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Microwaves, Antennas and Propagation, IEE Proceedings H

Issue 1 • Date February 1985

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Displaying Results 1 - 14 of 14
  • Rigorous field theory analysis of quasiplanar waveguides

    Page(s): 1 - 6
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (525 KB)  

    An accurate field theory solution for calculating the hybrid eigenmodes of quasiplanar structures is introduced which includes both the influence of the finite strip thickness and waveguide housing grooves. Using the transverse resonance method the size of the characteristic matrix equation is kept constant even for an increasing number of discontinuities. Dispersion characteristics of various structures consisting of at least one isolated strip are presented. The fundamental EH0-modes mainly depend on the finite strip thickness, while increasing waveguide grooves lead to a significant reduction of higher-order-mode cutoff frequencies. View full abstract»

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  • Finite-element analysis of the shielded cylindrical dielectric resonator

    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (902 KB)  

    Results are presented of the application of the finite-element method to evaluate the resonant frequency and external Q-factor Qe of a cylindrical dielectric resonator operating in the TE01¿¿-mode, taking into account the effects of the conducting shield and the supporting substrate. Normalised design charts covering a wide range of practical geometrical and physical parameters are presented. Measured values of the resonant frequency and external Q-factor compare well with the theory. View full abstract»

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  • Noise parameters of embedded noisy two-port networks

    Page(s): 17 - 22
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (539 KB)  

    Embedding networks such as bias or feedback elements etc. modify the noise performance of a twoport. This influence is investigated for both lumped and distributed embedding networks and formulas are derived for noise parameters of the embedded network. View full abstract»

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  • Phase constant characteristics of generalised asymmetric three-coupled microstrip lines

    Page(s): 23 - 26
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (460 KB)  

    Phase constant characteristics of generalised asymmetric three-coupled microstrip lines are presented and discussed. The influence of various structural parameters, as well as the effects of dispersion, are incorporated to show the behaviour of three fundamental guided modes. View full abstract»

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  • Permittivity measurements using a frequency-tuned microwave TE01 cavity resonator

    Page(s): 27 - 32
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (797 KB)  

    A measuring system for determining the complex permittivity of low-loss solids using a frequencytuned TE01 cavity resonator of fixed length is described. Its mechanical construction is simple, and measurements, in particular of the real part ¿¿' of the permittivity, can be performed within a relatively short measuring time with high precision ($$$¿¿¿¿'/¿¿'|< 7 ¿¿ 10¿¿4), for a large number of frequencies in a given frequency band. The method is compared with the standard method where a length-tuned resonator is involved. Theoretical error investigations and practical measurements at frequencies of about 10 GHz on polymers and fused silica are carried out showing that the uncertainties have comparable values in both methods. View full abstract»

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  • Exact ray path calculations in a modified Bradley/Dudeney model ionosphere

    Page(s): 33 - 38
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (571 KB)  

    Bradley and Dudeney's model of the vertical distribution of the ionospheric electron concentration consists of three distinct sections. Both the E-region and F2-region are described by parabolic variations. A linear increase is assumed to exist between the E-region peak and the F2-region. This model is currently recommended by the International Radio Consultative Committee (CCIR) for use in long-term HF sky-wave prediction work. If a slightly modified electron-concentration profile is adopted, it is possible to derive exact expressions which describe some important characteristics of oblique ray paths in the model ionosphere. Ground range, group path, phase path and apogee height can all be computed using this technique. Collisions and the effect of the earth's magnetic field are ignored. These expressions have been used for several applications where a knowledge of multipath structure on ionospheric paths is necessary. View full abstract»

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  • Model of rainfall-rate distribution for radio system design

    Page(s): 39 - 43
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (407 KB)  

    Owing to the interest raised by the precipitation effects in the design of satellite and terrestrial microwave radiolinks, it is necessary to have a simple and valuable mathematical model which can represent, with good accuracy, the whole rain-rate distribution, from lowest rain-rate values to the tail of this distribution. Previously the author suggested a two-parameter model which adequately represents the rainfall intensity cumulative distributions for several hydrometeorological zones of the world. This model has log-normal asymptotic behaviour for low rainfall rates, and gamma asymptotic behaviour for the high ones. The present paper deals with a further improvement by expressing both parameters as a function of the rainfall rate exceeded during 0.01% of the time, and recommended by the CCIR to evaluate the availability of microwave radio links. View full abstract»

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  • Generalised array pattern synthesis using the projection matrix

    Page(s): 44 - 46
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (393 KB)  

    An analytic solution to the problem of array pattern synthesis having null and norm constraints is given. We show that the required complex weight vector can be obtained by finding the eigenvector corresponding to the maximum eigenvalue of a Hermitian matrix. The generality of the method is illustrated by applying it to synthesise patterns with multiple look directions. View full abstract»

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  • General design of two-reflector antennas

    Page(s): 47 - 52
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (494 KB)  

    A new description of the profiles of the main reflector and subreflector of a dual-reflector antenna is given in terms of a single parameter, the angle subtended by the normal to the main reflector and the axis of the system. It is shown that the same parameter describes the nature of the focusing in both the illuminating beam and the image space. Hence, quite general illumination, focusing and main reflector profiles can be considered. The results are illustrated for subreflectors in the concave hemisphere and paraboloid, for axial illumination and offset conditions, and the application of the method to amplitude shaping or the Abbe sine condition is discussed. View full abstract»

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  • Decomposition of antenna signals into plane waves

    Page(s): 53 - 57
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (762 KB)  

    A modification of Prony' method, in which an attempt is made to constrain the roots of the polynomial to the unit circle, is used to resolve a number of plane waves illuminating a uniformly spaced line array. A least squares method based on the eigenstructure of a certain correlation matrix is developed to handle the overdetermined case when there are excess numbers of antenna elements. Angle estimate variance is compared to the Cramer-Rao lower bound and with the forward-backward linear predictor method. View full abstract»

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  • Book review: Microwave Imaging with Large Antenna Arrays

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    Freely Available from IEEE
  • General method for the computation of radiation in stratified media

    Page(s): 58 - 62
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (591 KB)  

    A general universal computational method for the general electromagnetic problem in stratified media is established. Computations are successfully performed for the field of a horizontal magnetic dipole in a microwave substrate backed by a conducting plane. The general field problem in stratified media is expressed in the form of integrals over kp. The integrands involve Bessel functions which are difficult to integrate. By using the fast Fourier transform (FFT) techniques, the integrals are computed numerically. A shortcoming of this method is that its usefulness is limited to near and intermediate fields. This method is applicable to many electromagnetic problems in microwaves, geophysical sciences, printed circuits etc View full abstract»

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  • Optimising the synthesis of shaped beam antenna patterns

    Page(s): 63 - 68
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (789 KB)  

    A technique is introduced which uses the conventional polynomial representation of the antenna pattern produced by an equispaced linear array. Certain roots are displaced from the unit circle radially, to fill a portion of the pattern, which before this displayed lobes interspersed by deep nulls. The angular and radial positions of all the roots are simultaneously adjusted so that the amplitude of each ripple in the shaped region and the height of each sidelobe in the nonshaped region are individually controlled. Applications to a cosec2 ¿¿ ¿¿ cos ¿¿ pattern and to a flat-topped beam are presented. Experimental validation is also offered. View full abstract»

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  • Technical memorandum. Fast, accurate computational method for asymmetric coupled microstrip parameters

    Page(s): 69 - 70
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (267 KB)  

    An accurate and direct method is introduced for determining the design parameters of asymmetric coupled microstrip lines for any substrate material, in terms of known design parameters for any other substrate material. To check the accuracy of the method two examples are given. In the first example a quartz substrate is considered, while in the second example a teflon substrate is considered. In both examples, the known parameters are that of asymmetric coupled lines on an alumina substrate View full abstract»

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