Interference mitigation in a capacitive sensing device

• US 9,760,205 B2
• Filed: 04/30/2015
• Issued: 09/12/2017
• Est. Priority Date: 04/30/2015
• Status: Active Grant

• Current Assignee: Synaptics Incorporated
• Original Assignee: Synaptics Incorporated
• Inventors: Stevenson, Matthew
• Primary Examiner(s): Edouard, Patrick
• Assistant Examiner(s): JAVED, MAHEEN I
• Application Number:
  US14/701,468
• Publication Number:
  US 20160320896A1
• Time in Patent Office: 866 Days
• 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 3/04166 Details of scanning methods, e.g. sampling time, grouping of sub areas or time sharing with display driving Synchronisation with the driving of the display or the backlighting unit to avoid interferences generated internally G06F3/04184
• CPC Class Codes: G06F 3/04182 Filtering of noise external to the device and not generated by digitiser components
• CPC Class Codes: G06F 3/0443 using a single layer of sensing electrodes
• 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
• 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

In an example, a processing system for a capacitive sensing device includes a sensor module having sensor circuitry coupled to a first plurality of sensor electrodes. The sensor module is configured to receive resulting signals from the plurality of sensor electrodes using a capacitive sensing signal having a plurality of capacitive sensing bursts and a sensing frequency. The sensor module is further configured to introduce at least one phase shift between a respective at least one pair of the plurality of capacitive sensing bursts. The processing system further includes a determination module configured to determine capacitive measurements based on the resulting signals.

Claims

1. A processing system for a capacitive sensing device, comprising:

a sensor module comprising sensor circuitry coupled to a first plurality of sensor electrodes, the sensor module configured to;

receive resulting signals from the plurality of sensor electrodes using a capacitive sensing signal having a plurality of capacitive sensing bursts and a sensing frequency; and

introduce at least one phase shift between a respective at least one pair of the plurality of capacitive sensing bursts; and

a determination module configured to determine capacitive measurements based on the resulting signals;

wherein the sensor module is configured to determine the at least one phase shift from an analytical metric quantifying susceptibility of the capacitive measurements versus interference frequency by minimizing a first function, the first function being variance of a second function over frequency, the second function being variance of the capacitive measurements over time.

2. The processing system of claim 1, wherein:

the plurality of sensor electrodes comprise a first set of sensor electrodes disposed along a first axis;

the sensor circuitry is coupled to a second set of sensor electrodes disposed along a second axis;

the sensor module is configured to;

receive additional resulting signals from the second set of sensor electrodes using a capacitive sensing signal having an additional plurality of capacitive sensing bursts and the sensing frequency; and

introduce at least one phase shift between a respective at least one pair of the additional plurality of capacitive sensing bursts; and

the determination module is configured to determine additional capacitive measurements based on the additional resulting signals.

3. The processing system of claim 2, wherein:

the capacitive measurements comprise a combination of a plurality of absolute capacitive measurements along the first axis corresponding to the plurality of capacitive sensing bursts; and

the additional capacitive measurements comprise a combination of a plurality of absolute capacitive measurements along the second axis corresponding to the additional plurality of capacitive sensing bursts.

4. The processing system of claim 1, wherein the plurality of capacitive sensing bursts comprises a sequence of at least three capacitive sensing bursts.

5. The processing system of claim 1, wherein the sensor module is configured to introduce the at least one phase delay by modulating polarity of the at least one pair of the plurality of capacitive sensing bursts.

6. The processing system of claim 1, wherein the sensor module is configured to introduce the at least one phase delay by inserting a time delay between the respective at least one pair of the plurality of capacitive sensing bursts.

7. The processing system of claim 1, wherein the capacitive measurements comprise a combination of a plurality of absolute capacitive measurements corresponding to the plurality of capacitive sensing bursts.

8. The processing system of claim 1, wherein the capacitive measurements comprise a combination of a plurality of transcapacitive measurements corresponding to the plurality of capacitive sensing bursts.

9. The processing system of claim 1, wherein:

the plurality of sensor electrodes comprise a set of receiver electrodes;

the sensor circuitry is coupled to a set of transmitter electrodes;

the resulting signals comprise effects of the capacitive sensing signal emitted by at least one of the transmitter electrodes and at least one input object.

10. A method of operating a capacitive sensing device having a plurality of sensor electrodes, the method comprising:

receiving resulting signals from the plurality of sensor electrodes using a capacitive sensing signal having a plurality of capacitive sensing bursts and a sensing frequency;

introducing at least one phase shift between a respective at least one pair of the plurality of capacitive sensing bursts;

determining capacitive measurements based on the resulting signals; and

determining the at least one phase shift based on an analytical metric quantifying susceptibility of the capacitive measurements versus interference frequency by minimizing a first function, the first function being variance of a second function over frequency, the second function being variance of the capacitive measurements over time.

11. The method of claim 10, wherein the operation of introducing the at least one phase shift comprises inserting at least one time delay between the respective at least one pair of the plurality of capacitive sensing bursts.

12. The method of claim 11, wherein each of the at least one time delay is less than a cycle of the sensing frequency.

13. The method of claim 11, wherein each of the at least one time delay is greater than a cycle of the sensing frequency.

14. The method of claim 10, wherein the operation of introducing the at least one phase shift comprises modulating polarity of the at least one pair of the plurality of capacitive sensing bursts.

15. The method of claim 10, wherein the capacitive measurements comprise a combination of a plurality of absolute capacitive measurements corresponding to the plurality of capacitive sensing bursts.

16. The method of claim 10, wherein the capacitive measurements comprise a combination of a plurality of transcapacitive measurements corresponding to the plurality of capacitive sensing bursts.

17. An input device, comprising:

a plurality of sensor electrodes; and

a processing system, coupled to the plurality of sensor electrodes, the processing system configured to;

receive resulting signals from the plurality of sensor electrodes using a capacitive sensing signal having a plurality of capacitive sensing bursts and a sensing frequency;

introduce at least one phase shift between a respective at least one pair of the plurality of capacitive sensing bursts;

determine capacitive measurements based on the resulting signals; and

determine the at least one phase shift based on an analytical metric quantifying susceptibility of the capacitive measurements versus interference frequency by minimizing a first function, the first function being variance of a second function over frequency, the second function being variance of the capacitive measurements over time.

18. The input device of claim 17, wherein the processing system is configured to introduce the at least one phase delay by modulating polarity of the at least one pair of the plurality of capacitive sensing bursts.

19. The input device of claim 17, wherein the processing system is configured to introduce the at least one phase delay by inserting a time delay between the respective at least one pair of the plurality of capacitive sensing bursts.