Study on Multi Thin Film Coupled Transmission Line Common Mode Filter Design
Date Issued
2008
Date
2008
Author(s)
Wei, Cheng-Fan
Abstract
Thin-film common mode filter is applied to suppress the common mode noise which results from non-perfect-symmetric circuit or external radiation. This work derives a method which predicts the electric performance of thin-film coupled transmission line common filter from component dimensions and material property. This work sets up a mathematical model and expresses the electric performance of thin-film coupled transmission line common filter with quasi-analytical formulae. Firstly, this work derives mixed-mode scattering parameter transformation by lossy coupled transmission line model. This work constructs the distributed equivalent circuit model of thin-film coupled transmission line common filter, and derives the analytical formulae of the distributed parameters; then puts them into the transformation above and rearranges to obtain the mixed-mode scattering parameters we concern. This work utilizes FEM simulator to construct several components to verify the formulae prediction and the influence on the filter while changing related parameters; also to verify the influence on the filter while the magnetic loss (frequency-dependent or frequency-independent) of the ferrite layer is considered; finally, to verify the prediction of the first lowest peak of Scc21 of thin-film coupled transmission line common filter. According to the verification, it shows that the method this work introduces is effective and corresponds with physical sense. The method that directly predicts the electric performance from component dimensions and material property also provide a reference for filter design. In the future, one can optimize the common mode filter design by this work and can also extend this work to analyze other thin-film common mode filter with various type of transmission line layout.
Subjects
thin-film coupled transmission line common filter
lossy coupled transmission line
mixed-mode scattering parameter transformation
distributed equivalent circuit model
distributed parameters
magnetic loss
the first lowest peak of Scc21
Type
thesis
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