theorem is utilized to set up a pair of operator equations which are then reduced to matrix form using the method of moments. It is shown that only a part of the moment matrix needs to be recalculated for coupling to different regions. The basic procedure has been illustrated by considering the example of two identical wave-guidescoupled through an aperture in the common broad wall. View full abstract»

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  • Low-cost flat-plate array with squinted beam for dbs reception

    Page(s): 509 - 514
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (797 KB)  

    There is a great deal of interest in the replacement of reflector antennas by low-cost wall-mounted fiat-plate antennas for the reception of satellite signals. The paper describes the extent to which combline microstrip technology can be used to obtain a squinted, circularly polarised beam at very low cost. The antenna presented consists of a simple travelling wave printed structure comprising a foam/metal sandwich with metal strip polariser. Performance parameters such as bandwidth, dissipative loss and pattern quality are examined and the effect of manufacturing tolerances are discussed. Finally, comparisons are made with reflector antennas and other flat-plate designs, with particular reference to the DBS specification; the possibility of introducing beam control capabilities into the array is con-sidered. It is concluded that the development of suitable low-cost substrates is a key issue and electronic beam control raises problems of a more fundamental nature. View full abstract»

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  • Design and analysis off a six-port receiver for use in near-field antenna measurements

    Page(s): 515 - 520
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (717 KB)  

    The configuration, analysis and calibration of a six-port based receiver for near-field antenna measurements is described. The receiver operates in an approximate manner in which the transmission coefficient is obtained from a single measurement. Design rules are given which keep the operational errors of the device smaller than those introduced by the approximations inherent in the near-field measurement theory. Tests show that the receiver is accurate and stable when operated in a dynamic range of approximately 50 dB. The suitability of the six-port receiver in near-field measurement systems is demonstrated through the measurement of radiation patterns of horn antennas. View full abstract»

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  • Application of Pocklington's equation to analysis of dipole frequency-selective surfaces of finite size

    Page(s): 521 - 526
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (647 KB)  

    Pocklington's equation is applied to arrays of linear dipoles. An integral equation for the currents induced in each dipole is derived for plane-wave illumination. The equation is solved by the method of moments. The current mode amplitudes for a 5 ¿¿ 5 array and a 20 ¿¿ 5 array are compared with those given by the standard modal analysis of an infinite periodic array using the same set of basis functions. In the latter case predicted transmission responses in the frequency range 18¿¿40 GHz link the calculations to experiment. The effect of the edge region on the induced current phasors and on the scattered fields is discussed. Near the resonance frequency for TE incidence there is a pronounced amplitude variation across the 20 ¿¿ 5 array. The analysis described in the paper is not restricted to periodic lattices. View full abstract»

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  • More about rainfall rates and their prediction for radio systems engineering

    Page(s): 527 - 537
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1172 KB)  

    Owing to the interest raised by the effect of precipitation on the design of satellite or terrestrial radiocommunication systems at high frequencies, it is important to have at our disposal a mathematical or semiempirical model which correctly accounts for rainfall rate cumulative distributions whatever the climatic region. In the paper an empirical model is suggested, based on two parameters: the rain rate value R0.01(mm/h) in the considered location, and a parameter which depends on the geographical characteristics of this location. This model allows the calculation of instantaneous rain rate cumulative distributions, depending on the use of CCIR hydrometeorological zones, or CCIR contours of rainfall intensities exceeded for 0.01% of the time: R0.01 (mm/h). View full abstract»

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  • Comparative study of reflector antennas for small earth stations

    Page(s): 538 - 544
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (554 KB)  

    For a small earth station, a detailed comparative study of three types of dual offset reflector antenna is presented. These are the shaped dual-reflector antenna, the sector-shaped paraboloidal reflector antenna and the spherical offset reflector antenna. The efficiency, the radiation patterns and the complexity of fabrication are some of the aspects considered. View full abstract»

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  • Analysis of broad side coupled inhomogeneous cylindrical striplines

    Page(s): 545 - 549
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (471 KB)  

    A method of analysis for inhomogeneous broad side coupled cylindrical striplines is described. It is found that unequal phase velocities for even and odd modes can be obtained with these lines, thus making them advantageous for the design of cylindrical stripline directional couplers.The data for even and odd mode impedances, effective dielectric constants and mode phase-velocity ratios are presented. The effect of environmental changes on an otherwise planar structure is studied by extending the present analysis to cylindrically warped broad side coupled striplines. View full abstract»

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  • Method of reducing mode-degeneracy problem in annular-ring patch antennas

    Page(s): 550 - 556
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (682 KB)  

    The annular-ring patch antenna with an extended ear at its outer periphery is analysed. A mode matching technique (MMT) is utilised and is improved by incorporating the mutual coupling effect between the two radiating edges. The formulations for the wall admittances including the extended ear are also developed. The analysis shows that for an annular bandwidth of the TM12 mode is increased by increasing its inner radius. It also moves the resonant frequency of the TM02 mode towards that of the TM12 mode, overlap-ping their bandwidths and causing mode degeneracy. The addition of an extended ear separates the mode resonances and removes their degeneracy and, therefore, the usable range of frequency for a particular mode is increased. An annular ring with the extended ear is fabricated and tested. The numerical results of the improved MMT agree more closely with the experimental data than those obtained using the conventional MMT used in the literature. View full abstract»

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  • Short-pulse excitation off reflector antennas

    Page(s): 557 - 559
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (248 KB)  

    The transient build-up and decay of the radiated field produced by a short pulse in a reflector antenna are examined. The transient time is proportional to diameter, and inversely pro-portional to f/D, thus Cassegrain reflectors have better short-pulse response. View full abstract»

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  • Technical memorandum estmating the residual error from calibrating a reflectometer with a sliding termination

    Page(s): 560 - 562
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (362 KB)  

    A sliding termination is often used to approximate to ¿¿ = 0 when calibrating a reflect-ometer with equivalent generator mismatch ¿¿G. The paper shows that a residual error of ¿¿G*|¿¿T|2 results (where |¿¿T| is the amplitude of reflection from the variable phase load and * denotes complex conjugate) and compares this error with the precision of available calibration standards. View full abstract»

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  • Technical memorandum higher mode resonances of high permittivity square cuboid dielectric resonators on integrated circuit substrates

    Page(s): 563 - 565
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (382 KB)  

    The resonant frequencies of low and high order modes of square cuboid, high permittivity dielectric resonators have been studied, both theoretically and experimentally for the case of a resonator on a substrate, such as an integrated circuit. A previous analysis for an isolated rectangular resonator has been extended for the present case and Fortran IV programs have been written to calculate the resonant mode frequencies as a function of the aspect ratios of the resonators. The dimensions of resonators for various aspect ratios ranging from 0.2 to 0.9 were calculated, keeping the frequency of the fundamental TE 11¿¿mode constant at 8.2 GHz. The resonators were made from zirconium titanium stanate (¿¿r = 34.3) for the experimental determination of resonant frequencies. There was a good agreement between the theoretical and experimental values of the resonant frequencies of the various modes. It was shown from the determination of the values of Q of the various modes that the E13¿¿ mode offers a higher value of Q than the corresponding fundamental TE11¿¿ mode. View full abstract»

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  • Technical memorandum simple solution of dispersion characteristics of shielded stripline

    Page(s): 566 - 568
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (314 KB)  

    An analytical technique is presented to analyse the propagation constant of the TEM-like mode as well as higher-order modes in shielded microstrip transmission line, particularly at the most-needed high-frequency region. The method is quite general and is based on a variational expression for the propagation constant inside the structure. A simple expression is developed for the characteristic equation of the TEM-like modes, which is quite accurate particularly at high fre-quencies. Further, the method is equally valid for open structure by proper adjustment of the parameters. View full abstract»

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