Driven shield for capacitive to touchpads

• US 8,581,881 B2
• Filed: 08/14/2012
• Issued: 11/12/2013
• Est. Priority Date: 03/29/2007
• Status: Active Grant

• Current Assignee: Cirque Corporation
• Original Assignee: Cirque Corporation
• Inventors: Bytheway, Jared G.
• Primary Examiner(s): Dharia, Prabodh M
• Application Number:
  US13/585,443
• Publication Number:
  US 20120327022A1
• Time in Patent Office: 455 Days
• Field of Search: 345157-174, 178 1801- 1806, 324658-662, 324/688, 324/686, 737/18, 737/24, 341/33
• 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 comprising:

1) providing a plurality of drive electrodes for generating a signal and a plurality of sense electrodes, each one of the plurality of sense electrodes disposed between each of the plurality of drive electrodes for measuring a portion of the signal that is coupled to each of the plurality of sense electrodes;

2) providing a plurality of driven shield electrodes in sets of two, wherein one driven shield electrode is disposed immediately adjacent to and on each side of each of the plurality of sense electrodes to thereby separate the plurality of sense electrodes from the plurality of drive electrodes, each set of the plurality of driven shield electrodes being electrically coupled to the sense electrode between them for receiving a modified signal from the sense electrode between them, the two immediately adjacent driven shield electrodes at least partially shielding the sense electrode between them from undesired electrical and capacitive signals, including stray capacitive signals from the plurality of drive electrodes; and

3) providing a buffer between each of the sense electrodes and the two immediately adjacent driven shield electrodes to generate the modified signal and to thereby increase a signal to noise ratio on each of the sense electrodes by reinforcing the signal on each of the sense electrodes.

2. The method as defined in claim 1 wherein the method further comprises providing an amplifier between each of the sense electrodes and the two immediately adjacent driven shield electrodes to generate the modified signal and to thereby increase a signal to noise ratio on each of the sense electrodes.

3. The method as defined in claim 1 wherein the method further comprises:

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

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

4. The method as defined in claim 3 wherein the method further comprises providing a buffer between the at least one of the plurality of sense electrodes and the driven shield substrate to generate the modified signal and to thereby increase a signal to noise ratio on the at least one of the plurality of sense electrodes.

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

6. The method as defined in claim 4 wherein the method further comprises reducing stray capacitance between the at least one of the plurality of drive electrodes and the at least one of the plurality of sense electrodes to thereby increase the strength of the portion of the signal that is coupled to the at least one of the plurality of sense electrodes.

7. The method as defined in claim 6 wherein the method further comprises shielding the at least one of the plurality of sense electrodes from electrical noise to thereby increase the strength of the portion of the signal that is coupled to the at least one of the plurality of sense electrodes.