Transformer

A circuit system, comprising:

• a transformer, wherein the transformer comprises:
• a first coil;
• and
• a second coil;
• wherein the first coil is magnetically coupled to the second coil;
• wherein the first coil comprises a plurality of sub-coils, the plurality of sub-coils comprise a first sub-coil and a second sub-coil, a first magnetic field formed by the first sub-coil passes through a plane of the transformer in a first manner, a second magnetic field formed by the second sub-coil passes through the plane in a second manner, the first manner comprises passing through the plane in a first direction, the second manner comprises passing through the plane in a second direction, and the second direction is opposite from the first direction;
• wherein the first sub-coil comprises a first port of the first coil and a second port of the first coil, and the second coil comprises a third port and a fourth port;
• wherein the first port, the second port, the third port, and the fourth port are on a same side of a line separating the first sub-coil and the second sub-coil;
• and
• a third magnetic field formed by the second coil passes through the plane of the transformer in a third manner, the third manner comprises passing through the plane in a third direction, and the third direction is opposite from the first direction,
• wherein the first sub-coil surrounds a first area, wherein the second sub-coil surrounds a second area, wherein the second coil surrounds a third area, wherein a third projection of the third area on the plane at least partially overlaps a first projection of the first area on the plane,
• wherein the first port, the second port, the third port, and the fourth port are on a same side of a second line dividing the first sub-coil into a first portion and a second portion and dividing the second coil into a third portion and a fourth portion, the first portion including the first port and the second port, the third portion including the third port and the fourth port, the second line passing through a center of the first area and parallel to the line,
• wherein the second coil is a single coil without any sub-coil forming an additional magnetic field in a manner different from the third manner, and
• wherein the third projection of the third area on the plane does not overlap a second projection of the second area on the plane.