Location sensing system and method employing adaptive drive signal adjustment

• US 8,089,474 B2
• Filed: 12/28/2006
• Issued: 01/03/2012
• Est. Priority Date: 12/28/2006
• Status: Active Grant

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Geaghan, Bernard O., Libbey, Albert H.
• Primary Examiner(s): Lao, Lun-Yi
• Assistant Examiner(s): SUTEERAWONGSA, JARURAT
• Application Number:
  US11/617,337
• Publication Number:
  US 20080158165A1
• Time in Patent Office: 1,832 Days
• Field of Search: 345/179, 345/156, 345173-174, 178/18.01, 178/18.03, 178/18.07, 178/19.01
• US Class Current: 345/174
• CPC Class Codes: G06F 3/03545 Pens or stylus

Abstract

Systems and methods provide for adaptive drive signal adjustment to improve reception of a stylus signal at a location sensor. A location sensing system includes an untethered stylus comprising circuitry configured to receive a drive signal and transmit a stylus signal. The circuitry is configured to be energized by the received drive signal and includes frequency-sensitive circuitry. A location sensor includes a controller and a sensing array. The location sensor is configured to generate the drive signal and receive the stylus signal. The controller is configured to adjust a parameter of the drive signal that improves receptivity of the stylus signal by the location sensor.

Claims

1. A location sensor system, comprising:

an untethered stylus comprising circuitry configured to receive a drive signal and transmit a stylus signal, the circuitry configured to be energized by the received drive signal and comprising frequency-sensitive circuitry; and

a location sensor comprising a controller and sensing array, the location sensor configured to generate the drive signal and receive the stylus signal, the controller configured to adjust a parameter of the drive signal that improves receptivity of the stylus signal by the location sensor;

wherein

the controller is configured to;

adjust the frequency of the drive signal to switch back and forth between frequencies higher and lower than an estimated resonance frequency of the frequency-sensitive circuitry;

determine a magnitude of the stylus signal at each of the adjusted drive signal frequencies; and

adjust the drive signal frequency in a manner that increases the stylus signal magnitude.

2. The system of claim 1, wherein the controller is configured to adjust a parameter of the drive signal that increases a magnitude of the stylus signal.

3. The system of claim 1, wherein the controller is configured to adjust a parameter of the drive signal that modifies a phase of the stylus signal.

4. The system of claim 1, wherein the controller is configured to adjust a parameter of the drive signal that increases a signal-to-noise ratio of the stylus signal.

5. The system of claim 1, wherein the controller is configured to measure a parameter of the stylus signal as the drive signal parameter is adjusted over a range of parameter values.

6. The system of claim 5, wherein the stylus signal parameter is a magnitude of the stylus signal.

7. The system of claim 5, wherein the stylus signal parameter is a phase of the stylus signal.

8. The system of claim 1, wherein the controller is configured to adjust a frequency of the drive signal to match a resonance frequency of the frequency-sensitive circuitry of the stylus.

9. The system of claim 1, wherein the controller is configured to adjust a frequency of the drive signal to track changes of a resonance frequency of the frequency-sensitive circuitry of the stylus.

10. The system of claim 1, wherein the controller is configured to:

determine a location of the stylus relative to the sensing array based on absolute values of stylus signal magnitudes at both higher and lower frequencies.

11. The system of claim 1, wherein the stylus circuitry is configured to modulate the magnitude of the stylus signals at the higher and lower frequencies in a predetermined frequency or code sequence, and the controller further configured to demodulate the predetermined frequency or code sequence as a stylus status indication.

12. The system of claim 1, wherein a resonance frequency of the frequency-sensitive circuitry of the stylus changes in accordance with a status change of the stylus, and the controller is configured to detect the change in stylus status by measuring a change of the drive signal frequency needed to match the resonance frequency of the frequency-sensitive circuitry.

13. The system of claim 12, wherein the controller is configured to detect the change in stylus status by measuring a rate of change of the drive signal frequency.

14. The system of claim 1, wherein the stylus comprises switch circuitry coupled to the frequency-sensitive circuitry and comprising one or more switches actuatable by a user of the stylus, a resonance frequency of the frequency-sensitive circuitry changing in response to actuation of the one or more switches, and the controller configured to adjust a frequency of the drive signal to match the changed resonance frequency of the frequency-sensitive circuitry.

15. The system of claim 14, wherein the one or more switches correspond to one or more of a user-initiateable function, a mouse function, a stylus pressure measurement, and a stylus tip switch function.

16. The system of claim 1, wherein the location sensor comprises:

a modulator configured to modulate the drive signal at a drive signal frequency corresponding to a resonance frequency of the frequency-sensitive circuitry of the stylus; and

a demodulator that is synchronized with the drive signal frequency.

17. The system of claim 1, wherein the controller is configured to coordinate simultaneous transmission of the drive signal and reception of stylus signal.

18. A method of controlling an operating frequency of a location sensor with an untethered stylus, comprising:

receiving, at the stylus, a drive signal generated at the location sensor;

energizing the stylus and producing a signal at the stylus in response to receiving the drive signal;

receiving the stylus signal at the location sensor; and

adjusting a parameter of the drive signal that improves receptivity of the stylus signal at the location sensor;

wherein

adjusting the parameter of the drive signal comprises;

adjusting the frequency of the drive signal to switch back and forth between frequencies higher and lower than an estimated resonance frequency of frequency-sensitive circuitry of the stylus;

determining a magnitude of the stylus signal at each of the adjusted drive signal frequencies; and

adjusting the drive signal frequency in a manner that increases the stylus signal magnitude.

19. The method of claim 18, wherein adjusting the parameter of the drive signal increases a magnitude of the stylus signal.

20. The method of claim 18, wherein adjusting the parameter of the drive signal modifies a phase of the stylus signal.

21. The method of claim 18, wherein adjusting the parameter of the drive signal increases a signal-to-noise ratio of the stylus signal.

22. The method of claim 18, further comprising measuring a parameter of the stylus signal as the drive signal parameter is adjusted over a range of parameter values, the stylus signal parameter comprising at least one of a magnitude of the stylus signal and a phase of the stylus signal.

23. The method of claim 18, wherein adjusting the parameter of the drive signal comprises adjusting a frequency of the drive signal to match a resonance frequency of frequency-sensitive circuitry of the stylus.

24. The method of claim 18, wherein adjusting the parameter of the drive signal comprises tracking changes of a resonance frequency of frequency-sensitive circuitry of the stylus.

25. The method of claim 18, wherein adjusting the parameter of the drive signal comprises:

determining a location of the stylus relative to the location sensor based on absolute values of stylus signal magnitudes at both higher and lower frequencies.

26. The method of claim 18, wherein adjusting the parameter of the drive signal comprises:

modulating the magnitude of the stylus signals at the higher and lower frequencies in a predetermined frequency or code sequence; and

demodulating, at the location sensor, the predetermined frequency or code sequence as a stylus status indication.

27. The method of claim 18, further comprising:

changing a resonance frequency of frequency-sensitive circuitry of the stylus in accordance with a status change of the stylus; and

detecting, at the location sensor, the change in stylus status by measuring one or both of a change and a rate of change of the drive signal frequency needed to match the resonance frequency of the frequency-sensitive circuitry of the stylus.

28. The method of claim 18, wherein transmitting the drive signal and receiving the stylus signal at the location sensor are effected simultaneously.