Coil-on-chip: Design of integrated coils for inductive telemetry system

This paper evaluates considerations to design integrated coils for telemetry applications. Usually inductive links have a low efficiency for small sizes coils, because they have low coupling coefficient (k → 0.1) and low quality factor due to the CMOS metals. However, the geometry of the coil can significantly improve the coupling and the transmitted energy. Some studies use generalizations to make the calculation of self-resonant frequency, which must be over the working resonance frequency. These generalizations normally presents a self-resonance frequency below the experimental frequency, that mean a design with fewer turns than are possible (fewer induced magnetic field). This paper evaluates a geometry-based method to calculate the self-resonant frequency to design integrated coils, in order to maximize area using as many turns as possible (to increase induced magnetic field). This geometry-based method can be used with integrated coils with and without dielectric oxide between the coil and the substrate. It also generates a circuital model for a better estimation of self-resonance frequency.