Electromagnetic Network Models of Planar Coils on a Thin or Thick Magnetic Layer

A method is presented to determine the magnetic reluctance of a thin or a thick magnetic layer of permeability ¿ underneath a planar coil based on inductance measurements. The procedure is substantiated on the basis of the linear electromagnetic network model. The influence of the involved magnetic reluctances on the inductance is analyzed by a transformation into the electrical domain applying linear network theory. From inductance measurements the individual contributing inductances can be calculated and from the back transformation into the magnetic domain the reluctances and further parameters, such as the magnetic field strength for a given electrical current or the permeability. Analytical results are compared with FEM simulations and with measurements obtained from a magnetostrictive bending sensor.