Patent ID: 7253712
Filing Date: 2007-08-07
Classification: H01F,H01L,H03H

Abstract:
1. An on-chip three-metal layer balanced-to-unbalanced (BALUN) transformer comprising: a first winding conductive path formed in a first metal layer defining a multiple turn primary inductor of the BALUN transformer, the first winding conductive path having a first port at one end of the first winding conductive path and a second port at the other end of the first winding conductive path; and, a second winding conductive path having a plurality of symmetrical winding segments formed in a second metal layer; shunts formed in a third metal layer and electrically connecting the winding segments at respective intersections, thereby forming a secondary inductor of the BALUN transformer, the secondary inductor having a third port and a fourth port and further having a center tap connection from a position essentially at the middle of the secondary inductor as a fifth port; the secondary inductor conductive path being displaced vertically and horizontally from the first winding conductive path to reduce capacitive coupling between the primary inductor and the secondary inductor while maintaining a sufficient magnetic coupling between the first winding conductive path and the secondary inductor.