an insulating layer;

first and second winding portions symmetrically arranged on the insulating layer, wherein each winding portion comprises first and second semi-circular conductive traces concentrically arranged from the outside to the inside, and each semi-circular conductive trace has a first end and a second end;

a first upper cross-connection and a first lower cross-connection crossly and respectively connected to the corresponding second ends of the first and second semi-circular conductive traces; and

first and second interconnections respectively disposed in the insulating layer under the semi-circular conductive traces connected to both ends of the first upper cross-connection, wherein each interconnection comprises at least one conductive layer and a plurality of conductive plugs electrically connected between the conductive layer and the corresponding semi-circular conductive trace.