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Analysis of a Waveguide with a RoundEnded Wide Straight Slot by the Method of Moments Using NumericalEigenmode Basis Functions
Miao ZHANG Takuichi HIRANO Jiro HIROKAWA Makoto ANDO
Publication
IEICE TRANSACTIONS on Communications
Vol.E87B
No.8
pp.23192326 Publication Date: 2004/08/01 Online ISSN:
DOI: Print ISSN: 09168516 Type of Manuscript: PAPER Category: Antenna and Propagation Keyword: roundended slot, waveguide, numerical eigenmode basis functions, Method of Moments, finite element method, equivalentarea modification,
Full Text: PDF(1004.9KB)>>
Summary:
A roundended wide straight slot cut in the broad wall of a rectangular waveguide is analyzed by the Method of Moments (MoM) using numerical eigenmode basis functions derived by the edgebased finite element method (FEM), referred to as MoM/FEM. The frequency characteristics of the calculated transmission coefficients are compared with the measured ones, and good agreement is observed for a wide variety of antenna parameters. For simpler analysis that does not use MoM/FEM, an equivalent rectangular slot approximation for a roundended slot is discussed. The resonant frequencies of empirically introduced "equalarea" and "equalperimeter" slots are compared with those of roundended slots for a wide variety of parameters such as slot width, wall thickness and dielectric constant inside the waveguide. Based upon MoM/FEM, which can be a reliable reference, it is found that the equalarea slot always gives a better approximation of the order of 1% over that of the equalperimeter one which is of the order of 5%. For higher accuracy, a new rectangular slot approximation of a roundended slot is proposed to be a linear combination of equalarea and equal perimeter approximation. The error is around 0.25% for a wide variety of parameters such as slot widthtolength ratio, wall thickness and dielectric constant of the filling material inside the waveguide.


