Ground Guard for Capacitive Sensing

• US 20090267916A1
• Filed: 04/25/2008
• Published: 10/29/2009
• Est. Priority Date: 04/25/2008
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: HOTELLING, Steve Porter
• Granted Patent: US 8,487,898 B2
• Time in Patent Office: Days
• US Class Current: 345/174
• CPC Class Codes: G06F 2203/04107 Shielding in digitiser, i.e. guard or shielding arrangements, mostly for capacitive touchscreens, e.g. driven shields, driven grounds
• 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

A touch sensor panel is disclosed including the use of ground guards or ground isolation bars to improve the touch event detection capabilities of the touch sensor panel. Ground isolation bars can be formed between connecting traces and adjacent sense lines to shunt near-field lines to ground and reduce unwanted capacitive coupling between the connecting traces and the sense lines. Ground guards can be formed between the drive and sense lines to partially or fully surround a sense line and shunt near-field lines to ground and improve the touch event detection capabilities of the sensor.

Claims

1. A capacitive touch sensor panel, comprising:

a plurality of sense lines formed on a single layer and supported on one side of a substrate;

a plurality of drive lines formed on the same side of the substrate as the plurality of sense lines, the plurality of sense lines and the plurality of drive lines forming an array of capacitive sensors; and

one or more ground guards formed adjacent to one or more of the sense lines for shunting electric field lines that would otherwise couple stray capacitance onto the sense lines.

2. The touch sensor panel of claim 1, the one or more ground guards configured for shunting near-field electric field lines that would otherwise couple stray capacitance onto the sense lines.

3. The touch sensor panel of claim 1, the plurality of drive lines formed from a plurality of polygonal areas.

4. The touch sensor panel of claim 3, the one or more ground guards formed between one or more of the polygonal areas and the one or more sense lines for shunting electric field lines from the one or more polygonal areas.

5. The touch sensor panel of claim 3, further comprising a plurality of connecting traces routed adjacent to the polygonal areas and formed on the same side of the substrate as the plurality of sense lines, each connecting trace coupled to a different polygonal area, the one or more ground guards formed between one or more of the connecting traces and the one or more sense lines for shunting electric field lines from the connecting traces.

6. The touch sensor panel of claim 1, the touch sensor panel integrated within a computing system.

7. The touch sensor panel of claim 5, the computing system integrated within a mobile telephone.

8. The touch sensor panel of claim 5, the computing system integrated within a media player.

9. A method for improving a touch detection capability of a capacitive touch sensor panel having a plurality of drive lines and a plurality of sense lines formed on a same side of a single substrate, comprising:

protecting one or more of the sense lines with one or more ground guards formed adjacent to the one or more sense lines, the ground guards for shunting electric field lines that would otherwise couple stray capacitance onto the one or more sense lines.

10. The method of claim 9, further comprising configuring the one or more ground guards for shunting near-field electric field lines.

11. The method of claim 9, further comprising forming the plurality of drive lines from a plurality of polygonal areas.

12. The method of claim 11, further comprising forming the one or more ground guards between one or more of the polygonal areas and the one or more sense lines for shunting electric field lines from the one or more polygonal areas.

13. The method of claim 11, further comprising:

routing a plurality of connecting traces adjacent to the polygonal areas on the same side of the substrate as the plurality of sense lines;

coupling each connecting trace to a different polygonal area; and

forming the one or more ground guards between one or more of the connecting traces and the one or more sense lines for shunting electric field lines from the connecting traces.

14. A method for improving a touch detection capability of a capacitive touch sensor panel having a plurality of drive lines and a plurality of sense lines formed on a same side of a single substrate, comprising:

providing one or more paths to ground adjacent to one or more of the sense lines for shunting electric field lines that would otherwise couple stray capacitance onto the one or more sense lines.

15. The method of claim 14, further comprising configuring the one or more paths to ground for shunting near-field electric field lines that would otherwise couple stray capacitance onto the sense lines.

16. The method of claim 14, further comprising forming the plurality of drive lines as a plurality of polygonal areas.

17. The method of claim 16, further comprising forming the one or more paths to ground between one or more of the polygonal areas and the one or more sense lines for shunting electric field lines from the one or more polygonal areas.

18. The method of claim 14, further comprising:

routing a plurality of connecting traces adjacent to the polygonal areas on the same side of the substrate as the plurality of sense lines;

coupling each connecting trace to a different polygonal area; and

forming the one or more paths to ground between one or more of the connecting traces and the one or more sense lines for shunting electric field lines from the connecting traces.

19. A mobile telephone including a touch sensor panel, the touch sensor panel comprising:

a plurality of sense lines formed on a single layer and supported on one side of a substrate;

a plurality of drive lines formed on the same side of the substrate as the plurality of sense lines, the plurality of sense lines and the plurality of drive lines forming an array of capacitive sensors; and

one or more ground guards formed adjacent to one or more of the sense lines for shunting electric field lines that would otherwise couple stray capacitance onto the sense lines.

20. A media player including a touch sensor panel, the touch sensor panel comprising:

a plurality of sense lines formed on a single layer and supported on one side of a substrate;

a plurality of drive lines formed on the same side of the substrate as the plurality of sense lines, the plurality of sense lines and the plurality of drive lines forming an array of capacitive sensors; and

one or more ground guards formed adjacent to one or more of the sense lines for shunting electric field lines that would otherwise couple stray capacitance onto the sense lines.