US Patent 7841070 Method of fabricating a transformer device

A planar transformer or balun device, having small trace spacing and high mutual coupling coefficient, and a method of fabricating the same is disclosed. The method may comprise providing a first and a second inductor on a primary and a second substrate respectively, interleaving at least partially the first inductor with the second inductor, coupling the primary and the secondary substrates to form a unitary structure, and providing electrical contacts to couple the first and second inductors with another device or circuit.