Noise reduction within an electronic device using automatic frequency modulation

• US 7,986,193 B2
• Filed: 01/03/2007
• Issued: 07/26/2011
• Est. Priority Date: 01/03/2007
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Krah, Christoph Horst
• Primary Examiner(s): Pascal; Robert
• Assistant Examiner(s): Goodley; James E
• Application Number:
  US11/650,045
• Publication Number:
  US 20080157893A1
• Time in Patent Office: 1,665 Days
• Field of Search: 331/4, 331/44, 345/173, 345/174
• US Class Current: 331/44
• CPC Class Codes: G06F 3/0418 for error correction or compensation, e.g. based on parallax, calibration or alignment
• 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: H03L 7/097 using a comparator for comparing the voltages obtained from two frequency to voltage converters

Abstract

Disclosed is a system and method for providing an oscillating signal of relatively precise frequency without using a signal provided by a crystal as a reference. Disclosed is a feedback oscillator circuit configured to output an oscillating signal having a frequency defined by a reference signal. The oscillating signal can be sent to one or more circuits including at least one frequency sensitive element. The frequency sensitive element produces an output signal which depends on the frequency of the oscillating signal. A controller controls the reference signal in order to cause an attribute of the output signal to have a value within a desired range.

Claims

1. An electronic device comprising:

an oscillator module configured to generate an oscillating signal of a frequency based on a tuning value input at a tuning input of the oscillator module;

a result signal generator configured to provide a result signal which is at least partially based on the oscillating signal; and

a controller connected to the tuning input of the oscillator module and the result signal generator and configured to

apply a plurality of different tuning values to the tuning input of the oscillator module,

for each applied tuning value, obtain and save repeated samples of the result signal during a time period at which the tuning value is applied, determine a respective noise value derived from the saved samples, the noise value computed from those saved samples that are at or below a certain threshold, while excluding from the determination of the noise value any saved samples obtained during that time period that exceed the threshold and are considered to be caused by a touch event, the noise value being indicative of a level of noise which appears at the result signal while the applied tuning value is being applied, and perform touch detection using the saved samples regardless of the noise value determination,

select one or more low noise tuning values of the plurality of different tuning values, the low noise tuning values being associated with low respective noise values, and

apply a low noise tuning value of the one or more low noise tuning values to the tuning input of the oscillating circuit.

2. The electronic device of claim 1, wherein the oscillator module is free of any crystal oscillators and does not rely on any crystal oscillators to generate the oscillating signal.

3. The electronic device of claim 2, wherein the controller is further configured to enter a frequency initialization mode, wherein the applying a plurality of different tuning values, determining a respective noise value, selecting one or more low noise values and applying one of the one or more noise values are performed during the frequency initialization mode, and the controller is further configured to enter an ordinary operation mode and proceed with ordinary operation while continuing to apply the low noise tuning value to the tuning input of the oscillating circuit.

4. The electronic device of claim 1, wherein the controller is a generally programmable processor.

5. The electronic device of claim 1,

wherein the device further comprises a multi-touch panel configured to receive a stimulation signal whose frequency is based on the oscillating signal, and to output a panel output signal based on the stimulation signal, wherein the result signal generated by the result signal generator is based on the panel output signal.

6. The electronic device of claim 5, wherein noise in the result signal is at least partially caused by noise in the panel output signal and the noise in the panel output signal is at least partially caused by interactions of the stimulation signal with other signals at the multi-touch panel.

7. The electronic device of claim 5, wherein the multi touch panel also features display functionality and includes two or more layers comprising:

one or more touch sensitive layers, configured to perform multi-touch functionality, receive the stimulation signal and output the panel output signal; and

one or more display related layers configured to perform display functionality, and receive a display related signal,

wherein the display related signal at least partially causes the noise of the panel output signal.

8. The electronic device of claim 7, wherein the display related signal is the sum of a plurality of component signals each having a different component frequency, said component signals causing noise of a plurality of different component frequencies in the panel output signal.

9. The electronic device of claim 8, wherein each tuning value of the plurality of tuning values is associated with a respective resulting frequency in the panel output signal, and the one or more low noise tuning values are associated with resulting frequencies different than the component frequencies.

10. The electronic device of claim 8, wherein the display related signal is a square wave signal.

11. The electronic device of claim 5, wherein the one or more low noise tuning values are two or more low noise tuning values and the controller is further configured to apply two or more of the two or more low noise tuning values in periodic succession.

12. The electronic device of claim 5, wherein the controller is further configured to retrieve one or more previously defined expected low noise stimulation frequencies, and correlate the expected low noise stimulation frequencies and the low noise tuning values to derive a relationship between various tuning values and the stimulation frequencies that result from said various tuning values.

13. The electronic device of claim 5, wherein the multi-touch panel further includes a band pass filter and the controller is configured to only select low noise tuning values which result in stimulation frequencies which are within the pass band of the band pass filter.

14. The electronic device of claim 5, wherein the multi-touch panel is also a proximity sensing panel.

15. The electronic device of claim 1, wherein the low noise tuning values are associated with the lowest noise values.

16. The electronic device of claim 1, wherein the electronic device is a digital audio player.

17. The electronic device of claim 1, wherein the electronic device is a mobile telephone.

18. The electronic device of claim 1, wherein the electronic device further comprises a memory connected to the controller and the controller is further configured to save the low noise tuning values in a frequency hopping table in the memory.

40. The electronic device of claim 1, wherein the traversal circuit is a multi-touch panel.

19. A method for generating an oscillating signal in an electronic device the method comprising:

applying a plurality of different tuning values to an oscillator module;

generating, by the oscillator module, an oscillating signal whose frequency is based on a currently applied tuning value;

providing a result signal at least partially based on the oscillating signal;

for each applied tuning value, obtaining and saving repeated samples of the result signal during a time period at which the tuning value is applied, determining a respective noise value derived from the saved samples, the noise value computed from those saved samples that are at or below a certain threshold, while excluding from the determination of the noise value any saved samples obtained during that time period that exceed the threshold and are considered to be caused by a touch event, the noise value being indicative of a level of noise which appears at the result signal while the applied tuning value is being applied, and performing touch detection using the saved samples regardless of the noise value determination;

selecting one or more low noise tuning values of the plurality of different tuning values, the low noise tuning values being associated with low respective noise values; and

applying a low noise tuning value of the one or more low noise tuning values to the tuning input of the oscillating circuit.

20. The method of claim 19, wherein generating of the oscillating signal is performed without use of crystal oscillators or any signals depending from crystal oscillators.

21. The method of claim 19, wherein the determining of a respective noise value is performed by a controller and the controller is a generally programmable processor.

22. The method of claim 19, further comprising:

generating a stimulation signal whose frequency is based on the oscillating signal;

sending the stimulation signal to a multi-touch panel; and

producing a panel output signal by the multi-touch panel, the panel output signal being based on the stimulation signal,

wherein the result signal is based on the panel output signal.

23. The method of claim 22, wherein noise in the result signal is at least partially caused by noise in the panel output signal and the noise in the panel output signal is at least partially caused by interactions of the stimulation signal with other signals at the multi-touch panel.

24. The method of claim 22, wherein the multi touch panel also features display functionality and the method further comprising sending a display related signal to the multi touch panel, wherein the display related signal interacts with the stimulation signal to at least partially cause the noise of the panel output signal.

25. The method of claim 24, wherein the display related signal is the sum of a plurality of component signals of plurality of different component frequencies, said component signals causing noise of the plurality of different component frequencies in the panel output signal.

26. The method of claim 25, wherein each tuning value of the plurality of tuning values is associated with a respective resulting frequency in the panel output signal, and the one or more low noise tuning values are associated with resulting frequencies different than the component frequencies.

27. The method of claim 25, wherein the display related signal is a square wave signal.

28. The method of claim 22, wherein the one or more low noise tuning values are two or more low noise tuning values and the method further comprises applying two or more of the two or more low noise tuning values in periodic succession to produce a stimulation signal having a periodically changing frequency.

29. The method of claim 22, wherein the controller is further configured to retrieve one or more previously defined expected low noise stimulation frequencies, and use the expected low noise stimulation frequencies and the low noise tuning values to derive a relationship between various tuning values and the stimulation frequencies that result from said various tuning values.

30. The method of claim 22, wherein the multi-touch panel further includes a band-pass filter and the applying a low noise tuning value comprises applying a low noise tuning value which results in a stimulation frequency which is within the pass band of the band pass filter.

31. The method of claim 22, wherein the multi-touch panel is also a proximity sensing panel.

32. The method of claim 19, wherein the low noise tuning values are associated with the lowest noise values.

33. The method of claim 19, further including saving the low noise tuning values in a frequency hopping table.

41. The method of claim 19, wherein the traversal circuit is a multi-touch panel.

34. A digital audio player comprising:

an oscillator module configured to generate an oscillating signal of a frequency based on a tuning value input at a tuning input of the oscillator module;

a result signal generator configured to provide a result signal which is at least partially based on the oscillating signal; and

a controller connected to the tuning input of the oscillator module and the result signal generator and configured to

apply a plurality of different tuning values to the tuning input of the oscillator module,

for each applied tuning value, obtain and save repeated samples of the result signal during a time period at which the tuning value is applied, determine a respective noise value derived from the saved samples, the noise value computed from those saved samples that are at or below a certain threshold, while excluding from the determination of the noise value any saved samples obtained during that time period that exceed the threshold and are considered to be caused by a touch event, the noise value being indicative of a level of noise which appears at the result signal while the applied tuning value is being applied, and perform touch detection using the saved samples regardless of the noise value determination,

select one or more low noise tuning values of the plurality of different tuning values, the low noise tuning values being associated with low respective noise values, and

apply a low noise tuning value of the one or more low noise tuning values to the tuning input of the oscillating circuit.

35. A mobile telephone comprising:

an oscillator module configured to generate an oscillating signal of a frequency based on a tuning value input at a tuning input of the oscillator module;

a result signal generator configured to provide a result signal which is at least partially based on the oscillating signal; and

a controller connected to the tuning input of the oscillator module and the result signal generator and configured to

apply a plurality of different tuning values to the tuning input of the oscillator module,

for each applied tuning value, obtain and save repeated samples of the result signal during a time period at which the tuning value is applied, determine a respective noise value derived from the saved samples, the noise value computed from those saved samples that are at or below a certain threshold, while excluding from the determination of the noise value any saved samples obtained during that time period that exceed the threshold and are considered to be caused by a touch event, the noise value being indicative of a level of noise which appears at the result signal while the applied tuning value is being applied, and perform touch detection using the saved samples regardless of the noise value determination,

select one or more low noise tuning values of the plurality of different tuning values, the low noise tuning values being associated with low respective noise values, and

apply a low noise tuning value of the one or more low noise tuning values to the tuning input of the oscillating circuit.

36. An electronic device including a first module and a second module, the first module including a first clock generator for generating a first clock signal for the first module, the second module including a second clock generator for generating a second clock signal for the second module, the first clock generator including a crystal oscillator on which the frequency of the first clock signal is based, the second clock generator being free of any crystal oscillators, wherein:

the first module is configured to generate a first output signal at frequency based on the frequency of the first clock signal; and

the second module is configured to

generate a second output signal at frequency based on the second clock signal,

send the second output signal through a traversal circuit

obtain and save repeated samples of an output of the traversal circuit during a time period at which the second output signal is applied,

sense any noise that has appeared on the output of the traversal circuit as a result of sending the second output signal through the traversal circuit, said noise being at least partially dependent on the first output signal, the sensed noise computed from those saved samples that are at or below a certain threshold, while excluding from the sensed noise any saved samples obtained during that time period that exceed the threshold and are considered to be caused by a touch event,

perform touch detection using the saved samples regardless of the sensed noise, and

control the frequency of the second clock signal based on the sensed noise.

37. The electronic device of claim 36, wherein the second module is further configured to:

vary the frequency of the second clock signal to cause variations of the frequency of the second output signal;

detect the level of noise appearing at each frequency of the second output signal; and

control the frequency of the second clock signal by using frequencies associated with one or more detected levels of noise as reference points.

38. The electronic device of claim 37, wherein controlling the frequency of the second clock signal is accomplished by sending a tuning value to the second clock generator, the device further including a frequency transfer function generation module for generating a frequency transfer function based on the detected levels of noise, their associated tuning values, and one or more predefined expected frequency values at which predefined levels of noise are expected to appear.

39. The electronic device of claim 38, wherein the electronic device includes a multi-touch display panel configured to provide display functionality and to sense multiple touches from a user, the first module is a display module configured to provide the display functionality and the second module is a touch sensitive panel module configured to provide touch sensing functionality.

42. The electronic device of claim 36,

wherein the traversal circuit is a multi-touch panel.

43. A touch sensitive device comprising:

a touch sensor panel; and

a touch subsystem communicatively coupled to the touch sensor panel and configured for

applying a series of stimulation signals of different frequencies to one or more drive lines of the touch sensor panel,

receiving one or more sense signals from the touch sensor panel resulting from each of the stimulation signals of different frequencies,

obtaining and saving repeated samples of the one or more sense signals during a time period at which stimulation signals of a particular frequency are applied,

determining a noise value from the saved samples for each of the stimulation signals of different frequencies, the noise value computed from those saved samples that are at or below a certain threshold, while excluding from the determination of the noise value any saved samples obtained during that time period that exceed the threshold and are considered to be caused by a touch event,

performing touch detection using the saved samples regardless of the noise value determination,

selecting one or more low noise stimulation signals corresponding to one or more low noise frequencies as determined by the noise values, and

applying a low noise stimulation signal to the touch sensor panel.

44. The touch sensitive device of claim 43, the touch subsystem further configured for applying the series of stimulation signals of different frequencies in a frequency initialization mode, and applying the low noise stimulation signal in an ordinary operation mode.

45. The touch sensitive device of claim 43, the touch subsystem further configured for:

determining the noise values for the low noise stimulation signals for a previous and current time; and

if a difference between the noise values for the previous and current time exceed a predetermined threshold indicative of drift, adjusting the selected low noise stimulation signals until their noise values improve to a predetermined acceptable level.

46. A method of operating a touch sensor panel, comprising:

stimulating the touch sensor panel with a series of stimulation signals of different frequencies;

obtaining and saving repeated samples of one or more sense signals obtained from the touch sensor panel during a time period at which stimulation signals of a particular frequency are applied;

determining a noise value from the saved samples for each of the stimulation signals of different frequencies, the noise value computed from those saved samples that are at or below a certain threshold, while excluding from the determination of the noise value any saved samples obtained during that time period that exceed the threshold and are considered to be caused by a touch event;

performing touch detection using the saved samples regardless of the noise value determination; and

applying a low noise stimulation signal to the touch sensor panel as determined by the noise values.

47. The method of claim 46, further comprising determining the noise values in a frequency initialization mode, and applying the low noise stimulation signal in an ordinary operation mode.

48. The method of claim 46, further comprising:

detecting frequency drift in the low noise stimulation signal; and

if the frequency drift exceeds a predetermined threshold, adjusting the selected low noise stimulation signal until its noise value improves to a predetermined acceptable level.