Patent ID: 7808356
Filing Date: 2010-10-05
Classification: H01F,H01L,H03H,Y10T

Abstract:
1. An on-chip four-metal layer balanced-to-unbalanced (BALUN) transformer having a symmetrical primary inductor, the BALUN transformer comprises: first winding conductive paths formed in a first metal layer having a plurality of winding segments; shunts formed in a second metal layer and electrically connecting the first metal layer winding segments at respective intersections, thereby forming a primary inductor, the primary inductor having a first port at a first end and a second port at a second end of the primary inductor; second winding conductive paths comprised of a plurality of winding segments formed in a third metal layer; shunts formed in a fourth metal layer electrically connecting the third metal layer winding segments at respective intersections to form a secondary inductor, the secondary inductor having a third port and a forth port symmetrically positioned at each end of the secondary inductor, and further having a center tap connection from a position at the middle of the secondary inductor as a fifth port; the primary inductor and the secondary inductor each being essentially symmetrical inductors; the second winding conductive paths being horizontally displaced from the first winding conductive path to reduce capacitive coupling between the primary inductor and the secondary inductor while maintaining a magnetic coupling between the first winding conductive path and the second winding conductive path.