Augmented nodal matrices and normal trees
Discrete Applied Mathematics
PABTEC: passivity-preserving balanced truncation for electrical circuits
IEEE Transactions on Computer-Aided Design of Integrated Circuits and Systems
On generalized inverses of singular matrix pencils
International Journal of Applied Mathematics and Computer Science - Semantic Knowledge Engineering
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The present work explores some effects of the replacement of capacitors by inductors and vice versa in state and semistate models of lumped circuits. Such a replacement, when performed together with an inversion of the capacitance and inductance matrices, yields a transformation of the form λ→λ-1 in the system spectra. In the semistate context, this covers in particular extremal cases in which null eigenvalues or infinite ones with higher index appear in the matrix pencil associated with the model; these cases describe certain pathological circuit configurations. This approach leads to a discussion of new properties of strictly passive circuits; specifically, from the known fact that the index of strictly passive circuits does not exceed two, we derive that the index of null eigenvalues in this setting cannot exceed one. This precludes in particular Takens-Bogdanov degeneracies, defined by an index-two double-zero eigenvalue, in strictly passive circuits. Although the results are addressed in a linear context, they can be extended via linearization to non-linear problems, as it is the case in the transformation of singularity-induced bifurcation phenomena into steady bifurcations discussed at the end of the paper. Copyright © 2006 John Wiley & Sons, Ltd.