Design of high frequency inductors based on magnetic films

Abstract

Magnetically coated stripe inductors with conductor insulated from the magnetic film and with conductor in direct electrical contact with the magnetic film are analyzed. A simple equivalent circuit model shows that for the structure without insulation, regardless of the fact that the dc resistivity of the magnetic film is much higher than that of the conductor, most of the driving current flows in the magnetic film at frequencies where the impedance of the device is dominated by inductance, i.e., where the quality factor Q>1. This effect of current re-distribution significantly lowers the performance of the device. A design is proposed having insulation layers to avoid current flow in the magnetic film, which is broken up in sections along the conductor stripe to avoid displacement currents in the system.