Noise filtering devices, systems and methods for capacitance sensing devices

Patent metadata

Field	Value
Publication number	US-9841840-B2
Application number	US-201514848237-A
Country	US
Kind code	B2
Filing date	Sep 8, 2015
Priority date	Feb 7, 2011
Publication date	Dec 12, 2017
Grant date	Dec 12, 2017

Abstract

A capacitance sensing system can filter noise that presents in a subset of electrodes in the proximity of a sense object (i.e., finger). A capacitance sensing system can include a sense network comprising a plurality of electrodes for generating sense values; a noise listening circuit configured to detect noise on a plurality of the electrodes; and a filtering circuit that enables a filtering for localized noise events when detected noise values are above one level, and disables the filtering for localized noise events when detected noise values are below the one level.

First claim

What is claimed is:

1. A capacitance sensing system, comprising:
a sense network including a sense surface having a plurality of electrodes and configured to generate a plurality of position detection signals in response to a touch event on the sense surface;
a noise listening circuit coupled to the sense network, wherein the noise listening circuit is configured to detect noise in the plurality of position detection signals associated with the plurality of electrodes and compare the detected noise in the plurality of position detection signals to a first noise threshold value; and
a filtering circuit coupled to the noise listening circuit, wherein the filtering circuit is configured to, for each of the plurality of position detection signals:
in accordance with a determination that the detected noise in the respective position detection signal is greater than the first noise threshold value, determine that the touch event occurs on or proximate to a subset of electrodes corresponding to the respective position detection signal, and provide an extended scan and local noise filtering to process the respective position detection signal, wherein local noise filtering removes local noise caused on the respective subset of electrodes by the touch event; and
in accordance with a determination that the detected noise in the respective positon detection signal is not greater than the first noise threshold value, provide a standard scan and non-local noise filtering to process the respective position detection signal;
wherein the extended scan includes a larger number of sample operations or lasts a longer duration than those of the standard scan.

2. The capacitance sensing system of claim 1 , wherein the plurality of electrodes includes a plurality of transmit electrodes and a plurality of receive electrodes.

3. The capacitance sensing system of claim 2 , further comprising:
a mutual capacitance sensing circuit that senses a mutual capacitance between the plurality of transmit electrodes and the plurality of receive electrodes, wherein the noise listening circuit is configured to detect noise on one or more of the receive electrodes.

4. The capacitance sensing system of claim 2 , wherein the noise listening circuit is configured to detect noise on one or more transmit electrodes simultaneously with detecting noise on one or more of the receive electrodes.

5. The capacitance sensing system of claim 2 , further comprising:
switching circuits configured to:
couple one or more of the receive electrodes to an analog-to-digital converter to generate digital sense values; and
in accordance with a noise listening mode, configure one or more paths to the sense network to enable the noise listening circuit to detect local noise in the digital sense values.

6. The capacitance sensing system of claim 2 , further comprising:
switching circuits configured to couple each of the plurality of transmit electrodes to a signal generator circuit for touch detection, and to ground for noise detection and filtering.

7. The capacitance sensing system of claim 1 , further comprising:
an alarm circuit that generates an alarm signal to identify an alarm condition when the detected noise is greater than a second noise threshold value that is substantially larger than the first noise threshold value.

8. The capacitance sensing system of claim 1 , further comprising a display overlaid with the sense network, wherein the noise listening circuit is configured to detect noise from a charging device coupled to the capacitance sensing system.

9. The capacitance sensing system of claim 1 , wherein the filtering circuit further comprises a common mode noise filter configured to enable non-local noise filtering in accordance with the determination that the detected noise is not greater than the first noise threshold value.

10. The capacitance sensing system of claim 1 , wherein the filtering circuit includes a median filter configured to enable local noise filtering in accordance with the determination that the detected noise is greater than the first noise threshold value.

11. The capacitance sensing system of claim 10 , wherein the filtering circuit further includes a non-linear filter configured to enable local noise filtering in accordance with the determination that the detected noise is greater than the first noise threshold value.

12. A method for controlling noise, comprising:
at a capacitive sensing system including a sense network with a sense surface having a plurality of electrodes, the sense network being configured to generate a plurality of position detection signals in response to a touch event on the sense surface, the capacitive sensing system further including one or more processors and memory storing instructions for execution by the one or more processors:
detecting noise in the plurality of position detection signals associated with the plurality of electrodes;
comparing the detected noise in the plurality of position detection signals to a first noise threshold value; and
for each of the plurality of position detection signals:
in accordance with a determination that the detected noise in the respective position detection signal is greater than the first noise threshold value, determining that the touch event occurs on or proximate to a subset of electrodes corresponding to the respective position detection signal, and providing an extended scan and local noise filtering to process the respective position detection signal, wherein local noise filtering removes local noise caused on the respective subset of electrodes by the touch event; and
in accordance with a determination that the detected noise in the respective positon detection signal is not greater than the first noise threshold value, providing a standard scan and non-local noise filtering to process the respective position detection signal;
wherein the extended scan includes a larger number of sample operations or lasts a longer duration than those of the standard scan.

13. The method of claim 12 , wherein the plurality of electrodes includes a plurality of transmit electrodes and a plurality of receive electrodes.

14. The method of claim 13 , further comprising:
sensing a mutual capacitance between the plurality of transmit electrodes and the plurality of receive electrodes, wherein the noise listening circuit is configured to detect noise on one or more of the receive electrodes.

15. The method of claim 13 , wherein the noise listening circuit is configured to detect noise on one or more transmit electrodes simultaneously with detecting noise on one or more of the receive electrodes.

16. The method of claim 12 , further comprising:
identifying an alarm condition when the detected noise is greater than a second noise threshold value that is substantially larger than the first noise threshold value.

17. A non-transitory computer readable storage medium storing one or more programs configured for execution by one or more processors, the one or more programs comprising instructions for:
at a capacitive sensing system including a sense network with a sense surface having a plurality of electrodes, the sense network being configured to generate a plurality of position detection signals in response to a touch event on the sense surface, the capacitive sensing system further including one or more processors and memory storing instructions for execution by the one or more processors:
detecting noise in the plurality of position detection signals associated with the plurality of electrodes;
comparing the detected noise in

Assignees

• Parade Tech Ltd

Inventors

• Vallis Darrin
• Kremin Victor
• Maharyta Andriy
• Boychuk Yuriy
• Konovalov Anton
• Karpin Oleksandr
• Musijchuk Ihor
• Klein Hans
• Grivna Edward

Classifications

• G01R35/005

  Calibrating; Standards or reference devices, e.g. voltage or resistance standards, "golden" references (G01R33/0035, G01R35/002 take precedence) · CPC title

• G01R29/26

  Measuring noise figure; Measuring signal-to-noise ratio · CPC title

• H04B1/0475

  with means for limiting noise, interference or distortion (H04B1/0483 takes precedence) · CPC title

• G06F3/0418 Primary

  for error correction or compensation, e.g. based on parallax, calibration or alignment · CPC title

• G06F3/044

  by capacitive means · CPC title