OSCILLATOR CIRCUIT FOR USE IN AN UNTETHERED STYLUS

• US 20080150917A1
• Filed: 12/20/2006
• Published: 06/26/2008
• Est. Priority Date: 12/20/2006
• Status: Abandoned Application

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Vos, Martin J., Libbey, Albert H.
• Application Number:
  US11/613,571
• Publication Number:
  US 20080150917A1
• Time in Patent Office: Days
• US Class Current: 345/179
• CPC Class Codes: G06F 3/03545 Pens or stylus
• CPC Class Codes: G06F 3/046 by electromagnetic means

Abstract

An untethered stylus is configured to cooperate with a location sensing device that generates a continuously varying magnetic drive signal that powers the stylus. The stylus includes a housing having a tip, a shield, and an antenna arrangement coupled between the tip and shield. A resonant circuit of the antenna arrangement is tuned to a frequency of the magnetic drive signal. An oscillator circuit, coupled to and powered by the antenna arrangement, is configured to oscillate at a frequency corresponding to data to be communicated from the stylus, and to amplitude modulate a voltage developed at the stylus tip at the oscillator circuit frequency. Repetitive current draw from the antenna arrangement to power the oscillator circuit repetitively reduces a voltage at the tip, such that the tip voltage is amplitude modulated at the oscillator circuit frequency.

Claims

1. An untethered stylus configured to cooperate with a location sensing device, the location sensing device configured to generate a continuously varying magnetic drive signal that powers the stylus, the stylus comprising:

a housing comprising a tip and a shield;

an antenna arrangement coupled between the tip and shield, the antenna arrangement comprising a resonant circuit tuned to a frequency of the magnetic drive signal; and

an oscillator circuit coupled to the antenna arrangement and powered by the antenna arrangement, the oscillator circuit configured to oscillate at a frequency corresponding to data to be communicated from the stylus, the oscillator circuit configured to amplitude modulate a voltage developed at the tip at the oscillator circuit frequency.

2. The stylus of claim 1, wherein the oscillator circuit comprises a phase shift oscillator.

3. The stylus of claim 1, wherein the oscillator circuit comprises a FET phase shift oscillator.

4. The stylus of claim 1, wherein the data comprises analog data.

5. The stylus of claim 1, wherein the data comprises digital data.

6. The stylus of claim 1, wherein the data comprises stylus status data.

7. The stylus of claim 1, wherein the antenna arrangement comprises a ferrite rod coil antenna coupled in parallel with a capacitor.

8. The stylus of claim 1, wherein repetitive current draw from the antenna arrangement to power the oscillator circuit repetitively reduces a voltage at the tip, such that the tip voltage is amplitude modulated at the oscillator circuit frequency.

9. The stylus of claim 1, wherein the oscillator circuit is configured to oscillate at a plurality of frequencies corresponding to a plurality of data to be communicated from the stylus, wherein a voltage at the tip is amplitude modulated at the plurality of oscillator circuit frequencies.

10. The stylus of claim 9, wherein the stylus comprises a plurality of user-actuatable switches coupled to the oscillator circuit, each of the plurality of user-actuatable switches corresponding to one of the plurality of oscillator circuit frequencies.

11. The stylus of claim 10, wherein at least some of the plurality of user-actuatable switches correspond to one or more mouse functions.

12. The stylus of claim 1, wherein the location sensing device comprises a digitizer.

13. The stylus of claim 1, wherein the location sensing device comprises a digitizer and a touch-sensitive sensor.

14. The stylus of claim 1, wherein the location sensing device comprises an amplitude demodulator configured to demodulate the tip voltage amplitude modulation to produce a sinusoid at the oscillator circuit frequency, and a frequency demodulator configured to recover the stylus data.

15. A method implemented in an untethered stylus for use with a location sensing device, comprising:

receiving a continuously varying magnetic drive signal generated by the location sensing device;

powering an oscillator circuit of the stylus in response to receiving the drive signal;

generating a data signal at a frequency of the oscillator circuit; and

amplitude modulating a voltage signal readable by the location sensing device using the data signal.

16. The method of claim 15, wherein the oscillator circuit comprises a phase shift oscillator.

17. The method of claim 15, wherein the oscillator circuit comprises a FET phase shift oscillator.

18. The method of claim 15, wherein the data signal comprises analog data.

19. The method of claim 15, wherein the data signal comprises digital data.

20. The method of claim 15, wherein the data signal comprises stylus status data.

21. The method of claim 15, wherein:

generating the data signal comprises generating each of a plurality of data signals at one of a plurality of oscillator circuit frequencies; and

amplitude modulating the voltage signal comprises amplitude modulating the voltage signal using the plurality of data signals.

22. The method of claim 21, wherein the stylus comprises a plurality of user-actuatable switches each producing one of the plurality of data signals.

23. The method of claim 22, wherein at least some of the plurality of user-actuatable switches correspond to one or more mouse functions.

24. The method of claim 15, further comprising amplitude demodulating the voltage signal at the location sensing device to produce a sinusoid at the oscillator circuit frequency.

25. The method of claim 24, further comprising frequency demodulating the voltage signal at the location sensing device to recover the data signal.

26. The method of claim 15, further comprising determining a location of the stylus relative to the location sensing device.

27. The method of claim 26, further comprising determining a location of a finger touch relative to the location sensing device.

28. An apparatus implemented in an untethered stylus for use with a location sensing device, comprising:

an antenna arrangement for receiving a continuously varying magnetic drive signal generated by the location sensing device;

means, powered by the antenna arrangement, for oscillating at a frequency corresponding to data to be communicated from the stylus; and

means, powered by the antenna arrangement, for amplitude modulating a stylus tip voltage at the frequency of oscillation.

29. The apparatus of claim 28, further comprising means for demodulating the voltage signal.