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IEE Proceedings H (Microwaves, Antennas and Propagation)

Volume 139, Issue 4, August 1992

Volumes & issues:

Volume 139, Issue 4

August 1992

Noise temperatures of multiresponse systems
Electromagnetic scattering by a uniaxially anisotropic sphere
  • Author(s): K.-L. Wong  and  H.-T. Chen
  • Source: IEE Proceedings H (Microwaves, Antennas and Propagation), Volume 139, Issue 4, p. 314 –318
  • DOI:  10.1049/ip-h-2.1992.0056
  • Type: Article
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  • p. 314 –318 (5)
    The problem of electromagnetic scattering by a uniaxially anisotropic sphere is studied for both dielectric and absorbing cases. The fields of the TM ro ř wave inside a uniaxial sphere can be derived to be expressed in series of Bessel functions, as in the isotropic case, but with the order of function determined by the anisotropic ratio (AR = εθ/εr). For the TE to ř wave, the uniaxial medium can be treated as an isotropic material characterised by εθ only, which is the permittivity parallel to the boundary surface of the medium. Wave propagation is not affected by the f directed permittivity. The effects of uniaxial anisotropy on the radar cross section (RCS) are also considered. It is found that the uniaxial anisotropy greatly influences the scattering behaviour of a spherical dielectric object. For an absorbing sphere, however, the uniaxial anisotropy no longer plays a significant role as in a dielectric sphere, and the dependance of the RCS on uniaxial anisotropy is found to be predictable. Details of theoretical treatment and numerical results are presented.
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Technical Memorandum: Complex gyrator circuit of junction circulators using weakly magnetised ring resonators
Open resonators powered by a rectangular waveguide
Characterisation of gaas fet and hemt chips and packages for accurate hybrid circuit design
Identification of passive intermodulation product generation on microwave reflecting surfaces
Electromagnetic field computations in a three-dimensional cavity with a waveguide junction of a frequency standard
Simplified tape model of arbitrarily-loaded helical slow-wave structures of a travelling-wave tube
  • Author(s): A.K. Sinha ; R. Verma ; R.K. Gupta ; L. Kumar ; S.N. Joshi ; P.K. Jain ; B.N. Basu
  • Source: IEE Proceedings H (Microwaves, Antennas and Propagation), Volume 139, Issue 4, p. 347 –350
  • DOI:  10.1049/ip-h-2.1992.0062
  • Type: Article
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  • p. 347 –350 (4)
    A simplified tape model has been proposed to obtain the dispersion relation for helical slow-wave structures loaded in a complex manner. It combines the tape model results of field analysis for a helix in free space with the sheath model results of equivalent circuit analysis of the structure with complex loading, which are available in the literature. The dispersion relation obtained by the proposed model, for a helix supported by arbitrarily shaped dielectric support bars in a vanemetal envelope, is found to be identical with that obtained using the tape model of Sensiper for helix in free space extended to the case of a loaded helix. The structure considered is quite general. It includes both anisotropic as well as inhomogeneous loading of the helix. Any specific structure of interest may be interpreted as a special case of this structure. The theoretical results are compared with experimental results reported in the literature.
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Analysis of discontinuities in waveguiding structures by MAB method
  • Author(s): J. Macháč
  • Source: IEE Proceedings H (Microwaves, Antennas and Propagation), Volume 139, Issue 4, p. 351 –357
  • DOI:  10.1049/ip-h-2.1992.0063
  • Type: Article
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  • p. 351 –357 (7)
    The method of minimal autonomous blocks is briefly described. A universal code computing reflectivity and transmissivity of discontinuities in waveguide structures was developed on the basis of the MAB method. This technique is applied to the solution of dielectric cylinders, metal ridges and bandpass filters in a rectangular waveguide, as well as on shunt posts in a microstrip line. Special attention was given to E-plane tee junctions in rectangular waveguides; scattering matrices are evaluated and approximated by the proper function with dependence on frequency and branch waveguide height.
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Large-current radiators
New approach to antenna testing from near field phaseless data: the cylindrical scanning
  • Author(s): T. Isernia ; G. Leone ; R. Pierri
  • Source: IEE Proceedings H (Microwaves, Antennas and Propagation), Volume 139, Issue 4, p. 363 –368
  • DOI:  10.1049/ip-h-2.1992.0065
  • Type: Article
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  • p. 363 –368 (6)
    A new method for recovering the complex near and far field from amplitude distributions collected over two near zone surfaces is proposed. By exploiting the mathematical properties of the radiated fields and choosing an appropriate functional of the data, the solution is found through the minimisation of the introduced functional. All details of the resulting iterative procedure are worked out for the cylindrical scanning in the three dimensional vector case where the implementation turns out to be effective thanks to a proper use of the FFT algorithm. It is shown that this new approach allows the solution to be obtained starting from a completely arbitrary point, so avoiding the local minima problem.
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Graphical depiction of the electromagnetic fields of hermite—gaussian modes
Design of a three-dimensional gap-coupled suspended substrate stripline bandpass filter
  • Author(s): Y.-C. Chiang ; C.-K.C. Tzuang ; S. Su
  • Source: IEE Proceedings H (Microwaves, Antennas and Propagation), Volume 139, Issue 4, p. 376 –384
  • DOI:  10.1049/ip-h-2.1992.0067
  • Type: Article
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  • p. 376 –384 (9)
    A three-dimensional gap-coupled suspended substrate stripline (SSS) bandpass filter, based on the modified configuration of the classic end-coupled filter, is presented. It consists of printed half-wavelength resonators placed on the same and/or the opposite sides of the suspended substrate. These resonators orient themselves in arbitrary directions. Such an arrangment makes the new filter highly flexible to interface with other microwave subcircuit modules. The filter is constructed in a bent channelised housing that suppresses any possibility of exciting higher-order modes, except the dominant quasi-TEM mode of propagation. Consequently, the channelised filter is free from any coupling between itself and other microwave circuit components within the system. Two look-up tables, derived from a variational three-dimensional quasi-TEM spectral-domain analysis of the discontinuity problems associated with the adjacent gap-coupled resonators, are incorporated into the computer-aided design of the new filter. The de-embedded discontinuity parameters are validated by comparing them with those obtained by experiment and full-wave approaches for the microstrip open-end and the SSS end-coupled problems, respectively. The measured results for the experimental 21–22 GHz bandpass filter agree very well with the theoretic predictions considering the conductor losses (5.57 × 10−3 dB/mm) of the SSS. It has less than 1.4 dB insertion loss and greater than 10 dB return loss in the passband.
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Plural hybrid mode multiflare conical horn with reduced cross polarisation and sidelobe levels
  • Author(s): R.A. Nair
  • Source: IEE Proceedings H (Microwaves, Antennas and Propagation), Volume 139, Issue 4, p. 385 –391
  • DOI:  10.1049/ip-h-2.1992.0068
  • Type: Article
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  • p. 385 –391 (7)
    A new horn antenna exhibiting low cross polarisation and sidelobe levels over a wide frequency band is investigated both analytically and experimentally. The antenna consists of a dielectric loaded multiflare conical metal horn that can support the balanced hybrid modes. The higher order modes excited with appropriate relative amplitude and phase by the dominant HE11 mode incident on a symmetric discontinuity in an oversized cone of a multiflare horn are utilised to effect sidelobe reduction with low cross polarisation. The technique of dielectric loading is combined with multimode operation to contribute to increased directivity and on axis gain. Analytical results show good overall agreement with experimental measurements in the 10–16 GHz frequency band. This new type of multimode horn is potentially simple to design, analyse and manufacture yet exhibits many of the desirable features of the corrugated horn. Hence, the proposed multimode dielectric loaded multiflare conical horn, with its improved performance of better directivity and on axis gain at low cross polarisation and sidelobe levels, represents an attractive alternative to the corrugated horn antenna for satellite communications.
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Reconstruction of the excitation of an array antenna from the measured near-field intensity using phase retrieval
  • Author(s): J.A. Lord ; G.G. Cook ; A.P. Anderson
  • Source: IEE Proceedings H (Microwaves, Antennas and Propagation), Volume 139, Issue 4, p. 392 –396
  • DOI:  10.1049/ip-h-2.1992.0069
  • Type: Article
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  • p. 392 –396 (5)
    A technique is described to reconstruct the source distribution on an array antenna from the measured radiated intensity and the configuration of the elements. The complex source fields are calculated from the measured intensity by means of an iterative algorithm that includes a matrix deconvolution procedure to improve the accuracy of the reconstruction. This algorithm has been evaluated using the data obtained from a near-field planar scan of a slotted waveguide array and validated by comparison with the deconvolved holographically reconstructed source distribution.
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