Capacitance link effect caracterisation in the tapped on-chip planar transformer

Abstract

In this paper, we present the theoretical model validation of an integrated planar transformer used in MEMS electrodynamic microsensor. The structure consists of two planar inductors: an outer fixed one and an inner suspended one. If the outer inductor is biased by an AC voltage, a mutual inductance link will be created between both inductors. We present an analytical approach to determine the induced voltage when applying an AC supply current to the outer inductor. In the paper, we discuss the difference between the analytical results with and the characterization. The difference is basically due to the coupling capacitance between the inner and the outer inductors and not only, as we expected, due to the mutual inductance. The introduction of the coupling capacitance, estimated to be around 1.7pF, to our simulation confirmed the measurement performed on the planar integrated transformer.