A new numerical approach based on least-squares error minimization is studied for the accurate analysis of electromagnetic problems. The approach whic~ is applicable in principle to any field problem has two specific advantages over the existing methods; firstly, it is rigorously convergent in contrast to point-matching or Fourier rnatching; secondly, free parameters can be chosen to guide convergence between a generally decreasing upper bound and an increasing lower bound. The first structure that is analysed by the new approach is an abrupt coaxial-to-circular waveguide junction, The device is of interest in immittance standardization and measurement. Values of the equivalent discontinuity capacitance of the junction are evaluated to an accuracy of within +0.1 femto farads. These results confirm independent published figures, and can be used for standards work. Another' structure that is studied is in support of the work on microwave dielectric measurements, where a microwave bridge is used with the material under test ,filling a length of a rectangular waveguide. In making measurements, corrections and optimizing the layout, theoretical results are needed for the scattering coefficients of a dielectric taper in the bridge. Again using the least-squares approach, the problem here is successfully solved. Two automatic and efficient schemes are proposed and developed which give accurate resultsfor a wide range of frequency, taper angle, and dielectric permittivity. Theory is also developed, related to measurement on a dielectric slab in the bridge, to account for the sample only partially filling the waveguide. The effects on the inferred metallic and dielectric losses are analysed, and accurate results are presented
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:470103 |
| Date | January 1977 |
| Creators | Razaz, M. |
| Publisher | University College London (University of London) |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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