Via-less patterned ground structure common-mode filter
Disclosed herein are multi-layer metal circuits, such as printed circuit boards (PCBs), with single-sided, partially-shielded, or fully-shielded via-less common-mode filters. The multi-layer metal circuits comprise at least one shield layer, at least one signal trace, and at least one reference layer (e.g., ground). The reference layer comprises a pattern of the via-less common-mode filter. The pattern may comprise, for example, a single piece-wise linear segment, or two or more disjoint and non-intersecting segments (which may be strictly linear or piece-wise linear). The reference layer is electrically isolated from the shield layer, and thus the via-less common-mode filters do not require vias. In addition to being used in PCBs, the disclosed multi-layer metal circuits may also be used in other applications, such as integrated circuits (e.g., implemented in semiconductor chips).
1. A multi-layer metal circuit, comprising:
a shield layer;
a signal trace layer comprising at least one signal trace; and
a ground layer disposed between the shield layer and the signal trace layer, the ground layer comprising a pattern of a via-less common-mode filter.
2. The multi-layer metal circuit recited in claim 1 , wherein the pattern comprises a first section and a second section, the first and second sections being disjoint and non-intersecting.
3. The multi-layer metal circuit recited in claim 2 , wherein:
the first section is a linear segment and the second section is (a) an omega-shaped segment or (b) a U-shaped segment.
4. The multi-layer metal circuit recited in claim 2 , wherein the pattern has a T-shape.
5. The multi-layer metal circuit recited in claim 4 , wherein a length of the via-less common-mode filter is between approximately 2 mm and approximately 7 mm.
6. The multi-layer metal circuit recited in claim 4 , wherein a length of the via-less common-mode filter is between approximately 2.5 mm and approximately 3.5 mm, and a width of the via-less common-mode filter is between approximately 1 mm and approximately 2 mm.
7. The multi-layer metal circuit recited in claim 2 , wherein the pattern further comprises a third section, wherein at least one dimension of the third section is substantially identical to a corresponding dimension of the second section.
8. The multi-layer metal circuit recited in claim 2 , wherein the pattern further comprises a third section, wherein a shape of the third section is substantially identical to a shape of the second section.
9. The multi-layer metal circuit recited in claim 8 , wherein the first section is linear, and the second and third sections are U-shaped.
10. The multi-layer metal circuit recited in claim 1 , wherein the pattern has an L-shape or a rectangular shape.
11. The multi-layer metal circuit recited in claim 1 , wherein the shield layer is a first shield layer, the ground layer is a first ground layer and is disposed on a first side of the signal layer, and further comprising:
a second shield layer; and
a second ground layer disposed between the second shield layer and a second side of the signal trace layer, the second ground layer comprising a mirror image of the pattern.
12. A data storage device comprising the multi-layer metal circuit recited in claim 1 .
13. A method of manufacturing the multi-layer metal circuit recited in claim 1 , the method comprising etching the pattern into the ground layer.
14. A printed circuit board, comprising:
a shield layer;
at least one signal trace;
a reference layer disposed between the shield layer and the at least one signal trace; and
a common-mode filter etched into the reference layer,
wherein the common-mode filter is electrically isolated from the shield layer.
15. The printed circuit board recited in claim 14 , wherein the common-mode filter comprises a plurality of segments.
16. The printed circuit board recited in claim 15 , wherein the plurality of segments comprises at least one piece-wise linear segment.
17. The printed circuit board recited in claim 16 , wherein the plurality of segments further comprises at least one linear segment.
18. The printed circuit board recited in claim 15 , wherein the plurality of segments comprises a first segment and a second segment, wherein the first and second segments are substantially identical.
19. The printed circuit board recited in claim 15 , wherein the plurality of segments comprises a first segment and a second segment, wherein at least one dimension of the first segment differs from a corresponding dimension of the second segment.
20. The printed circuit board recited in claim 14 , wherein the common-mode filter comprises at least one piece-wise linear segment.
21. A data storage device comprising the printed circuit board recited in claim 14 .
22. A method of manufacturing the printed circuit board recited in claim 14 , the method comprising:
fabricating the shield layer;
fabricating the reference layer;
etching the common-mode filter into the reference layer; and
fabricating the at least one signal trace.