Efficient analysis and reduction of magnetic near-field-coupling in mixed-signal PCBs via the reciprocity principle

The problem of analysis and reduction of the magnetic near-field coupling on the PCB-level is investigated by exploiting the reciprocity principle. The magnetic near-field coupling is described by the mutual inductance between victim and aggressor circuit. Based on the reciprocal magnetic field of the victim circuit, two methods are introduced, which can reduce this mutual inductance by magnetic flux compensation through a novel guard trace design or optimal placement of critical components. The proposed reduction methods are demonstrated by an example of a real hearing aid´s PCB and validated by 3D fullwave-simulation.