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Microwaves, Optics and Acoustics, IEE Journal on

Issue 6 • Date November 1979

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Displaying Results 1 - 10 of 10
  • Double knife-edge diffraction for curved screens

    Publication Year: 1979 , Page(s): 221 - 223
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (303 KB)  

    The known solution for double knife-edge diffraction between parallel staggered plates is extended to include curved screens. The result is used in calculating the radiation field of a Cassegrain antenna. View full abstract»

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  • Computation of electromagnetic fields guided by a cylindrical inhomogeneity in a homogeneous medium of infinite extent

    Publication Year: 1979 , Page(s): 224 - 230
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (922 KB)  

    A rigorous numerical method is presented for computing time-harmonic electromagnetic fields that are guided by a transparent, lossless inhomogeneity in a homogeneous medium of infinite extent. Geometrically, the inhomogeneity is a cylinder of arbitrary cross-section. The structure is typical for a uniform open waveguide. On using the wave functions of the circular cylinder outside a cylinder that surrounds the inhomogeneity, and on transforming the electromagnetic-field equations inside this cylinder into a system of first-order ordinary differential equations, a two-point differential eigenproblem is obtained that is solved using standard techniques. Results are presented for waveguides with an equilaterally triangular and a rectangular cross-section, respectively. The latter is studied in detail. View full abstract»

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  • Rays and modes on step-index multimode elliptical waveguides

    Publication Year: 1979 , Page(s): 231 - 238
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (749 KB)  

    Generalised geometric optics are applied to the classification of rays within an optical waveguide of elliptical cross-section. We find four classes of ray paths; (i) bound, (ii) tunnelling, (iii) refracting and (iv) paths that both tunnel and refract. The last class is not found on circular waveguides. The corresponding classes of modes are established from electromagnetic theory. A simple expression for the attenuation of each tunnelling mode is given in the weakly guiding approximation for slight eccentricity, and is shown to be analytically equivalent to the attenuation of the corresponding family of tunnelling rays, when ray-power loss is averaged over all reflections. This equivalence also justifies the use of local ray power-transmission coefficients in the description of ray attenuation. View full abstract»

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  • Erratum: High-frequency behaviour of microstrip open-circuit terminations

    Publication Year: 1979
    Save to Project icon | PDF file iconPDF (45 KB)  
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  • Mode dispersion, material dispersion and profile dispersion in graded-index single-mode fibres

    Publication Year: 1979 , Page(s): 239 - 246
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (847 KB)  

    A study of single-mode fibres shows that in the normal operating region the cladding has as much effect on the propagation constant as does the core. A detailed analysis shows that the complex expression for pulse dispersion can be arranged in three groups of terms which may be defined as composite material dispersion, waveguide dispersion and composite profile dispersion. The analysis has been applied to a fibre for which the material dispersion parameters are accurately known and it is found that zero total dispersion can be obtained at a wavelength which depends on the profile and the core diameter but may be selected within a range roughly 1.3¿¿2 ¿¿m. However, there are severe requirements on the control of core diameter and profile. View full abstract»

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  • Dual reflectors for shaped beams and zero cross polarisation

    Publication Year: 1979 , Page(s): 247 - 252
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (600 KB)  

    Offset dual doubly-curved reflector-antenna systems are designed on the basis of geometrical optics to produce a shaped beam (cosec2 pattern) in the vertical plane and a narrow beam in the transverse plane with zero cross polarisation. Two configurations of ray-path geometry are identified and the main parameters are investigated. Blockage effects can be removed by judicious choice of parameter values. View full abstract»

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  • Magnetically tunable millimetre-wave filter with single-crystal barium ferrite

    Publication Year: 1979 , Page(s): 253 - 254
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (220 KB)  

    Barium-ferrite (BaFe12O19) single crystals with a high anisotropy field and low millimetre-wave (mm-wave) losses have been grown from high-temperature solutions. The high internal field (17/4¿¿ MA/m) considerably reduces the external magnetic field required for spin resonance at mm-wave frequencies. Due to the progress in single-crystal barium-ferrite technology, it is possible to extend the tuning range of filters up to 90 GHz. A compact tunable filter, similar to y.i.g.-filters, has been built and the first results are reported. View full abstract»

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  • Reflection behaviour of the calculable Y-type waveguide standard mismatch

    Publication Year: 1979 , Page(s): 255 - 258
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (431 KB)  

    The reflection behaviour of a new waveguide standard mismatch has been investigated, consisting of a Y-type power divider terminated by a movable short circuit and a matched load, and generating calculable values of the voltage standing wave ratio (V.S.W.r) ¿¿ 2. A detailed theoretical analysis which considers the influence of residual reflections on the generated V.S.W.r. has been confirmed by experiments. These reflections occur if the power divider is not perfectly matched, or if it is terminated by a nonideal load. By means of simple error formulas, it can be shown that the deviations of the calculated v.s.w.r. from the actually generated v.s.w.r. due to residual reflections remain small. View full abstract»

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  • Scattering- matrix theory of the performance of acoustic-surface-wave interdigital transducers

    Publication Year: 1979 , Page(s): 259 - 264
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (634 KB)  

    A transducer can be regarded as an array of elementary radiators whose performance can be described by a primitive scattering matrix. The overall performance of a composite transducer can be calculated by matrix methods from the primitive matrices of its elementary radiators. The method is used to calculate the performances of simple delay lines, unidirectional transducers, and delay lines using unidirectional transducers. Expressions are also obtained for the elements of the primitive scattering matrix in terms of the components of a simple equivalent circuit. View full abstract»

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  • Measurement of thickness-shear-stress distribution of the oscillating plano-convex AT-cut quartz-crystal resonator

    Publication Year: 1979 , Page(s): 265 - 271
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (725 KB)  

    The paper compares measured and calculated thickness-shear-stress distributions of a plano-convex AT-cut quartz-crystal resonator oscillating at its fundamental, 3rd overtone and 5th overtone thickness-shear resonant vibration frequencies. The calculated resonant frequencies and the vibration-stress distribution calculated numerically using a finite-element method show good agreement with those obtained experimentally. View full abstract»

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