DRIVEN SHIELD FOR CAPACITIVE TOUCHPADS

• US 20090009485A1
• Filed: 03/31/2008
• Published: 01/08/2009
• Est. Priority Date: 03/29/2007
• Status: Active Grant

• Current Assignee: Cirque Corporation
• Original Assignee: Cirque Corporation
• Inventors: Bytheway, Jared G.
• Granted Patent: US 8,243,043 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 3/044 by capacitive means
• CPC Class Codes: H03K 2217/960765 Details of shielding arrangements

Abstract

A conductive shield that is disposed near the sensor, wherein a signal is driven on the shield that is similar to the signal induced on the sensor, thereby reducing stray capacitances and protecting the sensor from external noise sources, and resulting in a stronger signal reaching the sensor.

Claims

1. A method for shielding a portion of a capacitive sensor used in a touchpad, said method comprised of the steps of:

1) providing at least one drive electrode for generating a signal and at least one sense electrode for measuring a portion of the signal that is coupled to the at least one sense electrode; and

2) providing a driven shield electrode that is electrically coupled to the at least one sense electrode for receiving a modified signal from the at least one sense electrode, and wherein the driven shield electrode is disposed adjacent to the at least one sense electrode to thereby at least partially shield the at least one sense electrode from undesired electrical and capacitive signals.

2. The method as defined in claim 1 wherein the method further comprises the step of providing a buffer between the at least one sense electrode and the driven shield electrode to generate the modified signal and to thereby increase a signal to noise ratio on the at least one sense electrode.

3. The method as defined in claim 1 wherein the method further comprises the step of providing an amplifier between the at least one sense electrode and the driven shield electrode to generate the modified signal and to thereby increase a signal to noise ratio on the at least one sense electrode.

4. The method as defined in claim 2 wherein the method further comprises the steps of:

1) providing a driven shield substrate, wherein the at least one drive electrode and the at least one sense electrode are attached to the driven shield substrate;

2) electrically coupling the driven shield substrate to the at least one sense electrode to thereby receive the modified signal from the at least one sense electrode, and wherein the driven shield substrate is positioned so as to at least partially shield the at least one sense electrode from undesired electrical and capacitive signals.

5. The method as defined in claim 4 wherein the method further comprises the step of providing a buffer between the at least one sense electrode and the driven shield substrate to generate the modified signal and to thereby increase a signal to noise ratio on the at least one sense electrode.

6. The method as defined in claim 4 wherein the method further comprise the step of providing an amplifier between the at least one sense electrode and the driven shield substrate to generate the modified signal and to thereby increase a signal to noise ratio on the at least one sense electrode.

7. The method as defined in claim 5 wherein the method further comprises the step of reducing stray capacitance between the at least one drive electrode and the at least one sense electrode to thereby increase the strength of the portion of the signal that is coupled to the at least one sense electrode.

8. The method as defined in claim 7 wherein the method further comprises the step of shielding the at least one sense electrode from electrical noise to thereby increase the strength of the portion of the signal that is coupled to the at least one sense electrode.

9. A system for shielding a capacitive sensor used in a touchpad, said system comprised of:

at least one drive electrode and means for generating a signal thereon;

at least one sense electrode and means for measuring a portion of the signal that is coupled to the at least one sense electrode; and

a driven shield electrode that is electrically coupled to the at least one sense electrode for receiving a modified signal from the at least one sense electrode, and wherein the driven shield electrode is disposed adjacent to the at least one sense electrode to thereby at least partially shield the at least one sense electrode from undesired electrical and capacitive signals.

10. The system as defined in claim 9 wherein the system is further comprised of a buffer disposed between the at least one sense electrode and the driven shield electrode to thereby generate the modified signal.

11. The system as defined in claim 9 wherein the system is further comprised of an amplifier disposed between the at least one sense electrode and the driven shield electrode to thereby generate the modified signal.

12. The system as defined in claim 10 wherein the system is further comprised of a driven shield substrate, wherein the at least one drive electrode and the at least one sense electrode are attached to but electrically isolated from the driven shield substrate, wherein the driven shield substrate is electrically coupled to the at least one sense electrode to thereby receive the modified signal from the at least one sense electrode, and wherein the driven shield substrate is positioned so as to at least partially shield the at least one sense electrode from undesired electrical and capacitive signals.

13. The system as defined in claim 12 wherein the system is further comprised of a buffer disposed between the at least one sense electrode and the driven shield substrate to thereby generate the modified signal.

14. The system as defined in claim 12 wherein the system is further comprised of an amplifier disposed between the at least one sense electrode and the driven shield substrate to thereby generate the modified signal.

15. The system as defined in claim 9 wherein the system is further comprised of a plurality of drive electrodes.

16. The system as defined in claim 15 wherein the system is further comprised of a plurality of sense electrodes.

17. A system for shielding a capacitive sensor used in a touchpad, said system comprised of:

at least one drive electrode and means for generating a signal thereon;

at least one sense electrode and means for measuring a portion of the signal that is coupled to the at least one sense electrode;

a driven shield electrode;

a driven shield substrate, wherein the driven shield electrode and the driven shield substrate are electrically coupled to the at least one sense electrode for receiving a modified signal from the at least one sense electrode, wherein the at least one drive electrode, the at least one sense electrode and the driven shield electrode are coupled to the driven shield substrate, and wherein the driven shield electrode and the driven shield substrate are disposed adjacent to the at least one sense electrode to thereby at least partially shield the at least one sense electrode from undesired electrical and capacitive signals.

18. The system as defined in claim 17 wherein the system is further comprised of a buffer disposed between the at least one sense electrode on one side, and the driven shield electrode and the driven shield substrate on the other side, to thereby generate the modified signal.

19. The system as defined in claim 17 wherein the system is further comprised of an amplifier disposed between the at least one sense electrode on one side, and the driven shield electrode and the driven shield substrate on the other side, to thereby generate the modified signal.

20. A system for shielding a capacitive sensor used in a touchpad, said system comprised of:

at least one drive electrode and means for generating a signal thereon;

at least one sense electrode and means for measuring a portion of the signal that is coupled to the at least one sense electrode; and

a driven shield substrate, wherein the at least one sense electrode and the at least one drive electrode are attached to the driven shield substrate, and wherein the driven shield substrate is electrically coupled to the at least one sense electrode for receiving a modified signal from the at least one sense electrode to thereby at least partially shield the at least one sense electrode from undesired electrical and capacitive signals.

21. The system as defined in claim 20 wherein the system is further comprised of a driven shield electrode that is electrically coupled to the at least one sense electrode for receiving the modified signal from the at least one sense electrode, and wherein the driven shield electrode is disposed adjacent to the at least one sense electrode to thereby at least partially shield the at least one sense electrode from undesired electrical and capacitive signals.