Base capacitance compensation for a touchpad sensor

• US 20070079996A1
• Filed: 10/03/2006
• Published: 04/12/2007
• Est. Priority Date: 10/07/2005
• Status: Active Grant

• Current Assignee: Elan Microelectronics Corporation
• Original Assignee: Elan Microelectronics Corporation
• Inventors: Tang, Kuan-Chun, Lee, Wen-Kai
• Granted Patent: US 8,040,325 B2
• Time in Patent Office: Days
• US Class Current: 178/18.60
• CPC Class Codes: G06F 3/0443 using a single layer of sensing electrodes
• CPC Class Codes: G06F 3/0446 using a grid-like structure of electrodes in at least two directions, e.g. using row and column electrodes

Abstract

Methods are provided for base capacitance compensation of traces in a touchpad sensor. Compensation areas are calculated by evaluating the differences between the base capacitances of the traces, or the differences between the base capacitances of the traces and a target value. The compensation areas are electrically connected to respective traces to equalize the base capacitances of the traces. Alternatively, a relationship between the areas of the traces and the distances from the traces to a grounding layer for equalizing the base capacitances of the traces is derived and from which the areas of the traces or the position of the grounding layer are adjusted.

Claims

1. A base capacitance compensation for a touchpad sensor, comprising the steps of:

with a first trace as a reference, calculating a compensation area for a second trace; and

electrically connecting the compensation area to the second trace for equalizing the base capacitances of the first and second traces.

2. The compensation of claim 1, wherein the step of calculating a compensation area for a second trace comprises the steps of:

calculating the base capacitances of the first and second traces;

calculating the difference between the base capacitances of the first and second traces; and

determining the compensation area from the difference.

3. The compensation of claim 2, wherein the compensation area is the product of the difference and a distance from where the compensation area is to a grounding layer divided by a dielectric constant.

4. The compensation of claim 3, wherein the compensation area is in a device layer, the sensing layer including the first trace, or the sensing layer including the second trace.

5. The compensation of claim 1, wherein the first and second traces are in a same sensing layer.

6. The compensation of claim 1, wherein the first and second traces are in two sensing layers respectively.

7. The compensation of claim 1, wherein the first and second traces are perpendicular to each other.

17. The compensation of claim 1, wherein the two traces are perpendicular to each other.

8. A base capacitance compensation for a touchpad sensor, comprising the steps of:

with a target value as a reference, calculating two compensation areas for two traces; and

electrically connecting the compensation areas to the traces respectively, for equalizing the base capacitances of the traces.

9. The compensation of claim 8, wherein the step of calculating two compensation areas for two traces comprises the step of:

calculating the base capacitance of the first trace;

calculating the difference between the base capacitance of the first trace and the target value; and

determining the first compensation area for the first trace from the difference.

10. The compensation of claim 9, wherein the first compensation area is the product of the difference and a distance from where the first compensation area is to a grounding layer divided by a dielectric constant.

11. The compensation of claim 10, wherein the first compensation area is in a device layer, the sensing layer including the first trace, or the sensing layer including the second trace.

12. The compensation of claim 8, wherein the step of calculating two compensation areas for two traces comprises the step of:

calculating the base capacitance of the second trace;

calculating the difference between the base capacitance of the second trace and the target value; and

determining the second compensation area for the second trace from the difference.

13. The compensation of claim 12, wherein the second compensation area is the product of the difference and a distance from where the second compensation area is to a grounding layer divided by a dielectric constant.

14. The compensation of claim 12, wherein the second compensation area is in a device layer, the sensing layer including the first trace, or the sensing layer including the second trace.

15. The compensation of claim 8, wherein the two traces are in a same sensing layer.

16. The compensation of claim 8, wherein the two traces are in two sensing layers respectively.

26. The compensation of claim 13, wherein the two traces are perpendicular to each other.

18. A base capacitance compensation for a touchpad sensor, comprising the steps of:

calculating the base capacitances of two traces in two sensing layers respectively;

deriving a relationship between the areas of the traces and the distances of the traces to a grounding layer for equalizing the base capacitances of the traces; and

adjusting the areas of the traces or the position of the grounding layer based on the relationship.

19. The compensation of claim 18, wherein the relationship is the area of the first trace and the distance from the first trace to the grounding layer have a ratio equal to that of the area of the second trace and the distance from the second trace to the grounding layer.

20. The compensation of claim 18, wherein the two traces have different areas.

21. The compensation of claim 18, wherein the two traces have a same area.

22. The compensation of claim 18, wherein the two traces are equally spaced from the grounding layer.

23. The compensation of claim 18, wherein the two traces are unequally spaced from the grounding layer.

24. The compensation of claim 18, wherein the grounding layer is between the two sensing layers.

25. The compensation of claim 18, wherein the grounding layer is not between the two sensing layers.