Frequency selection with two frequency sets of multiple operating frequencies in a mutual capacitance sensing devices

• US 9,209,802 B1
• Filed: 09/27/2012
• Issued: 12/08/2015
• Est. Priority Date: 02/24/2012
• Status: Active Grant

• Current Assignee: Parade Technologies, Ltd.
• Original Assignee: Parade Technologies, Ltd.
• Inventors: Maharyta, Andriy, Musijchuk, Ihor
• Primary Examiner(s): Phan, Huy Q
• Assistant Examiner(s): Frederiksen, David
• Application Number:
  US13/629,281
• Time in Patent Office: 1,167 Days
• Field of Search: 324/681, 324/612, 324/613, 324/614, 345/173, 345/174, 370/254, 702/69
• US Class Current: 1/1
• 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 3/0446 using a grid-like structure of electrodes in at least two directions, e.g. using row and column electrodes
• CPC Class Codes: H03K 17/955 using a capacitive detector
• CPC Class Codes: H03K 17/9622 using a plurality of detectors, e.g. keyboard
• CPC Class Codes: H03K 2217/960705 Safety of capacitive touch and proximity switches, e.g. increasing reliability, fail-safe
• CPC Class Codes: H03K 2217/960775 Emitter-receiver or "fringe" type detection, i.e. one or more field emitting electrodes and corresponding one or more receiving electrodes

Abstract

Apparatuses and methods of frequency selection algorithms and frequency set selection are described. One method monitors a signal on the electrodes of a sense network, determine a first group of noise metrics of noise in the signal, determine a second group of noise metrics. The method switches from a first operating frequency in a first set to a second operating frequency in the first frequency set based on the first group of noise metrics and switches from the first operating frequency in the first set to a third operating frequency in a second frequency set based on the second group of noise metrics.

Claims

1. A method comprising:

monitoring a signal on a plurality of electrodes of a sense network, the sense network to operate in a first frequency set or a second frequency set, each comprising a plurality of operating frequencies;

determining a first group of one or more noise metrics of noise in the signal;

determining a second group of one or more noise metrics of the noise in the signal;

performing a frequency hop within the first frequency set based on the first group of one or more noise metrics, wherein the frequency hop switches from a first operating frequency to a second operating frequency within the first frequency set; and

performing a frequency set hop from the first frequency set to the second frequency set based on the second group of one or more noise metrics, wherein the frequency set hop switches from the first operating frequency in the first frequency set to an operating frequency in the second frequency set.

2. The method of claim 1, wherein a first separation in frequencies between the first frequency set and the second frequency set is greater than a second separation in frequencies within the first frequency set.

3. The method of claim 1, wherein the first frequency set comprises three or more non-overlapping frequency bands, each centered at one of three operating frequencies of the first frequency set.

4. The method of claim 3, wherein the second frequency set comprises three or more non-overlapping frequency bands, each centered at one of three operating frequencies of the second frequency set.

5. The method of claim 3, wherein the second frequency set comprises two non-overlapping frequency bands, each centered at one of two operating frequencies of the second frequency set.

6. The method of claim 1, wherein the switching from the first frequency set to the second frequency set comprises switching from the first operating frequency to one of the plurality of operating frequencies in the second frequency set that is farthest away in frequency from the first operating frequency.

7. The method of claim 1, wherein the determining the second group of one or more noise metrics comprises:

obtaining a plurality of sub-conversions representing capacitance values measured on the plurality of electrodes;

calculating a third noise metric (NM3) based on the plurality of sub-conversions, wherein the NM3 represents an energy of the noise in the signal; and

calculating a first noise metric (NM1) based on the plurality of sub-conversions, wherein the NM1 represents an average sum of absolute value maximums among the sub-conversions in a number of conversions, wherein the second group of one or more noise metrics comprises the NM1 and the NM3,

wherein the determining the first group of one or more noise metrics comprises calculating a second noise metric (NM2) based on the plurality of sub-conversions, and

wherein the first group of one or more noise metrics comprises the NM2 and the NM1.

8. The method of claim 7, wherein the calculating the NM1, NM2, and NM3 comprises calculating the NM1, NM2, and NM3 based on the following equations:

9. The method of claim 1, wherein the determining whether the frequency set hop is needed comprises at least one of:

determining that the plurality of operating frequencies in the first set exceed a threshold noise level after a specified number of cycles through the plurality of operating frequencies in the first frequency set;

or

determining that a third noise metric (NM3), calculated from a plurality of sub-conversions exceeds a threshold value, wherein the NM3 represents an energy of the noise in the signal.

10. The method of claim 7, further comprising:

identifying the plurality of operating frequencies in a current set of the first frequency set and the second frequency set with a minimum noise metric of the NM2;

switching from a current operating frequency of the plurality of operating frequencies in the current set to the operating frequency with the minimum noise metric of the NM2; and

determining whether a frequency set hop from the current set to another set is needed based on the first group of one or more noise metrics regardless of the NM2 in the current set.

11. A capacitance sensing system, comprising:

a memory device; and

a controller coupled to the memory device, wherein the controller is configured to receive a signal from a sense network comprising a plurality of electrodes to detect a conductive object proximate to the plurality of electrodes, wherein the controller comprises;

a noise listening circuit configured to;

determine a first group of one or more noise metrics of noise in the signal; and

determine a second group of one or more noise metrics of the noise in the signal; and

a frequency selection state machine configured to;

perform a frequency hop within a first frequency set based on the first group of the one or more noise metrics, wherein the frequency hop switches from a first operating frequency in the first frequency set to a second operating frequency in the first frequency set; and

perform a frequency set hop from the first frequency set to a second frequency set based on the second group of the one or more noise metrics, wherein the frequency set hop is switches from the first operating frequency in the first frequency set to an operating frequency in the second frequency set.

12. The capacitance sensing system of claim 11, wherein a first separation in frequencies between the first frequency set and the second frequency set is greater than a second separation in frequencies within the first frequency set.

13. The capacitance sensing system of claim 11, wherein the first frequency set comprises three or more non-overlapping frequency bands, each centered at one of three operating frequencies of the first frequency set, and wherein the second frequency set comprises two or more non-overlapping frequency bands, each centered at one of two operating frequencies of the second frequency set.

14. The capacitance sensing system of claim 11, wherein the noise listening circuit is configured to:

obtain a plurality of sub-conversions representing capacitance values measured on the plurality of electrodes;

calculate a third noise metric (NM3) based on the plurality of sub-conversions, wherein the NM3 represents an energy of the noise in the signal;

calculate a first noise metric (NM1) based on the plurality of sub-conversions, wherein the NM1 represents an average sum of absolute value maximums among the sub-conversions in a number of conversions; and

calculate a second noise metric (NM2) based on the plurality of sub-conversions,

wherein the second group of one or more noise metrics comprises the NM1 and the NM3, and

wherein the first group of one or more noise metrics comprises the NM2 and the NM1.

15. The capacitance sensing system of claim 14, wherein the noise listening circuit is configured to calculate the NM1, NM2, and NM3 based on the following equations:

16. The capacitance sensing system of claim 11, wherein the noise listening circuit is configured to switch from the first operating frequency to an operating frequency in the second frequency set that is farthest away in frequency from the first operating frequency, when performing the frequency set hop.

17. A host device, comprising:

a display;

a capacitance sensing array disposed in connection with the display;

a touch screen controller coupled to the capacitance sensing array, wherein the touch screen controller comprises;

a capacitance sensing circuit coupled to the capacitance sensing array; and

a noise listening circuit coupled to the capacitance sensing array, wherein the noise listening circuit is configured to;

determine a first group of one or more noise metrics of noise in a signal;

determine a second group of one or more noise metrics of the noise in a signal;

perform a frequency hop within a first frequency set based on the first group of the one or more noise metrics, wherein the frequency hop switches from a first operating frequency in a first frequency set to a second operating frequency in the first frequency set; and

performing a frequency set hop from the first frequency set to a second frequency set based on the second group of the one or more noise metrics, wherein the frequency set hop switches from the first operating frequency in the first frequency set to an operating frequency in the second frequency set.

18. The host device of claim 17, wherein the first frequency set comprises three or more non-overlapping frequency bands, each centered at one of three operating frequencies of the first frequency set, and wherein the second frequency set comprises two or more non-overlapping frequency bands, each centered at one of two operating frequencies of the second frequency set.

19. The host device of claim 17, wherein the noise listening circuit is configured to switch from the first operating frequency in the first frequency set to an operating frequencies in the second frequency set that is farthest away in frequency from the first operating frequency when performing the frequency set hop.