VARIABLE PROFILE COMMON MODE FILTER

• US 20130033451A1
• Filed: 09/28/2011
• Published: 02/07/2013
• Est. Priority Date: 08/05/2011
• Status: Active Grant

• Current Assignee: Parade Technologies, Ltd.
• Original Assignee: Parade Technologies, Ltd.
• Inventors: Olson, Dana
• Granted Patent: US 9,836,163 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 3/04182 Filtering of noise external to the device and not generated by digitiser components
• CPC Class Codes: G06F 3/0445 using two or more layers of sensing electrodes, e.g. using two layers of electrodes separated by a dielectric layer

Abstract

A method and apparatus to remove direct coupled noise caused by a contact between a touch object and a capacitive sense array.

Claims

1. A method of estimating noise, comprising:

receiving data indicative of a contact between a touch object and a sensing device; and

adjusting the data to remove direct coupled noise caused by the contact between the touch object and the sensing device.

2. The method of claim 1, further comprising:

determining a noise estimate of the direct coupled noise caused by the contact between the touch object and the sensing device.

3. The method of claim 2, wherein the data indicative of the contact comprises two or more sets of capacitance values and wherein the method further comprises:

determining a difference between the two or more sets of capacitance values; and

determining a noise vector based on the difference between the two or more sets of capacitance values.

4. The method of claim 3, further comprising:

determining a correlation of the noise vector with at least one of the two or more sets of capacitance values;

high pass filtering the correlation to obtain a filtered correlation; and

determining the noise estimate based on the filtered correlation.

5. The method of claim 2, wherein adjusting the data further comprises:

subtracting the noise estimate from the data indicative of the contact.

6. The method of claim 1, wherein the direct coupled noise is further caused by a charging device.

7. The method of claim 2, wherein the noise estimate is less than or equal to a threshold value.

8. The method of claim 1, wherein a noise amplitude profile of the direct coupled noise is a scaled version of an amplitude profile of the contact between the touch object and the sensing device.

9. The method of claim 1, wherein the direct coupled noise is in a same frequency as a signal generated by the contact.

10. An apparatus, comprising:

a processing device configured to remove direct coupled noise caused by a contact between a touch object and a capacitive sense array.

11. The apparatus of claim 10, wherein the processing device is further configured to:

receive data indicative of the contact between the touch object and the capacitive sense array;

determine a noise estimate of the direct coupled noise caused by the contact between the touch object and the capacitive sense array; and

adjust the data indicative of the contact, based on the noise estimate of the direct coupled noise.

12. The apparatus of claim 10, wherein the direct coupled noise is in a same frequency as a signal generated by the contact.

13. The apparatus of claim 11, wherein the data indicative of the contact comprises two or more sets of capacitance values.

14. The apparatus of claim 13, wherein the processing device is further configured to determine a difference between the two or more sets of capacitance values.

15. The apparatus of claim 14, wherein the processing device is further configured to determine a noise vector, based on the difference between the two or more sets of capacitance values.

16. The apparatus of claim 15, wherein the processing device is further configured to:

determine a correlation of the noise vector with at least one of the two or more sets of capacitance values;

high pass filter the correlation to obtain a filtered correlation; and

determine the noise estimate based on the filtered correlation.

17. The apparatus of claim 11, wherein the processing device is configured to adjust the data indicative of the contact between the touch object and the capacitive sense array by subtracting the noise estimate from the data indicative of the contact.

18. A non-transitory machine readable storage medium including instructions that, when executed by a processing device, cause the processing device to perform a method comprising:

receiving data indicative of a contact between a touch object and a capacitive sense array;

determining a noise estimate of direct coupled noise caused by the contact between the touch object and the capacitive sense array; and

adjusting the data indicative of the contact, based on the noise estimate of the direct coupled noise.

19. The non-transitory machine readable storage medium of claim 18, wherein the data indicative of the contact comprises two or more sets of capacitance values and wherein the method further comprises:

determining a difference between the two or more sets of capacitance values; and

determining a noise vector, based on the difference between the two or more sets of capacitance values.

20. The non-transitory machine readable storage medium of claim 19, the method further comprising:

determining a correlation of the noise vector with at least one of the two or more sets of capacitance values;

high pass filtering the correlation to obtain a filtered correlation; and

determining the noise estimate based on the filtered correlation.